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Installation of reinforced concrete structures

Installation of structures for one-story industrial buildings. When installing one-story industrial buildings, the method of longitudinal installation is used, when the assembly is carried out in separate spans, and the method of transverse or sectional installation, when the assembly is carried out on separate sections of the object.

Depending on the width of the span of the building, the mass of the elements to be mounted and the lifting capacity of the crane, its movement during the installation of structures is carried out in the middle of the span or along its edges. When choosing the movement of the crane, it is necessary to strive to ensure that the length of the paths for its movement and the number of stops are minimal.

Unlike metal frames, assembled panel-by-panel (complex), buildings made of precast concrete elements are mounted in a separate way, which is due to the need to monolith the joints of structures before installing subsequent elements on them. Installation of roof structures can be started only after the concrete has reached the joints of columns with foundations of 70% strength. For the commissioning of the building for the following work in separate parts, the entire scope of work is divided into grips limited by spans, expansion joints or separate sections, depending on the size of the workshop.

With the simultaneous operation of several assembly mechanisms, assembly is carried out in several parallel threads.

Prefabricated structures of single-storey industrial buildings are mounted, as a rule, with jib cranes in the following sequence: foundation blocks, columns, foundation beams, crane beams, trusses or beams and roof slabs.

In the case of installation of frames for prefabricated reinforced concrete industrial buildings, on-site warehouses are not organized, which is explained by the relatively close location to the assembly sites of manufacturers and the possibility of supplying structures directly to the installation site.

When organizing the supply of structures in the required sequence and on time, installation is carried out from vehicles (installation "from wheels"). If it is not possible to organize the assembly "from wheels", the structures are transported by road to the area of \u200b\u200bthe assembly crane. The unloading of structures is carried out with a lighter crane, or an assembly crane in the third shift, since it is irrational to use the main assembly mechanism for unloading and laying out structures on day shifts. To ensure uninterrupted installation, the stock of structures should be at least 5 days.

In fig. 181 shows a diagram of the installation of a workshop with three spans of 24 m.

Installation of structures for multi-storey industrial buildings. When erecting multi-storey industrial buildings, horizontal (floor-by-floor) or vertical (in parts of the building to the entire height) installation methods are used. In this case, structures are usually mounted using an integrated method that ensures the spatial rigidity of each separate part (cell) of the building.

Figure: 181. Workshop assembly scheme: 1 - SKG-30 crane with a boom of 25 m; 2 - half-farm; 3 - stand for enlarging farms; 4 - cover plates

Installation of prefabricated elements of the underground part is carried out using jib or tower cranes. Tower cranes in this case are installed with the expectation of their use for the installation of the above-ground part of the building without re-laying the crane runways. Prefabricated structures of the aboveground part are mounted using tower cranes, which are installed on one or both sides (with many spans) of the building, or jib cranes with tower-boom equipment.

The order of assembly of precast concrete structures of multi-storey industrial buildings depends mainly on the structural scheme of these buildings. The main condition for the installation of building structures of any structural scheme is to ensure the stability of the assembled part of the building and its individual elements. The installation of the structures of the next floor (tier) is started only after the design fixing of the structures of the previous floor and the concrete has reached 70% strength. These conditions for the erection of the frame impose certain requirements on the choice of the mounting mechanism and on its installation.

The mounting mechanism should be located outside the frame and move along the building, blocking it with its boom. With a large width of the building and the impossibility of covering it completely from one side, the frame is mounted with two cranes moving on both sides of the building.

The high building heights and the floor-by-floor installation method require a large underboom space, which can be achieved by using a high tower crane or a jib crane with jib equipment.

To reduce the overall construction time and the possibility of accelerating the delivery of the frame for adjacent construction work, the building is divided into turns. The breakdown in turn is determined by expansion joints. Each section of the frame is divided into sections within a floor. The number of grips on the floor should not be less than two, so that on the first of them work on the installation of frame elements is carried out, and on the second, at this time, to carry out the design fastening of the joints and their holding, if necessary. The size of the grips is determined from the condition of equal duration of work on each grip, so that there is no crane downtime.

Figure: 182. Scheme of installation of a multi-storey industrial building: 1 - frame; 2 - tower cranes BK.SM-14

Unlike single-storey buildings, elements in multi-storey buildings made of precast concrete structures are assembled in a complex manner. First, four columns of one cell are installed, then girders are mounted in this cell and spacer plates are placed in it between the columns. At the end of the installation of the elements of one cell, the elements of the other are installed in the same sequence, etc.

During the installation of the columns, they are temporarily fixed and verified with the help of a theodolite. Fastening is carried out using conductors, guy wires or struts with screw couplings, with their fastening to the slinging loops of the underlying slabs and crossbars. Conductors are used single or group (for two or four columns). Conductors are moved from one place to another, as well as to the floors of the building being erected by assembly cranes. After temporary fastening and verification of the correct installation of the columns, they are finally fixed by electric welding of embedded parts. Column joints are welded before installing the rest of the frame elements. Fastening of girders to columns and slabs to girders is also carried out by welding embedded steel parts.

In fig. 182 shows an installation diagram of a multi-storey industrial building.

Installation of power line supports. In the construction of power lines (PTL), along with metal and wood, prefabricated reinforced concrete supports are also widely used. Supports from the factory are delivered to the place of their installation using rail or road transport. Moreover, the equipping of the support with traverses, headband and other details is performed before sending it to the picket. Loading, transportation and unloading of reinforced concrete supports is carried out with extreme caution, as they are easily damaged. Long posts are loaded using mounting traverses. When transported by rail, long racks are loaded onto trailers from three platforms, and they are rigidly tied only to the middle platform; on the extreme platforms, the racks are laid on wooden pads without binding to ensure that they can slide on curved sections of the path. When transporting on vehicles with semi-trailers, channels are used as linings.

Reinforced concrete supports delivered to the picket without traverses are connected to steel traverses by means of bolts that pass through holes in the corners of the traverse and through steel pipes embedded in the rack when it is made. Fastening can also be done with steel straps that wrap around the rack.

Figure: 183. The scheme of lifting the reinforced concrete support of the power transmission line

When assembling the anchor plane supports on cable guys with two traverses, both racks and traverses are laid out on a leveled platform near the installation site. Then the racks are connected to the traverses and the ends of the guy wires are attached. The support assembled in this way has sufficient rigidity to lift it entirely without the use of temporary ties by the posts. Reinforced concrete supports with steel traverses are suspended by means of jib cranes. The lifting of supports with heavier reinforced concrete traverses is carried out by a tractor with a falling boom (Fig. 183). In contrast to steel supports, the ends of the lifting cable with a reinforced concrete support height of 15 m or more are fixed on the rack in two places - under the upper and lower traverses in order to reduce the assembly forces in it. At the beginning of the ascent, the bottom of the support rests against the wall of the excavation, so that a lower brake cable is not required. The braces required at the end of the lift when the boom is out of service are attached to the strut under the center boom.

Methods and technology for assembling elements of frame buildings depend on their design solutions, number of storeys and available installation equipment.

The frames of multi-storey buildings with two-storey cut columns are recommended to be mounted using group or articulated conductors. This provides a forced fixation of the columns in the design position during their installation, thereby reducing the amount of alignment work. The rest of the frame elements are mounted in a free method.

The frames of one-story and low-rise industrial and administrative buildings are recommended to be mounted in a limited-free method using single or group conductors.

The most important rule that must be followed for any organization and installation method is to ensure the stability of the structures being mounted. In this regard, any installed structure cannot be freed from the crane hook until it is securely fastened. The sequence of installation of the frame elements must be such as to ensure the rigidity and geometric invariability of the mounted part of it.

Taking into account this requirement, when erecting the frame of one-story industrial and other buildings, it is recommended to observe the following sequence: the first on each site (capture) to install the structures between which the links are located (vertical, horizontal, etc.). Each next structural element is attached to the previously installed connecting elements provided by the project: crossbars, ties or temporary struts and ties.

Prefabricated elements of multi-storey buildings in each grip (section) are mounted in the following sequence. First, the columns and crossbars of the frame are installed in the stiffening cell or starting from the end of the building (section) along its entire width and on all floors of the tier. After verifying the position of the columns and girders and their fastening, ties or tie panels and spacer slabs of floors between the columns are installed. Then, the internal panels of the staircase, staircases and marches, external wall panels of the staircase, ventilation blocks, sanitary cabins, wall panels of external walls and partitions are mounted. After assembling the elements of one section and securing them by welding, the crane is moved to the next section, and on the assembled section, welding work is completed, the joints are monolithic, and the floor slabs are mounted. Installation work is performed in the same sequence in all subsequent sections of the tier.

The installation of the second tier is started only after the alignment of the installed structures, welding of all assembly joints of the first tier and control of the correct installation of structures and the breakdown of axes and marks for the subsequent installation of structures with geodetic devices.

Before starting the installation of structures on each tier, which may include two or three floors (depending on the cutting of the columns along the height of the building), mark the main alignment axes of the building on the ceiling or column heads, determine the mounting horizon, mark the axial and other installation risks. Axis risks are measured each time from the main alignment axes and the relative position of adjacent axes is checked.

The most common multi-storey residential, public and industrial frame buildings are with frame cells 6 x 6 and 9 x 9 m, other spans are possible, for example, 12 m and intermediate ones. Floor height 3; 3.3; 3.6; 7.2 m. The width of buildings is usually 12; eighteen; 24 and 36 m. The upper floors can have halls up to 10.8 m high, with a span over the entire width of the building or part of it, including with or without bridge cranes. The length of the building is a multiple of the cell parameter.

For supporting frames, columns are used on one, two, three floors. Depending on the space-planning solutions, buildings are built with a transverse or longitudinal arrangement of crossbars, along which floor slabs are laid, respectively, in the longitudinal or transverse direction.

Building frame assembly is an interconnected process of assembling columns, girders, stiffening diaphragms, tie and interfloor floor slabs. The elements are installed in such a sequence that ensures the rigidity and spatial immutability of the frame. The sequence of installation in each specific case is determined by the project for the production of work and a set of installation equipment, which will be used to install and align structures: individual (single) or group fixtures.

Installation using individual means of assembly equipment.

In construction, individual means of assembly equipment are most often used, with the help of which structures are verified and temporarily fixed. The kits of individual mounting hardware for mounting multi-storey frames include (see diagram below, pos. A ... c): wedges and inserts, support beams, anchor devices, clamps, struts and horizontal struts, conductors. In contrast to the group individual means are more versatile and easy to use (Fig. 1).

Figure: 1 - Diagrams of installation of multi-storey columns using a set of individual means of assembly equipment: a - arrangement of columns and devices, b - securing the column with struts, c - a clamp for fastening the struts to the column; 1 - foundation glass, 2 - inventory beam, 3 - column, 4 - clamp, 5 - brace, 6 - brace hitch, 7 - wedges, 8 - anchor device, 9 - crimp rope

Wedges and wedge liners are used for aligning and securing columns in foundation glasses.

Support beams consist of two channels connected by strips and have loops in the upper part for attaching struts, and in the lower part - end stops for fixing to the foundation glasses (see the diagram above, pos. A, b).

Anchoring devices 8 represent a U-shaped frame with holes in the upper part through which a gripping hook moves, which is moved by a tension nut.

The clamp (see diagram above, pos. C) for attaching the brace to the column is made in the form of an angle stop, which is fixed to the column using a rope with a tensioner.

The struts 5 consist of telescopically connected pipes with tensioning towbars 6 and gripping devices at the ends for fastening to the hinges or lugs of the clamp and the hinges of the supporting beams or other structures.

Conductors are intended for temporary fixing and alignment of columns, which are joined in height with the heads of previously installed columns.

The columns of the first erection tier are installed using the same methods as in the erection of one-story buildings. However, at the same time, struts and struts are installed that hold the columns in such a way that they do not interfere with the laying of girders and tie plates between the columns. Before starting the installation of the columns, support beams 2 are laid on the grip (see diagram above) and fastened to the loops of the foundations using anchor devices. Support beams are not laid in those places where frame stiffness diaphragms are installed.

A clamp 4 is put on the mounted column in the warehouse and two braces 5 are hung on it, after which the column is strapped and lifted with a crane. The column submitted for installation is installed in the foundation glass and temporarily secured with the help of wedge liners (wedges) 7 and two struts 5. After that, the column is unstopped and verified. The column is installed in a vertical position using theodolites along two axes. As the installation progresses, the columns are embedded in the foundation glasses. The braces are removed from the columns after the frame has been unfastened with crossbars and slabs at the level of the two lower floors.

Crossbars are mounted after the columns (see diagram below, pos. A ... c). Before installation, the crossbars are cleaned, the reinforcement outlets are straightened and the embedded parts and the crossbars are dry supported on the column consoles. On each structural cell of the building, first the lower and then the upper crossbars are mounted. The workplace of the installers is at the inventory sites.

The works are performed in the following sequence. A third-class installer raises the crossbar and gives a command to the crane driver to lift. The driver moves the deadbolt to the installation site with a crane. The 5th grade installer supervises the crane operation. Installers of the 4th and 3rd categories, being on the adjustable platform-platforms, take the crossbar, put it on the shelves and verify it.

In the transverse direction, the crossbars are installed in the design position, aligning their axes (outlets of the upper reinforcement) with the axes (outlets of reinforcement) of the columns, in the longitudinal direction - observing equal areas of support of the ends of the crossbar on the console of the columns (the difference between the areas of support of the ends of the crossbar on the console should not exceed ± 5 mm).

After aligning the crossbars, their supporting embedded parts are tack-welded to the embedded parts of the column consoles, and the crossbar is unstopped (Fig. 2).

Figure: 2 - Installation of the crossbar: a - applying axial marks on the column, b - installing the crossbar, c - straightening the crossbar during alignment

After making sure that the columns and girders in the mounted cell are in the design position, the installers finally fix the girders with a bathtub by welding the outlets of reinforcement, welding of embedded parts, embedding the joints (after the delivery according to the certificate of welding). Then the frame stiffness diaphragms are mounted (see diagram below, pos. A, b) with a shelf replacing the crossbar (Fig. 3).

Figure: 3 - Installation of internal walls - stiffness diaphragms - in a frame building: a - installation, b - temporary fixing; 1 - brace, 2 - diaphragm with a shelf that replaces the crossbar, 3 - universal sling, 4 - adjustable clamp with a stand

For temporary fastening and alignment of the diaphragms, adjustable clamps are used 4. Stiffening panels of the frame without a shelf that replaces the crossbar are mounted before the crossbar is installed in this span. In this case, instead of temporary fastenings of the frame at the installation site of the diaphragm, equivalent fastenings are placed on the other side of the column, for example, horizontal braces-spacers. The organization of the workplace and the sequence of operations are shown in the diagram below, pos. a, b.

