CN111980165A - Large-span net rack external-expanding splicing integral jacking construction method - Google Patents

Abstract

The invention discloses a construction method for externally expanding, splicing and integrally jacking a large-span net rack, which belongs to the field of building construction, and aims to solve the technical problems of reducing the construction difficulty of a spherical shell, a cylindrical shell, a flat plate and various special-shaped stadium large-span net rack structures under complex conditions, reducing high-construction operation, improving safety and simultaneously ensuring construction quality, wherein the technical scheme is as follows: the construction method comprises the following specific steps: assembling and jacking: assembling the net rack on the ground, installing a jacking bracket when the net rack is assembled to the position of the stand, and stopping jacking when the net rack is jacked by the jacking bracket to a set height to meet the assembly of the next grid; symmetrically expanding and assembling: after the jacking operation is stopped, symmetrically expanding and assembling the completed space rigidity units from the center of the net rack, so that the net rack continuously extends to the periphery; adjusting the number and the positions of jacking points: when the net rack is expanded and spliced outwards, the number and the positions of the jacking points of the net rack are adjusted according to the calculation result; and (4) unloading and dismantling.

Description

Construction method of overall jacking of large-span grid frame with external expansion and assembly

technical field

The invention relates to the field of building construction, and is especially suitable for spherical shells, cylindrical shells, flat plates and projects with a lower chord elevation of 25m and below of various special-shaped grid frames, especially for grid structures in which welded joints, bolted ball joints and welded ball joints are mixed. Specifically, it is a large-span grid frame external expansion and assembly overall jacking construction method.

Background technique

With the construction of large-scale stadiums, theaters, and cultural and sports centers in various places, various types of large-span steel structure grids are more and more applied to building roofs. On the one hand, the steel structure grids of such projects have large spans, large volumes and high heights. On the other hand, because the grids are often erected in the center of the venue, there are often difficulties in hoisting the periphery of the hoisting machinery and high costs during construction. .

Therefore, how to reduce the construction difficulty of spherical shells, cylinder shells, flat plates and various special-shaped stadiums and large-span grid structures under complex conditions, reduce high-level work, improve safety and ensure construction quality is a technical problem that needs to be solved urgently.

SUMMARY OF THE INVENTION

The technical task of the present invention is to provide a large-span grid frame external expansion and assembly integral jacking construction method to solve how to reduce the construction difficulty of spherical shells, cylinder shells, flat plates and various special-shaped venues under the complex structure of large-span grid frames , reduce high-level work, improve safety while ensuring construction quality.

The technical task of the present invention is achieved in the following manner, the construction method for the overall jacking of the large-span grid frame is expanded and assembled, and the construction method is as follows:

Assembling and jacking: The grid is assembled on the ground, and the jacking bracket is installed when it is assembled to the stand position, and the grid frame is lifted to a set height by the jacking bracket (the jacking height is different for each time, determined according to the civil construction) to meet the next requirements. When the grid is assembled, stop the lifting work;

Symmetrical expansion and assembly: After the lifting work is stopped, the completed spatial rigidity unit will be symmetrically expanded and assembled from the center of the grid frame, so that the grid frame will continue to extend around;

Adjust the number and position of jacking points: when expanding and splicing outward, adjust the number and position of jacking points of the grid according to the calculation results;

Unloading and dismantling: Repeat assembly and jacking, symmetrically expand and assemble and adjust the number and position of jacking points until the net frame is raised to a position above the structural level. After the net frame is completed, the column top members are inserted, unloaded and removed for jacking. Installation, grid construction is completed.

As preferably, the technological process of this construction method is as follows:

S1. Preparation before construction;

S2, grid assembly;

S3, jacking point arrangement, install jacking device;

S4, quality and safety inspection;

S5, try jacking;

S6, official jacking up;

S7. External expansion and assembly and circulation improvement;

S8. Lift in place and dock the support;

S9, synchronous uninstall;

S10, remove the jacking device, and the installation is completed.

More preferably, the preparation before construction in the step S1 is as follows:

S101. Inventory the grid materials that have entered the site, classify and stack the balls and rods separately, and check the processing dimensions of the balls and rods to ensure the installation accuracy, otherwise they cannot be used;

S102. The sundries stacked on the site must be cleaned up to ensure the smooth progress of the project construction;

S103. Use MIDAS to calculate the number and position of the jacking frame according to the site conditions and structural shape, and perform stress and deformation calculation; after the grid frame is checked and calculated, if it is found that there is an overstressed rod, temporary reinforcement is performed, that is, the outer side of the rod is reinforced with a clamp ;

S104. Release the installation position of the jacking frame and the projection position of part of the lower chord ball according to the planned position. The position of the concrete structure below should be placed on the column beam position;

S105. Check the jacking equipment to ensure that the equipment operates normally during the jacking process;

S106. Check the foundation of the jacking equipment, the foundation should have sufficient strength, otherwise it should be dealt with in advance.