LECTURE 12. Installation of structures for industrial and civil buildings.

Features of the installation of buildings and structures

Installation methods are characterized by a complex of organizational and technological features.

Main organizational characteristics:

direction of development of the front of work;

sequence of installation operations;

the degree of enlargement of mounting elements;

dividing the course of installation work (in turn, stages) and structures (into seizures, units, etc.).

Technological features: peculiarities of performing individual operations for gripping (slinging), aiming, orientation and installation of mounting elements in the design position, their fastening, anti-corrosion protection, etc.

Installation of one-story industrial buildings. For one-story industrial buildings of light type with a reinforced concrete frame, a separate method of assembling structures is rational.

Single-storey industrial buildings of a heavy type are assembled mainly by an integrated method.

For industrial buildings with an area of \u200b\u200bmore than 30 thousand m 2 with metal structures of the coating, the use of the conveyor method of large-block assembly is economically and technologically justified.

Installation of dome, vaulted, structural and other coverings:

ground assembly in conductors with subsequent lifting of the shell structure to the design position;

assembly at design levels.

The choice of the installation method for large-span buildings is due to the fact that their dimensions in terms of plan exceed the radius of action of the assembly cranes, and some assembly elements (frame elements, arches, etc.), due to their large masses and dimensions, have to be assembled in parts using temporary assembly supports, or one-piece assembly, using the paired work of assembly cranes or hoists.

During the installation of structures, it is necessary to observe the technological sequence, which ensures the stability and geometric invariability of the mounted structures.

When assembling single-storey buildings, the movement paths of cranes and installation positions must be selected in such a way that as many elements as possible are mounted by the crane at each parking lot. So, for example, with a span of 12 m and a column spacing of 6 m, two, four or six mounting elements can be mounted with a crane moving in the middle of the span. With a span of 18 and 24 m, the crane can move along each installed row and mount up to four elements.

Installation of precast concrete columns is carried out using various grips and slings. In cases where the installation is carried out from vehicles or the column has insufficient bending strength, appropriate balancing devices are used to translate the structures into a vertical position while suspended. In this case, the slinging is carried out at two or more points. Installation, alignment and fastening of columns is carried out using wedges, braces, conductors.

The installation of rafter beams and trusses is carried out using traverses. Slinging of reinforced concrete trusses in order to avoid loss of their stability is carried out in two, three or four points. Before climbing the trusses, they hang braces (for its guidance), inventory spacers and mounting platforms. To ensure stability and geometric immutability, the first installed trusses\u003e or the beam should be fastened with braces made of steel Kai тта, and the subsequent ones - with spacers attached with clamps to the upper chords of the trusses (beams), or with special conductors (Fig.10.3). Typically, for trusses with a span of 18 m, one spacer is used, for spans of 24 and 30 m, two.

If there are no special instructions in the project for the production of works, it is recommended to lay the coating slabs according to the markings on the upper chords of the trusses (beams) in the following order: along metal trusses or lanterns - starting from the middle of the span with a symmetrical load; on reinforced concrete beams or trusses with lampless coverings - from one edge of the cover to the other: in spans adjacent to the previously mounted ones - from the mounted cover to the free end; on reinforced concrete trusses with a lantern - from the edge of the pavement to the lantern. Embedded parts of each slab in at least three support nodes must be welded to the embedded parts of the upper chord of the truss (beam); the first plate is welded at four points.

Installation of wall panels begins after the final fixing of all elements of the building frame.

Installation of multi-storey buildings. Multi-storey buildings are erected with one or more tower cranes, placed in such a way as to exclude "dead" areas outside the service areas.

When installing frameless panel buildings, the order of installation of panels is determined by the project for the production of works. Installation is carried out using individual or group installation equipment, while the edges of the element or the risks on it must be combined with the risks taken out from the alignment axes.

Figure: 10.3. Location of attachments and temporary fastening of trusses with inventory

spacers during the installation of roof structures: a - attachments of the farm;

b - installation diagram of spacers; 1- ladder; 2 - hinged ladder;

3 - hanging platforms; 4- safety rope; 5- inventory spacers;

6 - the position of the struts during the lifting of the truss; 7 - clamp; 8- rope;

9 - mounted part of the span; 10- clamp; 11 - full-turn hinge

The project for the production of works provides for the sequence of installation of panels, taking into account the following conditions:

Installation begins with the creation of rigid joints that ensure the spatial immutability of structures. These include the outside corners and stairwells of the building. Installation usually starts at the outer corners of the building, with the end wall corner panel usually placed first.

Assembly of prefabricated elements is carried out "on the crane", ie starts from the wall farther from the tap. In this case, visual communication of the crane operator with the installation site is provided, and safer working conditions are created, since the panels do not have to be moved over the previously supplied ones. With two construction cranes, installation starts at the outer corners of the building closest to each construction crane.

The outer wall panel should not be installed between previously supplied ones. This may compromise the stability of the panels or damage them.

Exterior wall panels, load-bearing interior wall panels and balcony slabs are installed during daylight hours.

Installation of internal wall panels is carried out with the help of individual assembly devices, group equipment, as well as special parts laid into the body of the panel during manufacture (the method of spatial self-fixation).

The panel, verified in the plan, is temporarily attached with struts to the floor slabs, the internal panels can be temporarily fastened with universal racks, clamps, ties.

When installation of frame-panel buildingsthe installation of the columns in the design position is usually carried out by a restricted free method using a frame-hinged indicator, or by a free method using a single or group conductor. The columns are temporarily secured with wedges, braces, portable jacks, conductors, or frame-hinged indicators. The height of the columns determines the height of the tier: for columns on one floor, the height of the tier is one floor; with columns on two floors - the height of the tier is two floors, etc. The installation of the next tier is carried out after installation, welding and monolithing of the beams and floor slabs of the underlying tier.

The installation of the crossbars is started after the concrete reaches the junction of the columns with the foundation at least 50% of the design strength in summer and 100% in winter. The location of the crossbars can be longitudinal and transverse. The girders must be centered along the axes of the columns, observing the design dimensions of their support on the column console.

The installation of the floor begins with the installation of spacer (tie) plates, first of the lower and then of the upper floor. The slab is fed to the installation site in an inclined position using a special sling. The laid slabs are welded at the four corners to the girder saws. Ordinary floor slabs are laid similarly to spacers.

After the installation of floor slabs and floor slabs, the installation of wall panels is started. Belt panels, resting on wall or floor slabs, are temporarily attached either to the column or to the slab with special clamps with struts or ties. The wall panels are attached with struts to the floor slabs or to the underlying belt panel with clamps with folding clamps.

Simultaneously with the installation of the panels, the joints are sealed.

The erection of buildings from volumetric blocks begins after the complete completion of all works of the zero cycle, from vehicles. Installation of additional elements is carried out from the on-site warehouse.

For blocks with linear support, wooden beacons are arranged, embedded in the cement-sand mortar of the block bed. For blocks with point support, support platforms are made of metal plates, which are recruited to the desired height, and a bed of cement-sand mortar is made around these support sites.

The slinging of the blocks is carried out with four-branch slings or special balancing traverses with manual or automatic adjustment, which make it possible to align the position of the block if its outer wall is thicker and more massive than the inner one.

The blocks are mounted starting from the middle of the floor to the ends, which reduces the accumulation of possible errors arising from inaccuracies in the manufacture and installation of blocks. A gap in height is allowed for no more than one floor.

Installation of steel structures. Metal columns are supported: directly on the foundation with a concreted and rubbed leveled surface; on steel support beams concreted into the foundation; on steel plates with a planed top surface. To support the steel plates, the base plates and column shoe soles must be milled at the factory. In this case, the column is installed without alignment. Calibration-free installation of columns allows you to reduce the labor intensity of installation by 30%.

The columns are fastened to the foundation with anchor bolts, onto which nuts are tightly screwed. When installing columns up to 15 m in height, in addition to the anchor bolts, they are fastened in the direction of least rigidity with at least two braces. With a column height of more than 15 m, the method of their fastening is determined by calculation.

Installation of crane beams, trusses and trusses is carried out after the alignment and final fastening of the columns and ties, ensuring the rigidity of their position.

Block assembly - assembly of structures previously enlarged into flat or spatial blocks. It allows to reduce the labor intensity and duration of construction of large industrial facilities. An example of a flat block is half-timbered columns connected by girders and ties, a spatial one - a block of two trusses with girders and ties. An indispensable requirement for a spatial block is its geometric immutability. Distinguish between assembly blocks of incomplete and full factory readiness. The latter are a complete part of a building or structure that does not require additional construction and installation work after installing it in the design position.

The assembly of blocks of incomplete factory readiness (for example, spatial dimensions 12x24, 12x36 m, etc.) is assembled on a conveyor line, which is a rail track located in the immediate vicinity of the object to be mounted with conductor bogies moving along it from post to post, on which assembly is in progress. The block design should make it possible to mount the coatings according to the block-to-block system.

The finished block on a trolley-conductor is transported to the installation site and, using powerful cranes or special cranes-installers, mounted on overhead cranes, is set to the design position.

This method (conveyor assembly and block assembly) is economically feasible when erecting one-story industrial buildings with an area of \u200b\u200bat least 30-50 thousand m 2.

The block-based construction method is based on the principle of block assembly. The essence of the method lies in the fact that at the design stage, objects are divided into large-sized, but transportable, structurally complete and equipped with technological equipment assembly blocks for the purpose of erecting and commissioning capacities in the shortest possible time and with minimal labor costs. Blocks are manufactured at the factory and delivered to the facility by road trains. Installation consists in installing the blocks in the design position, processing joints and connecting communications. From superblocks weighing 200-350 tons and more, various industrial buildings of almost any length with a height of 5.2 and 6.4 m with spans of 12 and 24 m can be mounted.

The block method of installation allows you to maximally transfer the volume of construction and installation work from the construction site to industrial production, sharply reduce post-installation processes and ultimately reduce the duration and cost of construction.

Safety precautions during installation work

The requirements of the rules for the safe conduct of installation work should be taken into account already at the initial stage of the design of the facility through the use of rational structural solutions and structures, for example, large blocks of coatings with their ground assembly, technological elements in the installation, ensuring their assembly with minimal manual labor and time, etc. .d.

Measures for the safe conduct of installation work should be provided for at the stage of development of the project for the production of work - through the use of such installation techniques and such a technological sequence of installation operations that would provide the most convenient access of the cranes to the installation positions, as well as the rigidity and stability of those installed earlier: mounted structures.

Control questions

What installation methods differ depending on the adopted sequence of installation of the building frame elements?

What methods are distinguished depending on the direction of installation of buildings?

What are the basic requirements for the transportation of building structures?

What are the main requirements for the storage of building structures (their position, stack sizes, etc.).

How is the pre-assembly of structures carried out?

What are the main technical specifications and features of the cranes?

How are erection cranes selected?

What do you know about the purpose and type of load handling devices?

How are one-story industrial buildings erected?

10. What are the basic conditions for safe handling of cranes?

Main literature: pp. 320-474, pp. 306-396, pp. 245-278

Additional literature: [ 10] pp. 155-252, pp. 54-152, pp. 305-336.

Installation of elements of reinforced concrete structures

Technology - Installation of building structures

Installation of prefabricated foundations

Installation of prefabricated foundations is usually carried out in a separate advanced flow during the erection of the underground part of the building. The breakdown of the installation sites of the foundations is carried out using longitudinal and transverse axes, fixed with a wire.

When installing foundations for columns to the bottom of the excavation, the position of the axes is transferred with a plumb line, fixing them with pins or pegs driven into the ground. On glass-type foundations, the middle of the side faces of the glass is determined and axial marks are applied to the upper face. When lowering the block to the base, the position of the block is controlled by risks.

The installation of a glass-type foundation must be carried out immediately in the design position in order to avoid disturbing the surface layer of the base. The position of the foundation block in height is verified using a level, controlling the mark of the bottom of the glass. The position of the block in the plan is checked with the slings not removed by aligning the marks (alignment and alignment axes) along two mutually perpendicular axes, a slight deviation is eliminated by moving the block with a mounting bar.

Upon completion of the installation of the foundation blocks, a geodetic survey of their position is carried out - high-rise and in plan. Based on the survey results, an executive scheme is drawn up, on which possible block displacements are indicated.

Installation of foundations:

1 - crawler crane; 2 - position of the foundation block before lifting; 3 - foundation block during installation

Permissible deviations of the installed cup-type foundation blocks from the design position: the displacement of the block axes relative to the alignment axes is not more than ± 10 mm, the deviation of the bottom of the glasses is 20 mm.

Column installation

Installation of glass-type foundations and, in general, the construction of structures for the underground part of the building are zero-cycle works and are carried out by an independent assembly flow. The above-ground part of the building is usually assembled by a mixed method, when columns are mounted and wall panels are hung by independent flows, and the installation of crane, truss and roof trusses is carried out in a complex manner, and the covering panels are laid.

For one-story industrial buildings, a nomenclature of prefabricated reinforced concrete columns with a height of up to 19.35 m and a weight of up to 26.4 tons, mounted in glass-type foundations, has been developed.

Before installing the columns, you must:

Fill the sinuses of the foundations;

Apply risks of alignment axes along four edges at the level of the upper plane of the foundations;

Cover the foundation glasses with shields to protect them from contamination;

Arrange roads for the passage of the assembly crane and cars;

Prepare areas for storing columns at the place of their installation;

Deliver the necessary assembly means, fixtures and tools to the installation area;

Check the position of all embedded parts of the columns;

Mark the alignment axes on the lateral edges of the columns.

Columns are preliminarily laid out at the places of installation on wooden pads with a thickness of at least 25 mm. The columns are laid out in such a way that the crane from the assembly stand can set them to the design position without changing the boom reach. Before installation, each column must be inspected so that it does not have deformations, damage, cracks, cavities, chips, exposed reinforcement, concrete overflows. It is necessary to check the geometric dimensions of the column, the presence of the mounting hole, the correct installation of the steel embedded parts.

Before or simultaneously with slinging, a column with a height of more than 12 m is equipped with ladders, hinged cradles, and braces.

Column slinging carried out by the mounting loops, by the mounting rod, passed through a special hole in the column. Friction grips or various self-balancing traverses are widely used, allowing the column to be lowered vertically onto the foundation. All of them must provide remote unlinking, eliminating the need to lift the worker to the slinging site after installing the column in the foundation glass. The columns are lowered by means of an assembly crane into the foundation glass on reinforced concrete pads or on a leveling layer of concrete mixture.