More preferably, the grid assembling in the step S2 is as follows:

S201. Install the lower chord plane grid, specifically including:

S20101. Align the axis and center line of the column, check the elevation with a spirit level, and correct any errors;

S20102. Install the lower string ball and rod in the central area of the grid frame to form a longitudinal plane grid; arrange the temporary fulcrum to ensure the equality of the lower string ball; when there is a requirement for arching, find the bottom of the slope on the temporary fulcrum;

S20103. Install the web rod and the upper string ball between the first units. The first cone is a small unit with one ball and four web rods. After it is in place, it is screwed into and fixed with the bottom string ball;

S20104. The second cone is a triangular cone with a ball, a chord, and two webs first, and then the other two webs are filled, and the grid frame of the first unit is installed in a cycle step by step;

S20105. Check the grid frame, grid size, longitudinal dimension and sag height of the grid frame; at the same time, check the position of the grid frame. If there is any discrepancy, adjust the position and height of the temporary fulcrum to calibrate the positioning size of the grid frame;

S202, install the upper chord inverted triangular mesh, specifically including:

S20201, starting from the side span, firstly make a triangular cone with one ball, one winding and two belly rods, and then a quadrangular pyramid with one ball, two windings and two belly rods;

S20202. Support the second inclined web bar on the lower chord ball, and tighten the upper chord bar above, so that the upper chord bar is gradually approached to the installed upper chord ball (push cone), screwed in, adjusted and tightened;

S20203. During the installation of the grid, check whether the axis of the grid is deviated from the axis of the building foundation at any time, and adjust it at any time;

S20204. Check the overall deflection of the grid frame, strictly control the size of the upper and lower chords of the grid frame, and ensure that each bolt is tightened in place;

S20205. Check the subsidence of each temporary fulcrum at any time during the installation process of the grid frame. If there is a drop, reinforce it in time.

More preferably, the mesh frame adopts a steel mesh frame, and the assembling process of the steel mesh frame is as follows:

(1) Position the temporary support point of the first lower chord grid on the ground;

(2) Complete the assembly of the first mesh lower chord on the temporary support point;

(3) Assemble a top chord ball and the web frame web bar connected to it into a whole and assemble the lower chord unit installed in place into an integral structure;

(4), assemble the lower chord member of the next cell grid;

(5), assemble a top chord ball and the web frame web rod connected to it and a top chord rod on one side into a whole and the installed bottom chord unit into an overall structure;

(6), repeat steps (4) and step (5) to continue the assembling of the remaining grid members;

(7), until the entire structure is assembled.

More preferably, in the process of determining the position of the jacking device in the step S3, it is ensured that each node ball is uniformly stressed during the jacking process, and the bottom of the jacking device is provided with a steel plate support to avoid the jacking device. Excessive pressure;

When the jacking device is on the concrete structure surface, set the support point at the position of the concrete column and beam, and determine whether it needs to be reinforced by checking calculation;

When the supporting point is not placed at the main beam, make a reserved hole in the floor in advance and deal with the ground, and at the same time, check the bearing capacity of the ground to ensure that the ground subsidence does not affect the construction quality and safety, and then install the jacking device. Go through the reserved hole and stand on the ground.

More preferably, the formal jacking in the step S6 is as follows:

S601. Use a total station to review the elevation and deformation of different azimuth points of the grid frame, and the allowable deviation of each elevation point is determined according to the construction check calculation of the grid frame;

S602. Pause for about 1.5m each time of jacking up, check the deviation of each point of the grid frame, and lift the grid frame to the predetermined elevation in stages and fix it;

S603. After being jacked up to a predetermined elevation and fixed, check the overall displacement and torsional deviation of the grid frame; when there is a large deviation, use the concrete structure as the tension point, and adjust the grid through the reverse chain;

S604. When the height is increased, the lower bracket is stressed. When the piston rod is fully extended, a support bracket is added. After the relevant bolts are tightened, the piston rod is retracted, and the upper bracket is stressed. When the piston rod is fully retracted, the lower bracket is retracted to the previous one. Move the cross bar (stressed bar) upward at the place where it can bear the force, and the horizontal bar should correspond to the position of the stress beam of the lower bracket;

S605. When dismantling, the upper bracket is stressed, the piston rod is retracted to no force, and the horizontal rod (stressed rod) is moved down. The horizontal rod should correspond to the position of the stressed beam of the lower bracket. Move the frame to the next support frame, so that the lower bracket is stressed, the upper bracket is not stressed, and a section of the support frame is removed.