Reconciliation and anchoring the columns installed in the foundations are carried out using a set of installation equipment. The design position of the column bottom at the bottom of the foundation glass, temporary fastening and vertical alignment of the columns are carried out using wedge inserts. The stability of the columns after installation is ensured by temporary fastenings, most often by conductors or wedge liners. The vertical alignment and correction of the columns is carried out using jacks; the deviation from the vertical and the displacement of the axes of the columns in the lower section should not exceed the standard values.

Columns up to 12 m in height are usually fixed in the foundation glasses only with the help of wedge inserts; for higher columns, conductors and braces are additionally used. The installed columns should be detached after they are securely fastened in the foundation glasses with wedge inserts, and, if necessary, with braces.

The inventory wedge insert consists of a body with a nut and a handle, a screw with a boss, and a wedge suspended by a hinge. Wedge liners are installed in the gaps between the column edges and the walls of the foundation glass. For gaps of more than 90 mm, additional inserts are used. When the screw is rotated with a wrench, under the action of the boss, the wedge moves in the body on the hinge, as a result, a thrust force is created between the wedge and the body of the glass. Before sealing the joint between the column and the foundation with a concrete mixture, a fence is installed on the wedge liner, which is removed from the glass immediately after the compaction of the rigid concrete mixture or after the start of setting with conventional mixtures.

Various types of conductors are used to temporarily secure the columns. The conditions for the use of different types of conductors, the procedure for performing work on the installation and alignment of columns with their use is stipulated by the work production project.

After aligning the columns, fixing them in the design position is carried out by concreting the joints with a concrete mixture on fast-hardening non-shrinking cement using a pneumatic blower. The wedge liners are removed only after the concrete has acquired the strength specified in the work plan or when the concrete reaches 50% of the design strength.

When installing columns, it is necessary to check the mark of the bottom of the foundation glass, the alignment of the risks on the edge in the lower part of the column with the center line on the upper edge of the foundation, the verticality of the columns, marks of the crane console and the column head. The alignment of the column axes and the alignment axes must be controlled along two axes, the verticality of the column must be ensured using one or two theodolites along two alignment axes or a zenith device using the vertical design method. The elevations of the support sites for crane beams and trusses are controlled by the method of geometric leveling.

Installation processes of reinforced concrete structures

Preparation of foundations for columns

The accuracy, labor intensity and duration of the installation of columns and other elements of the frame of industrial structures depends primarily on the correct arrangement of the foundations for the columns and the accuracy of the preparation of the supporting surfaces.

In the case of using glass-type reinforced concrete foundations of low height, their features should be taken into account. The upper level of these foundations is well below the level of the edge of the excavation. Columns on such foundations should be mounted with open pits.

Higher foundations, the upper level of which is approximately 0.15 m below the floor level, make it possible to lay foundation beams, fill pits, plan the site and arrange for underfloor preparation before installing the columns, to ensure favorable conditions for the operation of transport and installation equipment. In order to improve the conditions of transportation and installation, foundations with sub-columns are also used.

To ensure the accuracy and acceleration of the installation of the columns, it is required to correctly position the foundation glasses in the plan (the displacement of the axes is allowed no more than ± 10 mm); provide accurate design marks of the bottom of the glasses (tolerance ± 20 mm); maintain a given gap between the design position of the column faces and the walls of the glass. It is advisable to install a shallow pit in the bottom of the nozzle (Fig. 2), corresponding to the outlines of the end of the column, located along the alignment axes and providing a fixed installation of the column along the design axes. Metal molds are used to form a pit in the bottom of the glass.

One type of mold is used to construct pits when installing columns on the surface of the bottom of the foundation glass, previously poured to the design level. The design of this form, 7.5 cm high, is equipped with fastening screws for positioning it relative to the dividing axes. Another type of form is used when foundations are not poured to the design elevation. Unlike the first type, the mold is equipped with screws for installation not only along the design axes, but also at the design mark. The process of pouring and forming pits consists of the following operations: installation by a link of two installers of the 3rd, 4th grade, led by a surveyor, of the first type forms on the previously poured surfaces of foundations or forms of the second type in cases where the foundations were taken without pouring to the design mark; lubrication of established forms with technical oil; feeding fine fraction of concrete to the bottom of the glass and leveling with a plastering trowel; exposure of concrete for 2-3 hours of disassembling the forms.

After removing the molds, a pit remains at the bottom of the foundation glass with the outline of the supporting end of the column. Due to the pinching in the pit, the lower part of the columns does not shift from the design axes during vertical alignment, which often occurs and significantly delays the installation carried out using conventional technology. The whole process of pouring the bottom of the foundation, starting with the installation of the mold and ending with disassembly. according to experience, it takes 20-30 minutes.

Figure: 1. Diagram of supporting precast reinforced concrete columns in glass-type foundations: 1 - precast reinforced concrete columns; 2 - pit in the bottom gravy of the glass; 3 - foundation

Checking the state of structures

Checking the state of structures is carried out in order to ensure their correct and quick installation, connection in the design position and the reliability of their work in the structure. By checking prefabricated reinforced concrete structures, the following is established: the presence of grades and stamps of the Quality Control Department; availability of passports; compliance of the geometric dimensions of structures with working drawings; the presence of a mark on the structure of its mass; the absence of cracks, potholes and surface cavities in the concrete that exceed the permissible dimensions; lack of deviations from the geometric shape (straightness, horizontal support surfaces); the presence and correct location of embedded parts, the absence of sagging on them; the presence of an anti-corrosion coating on embedded parts; the presence of design and mounting holes and their diameter; the cleanliness of the holes (no concrete in them); compliance with the design of reinforcement outlets and the absence of cracks and unacceptable deformations in them; compliance with the design of mounting loops and the absence of deformations and cracks in them; the presence of axial marks on those elements that have no other reference points that ensure the possibility of their correct mutual installation; presence on unilaterally reinforced elements of signs indicating the correct position of the element during unloading and installation.

In terms of geometric dimensions and shape, prefabricated reinforced concrete structures for buildings should not have deviations from the design dimensions more than those given in SNiP I-B.5-62.

Large-scale assembly of structures

In the assembly blocks, the elements of the columns are enlarged in length, columns with girders, roof trusses with spans of 30-36 m, delivered in two halves, wall panels, sinkholes, bunkers and other structures. The enlargement is performed on special stands or in conductors. The elements to be enlarged are fed from the warehouse by crane and placed on the stand supports so that their longitudinal axes coincide. Then, the ends or outlets of the reinforcement are adjusted to achieve the alignment of the elements or individual rods. After installing additional clamps and welding the rods, formwork is installed and the joint is concreted. The grade of concrete with which the joint is concreted and its strength after hardening are established by the project. Usually, the brand is taken the same as that of the elements to be connected, or one brand higher.

Slinging structures

Slinging of prefabricated structures is carried out using slings, grippers or traverses. Gripping devices for slinging should provide convenient, quick and safe gripping, lifting and installation of structures in the design position and their unstitching. One of the important requirements for grippers is the ability to detach from the ground or directly from the crane cab. This requirement is best met by semi-automatic grippers.

Slings (Fig. 2, a, b) are made of steel ropes; they are of two main types - universal and lightweight. Universal slings are made in the form of a closed loop, lightweight ones are made of a piece of rope with hooks fixed at both ends, loops on thimbles or carabiners. Slings can be made with one, two, four or more branches, depending on the type and weight of the element being lifted.

Figure: 2. Slings: a - universal; b - lightweight with hook and loop; c - cable with two branches; d - the same, with four branches

Since with an increase in the angle a, the forces in the branches of the sling increase, which can cause a rupture or pulling out of the mounting loops, as well as increase the compressive forces in the lifted element, the angle a is taken no more than 50-60 °.

For installation work, slings made of steel ropes with a diameter of 12 to 30 mm are most often used with permissible loads per branch: universal slings from 2.15 (19.5 mm in diameter) to 5.25 tf (30 mm in diameter); lightweight slings from 0.65 (12 mm in diameter) to 5.25 tf (30 mm in diameter). When making slings with more than three branches, their equality in length should be observed, otherwise the load in the branches will be uneven. Equal distribution of the load on each of the branches of the sling is ensured in a four-branch sling and in a balance sling. The balance sling consists of a roller fixed between two cheeks, through which a lightweight sling is passed. The presence of a roller ensures an even distribution of the load on both ends of the sling, regardless of the position of the load.

Figure: 3. Diagram of efforts in the branches of the sling

Figure: 4. Slinging of columns with a universal sling: 1 - column; 2 - wooden lining; 3-sling

During operation, the slings wear out from crushing, abrasion in knots, rubbing of wires against the corners of structures, twisting and impacts. The service life of slings, usually from 2 to 3 months, can be increased if they are used economically: using wooden or steel spacers between the slings and the structure being lifted, etc.

In many cases, slinging of prefabricated reinforced concrete elements is carried out for loops (brackets) laid in concrete during the manufacture of products. The disadvantage of this method is the need for the cost of reinforcing steel for the device of loops.

The clamps allow lifting many reinforced concrete elements (columns, beams, trusses, slabs) without hinges. For this purpose, traverse slings, slings-grips, semi-automatic finger friction, tick-borne, cantilever, wedge and other grips are used.

Traverses in the form of beams or triangular trusses with suspended slings allow the suspension of the element being lifted at several points. When lifting loads with traverses, the compressive forces in the elements being lifted, arising from their own weight when using inclined slings, are excluded or reduced. Slinging of prefabricated reinforced concrete foundations under the columns is carried out for the loops embedded in the concrete, with a two-branch or four-branch sling. Slinging of columns is performed using universal (Fig. 4) and traverse slings (Fig. 5), sling-grippers or semi-automatic grippers. Slinging of columns with universal slings and slings-grippers is carried out in a girth. Traverse slings and grips are attached using a round rod (pin) passed through the hole left in the column during its manufacture. The disadvantage of slinging using universal and traverse slings (conventional grippers): when unstitching, the installer must climb onto the column to be installed. To avoid this, use sling grips or semi-automatic grippers.

Figure: 5. Slinging of columns with a traverse sling

Figure: 6. Lanyard-grip for the installation of columns: 1 - long cable loop; 2 - lifting rope pegla; 3 - for the bench press; 4, 5 - earrings; 6 - lifting bracket; 7 - glass with a spring-loaded pin; 8 - strapping cable; 9 - gaskets

The lanyard grip (Fig. 6) provides a strictly vertical position of the column during installation, convenience of slinging and unstitching. For columns measuring 40X40X600 cm with a mass of 3 tons, the gripping loops are made of a cable with a diameter of 16 mm, the lifting bracket and shackles are made of strip and sheet steel, gaskets are made of pipes with a diameter of 2 ”cut along the length. Turned pins with a diameter of 25-30 mm. The gripper sling is put on the column, stacked on pads, the lifting loop is thrown over the crane hook, the column is tightened and the lambs are fixed. At the end of the installation and fastening of the column, the retaining pin opens and the gripper freely comes off the column.

Semi-automatic gripper (Fig. 7) for mounting columns is a U-shaped frame with a box rigidly welded to it, on which an electric motor with a gearbox is placed, which drives a screw. The nut, moving along the screw, moves the locking pin along the box, which at the same time enters the space between the side edges of the frame or exits it. The frame is attached with cable rods to the beam traverse. The electric motor of the gripper is driven from the crane operator's cab, where the cable is pulled, or from the redundant control buttons installed on the gripper. To allow quick disconnection of the gripper from the crane, a plug connector is installed in the cable. The gripping device has a set of locking pins of various diameters, which can be easily changed at the installation site depending on the change in the mass of the column being lifted. The process of slinging and unstitching columns using grippers with remote control is carried out as follows.

The frame of the gripper is placed on the column prepared for installation so that the locking pin is against the lashing hole in the column. Then the button that turns on the electric motor is pressed, the locking finger is set in motion, enters the hole of the column, reaches the opposite side edge and stops with

limit switch. After lifting, installing and securing the column, the load is removed from the gripper and the crane operator, pressing a button in the cab, removes the locking pin from the hole in the column, thus releasing the gripper without the help of the installer.

To lift columns weighing up to 10 g, a friction grip is used (Fig. 8), which holds the mounted element by friction from the column's own weight. The gripper is detached by lowering the crane hook after securing the column to the foundation; at the same time, the gripper opens slightly and goes down the column.

Slinging of beams is performed with universal slings in a girth (Fig. 9), two-branch slings or traverses (Fig. 10) for loops, or through holes left in concrete. For slinging heavy beams and girders, the balancing traverse is suspended by means of two clamps and four branches of the sling to a ring put on the crane hook. Support clamps with carabiners are fixed at the ends of the traverse with adjustable bolts. Slinging of roof trusses is carried out using lattice or beam traverses with universal slings, slings with semi-automatic mechanical grippers (Fig. 11) or electric grippers. Slinging of trusses with the help of semi-automatic grippers is more perfect. Slinging is performed in a girth or through holes in the upper chord of the truss.

The semi-automatic gripper for lifting trusses (Fig. 12) consists of a rigid cross-beam, to which grips with a cable are suspended, similar to those described above, but with non-replaceable locking pins. When slinging the truss, the fingers of the grippers aimed at it pass under its upper belt. Once the truss has been set up and secured, the fingers slide back into the gripper boxes, freeing them and the support bar for the next operation.

Slinging of reinforced concrete wall panels, which are in a vertical position before being lifted, is usually performed with two-branch slings or traverses, hooking them into the loops embedded in the upper end of the panel. Slinging of floor slabs and coverings is carried out with four-branch slings or traverses for loops, or through mounting holes in concrete, or using cantilever grips.