More preferably, the step S7 is as follows:

S701. When the grid frame is lifted to the set height and can meet the requirements of the grid frame's expansion and assembly, stop lifting;

S702, expand and assemble the assembled micro-grid unit by hoisting; at the same time, according to the expansion size, add a lifting device according to the position determined by calculation in time;

S703. After the external expansion assembly and the installation of the jacking device are completed, try jacking again to ensure that the jacking devices installed in the front and rear are synchronized;

S704. During the process of expanding and assembling and cyclic jacking, pay attention to the installation and adjustment of cable wind ropes and knotted wire ropes; when jacking up to a height of 3 meters, in order to ensure the overall stability, add inclined supports to the jacking equipment; When jacking up to a height of 10 meters, the cable wind rope is used, and the cable wind rope cantilever angle is not less than 30 degrees, and the arrangement position is the four corners of the jacking truss.

More preferably, the lifting in place and the docking support in the step S8 are as follows:

S801. The grid frame is expanded and assembled to a predetermined range, and the jacking is stopped after it is jacked up to the support height;

S802. Review and adjust the height, displacement and torsional deviation of the grid frame, and complete the embedding work of the support rods after the adjustment is in place; at the same time, carry out the installation and elevation adjustment of the support to ensure the quality of the connection between the grid frame and the support;

S803 , after the grid frame is dropped and the support is stressed, the remaining cantilever node balls and rods are assembled until the grid frame is completely assembled.

More preferably, the synchronous unloading in the step S9 is as follows:

S901. Measure the elevation of the node in the middle of the grid before unloading;

S902. Under the control of the computer, the jacking device is lowered synchronously by 10mm each time, observe whether the jacking device is separated from the grid frame, and measure the elevation change of the middle node of the grid frame until the jacking device is completely separated from the grid frame;

In the step S10, the lifting device is removed, and the installation is completed as follows:

S1001. After removing the two sections of the jacking device, use a crane to hoist the remaining support frame as a whole and place it on the ground;

S1002. Dismantle on the ground, stack them neatly, and transport them off-site.

The large-span grid frame externally expanded and assembled integral jacking construction method of the present invention has the following advantages:

(1) The present invention successfully solves the construction problem under complex conditions of the large-span grid structure of venues. Through the application of the present invention, the project can be well controlled in terms of construction period, quality, cost and safety, and a good social benefits and economic benefits;

(2) The present invention adopts the 800*800mm standard section as the bearing device, which is convenient for installation and disassembly, and the standard section is welded with a round pipe and a flange, which is convenient for installation;

(3) The core equipment of hydraulic synchronous lifting technology is controlled by computer, which can automatically complete various functions such as synchronous lifting, load balancing, attitude correction, stress control, operation locking, process display and fault alarm. Modern advanced equipment integrating sensors and computers;

(4) The implementation of the present invention can ensure that the grid frame is assembled on the ground or in a lower space, with less high-altitude operations, reducing safety risks, and at the same time facilitating quality monitoring, which can be specific to each point and surface, reducing hidden dangers and ensuring quality;

(5) The present invention adopts the jacking method for installation, which avoids the influence of erecting scaffolds on the construction period, reduces the cost of measures, and at the same time, most of the work is done on the ground, which is almost not affected by weather such as wind and rain, which improves the work efficiency and shortens the time. construction period;

(6) For stadiums with grandstands, auxiliary rooms or basements, and grids placed on multi-storey buildings, the difficulty that the structural shape cannot be lifted as a whole at one time has been solved;

(7) The present invention reduces the cost of the project, shortens the construction period, and creates conditions for the on-time delivery of the project. The jacking process does not produce noise and all kinds of garbage, and all jacking devices can be used in a turnaround, which is in line with the concept of environmental protection; the application of the grid jacking method has received high attention in the industry, and has welcomed the observation and exchange of external units for many times. Played a good publicity role.

Description of drawings

The present invention will be further described below with reference to the accompanying drawings.