Figure: 7. Semi-automatic gripper for mounting columns: 1 - frame; 2 - cable rods; 3 - beam traverse; 4 - plug connector; 5 - cable; 6 - electric motor; 7 -box; 8 - nut; 9 - duplicate control button; 10 - screw; 11 - locking finger

Figure: 8. Frictional grip: 1 - traverse; 2 - pendants; 3 - fork couplers; 4 - stop strips; 5 - latches

Figure: 9. Slinging of crane beams with universal slings: 1 - beam; 2 - steel linings; 3 - slings

Figure: 10. Slinging of reinforced concrete beams, girders and girders: a - light beams; b - heavy beams, girders and crossbars; 1 - clamp; 2 - adjustable bolts; 3 - support clamps; 4 slings; 5 - balancing traverse; 6 - carbine

Slinging of plates is performed in four (Fig. 13, a) or more points. For slinging large-sized reinforced concrete slabs, three-traverse and three-block gripping devices with an increased number of suspension points are used, due to which the mounting stresses in the elements being lifted are reduced (Fig. 13, b). The three-traverse device can also be used to lift wall panels, flights of stairs, beams, columns and other prefabricated elements by grabbing them with three, two or one traverse. However, this device is metal-consuming, cumbersome and requires large efforts of the worker when tensioning the hangers with the crosshead while engaging the structure on the mounting loops. The three-block device does not have the above drawbacks (Fig. 13, c), but it requires a greater lifting height of the crane hook (by about 2 m), which can complicate the selection of an assembly crane for lifting floor slabs of the upper floors of buildings. Large-size slabs are also lifted using universal (Fig. 14) or spatial (Fig. 15) traverses, or universal counterbalancing slings (Fig. 16). The universal crosshead (fig. 14) consists of supporting beams made of two channels, each of which has guide rollers. On the end rings of each beam, a rope is fixed, which carries three blocks with hooks. The load-bearing beams are interconnected by two pipes with holes for installing a bolt, which fixes one or another distance between the load-bearing beams, depending on the width of the lifted panel.

Universal counterbalancing slings, also called balancing beams (fig. 16), consist of two five-ton blocks connected by a common ring, which is suspended from a crane hook.

Figure: 11. Schemes for slinging reinforced concrete trusses: 7 - truss; 2 - traverse; 3 - semi-automatic mechanical gripper; 4 - finger; 5 - the upper belt of the truss

Figure: 12. Semi-automatic gripper for mounting reinforced concrete trusses: 1 - grippers; 2 - rigid traverse; 3 - cable

Figure: 13. Slinging of slabs and floor panels: a - with a four-branch sling; b - three-traverse device e - three-block device

Ropes with a thickness of 19.5 mm are thrown through each of the blocks; carabiners are suspended at the ends of the ropes, and two-ton blocks with 13 mm thick ropes thrown over them, also ending with carabiners, are suspended at the ends of the ropes. The blocks are freely put on the axles, due to which the uniform tension of the ropes hanging from them is ensured and the uniform distribution of loads on all six carabiners of the gripper. With the help of such a device, the floor panels can be tilted to a horizontal position if they were transported vertically. Tilting is carried out by weight. This device is also used for lifting wall panels.

Plates with mounting holes are slinged using wedge or other grips. The wedge grip (Fig. 17) has the form of a bracket with branches connected by steel rods in three places; used for slinging floor panels. On the lower rod, as on an axis, there is an unequal piece of steel of a square cross section that can rotate. In the folded position, the axis of the segment (Fig. 17, a) coincides with the axis of the bracket, and in the unfolded position it takes a position perpendicular to the axis of the bracket (Fig. 17, b). When used for lifting the panel, the folded grip is inserted into its mounting hole, and the segment, due to the different weights of the shoulders, will tend to rotate 180 °; to prevent this, the gripper is raised until the segment touches the panel and fixed with a wedge.

Slinging of reinforced concrete floor slabs using cantilever grips suspended from the traverse (Fig. 18) does not require mounting loops in concrete. For better use of the lifting capacity of the erection cranes, it is advisable to use spatial traverses, with the help of which a package of several plates is simultaneously lifted. A traverse of this type (Fig. 19) consists of a steel triangular shape, at the ends of which two transverse traverse beams are attached with slings suspended from them to grip each slab. Design

the traverse allows three plates to be sequentially hooked onto the mounting hinges. With this method of lifting, the use of the erection crane is greatly improved. Panels of precast concrete shells are lifted using traverses (Fig. 20). For the installation of structures outside the range of cranes, special cantilever traverses are used (Fig. 21).

Lifting, aiming and installation on supports, alignment and temporary fastening of structures

In the process of performing installation work, it is necessary to pay special attention to the observance of the required sequence of installation of structures, temporary and permanent connections and their reliable fastening. Installation of each overlying tier of structures (crane beams, roof beams, trusses, columns, girders, floor slabs) can be started only after the elements of the underlying tier are finally secured and after the concrete at the joints of the supporting structures reaches 70% of the design strength. In the practice of construction, there are cases of collapse of structures due to the fact that some elements of connections were not supplied, not all elements of connections were securely fastened, the sequence of installation of elements was violated, other applicable norms and rules for the production of work on the installation of structures were not observed.

Figure: 14. Universal traverse for mounting large-size slabs: 1 - bearing beams; 2-guide rollers; 3- single-roll block; 4 - rope; 5 - end ring; 6 - pipe

Figure: 15. Spatial traverse for mounting large-sized slabs

Figure: 16. Universal balancing slings: 1 - carbines; 2 - ropes 13 mm thick; L - blocks with a carrying capacity of 2 g; 4, 7 - ropes with a thickness of 19.5 mm \\ 5 - blocks with a carrying capacity of 5 g; в - ring

Figure: 17. Wedge grip for slabs: a - in a folded position; b - in the deployed position; 1 - lower rod; 2 - steel section; 3 - wedge; c - floor panel thickness

Figure: 18. Cantilever grips for lifting floor slabs: 1 - clamp; 2 - loop

Figure: 19. Spatial traverse for lifting slabs in packages

Figure: 22. Traverse for lifting heavy structures with two cranes of different lifting capacity

Prefabricated structures for lifting to the object under construction should be fed in the required sequence directly under the hook of the assembly crane. The preliminary layout of structures at the lifting points is allowed only in individual cases, since it is always associated with the performance of unproductive rigging operations, clutters the construction site and complicates the work of the assembly crane.

Reinforced concrete columns, depending on their mass and length, supply conditions, characteristics of cranes, are lifted in the following ways: translational movement of the column with a crane, rotation of the column around the base, rotation of the column around the base and translational movement of the crane, rotation of the column and crane boom.

Heavy and tall reinforced concrete columns are lifted by moving the lower end on a trolley (Fig. 23) or turning around the base (Fig. 24). In the latter case, a pivot shoe is used. Such methods of lifting the columns make it possible to transfer part of the load to the trolley or shoe, which makes it possible to operate the crane at the beginning of the lifting at a greater boom reach, at which the crane's lifting capacity is less than the mass of the column. Reinforced concrete frames of industrial and other buildings and structures, made at the installation sites or enlarged from separate racks and crossbars, are lifted by turning from a horizontal position to a vertical one.

Figure: 23. Lifting a heavy and high reinforced concrete column: a - the position of the column when lifting; b - capture of the column; 1 - traverse; 2 steel roller (finger)

Figure: 24. The scheme of lifting a heavy reinforced concrete column with an increased boom outreach: 1 - traverse sling; 2 - column-3 - log spacer; 4 - rotary steel shoe; 5 - pipe of the swivel shoe; 6 - kerchief-7 - channel; 8 - corner

Figure: 25. Guidelines for the correct installation of a reinforced concrete column: a - on a glass foundation; b - on the column; в - elevation marks; 1 - risks on the foundation; 2 - risks on the column; 3 - axis of crane beams; E - the thickness of the glass gravy layer

The rotation is carried out around the bases of the posts located above the glasses of the foundations. In order to avoid the movement of the bases of the struts, the frame, tied by the brackets in the upper edge of the girder or in the girth, is lifted with a gradual change in the position of the hook of the assembly crane in the plan. After bringing the column or frame to a vertical position, it is guided and lowered onto the foundation or onto the abutting surface of the lower column. To control the correct installation on the foundation and the column, landmarks are applied. Such landmarks are the marks made with the help of a core on steel plates embedded in the upper edges of the foundation (Fig. 25, a) or grooves left on these edges during the manufacture of foundations, and marks on the columns (Fig. 25, b). The column is installed in such a way that the risks on it coincide with the risks on the foundation. Holding the column with a crane, its verticality is verified and temporary fastening. In the case of using special conductors, the final alignment is carried out after the column is temporarily fixed by the conductor.

Figure: 20. Traverses for mounting panels and shells: 1 - traverse; 2 - slings; 3 - pendants; 4 - crane hook; 5 - carbine

Figure: 21. Traverses for erection of structures outside the range of cranes: 1 - counterweight; 2 - sling; 3 - beam; Q - mass of the lifted load: G - mass of the counterweight

To ensure the accuracy of the installation of the columns and the entire frame of the building, it is necessary to prepare in advance the supporting surfaces of the foundations by pouring them with mortar to the design mark or by the device of fixed pits in combination with the manufacture of the supporting ends of the column with an accuracy of +5 mm, or using special equipment that does not require the preparation of the supporting surfaces.

One of such solutions, providing a fixed installation of reinforced concrete columns in the foundation glasses, can be the use of a tooling consisting of a metal frame with four fixing pins installed on the foundation and mounting angles fixed with tie bolts on the column. When using such equipment, the column is fixed to the frame with the help of pins inserted into the holes of the mounting tables and corners.

The sequence of work during the installation of columns using equipment, which has been tested so far experimentally, is as follows.

The frame is verified on the foundation. Its risks lead to the position of the center lines, the plane - to the horizontal level. The base is the surface in which the top points of the fingers are inserted into the holes of the support tables. First, one (accepted as a lighthouse) fixing finger is brought to the required level. Then the rest are brought to the same level. The frame is calibrated with jacks using a triangle laid on the surface of three fingers, including the lighthouse, and a water level. Jacks rotate with special socket wrenches included in the equipment set. The frame is brought to the horizontal position by two jacks. In this case, the first - lighthouse - remains stationary, the fourth - free - should not touch the surface of the foundation. After bringing the surfaces of the fingers to a horizontal position, this last jack is screwed in until it rests on the foundation. The frame is fixed in the adjusted position with hooks. The nuts on the hooks are tightened with force. Mounting angles are put on the column and fixed with tightening bolts. The nuts on the bolts are tightened with force. The fixing pins are removed from the holes of the support tables. The column is introduced into the frame with a crane. At the moment of aligning the holes of the mounting angles with the holes of the mounting tables, the fixing fingers are inserted. The fingers should be inserted in pairs, along one side of the column, not allowing them to be installed diagonally. One of the mounting corners should be pressed against the cheeks of the tables. Wedge washers are inserted into the gap between the other corner and the cheeks of the tables. The place of their installation is determined by a special sign on the tables.

Figure: 26. Frame alignment schemes: a - on the foundation; b - columns; 1 - conductor risks; 2 - supporting lighthouse jack; 3 - lighthouse shaft; 4 - unscrewed jack; 5 - jacks that set the shafts to the required level; 6 - shafts brought to the level of the lighthouse shaft; 7 - column

If, after installing the column, the solution poured into the glass and squeezed out by the column does not reach the upper edge of the foundation, a solution is added to the gaps between the column and the foundation. After the mortar (concrete) has acquired a strength of 25 kgf / cm2, the equipment is removed for reuse. Mounting equipment (frame, mounting angles, fixing means), made and installed with the accuracy specified by the project, provides the column with the design position without additional alignment. The correctness of the installation of the mounted columns is checked by control measurements: relative to the alignment axes of the building - one measurement for every five columns; relative to the marks of the supporting surfaces - one measurement for every 50 m2 of the area of \u200b\u200bthe structures; vertically - one measurement for every 200 m2 of the building area. Deviations of the mounted reinforced concrete structures from their design position should not exceed the tolerances given in SNiP III -B. 3-62 *.

Temporary anchorage of columns. The column installed in the foundation glass is calibrated and temporarily secured with wedges, adjustable wedges, wedge inserts, braces or struts, conductors. Reinforced concrete columns up to 12 m high can be temporarily secured by driving concrete, reinforced concrete, steel or oak wedges into the gaps between the side faces of the column and the walls of the glass. It is most advisable to use concrete or reinforced concrete wedges, which are left in the foundation glasses. However, it is impossible to straighten the columns with such wedges; therefore, they are used after installing the column in the design position, and when straightening, they use inventory metal wedges. Wooden wedges must be dry, otherwise, when they dry, the column may deviate from the vertical. Wooden wedges should also not be left in glasses for a long time in order to avoid swelling from the weather and possible damage to the structure. The length of the wedges is taken to be at least 250 mm with a bevel of one edge by 1/10, after driving their upper part should protrude from the glass by about 120 mm. To fix the column, one wedge must be placed at each of its edges up to 400 mm wide, and two wedges for larger edges. At the bottom, between the edges of the column and the walls of the glass, there must be a gap of at least 2-3 cm to be able to fill it with a concrete mixture. It is more effective to use inventory wedges or wedges.

The adjustable wedge consists of cheeks, pivotally connected to each other at one end; the cheek is flat, the cheek has the shape of an equal block prism. At the other end, the cheeks are connected by means of an adjustable screw passing through the nut in the cheek and connected to the cheek by means of a head. The latter fits into the slot of the channel welded to the flat cheek. A hinged-overhead bracket with a lock is attached to the cheek, with the help of which the device is attached to the wall of the foundation glass by means of a clamping screw.

Before installing the column, marks are applied on the edge of the foundation, indicating the position of the column faces. Then, on two adjacent sides of the glass, two adjustable wedges are installed so that the cheek rests with an edge against the wall of the foundation glass, and the flat cheek passes along the plane of the future position of the column face. Wedges are installed using a duralumin angle ruler. After installing a pair of adjustable wedges, the column is inserted into the glass so that its edges are pressed against the outer edges of the flat cheeks fixed by wedges. Next, two more adjustable wedges are installed along the free edges of the column and straightening and temporary fastening of the column are performed. When the clamping screw rotates, the cheek pivots around the supporting rib and presses the column with the lower end against the previously installed adjustable wedges, which ensures the alignment of the column position in the plan. By rotating the adjustable screws, the column is straightened and vertically aligned. The action of the wedge screws is used to pinch the column using flat cheeks at the level of the adjustable screws.

Figure: 27. Adjustable wedge for straightening and temporary fixing of columns in the foundation glass: 7.2 - cheeks; 3 - channel; 4 - nut; 5 - adjustable screw; 6 - hinged-but-overhead bracket; 7 - clamping screw

Figure: 28. Scheme of the wedge insert: 1 - body; 2 - column faces; 3 - screw; 4 - handle; 5 - glass wall; 6 - wedge; 7-gasket; 8 - boss; 9 - support for extracting the wedge insert; 10-nut; 11- ratchet wrench

The height of the adjustable wedge is taken to be equal to a third of the depth of the foundation glass, so that the joint of the column with the foundation can be sealed with a concrete mixture in two steps; first to the bottom of the wedges, then after removing them from the glass when the concrete reaches 25% of the design strength. The wedge insert (fig. 28) consists of an L-shaped steel body 250 mm high and 55 mm wide, a steel wedge, a screw and a boss. The wedge is pivotally suspended from the horizontal arm of the body. The hinge axis rotates freely and moves in longitudinal slots on the inner edges of the horizontal arm of the body. The screw rotates on a threaded bushing welded to the body. A boss is movably attached to the lower end of the screw. When screwing in the screw, the boss goes down along the vertical part of the body and pushes the wedge. The insert is equipped with a handle for easy carrying and installation. Wedge insert weighs 6.4 kg. Inventory wedge liners are installed during alignment in the gaps between the walls of the foundation glass and the column. In this case, the screw must be unscrewed so that the liner freely fits into the gap. The wedge insert rests with a horizontal shoulder on the glass wall. After installing the device, rotate the screw with a ratchet wrench, while the boss is lowered, pressing the wedge to the wall of the glass, and the body to the edge of the column. Simultaneously, two wedge liners are fixed, placing them on opposite sides of the column.

According to TsNIIOMTP, when using liners, the duration of the installation of the columns and the operation of the crane is reduced by about 15%, the consumption of steel is reduced, and the accuracy of installation is increased in comparison with driven steel wedges.

For stability, heavy columns of long length must, in addition to wedges, be strengthened with braces or rigid struts. The upper elements of the precast concrete columns are temporarily attached to the lower ones by erection welding. To ensure the stability of the upper element of the column, reinforcing outlets or overlays located at the corners of the column are welded, and after that the element is unstopped. In the same way, temporary fastening of columns on foundations is carried out at the joints with a pipe or reinforced concrete tooth. For the installation and alignment of reinforced concrete columns, single and group conductors have been developed and used. Single conductors can be divided into two types: freely supported on the foundation and fixed to the foundation.

Conductors of the first type do not perceive loads from the column mass. They are designed to expand the base of the column to a size that ensures its stability against overturning when freely supported on the foundation. When using such conductors, it is impossible to verify the position of the column in the plan, and for its straightening it is necessary to use horizontal jacks fixed on the upper part of the foundation glass. Such conductors can only be used to install light columns (up to 5 g in weight). Conductors of the second type are fixed in the foundations with screws, take the mass of the columns and are equipped with alignment devices. The fixing conductor of this type of the Uralstalkonstruktsiya trust is fixed to the foundation with four stop screws and takes the mass of the column through the support pins of two vertical screws, for which a steel roller is inserted into the column during its manufacture in a precisely adjusted position. The pins and ends of the roller are located in the slots between the stops. Having installed the column at the bottom of the foundation glass, raise it by 10-15 mm so that it can easily rotate in the trunnions. Then its position is verified vertically with racks in the transverse direction and with screws - in the longitudinal direction. With the help of such a conductor, reinforced concrete columns with a mass of 15-20 g were installed. For temporary fastening and alignment of high columns, group conductors are used, attached to the foundations with screws. These conductors ensure the stability of two columns simultaneously along and across the row. The general disadvantages of conductors are the complexity of their design, large mass and significant time spent on installing and aligning the columns (up to 1 hour). Improvement of conductors is possible by using aluminum alloys for their manufacture, improving the quality of nodal connections and alignment devices, and simplifying designs. Multi-tiered prefabricated reinforced concrete columns of high-rise frame buildings are joined together by welding steel embedded parts and monolithing of the joints. Their temporary fastening within each floor or tier is carried out by mounting welding (tacking) of linings or outlets of reinforcement, braces with tension couplings or conductors. The upper ends of the braces are fastened to the clamps put on the columns approximately in the middle, the lower ends - to the hinges of the floor panels, over which the column is mounted.

Temporary fastening of the first raised frame is performed with braces or struts (Fig. 31), and the subsequent ones are connected to the previously installed ones by means of two inclined braces and two horizontal struts. The frame racks are temporarily fixed with wedges, single conductors or assembly welding. Temporary fastening of frames is also carried out using spatial conductors.

Figure: 29. Temporary fastening of the alignment of reinforced concrete columns with a conductor-retainer 1 - stop screw; 2 - cremaler; 3 - limiter; 4 - support pin; 5 - mounted column; 6- steel roller; 7 - column foundation 8 - screw

Figure: 30. Temporary fastening of reinforced concrete frames during their installation: 1 - brace; 2- inclined guy; 3 - horizontal spacer

For temporary fastening and alignment of multi-tiered columns of multi-storey industrial buildings, single conductors are used. The jig (fig. 32) has corner posts, clamping and adjusting devices. The bottom jig fixes the jig to the head of the previously installed column. Adjustment devices are located in the middle and top of the racks. The adjusting device consists of four beams, adjusting screws and hinges. Three beams have one screw, and the fourth has two screws, which makes it possible to rotate the column around its vertical axis.

The jig with automatic lever grips, designed for temporary fastening and alignment of reinforced concrete columns of multi-storey buildings, is distinguished by a more advanced design. The conductor is installed on the previously mounted column of the lower tier. Before installing the column to be mounted in the clamping carriages, the automatic lever grippers are spread apart by springs. When lowering, the column moves apart the levers, which, together with the clamping carriages, provide centering and reliable grip of the column. The jig is equipped with two horizontal screw jacks mounted on the upper belt. The horizontal screws are connected with automatic grippers by bearing supports. The top chord is attached to the top ends of four vertical screw jacks. At the moment of gripping the column, the hinged supports of the lower chord, which is a frame-strapping, are automatically activated. Support-grips of the lower belt, on which vertical jacks are installed, are hinged to it. The hinge solution of the lower chord with the use of a lock and hooks contributes to the fact that the preliminary fixation of the conductor on the lower column, its installation in height and in the horizontal plane is carried out simply and quickly, without special alignment.

The column is calibrated in height and vertical using three vertical jacks, the rods of which can be raised to the same height (search for an elevation mark) or to different heights (search for the verticality of the column). Then the column is verified in the plane of the narrow edge by rotating horizontal screw jacks.

After the final alignment and fastening of the mating parts of the column, the jig is moved by crane to the next precast element.

In addition to single conductors, conductors are used for the installation of prefabricated reinforced concrete structures in multi-storey buildings: group for two columns; group space for the installation of four columns; spatial frames for mounting; volumetric (frame-hinged indicators) and others. The group spatial conductor is used in a set with two single ones for fastening and aligning the columns of industrial buildings. In this case, the process of installing four columns is carried out in the following sequence. Single conductors are fixed on the tops of two columns. Columns are installed in them and verified with the help of these conductors and theodolite. Then, using single conductors, the next two columns are temporarily fixed. For their alignment, a group spatial conductor is installed on the tops of the four columns. The latter is a rigid metal welded frame made of a corner and gas pipes. The frame in the plan corresponds to the dimensions of one cell of the columns 6X6 m. In the corners there are caps-bows, welded from sheet steel. Each hood is equipped with four adjusting pressure screws. In the upper walls of the pillars there are holes - windows with mounted sighting axes. At the level of the lower chord of the frame, a wooden flooring is made, on which installers work. There is a cable fence along the frame perimeter. To the upper chords of the diagonal trusses, four slinging loops are welded to move the conductor with a tower crane. The mass of the group conductor is 900-1000 kg. A single conductor is used for temporary fastening of the columns, which is a rigid spatial structure - a U-shaped frame with a hinged door, with fastening and adjusting screws. The conductor is fixed with the fixing screws on the head of the previously installed column. With the help of adjusting screws, it is placed in a vertical position, after which the column is taken.

Figure: 31. Conductor for installation and alignment of columns of multi-storey industrial buildings: a - section; b - installation diagram of the conductor; в - an adjusting device; d - clamping device; 1 - column; 2- corner post; 3 - column joint; 4 - previously installed column; 5 - mounted column; 6 - conductor; 7 - floor slabs; 8 - beam; 9- hinge; 10 - adjusting screw

Figure: 32. Scheme of the conductor: 1 - clamping carriage; 2 - automatic lever grip; 3 - springs; 4 - horizontal screw jack; 5-top belt; 6 - bearing support; 7 - vertical screw jack; 8 - hinged support of the lower belt; 9- lock; 10- hooks; 11 - column

Figure: 33. Scheme of the conductor for mounting frames: a - top view; 6 is a front view; c - side view

The column to be mounted is not brought into the conductor from above, as usual, but into the side door, and thus, the structure weighing about 5 g during installation is not over the installer's head, which ensures the safety of work and faster installation of the column into the design position.

Figure: 34. The sequence of installation of the conductor and prefabricated elements: 1, 2 - crane parking; 3, 4 - position of the conductor; 5-10, I-16 - sequence of installation of elements

The group conductor ensures the accuracy of installation of two columns in the design position at the same time, which determines the quality of further installation of the frame - crossbars, floor slabs and coatings. As a result of using this method of installation, the time for aligning the columns is reduced by ⁄3 and labor costs are almost 3 times.

Using spatial conductors, several frames are installed. One of such conductors is a spatial structure with dimensions 12X5.50XX3.6 m and a mass of about 2 tons, welded from angle steel (Fig. 33). The length of the conductor can be reduced to 9 or 6 m. The upper working platform of the conductor is covered with a boardwalk for the work of installers. Clamps are fixed to the conductor for temporary fastening of four frames from one position. During the installation process, the frames are held in the vertical plane by one clamp, fixed to the crossbar. After aligning and fixing the frames, the jig is moved to a new workplace by crane (Fig. 34). Frame-hinged indicators (RSI), proposed by S. Ya.Dutch, are a complex device consisting of spatial lattice scaffolds, on which a hinged (floating) frame with corner stops for fastening four columns, retractable and swivel cradles in the upper position at once for assemblers and welders.

Figure: 35. Sections of the frame-hinged indicator: a - transverse; b-longitudinal; 1 - wooden lining; 2-space ring scaffolds; 3, 7 - retractable swivel cradles; 4 - articulated indicator; 5 - fence; 5-ball bearings; S - split flange joint; 9 - stairs

RSHI can be made on one (4 columns), two (8 columns) or three (12 columns) cells, on one or two floors in height. RSHI is installed through the cell of the building and connected with calibration rods. The mass of the RSI per cell is 4-5 tons, the cost is 2-3 thousand rubles.

RSHI is installed with a crane and verified with a theodolite. After alignment (about 1 hour for two cells), columns are installed, each of which is fixed with corner stops.

Figure: 36. Scheme of the frame-hinged indicator (plan): 1 - longitudinal thrust; 2- clamping cable of the clamp; 3- clamp tensioner; 4 - rotary hoyut; 5 - transverse thrust; 6, 15 - brake attachment points of the frame; 7, 14 - longitudinal beams; 8, 10, 13 - movement mechanisms; 9 - folding clamp; 11 - braking units for fastening the frame; 12, 16 - cross beams

Temporary fastening of beams. Reinforced concrete beams with a ratio of their height to width up to 4: 1 are laid on horizontal supports without temporary fastening; with a larger height-to-width ratio, the mounted beams are fastened with spacers and ties with other firmly installed structures. For the temporary fastening of the roof beams installed on the columns, a special device is proposed, shown in Fig. 37. The rods with towbars tighten the grip fixed at the top of the beam end with the bolt passed through the hole at the top of the column, and steel brackets fix the position of the bolt.

Figure: 37. Device for installation of covering beams on columns: 1 - bolt; 2 - steel brackets; 3 - rods with towbars; 4 - capture

In the structures of the columns, permanent anchors are arranged on the supports, which greatly simplifies the fastening of the covering beams to them. Temporary fastening of trusses. When installing reinforced concrete trusses, their axes are combined with the risks on the columns and fixed on anchor bolts. The first truss is fastened with braces, tying the nodes of the upper belt adjacent to the ridge to the fixed parts of the structure or to special anchors; subsequent trusses are fastened along the ridge with an inventory screw spacer with previously installed spacers at the junctions of the braces to the upper chord. The temporary fastenings of the trusses are removed after creating a rigid system from the group of trusses and the covering elements laid on them. Disassembly of temporary fasteners. Temporary fastenings of prefabricated reinforced concrete structures (wedges, struts, braces, struts, conductors, etc.) are allowed to be removed after the concrete acquires 70% of the design strength at the joints.

Permanent fastening of structures

Permanent (design) fastening of structures is carried out by welding the reinforcement at the joints and their subsequent embedding. Prior to monolithing of the joints, corrosion protection of welded joints is performed. Welding of reinforcement at the joints of reinforced concrete structures, depending on the spatial position of the rods or seams, the diameter of the rods being welded and the type of joints, there are several types: a semi-automatic submerged-arc bath (horizontal and vertical butt joints), a manual bath (horizontal butt joints), a semi-automatic arc and manual arc (butt, lap and cross vertical and horizontal joints). It is possible to weld joints from low-carbon steels (class A-I, grade St. 3) at an air temperature of at least -30 ° С, and from medium-carbon steels (class A-II, grade St. 5 and 18G2S) and low-alloy steels not lower than - 20 ° C. At lower temperatures, measures are taken to maintain the air temperature at the welder's workplace not below the specified limits.

In order to reduce the effect of welding stresses on the strength of reinforced concrete structures, the reinforcing bars are welded in a certain sequence (Fig. 39). Welding quality control includes: preliminary control, during the welding process, quality control of welded joints. Preliminary checks are made for the compliance of the main and welding materials with the requirements of the technical conditions, the quality of preparation of the abutting elements for welding, and the adjustment of the equipment to the specified mode. During the welding process, the maintenance of the required mode and welding technology is monitored. Quality control of welded joints includes external examination, testing of specimens for strength, gamma ray transmission, etc. Allowable deviations in the dimensions of welded joints are given in SNiP III -B. 3-62 *.

Anticorrosion protection of welded joints of prefabricated reinforced concrete structures is performed by applying metallization, polymer or combined coatings to steel embedded parts, reinforcement joints at joints and fastening parts of enclosing structures: metallization-polymer or metallization-varnish-and-paint. Zinc is mainly used for metallization coatings. Metallized polymer coatings consist of zinc or zinc-coaluminum alloy and polymers (polyethylene, polypropylene, etc.). Zinc, primers (phenolic, polyvinyl butyryl, epoxy), paints (ethinol), varnishes (bi-fog resin, perchlorovinyl, epoxy, organosilicon, pentophthalic) are used in metallization and varnish coatings. The anti-corrosion coating is applied twice: at the factory, before the installation of embedded parts in the structure, and after the installation of structures on welded seams and on separate places of coatings damaged during welding of parts.

At the construction site, various coatings are applied in several ways: zinc - by flame spraying or electrometallization; zinc-polymer and polymer - by flame spraying; paints and varnishes - by applying a zinc sublayer, on which paints and varnishes are applied with paint spray guns or manually.

Figure: 38. The sequence of welding joints: a - columns with a foundation by two welders; b-the same, one welder; in - crossbar with a column; d - longitudinal bonds

Zinc coatings by gas flame spraying are applied in one layer, electrometallization in 2-3 layers (with a thickness of 0.1-0.15 mm) and 3-4 layers (with a coating thickness of 0.15-2.2 mm). Zinc-polymer coating in two layers - first a zinc sublayer, then a polymer layer. The polymer can be applied immediately after zinc. The polymer coating is also formed in two layers. In combined zinc and varnish coatings, a zinc subcoat is first applied, and then paint and varnish materials are applied in 2-3 layers. Each layer of paintwork must be dried at a positive temperature for several hours or even days (depending on the type of material), which is a disadvantage in terms of installation work. Therefore, it is better to use polymers instead of paints in combined coatings.

Anti-corrosion coatings are applied immediately after welding the elements and preparing the surfaces, avoiding breaks for more than 4 hours.

The surface must be free from grease, moisture and rust. After applying the coating, check the strength of its adhesion to the base, the thickness of the coating, the presence or absence of swelling and cracks. Milling joints. Sealing of joints and seams with mortar or concrete mixture is carried out only after verifying the correct installation of structural elements, acceptance of welded joints and performing anti-corrosion protection of metal embedded parts. When embedding, it is necessary to take into account that the concrete (mortar) in the joints of reinforced concrete structures perceives or does not perceive the design loads. So, at the joints of columns with foundations that do not have embedded parts, as well as in joints in which the connection of prefabricated elements is performed by welding the outlets of reinforcing rods, the concrete monolithically binds the elements and perceives the load.

In the joints with embedded steel parts, the concrete (mortar) filling is the filling between the prefabricated elements, protects the embedded parts from corrosion, but does not perceive the loads acting on the structure.

The strength and stability of prefabricated structures with joints, in which the concrete perceives the design loads, depend on the strength of the concrete in the embedding and on the adhesion of the embedded concrete to the strength of the prefabricated structure; the roughness of the abutting surface significantly increases the adhesion of the concrete at the joint. When embedding reinforced concrete columns in foundation glasses, as well as other monolithic joints that perceive design loads, to accelerate hardening and ensure the strength of the connection, rigid concrete mixtures of a higher grade are used than the concrete of the main structure (by 20% or more). It is advisable to use a concrete mixture on expanding cement, which is characterized by fast setting and hardening, does not shrink, which is very important for the density of the embedding, or stress cement. Use Portland cement grade not lower than 400. The sand is medium- or coarse-grained quartz. Crushed stone for concrete mix is \u200b\u200bchosen fine granite in order to ensure better filling of joints, size up to 20 mm. To increase the plasticity of the concrete mixture with a low water-cement ratio (0.4-0.45), sulfite-alcohol stillage is introduced into the composition, and aluminum powder is used to increase the density of concrete.

The most commonly used compositions of dry mortar or concrete mixtures (by weight): 1: 1.5; 1: 3; 1: 3.5; 1: 1.5: 1.5; 1: 1.5: 2. In order to activate the hardening of the solution (concrete), additives are introduced into the compositions: 3% semi-aqueous gypsum, 2% sodium chloride, up to 10% sodium nitrite, 10-15% potash by weight of the cement, or use concrete mixtures preheated by electric current. Potash should be added at temperatures up to + 15 °, since its use is ineffective at higher temperatures. High-strength polymer mortars and plastic concretes, hardening at a temperature not lower than + 16 ° C, are also used to embed the joints of prefabricated reinforced concrete structures. Therefore, in the case of their use at lower temperatures, the solution (concrete) in the joint zone is heated with electric heaters. Column joints are concreted in steel formwork. It consists of four steel panels with a thickness of 1.5 mm, bolted together. At the top of each panel there are pockets for filling and compacting the concrete mix. The formwork is held on the columns to be joined by means of wooden stops resting on the ceiling. The complexity of assembling such a formwork is 0.16 man-hours, concreting one joint - 0.75 man-hours. The formwork is removed 4 hours after concreting, and in the case of using fast-hardening concrete, it is removed earlier. A similar formwork is used for concreting the joints of girders with columns. The joints are filled with mortar (concrete) in a mechanized way using mortar pumps, pneumatic blowers, cement guns, syringe machines and other equipment. Pneumatic blowers and syringe machines are suitable for sealing joints with both concrete mixture and mortar; mortar pumps and cement guns - only with mortar. To create a wet mode of concrete hardening, the monolithic joints are covered with burlap, sawdust and systematically moistened for 3 days.

Casting joints in winter conditions. In winter conditions, when the joints are monolithic with concrete, which perceives the design forces, it is necessary: \u200b\u200bto warm the abutting surfaces to a positive temperature (+ 5-8 ° С); lay the concrete mixture heated to 30-40 ° С; withstand or warm up the laid mixture at temperatures up to 45 ° C until the concrete acquires at least 70% of the design strength.

The column-to-foundation joint surfaces can be heated in various ways: with low pressure steam; water (fill the joint cavity with water and then heat it with steam supplied through a hose); rod electrodes at low voltage current; electric heating devices. When warming up with water, it is necessary to ensure that after warming up the water is completely removed from the joint cavity.

Figure: 39. Schedule for determining the strength of concrete depending on temperature and heating time. Portland cement concrete

The concrete mixture, laid in the joint, is prepared with warming up the components or heated in bunkers with an electric current to 60-80 °. Along with heating and electric heating, antifreeze additives can be added to the concrete mixture for sealing joints at an outside air temperature up to - 15 ° C. Joints, the concrete of which does not perceive the design forces, at an outside air temperature of up to -15 ° C, can be monolithic with a concrete mixture (mortar) only with antifreeze additives, since such a mixture hardens even at negative temperatures; in this case, after laying in the joint, the mixture does not need to be heated; in the event of a sharp drop in the outside air temperature, it is enough to use insulated formwork. Solutions of calcium chloride CaCl2 salts are recommended as antifreeze additives; calcium chloride CaCl with sodium chloride NaCl; calcium chloride CaC12 with sodium chloride NaCl and ammonium chloride NH4C1; sodium nitrite NaN02, etc.

Figure: 40. Cementing the joint between the column and the foundation in winter conditions: a - the scheme of electric heating of the concrete of the joint with electrodes; b - heating the joint surface by electric cylinders; c - heating of the monolithic joint with electric furnaces; d - the same. with the help of a hothouse; 1 - foundation; 2 - column; 3 - electrode; 4 - transformer; 5 - switch; 6 - spotlights; 7 - electrodes

The use of antifreeze chemical additives of chloride salts when sealing joints with metal embedded parts and fittings is prohibited.

To increase the plasticity and water resistance of concrete at the joint, sulphite-alcohol stillage in an amount of up to 0.15% of the mass of cement is introduced into the concrete mixture with antifreeze additives.

If it is necessary to obtain high strength of the embedment in a short time (one day or less), concretes prepared with antifreeze additives can be subjected to artificial heating.

When monolithing joints with a concrete mixture without antifreeze additives, it is necessary to preheat the mating joint elements and heat the concrete until it acquires the required strength; design joints loaded with the design load in winter must be heated until 100% design strength of concrete at the joint is obtained and until 70% strength is obtained in other cases. The strength of concrete prepared on Portland cement, depending on the temperature and heating time, can be roughly determined according to the schedule.

Figure: 41. Heating and heating the joints of multi-tiered columns and joints of floor slabs with girders during monolithing in winter conditions: a - using thermoactive formwork; b - by means of heating elements; 1, 2 - steel sheets; 3- thermal insulation layer; 4 - three layers of an electrical insulating sheet with a nichrome wire in the middle; 5 - a spiral in a layer of sawdust moistened with a solution of sodium chloride; 6- layer of sand; 7- tubular electric heater; 8 - tarpaulin; 9 - clamp

Most often, heating is done with electric current, as well as with steam. For electric heating, electrodes are used (Fig. 40, a), tubular electric heaters or electric cylinders with tips introduced into the joint cavity (Fig. 40, b), thermoactive formwork, heating cassettes, reflective electric furnaces (Fig. 40, c) or electric heat (Fig. 40, d), electrode panels. It is advisable to heat and heat the joints of multi-tiered columns, as well as beams, using thermoactive formwork (Fig. 41). Either three layers of an electrical insulating sheet with nichrome wire on the middle layer, or a layer of mortar with embedded steel wire and a thermal insulation layer of mineral wool are placed in the cavity of the double formwork, consisting of inner and outer steel sheets. This formwork is made in accordance with the dimensions of the abutting elements and is held on them with a clamp. Concrete mix with a cone draft of 10-12 cm is loaded into the joint through a funnel built into the formwork. Tubular electric heaters (TEN) can be used to heat many joints both directly (Fig. 41, b) and as heating elements of cassettes (thermal panels) (Fig. 42), reflective furnaces and other devices. The tubular electric heating element is a metal hollow tube into which a nichrome wire spiral is pressed. The filler is fused magnesium oxide or quartz sand. The filler acts as electrical insulation.

Figure: 42. Heating cassettes: a - diagram of a set of cassettes for heating the column joint; b - diagram of cassettes; c - tubular electric heater; 1 - tubular electric heater; 2 - reflector; 3 - case; 4 - insulating sleeve; 5 - filler; 6 - spiral; 7 - fill

In fig. 41, b shows the heating of the joint between the floor slab and the girder (or beam) using a tubular electric heater, which is covered with a tarpaulin.

After warming up, which lasts about 4-5 hours, the tarpaulin and heating element are removed, the joint is concreted, covered with slag or sand, and the heating element is re-laid.

To embed the vertical joints of the columns, a universal heating formwork with automatic control of the heat treatment mode is used. It consists of a metal case, heating cassettes, power supply and control unit. The formwork body is used for placing concrete in the joint and is made of two halves, bolted together. Each half is made of sheet steel and has guide plates for attaching the heating cassettes and the power and control unit. The halves are interchangeable, each with a loading window. Heating cassettes are flat metal heat-insulating boxes with tubular electric heaters with a capacity of 0.5 kW and a voltage of 220 V. The working temperature of the heater surface is 600-700 ° C. There is an air gap between the heating element and the wall adjacent to the concrete. A reflective plate made of tinplate is installed under the heater. According to experience, the use of heating elements instead of spirals increases the reliability of the heating device, increasing its service life to 5000 hours, and also allows infrared heating. Three types of heating cassettes in various combinations provide heat treatment of the joint of any column section. The set of heating cassettes is inserted along the guides of the metal formwork and covers the joint on four sides.

The installation of the heating formwork on the column joint is carried out manually from halves with heating cassettes installed on them or element by element. The mass of a separate element of the heating cassette is 5.5-9 kg; the weight of the entire formwork for a column with a section of 250X500 mm is 70 kg.

The cassettes are connected to the network before concreting the joint. After a preliminary two-hour heating, the cassette joint cavities are turned off for concrete placement. Subsequent heat treatment of the concrete of the joint - heating up to 50 ° C and isothermal heating at a given temperature by periodic switching on and off of the current. Electricity consumption with automatic regulation and outdoor temperature up to -15 ° C is 35 kWh per joint. With manual regulation, it is equal to 50 kWh per joint.

The design of the crossbar and floor slab joint allows only one-sided peripheral heating. For this purpose, reflective ovens are used. The furnace is an inventory box 1300 mm long, made of two rolled metal sheets, between which there is a 50 mm thick mineral wool thermal insulation. The inner sheet is simultaneously a parabolic reflector, along the focal axis of which there are two tubular electric heaters with a capacity of 0.8 kW each with a mains voltage of 220 V. Each box has a cable outlet that ends in a three-phase plug, one of which has a grounding pin. Box weight 50 kg. To reduce heat and moisture loss, the box is covered with sawdust around the perimeter. Electricity consumption at an outdoor temperature of -15 °, a heating temperature of + 50 ° and its automatic regulation is 25 kWh per joint.

A power supply and control unit is used to automatically maintain a given constant temperature of concrete processing. It consists of a power cable, a thermostat and a control box. The metal box of the control box contains: a magnetic starter, a switch, a signal lamp and a terminal block for connecting the leads of the heating cassettes. The control box is inserted into the guides of the metal joint formwork. The thermostat has one pair of normally closed contacts that open when the temperature rises above the set one. The thermostat is connected to a 220 V network. Using it allows you to automate all types of heat treatment of concrete during installation.

Figure: 43. Schemes of a reflective furnace (a) and an electrode panel (b): 1 - body; 2 - tubular heater; 3 - cable outlet with plug connector; 4 - protective strip; 5-vapor barrier; 6 - terminals; 7 - conical pins; 8 - steel tires

Electrode panels are also used to heat the abutting elements. The panel contains three steel bars that serve as electrodes, with tapered pins that improve the contact of the electrodes with concrete.

TO Category: - Installation of building structures

Installation of foundations begins with a breakdown of the axes of the structure and their binding to the terrain. The axes are laid out by geodesists. The design elevation of the foot of the foundation is determined with a level. After this, the axes of the structure are transferred to the bottom of the pit. The axles are fixed on the rags. For strip foundations, two structural elements are mainly used: a trapezoidal or rectangular cushion block placed in the base of the foundation, and wall blocks or panels from which the foundation wall is erected. The basis for the strip foundations is a sand bed, which is laid on a protected or compacted with rubble soil at the bottom of a pit or trench. Installation of strip foundations begins with the laying of lighthouse blocks, which are verified and installed in strict accordance with the axes of the walls of the structure. Lighthouse blocks are installed at a distance of no more than 20 m from each other. Corner and intersection blocks are always beacons. A mooring cord is fixed along the inner, and sometimes along the outer edge of the lighthouse blocks. At a height of 20-30 cm from the installation site, the unit is oriented and lowered to the design position. The permissible deviations from the design position during the installation of strip foundations from precast concrete blocks should be no more than (mm):

• Reference Surface Marks ... 10
• Structural axes ... 20
• The width of the walls ... 15
• Opening width ... 15
• Surface and corners (from vertical), for the whole building ... 15
• Separate rows of blocks (from the horizontal), 10 m in length ... 15

Cushion blocks are laid one end-to-end or (with good bearing capacity of the base) with gaps that can reach 40-50 cm. Cushion blocks are laid along the entire perimeter of the building or within one enclosure. For the passage of pipelines and cable entries with continuous laying of cushion blocks, special mounting holes are left.

Blocks or panels of foundation walls are installed at design marks, filling the joints with cement mortar. Basement panels are usually welded to embedded elements in cushion blocks. During installation, the elements of the walls are verified both relative to the longitudinal axis and the vertical one. After the installation of all blocks along the upper edge of the wall, a leveling layer (mounting horizon) is made of cement mortar, the surface of which is brought to the design level. Installation work of the zero cycle is completed by the installation of a basement and a ceiling above the basement or underground. Strip foundations are usually mounted with a crane at the level of the planning, and not in a pit.

Installation of precast concrete foundations begins with a slab. After installing it in the design position, a bed of cement mortar is made on the slab, on which a block-glass is installed. Embedded parts are used to connect the glass to the plate. After welding the embedded parts, they are protected with an anti-corrosion coating. Installation of foundations of industrial buildings, made in the form of a single block, is carried out using a crane. The guidance of the foundation blocks to the design position is carried out by weight, after which the block is lowered to a prepared place and verified according to the risks of the axes, aligning them with the pins or risks that secure the position of the axes on the base. If installed incorrectly, the unit is lifted, the base is fixed and the installation procedure is repeated again. The correctness of the installation of the foundations vertically is checked with a level.

Reinforced concrete columns are mounted as follows. Before installation, check the position of the transverse and longitudinal axes of the foundations and the marks of the supporting surfaces of the foundations, the bottom of the glasses, the dimensions and position of the anchor bolts. Before installation, axial marks are applied to the columns along four edges at the top and at the level of the top of the foundations, and for columns intended for laying crane beams along them, in addition, the marks of the axes of the beams are applied to the consoles. Columns of industrial buildings are assembled by first laying them out at the installation site, or directly from vehicles. The columns are laid out in such a way that during the installation process you had to make a minimum of movements and various auxiliary works and there was free access for inspection, mounting of equipment and slinging. Columns in the installation area are laid out according to various schemes. With a linear layout, the columns are laid out in one line parallel to the axes of the building and the movement of the crane. Such a layout is carried out provided that the length of the column is less than the foundation step. When laying out in steps, the columns are placed parallel to the axis of the structure to be mounted and the axis of the crane penetration. Inclined layout is used when the size of the layout area is limited; the centered layout scheme is characterized by the fact that the trajectory of the crane boom rotation during the installation operation is a one-sided arc. The columns are not laid out flat, but so that in the process of lifting the bending moment from the weight of the column and rigging acts in the plane of the greatest rigidity of the column. This is especially important to consider when installing two-branch columns. When laying out, take into account the way in which the installation is to be carried out. It is more convenient to lift rectangular and two-branch columns from an edge position. Since the column can enter the platform in a flat position, the first operation during installation is to turn it onto an edge. After laying, the columns are inspected, checking their integrity and dimensions. At the same time, check the dimensions and depth of the glass under the column. Then, the column is equipped with ladders, fixtures, braces, etc.

The conditions for ensuring the correct position of the column during installation are provided for in the installation project. When the columns are lifted by the turning method, the lower end of the column is usually fixed in a special hinge fixed to the foundation. When lifting the columns by turning with sliding, the lower end of the column is pivotally attached to a special trolley, to a slide, or equipped with a spacer and a roller. Columns are strapped with various friction clamps, pin clamps with local or remote unstitching, and when mounting from vehicles - balancing traverses. One should strive to ensure that the column hangs on the crane hook in a vertical position and does not have to go up to unstitch it. Friction grips are put on the column with the beam removed. After installing and securing the beam, the column is lifted. The gripper holds the column due to the friction that occurs between the beams and the surface of the column when the cables are pulled.

Holes for pin grips must be provided during the manufacture of the columns. A cable is used to straighten pin grips used to lift light columns; for straightening heavy columns, the grippers are equipped with electric motors. From vehicles, the columns are mounted by swinging in suspension. To reduce the length of the crane boom during the massive installation of columns, booms equipped with a forked head are used. The lifting of the column (transferring it from a horizontal position to a vertical one) consists of three successively performed operations:

• transfer of the column from horizontal to vertical position;
• column feed to the foundation in a raised position;
• lowering the column to the foundation.

The column is lifted in one of the following ways:

• the crane moves from the top of the column to its base and simultaneously lifts the hook. The column gradually turns around the supporting rib. To avoid slipping, the shoe is reinforced with a guy. The movement of the crane and the lifting of the hook are performed in such a way that the cargo chain hoist is always in an upright position;
• the crane is stationary. Simultaneously with the lifting of the hook, the column shoe mounted on the trolley or the guide rail track lubricated with grease moves towards the vertical. These two methods are mainly used when lifting heavy columns and using cranes that cannot move with a suspended load;
• the crane is installed in such a way that the slinging point and the lower end of the column are at equal boom outreach. The column is lifted by turning the boom while operating the cargo chain hoist, which must always be vertical. The top of the column and the slinging point describe spatial curves. This method of lifting is used mainly for the installation of light and medium columns with jib cranes.

After lifting and installing the column in place, without releasing the crane hook, they begin to align their position. Lightweight reinforced concrete columns are calibrated using mounting crowbars and wedges, laid in the foundation glass, and special mechanical wedges. The correct position of the columns in the plan is achieved by combining axial marks on the column with axial marks on the foundation. The position of the columns is checked by a theodolite and a level.

Immediately before the installation of the columns, a leveling layer is laid in the foundations of the glass type, filling the gap between the bottom of the glass and the lower end of the column. The preparation is carried out from hard concrete, laid in a layer, the thickness of which is determined by measuring in nature the mark of the bottom of the glass and the length of the column. The column, after installation, compresses the fresh preparation with its weight; this achieves a uniform transfer of pressure to the bottom of the glass. Another way of securing the columns is as follows. On the foundation, the bottom of which is not concreted to the design mark by 5-6 cm, the support frame is installed, verified and securely fixed. To create the base surface, a forming device is used, which has special stamps and a vibrator. Then concrete is placed on the bottom of the glass and the forming device is lowered, directing its sleeves to the pins of the support frame, then the vibrator is turned on. Sinking under its own weight until it stops, the stamp of the forming device squeezes out the gravy in the concrete at the required mark with imprints of a certain shape, strictly oriented relative to the axes of the foundation; the excess concrete is squeezed upwards, after which the forming device is removed and transferred to the next foundations. The use of this method requires the manufacture of columns with increased accuracy.

Short columns of multi-storey buildings can be rafted close to their top. Slinging of reinforced concrete columns of one-story buildings to the upper end, as a rule, cannot be carried out, since its bending resistance may be insufficient. In most cases, slinging of such columns is performed at the level of the crane console. In this case, the column, during the turn, rests on the ground with its lower end and works in bending like a single-arm beam. The raised column must be vertical. To do this, you need to suspend it at a point located on a vertical line that passes through the center of gravity of the column. For lifting, a traverse with grips or slings is used, covering the column from both sides. If the bending strength of the column is insufficient, the number of suspension points is increased.

The methods of temporarily securing the columns after installation in the design position depend on the support structure of the columns and their dimensions. Columns installed on glass-type foundations must be cast in place immediately after installation. Prior to the acquisition of 70% of the design strength with concrete, subsequent elements cannot be installed on the columns, except for the assembly ties and struts, which ensure the stability of the columns along the row. Columns up to 12 m in height are temporarily fixed in the foundation glasses using wedges and conductors. Use wooden (hardwood), concrete and welded wedges; depending on the depth of the foundation glass, the wedges should be 25-30 cm long with a slope of no more than 1/10 (the length of the wedges is approximately taken at half the depth of the glass). At the edges of columns up to 400 mm wide, one wedge is placed, at the edges of a larger width - at least two. Wooden wedges should only be used for small jobs, as they make it difficult to seal joints and are difficult to remove. Wedges are used not only for pinching the column in the glass, but also for its slight displacement or rotation in the plan, if it is necessary to guide the alignment axes. Rigid conductors are used to temporarily secure the columns. Temporary fastening of columns with a height of more than 12 m by conductors is not enough; they are additionally fastened with braces in the plane of the greatest flexibility of the columns. Columns over 18 m high are secured with four braces. These devices must simultaneously provide stability along and across the row. The first two columns are fastened crosswise with braces, the next - with crane beams. Reinforced concrete columns of frame buildings are fixed by welding, as a rule, after the installation of the crossbars and welding of the embedded parts of the columns and crossbars. Installation of crane beams is carried out after installation, alignment and final fixing of the columns. Installation begins after the concrete at the junction between the column and the walls of the foundation gains at least 70% of the design strength (exceptions to this rule are specially stipulated in the work design, which simultaneously specifies measures to ensure the stability of the columns during the installation of crane beams and other elements). Before installation on the ground, the condition of the structures is inspected and the joints are prepared. They strap the beams with ordinary slings for mounting loops or in two places "noose" with universal strapping slings with their suspension to the traverse, the size of which is selected depending on the length of the beams. Due to their large length (6-12 m), the lifting of crane beams is most often carried out using special or universal traverses or two-branch slings equipped with safety angles. When choosing a grip of a particular structure, one should pay attention to the nature of the reinforcement of the beam flange and to the installation conditions. So, it is impossible to use tongs for the installation of crane beams, the shelves of which are not able to withstand the bending moment from the installation load. It is advisable to carry out the installation of crane beams with crane rails attached to them before lifting (with a beam length of 12 m). The rails are fixed temporarily; the final fastening is done after the installation of the beams and the alignment of the rail position. When aligning, check the position of the beams along the longitudinal axes and the mark of the upper shelf. To install the beams along the longitudinal axes, risks are applied to the column supports, and the risks of the middle of the wall are applied to the upper planks and ends of the beams.

In the process of reconciliation, the marks are aligned. The position of the crane beams during their installation is adjusted using a conventional assembly tool, and after laying them on the support consoles, without resorting to the assembly mechanism, using special devices. After alignment, the embedded parts are welded and the beam is unstopped. When installing beams, the following deviations are allowed; displacement of the longitudinal axis of the crane girder from the center axis on the supporting surface of the column ± 5 mm; marks of the upper flanges of the beams on two adjacent columns along the row and on two columns in one cross section of the span ± 15 mm.

Figure: 38.

Installation of beams and roof trusses in industrial buildings is carried out separately or combined with the installation of roof slabs (Fig. 38). When preparing the trusses for lifting, the heads of the columns and supporting platforms of the truss trusses are cleaned and adjusted and the axes are marked. For the alignment and temporary fixing of the trusses, a scaffold is arranged and the necessary devices are installed on the columns. The process of installing trusses includes the submission of structures to the installation site, preparation for lifting the trusses, slinging, lifting and installation on supports, temporary fastening, alignment and final fastening in the design position. The trusses are installed in the design position in such a sequence that ensures the stability and geometric invariability of the mounted part of the building. Installation is usually carried out "on the crane", which successively retreats from parking to parking. The slinging of the trusses is carried out using traverses, the slings of which are equipped with remote-controlled locks for slinging (slinging of reinforced concrete trusses is carried out in two, three or four points to avoid loss of stability). To ensure stability and geometric invariability, the first installed truss is fastened with wire rope braces, and the subsequent ones - with spacers attached with clamps to the upper chords of the trusses, or conductors. For trusses with a span of 18 m, one spacer is used, for spans of 24 and 30 m, two spacers are used, which are installed in 1/3 of the span. At a truss pitch of 6 m, the spacer is made of pipes, at a pitch of 12 m - in the form of a lattice girder made of light alloys. The spacers are attached to the truss prior to lifting. A hemp rope is tied to the free end of the pipe, with the help of which the spacer is lifted to the previously mounted truss to be connected to the clamps installed there. The spacers are removed only after the final fixing of the trusses and the laying of the covering slabs. The first trusses in the span are fastened with cables. When installing lanterns, their structures are attached to the trusses before installation and lifted together with the truss in one step.

After temporary fixing, the lantern is installed in the design position. The trusses are verified according to the risks present on the support sites of the trusses and columns, combining them during the installation process. To fix the trusses in the design position, the embedded parts in each support unit are welded to the base plate, which in turn is welded to the embedded parts of the column head. Washers of anchor bolts are welded along the contour. The first two trusses in the span must have a fence or special scaffolding for the period of installation of the covering plates. Unsinging of rafter beams and trusses is carried out only after their final fixing.

Installation of cover plates is carried out in parallel with the installation of trusses or after it. Installation of the coating can be carried out in two ways:

• longitudinal, when the slabs are mounted with a crane moving along the span;
• transverse when the crane moves across the spans. In this case, when choosing cranes, it is necessary to check whether the cranes can pass under the mounted trusses or crane beams.

It is advisable to equip cranes with special assembly jibs for the installation of roofing slabs of tall buildings. Sometimes, for the installation of covering slabs, which is carried out after the installation of trusses, it is advisable to use special roof cranes that are moved over the mounted slabs. Before installation, the coating slabs are stacked between the columns, or they are fed on vehicles directly for installation. The order and direction of installation of the plates is indicated in the project of the work. The sequence of installation of plates should ensure the stability of the structure and the possibility of free access for welding the plates. The location of the first slab should be marked on the truss. In skylights, slabs are usually laid from the edge of the roof towards the skylight. For slinging the covering slabs, four-branch slings and balancing traverses are used, and when using heavy-duty cranes - traverses with a garland suspension of the slabs. The laid cover plates are welded at the corners to the steel parts of the truss structures. Plates located between the first two mounted trusses are welded at four corners; located between the second and third trusses, as well as the following ones: the first during installation - in four corners, the rest - only in three, since one of the corners of each slab (adjacent to the previously installed slabs) is not available for welding. It is recommended to install the plates:

• on reinforced concrete trusses with lampless coverage - from one edge to the other;
• on reinforced concrete trusses with a lantern - from the edges of the pavement to the lantern, and on the lantern - from one edge to the other.

The installation of the first slab at the edge of the pavement is carried out from the suspended scaffold, and the subsequent slabs from the previously installed ones. The joints between the slabs of coverings can be repaired simultaneously with the installation or after it, if there are no special instructions in the work production project.

The installation of floor panels in multi-storey buildings is carried out using the main assembly mechanism, and in brick buildings - using a crane that supplies materials for masonry. To lift the floor slabs, slings or traverses of a balancing type are used, which make it possible to give a slight slope to the panel suspended from the crane hook. Floor panels in multi-storey frame buildings are laid in the same flow with the rest of the structures or after the completion of the installation of columns, girders and girders within a floor or an enclosure on a floor. The installation of floor panels begins after the construction of walls in frameless buildings and the laying and fastening of spacers, as well as girders or crossbars in frame buildings. Installation is started from one of the end walls after checking the mark of the reference plane of the top of the walls or crossbars (if necessary, they are leveled with a layer of cement mortar). The panels are lifted with a four-leg sling or a universal traverse. Room-sized panels are snapped over all mounting loops. If the panels were stored in an upright position, then before slinging them they are transferred to a horizontal position on the tilter. Using a universal sling, the slab is lifted from a panel locomotive or from a pyramid without a tilter. One or two of the first slabs are installed from the mounting scaffold tables, and the subsequent ones from the previously laid slabs. If the panels are laid on a surface leveled with a screed, then the bed is made from a plastic solution with a thickness of 2-3 mm. When laying the panels directly on the parts, the bed is made from an ordinary solution. If necessary, the panels are upset by squeezing out the solution during their horizontal movements. When installing the panel on the mortar, pay special attention to the width of the support platform, since it is forbidden to move the laid panels in a direction perpendicular to the supporting structures.

Sagging panels are reinstalled, increasing the thickness of the mortar bed. The thickness of the seams between adjacent panels is determined by sighting along the seam. If the plane of the panel is curved, it is laid in the places of abutment to walls or partitions so that the free edge is horizontal. A panel with a sagging middle is installed on a thickened bed so that the sag is divided in half between adjacent slabs. In multi-storey frame industrial buildings, first of all, so-called "spacer" plates are installed, located along the longitudinal axes of the building, and panels located along the walls. The order of installation of the remaining plates can be arbitrary, if it is not dictated by the project. Detangling is performed immediately after the panel is installed in the design position.

Installation of wall panels is a separate stage of installation work in industrial construction. It begins only after the completion of the installation of load-bearing structures in the structural block of the building. In frame buildings, the middle of the frame columns is most often taken as the position of the building axes. When installing the panel of the inner wall between the columns from their middle, lay on the floor with a meter a distance equal to half the thickness of the panel plus the length of the template (usually 20-30 cm); this is done in order not to accidentally destroy the risk, for example, when making a bed. If the panels do not join the columns, then the mooring is pulled along the plane of the adjacent columns, the required size is laid along it, and the position of the panel plane is fixed with two risks on the floor, taking into account the length of the template. For panels adjacent to columns, for example, stiffening walls, the marks fixing the position of the panel surfaces are applied to the column at a distance of 20-30 cm from the floor and ceiling. For the installation of panels of external walls adjacent to the columns, for example, in single-storey industrial buildings or multi-storey buildings with blank walls in several tiers, on the columns using a tape measure along the entire height of the column, the elevation marks of the seams of each tier are marked with risks. In large-block and large-panel buildings, in which the walls perceive vertical constants (from the mass of the building, equipment) and operational loads, the marking is performed using geodetic instruments. First, the main axes are transferred to the mounting horizon; for basement walls, cast-off is used; for subsequent floors, the method of oblique or vertical sighting is used.

Installation of wall panels in frame buildings is carried out in a specific sequence. Internal wall panels are installed in the course of building erection before installing the overlap of the overlying floor. The stiffening walls are fixed immediately after installation in accordance with the project. External wall panels, ensuring the stability of the frame structures, are also installed during installation with a lag of no more than one floor. Wall panels, which do not affect the stability of the frame, are most often mounted vertically in one-story buildings and horizontal in multi-story buildings. In heavy-framed industrial buildings, exterior wall panels are usually installed in vertical strips. In multi-storey civil buildings, external wall panels are supplied during installation with the same crane as the frame elements. In industrial single-storey and multi-storey buildings with a heavy frame, the outer walls are mounted in a separate stream using mobile cranes. Wall panels of all types are slinged, as a rule, with a two-branch sling. When installing multi-storey frame buildings, the length of the sling branches should be such that the hook and the lower block of the crane chain hoist when installing the panel are higher than the overlap of the next floor. The supply of wall panels to the installation site in frame buildings is complicated by the previously installed frame structures, therefore, when lifting, wall panels are kept from turning and hitting the structure with two guy wires made of hemp rope. The panel is installed on the bed vertically or with a slight slope outward of the building to ensure that the panel is firmly supported on the bed mortar. External tape panels are attached with two corner clamps to the columns; the wall and the panel of the blind area - with struts to the floor slabs. With the same devices, the panel is brought to the vertical in the plane of the wall. To check the verticality of the panels, a plumb line is most often used. Before removing the slings, the bottom of the panel is tacked by welding. Finally, the panels are fixed by welding them to the frame elements.

If the panels are mounted before the installation of the purlin or the girder, during slinging, two braces are tied to the panel from a hemp rope of such length that when the panel is fed 1.5 m above the top of the columns, the end of the guy is on the ceiling. The panel is lowered between the columns, turned 90 degrees from the design position, and temporarily fixed with a tray clamp or clamp to the column. The verticality of the panel is checked with a plumb line and the risks on the column. If the crossbar is installed, the slinged partition cannot be brought under the crossbar, therefore the top of the panel is re-fastened during its installation. To do this, holding the panel by the braces, it is lowered next to the crossbar and stopped at a height of 10-15 cm from the overlap. Pressing the bottom of the panel, set it on the mortar bed. If necessary, correct the position of the bottom of the panel. The top of the panel is temporarily secured with a chain or bracket. The chain is passed through the panel mounting hinges and wrapped around the crossbar, the open ends are connected. Window panels are installed during installation of wall panels or after installation. Window panels are installed one above the other, resting them on support consoles from corners of a large profile (150-200 mm), welded to columns or to embedded parts. Window panels are often mounted in enlarged blocks. Sometimes they are enlarged together with half-timbered houses, imposts. To do this, the bindings are assembled and attached to the bottom of the half-timbered elements. Top-hung lampposts are mounted from the cover plates manually or with the help of blocks and winches, and are fixed from attached or leaning ladders.

Installation of walls of large-block buildings is carried out within the grasp after the completion of the installation of all structures of the underlying tier. Blocks, as a rule, are strapped with a two-branch sling for two mounting loops. Tall wall blocks, if they are stored in a stack in a horizontal position, are first transferred in the same position to the site, where they are transferred to a vertical position.

It is impossible to tilt the blocks directly in the stack, since if the lower edge of the block slides off, the jerk of the crane boom can lead to an accident. If, during the installation of the upper floors of the building, light blocks are slinged with a four-branch sling, feeding two blocks to the floor at the same time, then during the installation of the first block, the second is temporarily placed on the ceiling above one of the internal load-bearing walls. If two textured blocks of the outer walls are lifted, then the inner edges of the blocks must touch when lifting. A mortar bed is arranged on a cleaned base. Lighthouses are laid near the outer edge of the block at a distance of 8-10 cm from the side edges. The correctness of the installation of the top of the block is checked by mooring and sighting at the previously installed blocks. The horizontalness of the top of the block in the longitudinal direction is controlled by the rule with the level and sighting at the previously installed blocks. The correctness of the installation of the top of the lintel block is checked by measuring the distance from the mark of the top of the block to the supporting quarter of the lintel with a meter or template, and the lighthouse blocks of the inner walls - to the top of the block. The top of the pediment blocks is checked against the dock stretched along the slope of the pediment.

Minor deviations in the position of the block along the pediment are corrected by displacing it along the longitudinal axis of the wall. You cannot move bulkhead blocks along the walls, as this can cause the blocks of the lower tier to move. Installation of panels of external walls of large-panel buildings begins:

• basement walls - after installation of foundations;
• walls of the first floor - after completion of work on the underground part of the building;
• on the second and subsequent floors - after the final fixing of all structures of the underlying floor.

On the mounting horizon, two beacons are installed for each side panel at a distance of 15-20 cm from the side faces. For exterior wall panels, beacons are located near the outer plane of the building. The panel fed by the crane is stopped above the installation site at a height of 30 cm from the ceiling, after which the panel is directed to the installation site, while controlling the correct lowering of the panel into place. The correctness of the installation in place of the base of the panels of the outer walls is checked along the edge of the walls of the underlying floor.

Installation of load-bearing panels of internal walls is carried out in the same way as external ones, with the installation of two beacons. Non-bearing panels and partitions are installed directly on the mortar. When installing gypsum concrete partitions in front of the bed, a strip of roofing felt, roofing felt or other waterproofing material 30 cm wide is placed on the base; the edges of the strip bent upwards during the construction of floors protect the partition from moisture. Mortar installation and alignment of transverse wall panels is greatly facilitated if the project provides for the panel to be inserted into the joint of the outer panels. In this case, the end ribs of the outer panels serve as guides. For temporary fastening of the end of the panel, adjacent to the outer wall, it is wedged; the free end of the panels and partitions is fastened with a triangular stand, the screw device at the top of the stand makes it easier to bring the panel into the wall plane. If the panel only adjoins the interior wall panels, the adjoining end is temporarily secured with a spacer or corner clamp.

Installation of reinforced concrete shells for public buildings (transport, sports, entertainment, shopping facilities, etc.) is carried out according to two main technologies for installing precast monolithic shells:

• at ground level - on a conductor with the subsequent lifting of the whole-assembled shell to the design level using erection cranes;
• at design marks.

The main method is the installation of prefabricated shells at design elevations, which is carried out on mounting support devices or with the support of enlarged shell elements on the supporting structures of the building - walls, contour trusses, etc.

A long cylindrical shell 12x24 m in size is assembled from side elements in the form of gable prestressed beams and curved slabs of 3x12 m in size. Installation of the building frame begins with the installation of columns. Depending on the parameters of the erection crane, two options for organizing the installation are used: in the first case, the crane beams are installed immediately after the installation of the columns in a separate stream, and the installation of the shell is carried out by a crane located outside the span of the shell being mounted; in the second, the assembly is carried out by a crane moving inside the erected span of the building. After their laying, temporary tubular supports are installed under the side elements, since before the joints are monolithic they are not able to perceive bending forces from the weight of the separately lying shell elements. The enlargement of the end plates with ties is carried out at the enlargement stands. After installation of all elements, the reinforcement outlets are welded and the joints are monolithic. The cutting is done after the concrete is set at the joints of 70% of the design strength.

Installation of free-standing shells (free-standing shells mean shells of 36x36 and 24x24 m from 3x3 m slabs, the shell of which rests on four diaphragm trusses that are not structurally connected with adjacent shells) is carried out using conventional erection cranes. Such shells are collected on special devices - inventory mobile conductors. The conductor moves along the railway tracks installed on a solid foundation - concrete preparation, precast slabs, ballast layer. When erecting a building with multiple shells, the complete assembly of the conductor is performed once, and then the conductor is moved to the next cell. Installation of the shell begins with the installation of a diaphragm truss located at the end of the span, then a second truss is installed along the outer wall. The trusses are fastened together with a spacer and fastened with guy wires. After that, the conductor is assembled by installing support carts, stands, two load-bearing trusses and lattice girders. After aligning and temporarily loosening the conductor with rigid ties between the trolleys (braces - behind the columns and spacers - to the trusses), part of the girders is removed and a third contour truss is mounted, which, after alignment with spacers, is attached to the conductor. After that, the crane is moved into the span and the installation of the corner plates of the shell and then the rest of the plates in the established sequence is started. The plates are placed on the support tables of the pre-calibrated lattice girders of the conductor. After installing half of the shell slabs, the crane leaves the cell, replaces the previously removed purlins, and then puts the fourth contour truss. The remaining slabs are mounted in the same mirror sequence.

In the construction of multi-span industrial buildings covered with double-curved shells measuring 36x38 or 24 * 24 m, inventory conductors are used, moving from position to position along the rails. In the span or simultaneously in several spans, conductors are installed and then raised to the design marks, which are mesh circular structures that repeat the outlines of the shell. Contour shell trusses are installed on the columns with the help of assembly cranes. After laying prefabricated plates, which is made from the contours of the shell to the center, and adjusting their position, butt joints are welded and the seams are monolithic. After the concrete at the joints reaches 70% of the design strength, the shell is unrolled, the jig is lowered into the transport position and moved along the rails to the adjacent position.

The installation of multiwave shells 18x24 m in size from 3x6 m slabs has the peculiarity that adjacent shells rest on a common contour truss 24 m long, and along the upper belt of 18-meter contour trusses, adjacent shells are monolithic. During the construction of a two- or three-span building, installation is carried out on two or three conductors. The order of assembly and installation of conductors is the same as for free-standing shells, but the assembly procedure is different: first, the first conductor is installed, then two 18-meter diaphragm trusses are installed and fastened to it - one extreme and one middle (in a single-span building - both extreme) and a 24-meter extreme farm. Before lifting, on 18-meter farms, a running platform and elements of steel inventory formwork are installed. After installation, alignment and unfastening of the trusses, the corner zones are welded and the shell elements begin to be mounted. When erecting a multi-span building, after fixing the trusses of the first shell, the trusses of the adjacent shells are installed. In order to avoid overturning, they are fastened together with rigid struts welded in the corner zones to the embedded parts of the upper chords. Thus, it is possible to install conductors in the remaining spans. The installation of the shell begins with laying the corner plates, then the contour plates of the far row and the middle row are installed. Ordinary slabs are laid on the conductor beams. After installing the middle row slabs, a 24-meter truss is placed, and then the last row of slabs is laid, which are mounted through the installed truss. After that, the outlets of fittings and embedded parts are welded. Prior to the monolithing of the joints, the installation of the first row of slabs in an adjacent shell must be performed. The grouting of the joints begins from the corner zones and the abutment of the slabs to the 18-meter trusses, and the rest of the joints are grout in the direction from the 24-meter trusses to the arch shelter.

Shells of double positive curvature with dimensions 18x24, 24x24, 12x36 and 18x36 m are mounted in enlarged blocks assembled on stands from 3x6 or 3x12 m panels. The panels are assembled into a mounting block on the stand by welding embedded parts and fastening with temporary assembly ties. The length of the enlarged block corresponds to the span of the shell. After that, the block is installed with a crane in the design position on the pre-assembled side elements.

Byte hanging covers are a type of reinforced concrete shells. They consist of a reinforced concrete contour with a mesh of steel ropes (cables) stretched over it and prefabricated reinforced concrete slabs laid on them. The byte network consists of longitudinal and transverse steel ropes located along the main directions of the shell surface at right angles to each other. The ends of the cables are anchored by means of special sleeves in the supporting reinforced concrete contour of the shell. When installing hanging coatings, a cable-stayed network of steel ropes is pulled over the reinforced concrete contour, which ensures the design curvature of the shell. Then, prefabricated reinforced concrete roof slabs are laid along the ropes and their temporary surcharge in the form of uniform filling of the shell with a piece load, the weight of which is taken equal to the weight of the roof and the temporary load. After that, the seams between the precast casing plates are monolithic. After the concrete reaches the design strength, the temporary surcharge is removed. Thus, prestressing is created in reinforced concrete slabs, and they are included in the overall work of the coating, which reduces the deformability of the suspended structure.