Accompanying drawing 1 is the flow chart of the construction method of large-span grid frame external expansion and assembling integral jacking;

Accompanying drawing 2 is the structural schematic diagram of node reinforcement;

Accompanying drawing 3 is the schematic diagram of support pad positioning in the steel grid assembling process;

Accompanying drawing 4 is the schematic diagram of the assembly of the first grid lower chord member in the steel grid assembling process;

Accompanying drawing 5 is the schematic diagram of the overall structure assembled with the lower chord unit installed in place in the steel mesh frame assembly process;

Accompanying drawing 6 is the schematic diagram of assembling the lower chord member of the next cell grid frame in the steel grid frame assembling process;

Accompanying drawing 7 is the schematic diagram of the overall structure assembled with the lower chord unit installed in place in the steel mesh frame assembly process;

Accompanying drawing 8 is the schematic diagram of the assembling of the remaining grid members in the steel grid assembling process;

Accompanying drawing 9 is the schematic diagram that the whole structure is assembled;

Figure 10 is a schematic diagram of the steel plate base of the jacking device;

Figure 11 is a schematic diagram of the basic treatment of the jacking device;

12 is a schematic diagram of the installation process of the jacking frame;

13 is a schematic diagram of the installation process of the oil cylinder;

Figure 14 is a schematic diagram of the cable wind rope pulling.

Detailed ways

With reference to the accompanying drawings and specific embodiments of the description, the construction method of the large-span grid frame outwardly expanding and assembling integral jacking of the present invention will be described in detail below.

Example 1:

The construction method of the large-span grid frame of the present invention is as follows:

(1) Assembling and jacking: The grid is assembled on the ground, and the jacking bracket is installed when it is assembled to the position of the stand, and the jacking bracket is used to lift the grid to a set height (the height of each jacking is different, and it is determined according to the civil construction) When the next grid assembly is satisfied, stop the lifting work;

(2) Symmetrical expansion and assembly: After the lifting work is stopped, the completed spatial rigidity unit will be symmetrically expanded and assembled from the center of the grid frame, so that the grid frame will continue to extend around;

(3) Adjust the number and position of jacking points: when expanding and splicing outward, adjust the number and position of jacking points of the grid according to the calculation results;

(4) Unloading and dismantling: Repeat assembly and jacking, symmetrical outward expansion assembly, and adjust the number and position of jacking points until the grid is raised to a position above the structural elevation, and the grid is completed. The lifting device is removed, and the grid construction is completed.

Example 2:

As shown in accompanying drawing 1, the large-span grid frame of the present invention expands and assembles the overall jacking construction method, and the technological process of this construction method is as follows:

S1. Preparation before construction; the details are as follows:

S101. Inventory the grid materials that have entered the site, classify and stack the balls and rods separately, and check the processing dimensions of the balls and rods to ensure the installation accuracy, otherwise they cannot be used;

S102. The sundries stacked on the site must be cleaned up to ensure the smooth progress of the project construction;

S103. Use MIDAS to calculate the number and position of the jacking frame according to the site conditions and structural shape, and perform stress and deformation calculation; after the grid frame is checked and calculated, if it is found that there is an overstressed rod, temporary reinforcement is performed, that is, the outer side of the rod is reinforced with a clamp , as shown in Figure 2;

S104. Release the installation position of the jacking frame and the projection position of part of the lower chord ball according to the planned position. The position of the concrete structure below should be placed on the column beam position;

S105. Check the jacking equipment to ensure that the equipment operates normally during the jacking process;

S106. Check the foundation of the jacking equipment, the foundation should have sufficient strength, otherwise it should be dealt with in advance.

S2, grid assembly; grid assembly is as follows:

S201. Install the lower chord plane grid, specifically including:

S20101. Align the axis and center line of the column, check the elevation with a spirit level, and correct any errors;

S20102. Install the lower string ball and rod in the central area of the grid frame to form a longitudinal plane grid; arrange the temporary fulcrum to ensure the equality of the lower string ball; when there is a requirement for arching, find the bottom of the slope on the temporary fulcrum;

S20103. Install the web rod and the upper string ball between the first units. The first cone is a small unit with one ball and four web rods. After it is in place, it is screwed into and fixed with the bottom string ball;

S20104. The second cone is a triangular cone with a ball, a chord, and two webs first, and then the other two webs are filled, and the grid frame of the first unit is installed in a cycle step by step;

S20105. Check the grid frame, grid size, longitudinal dimension and sag height of the grid frame; at the same time, check the position of the grid frame. If there is any discrepancy, adjust the position and height of the temporary fulcrum to calibrate the positioning size of the grid frame;

S202, install the upper chord inverted triangular mesh, specifically including:

S20201. Starting from the side span, firstly make a triangular cone with one ball, one winding and two abdominal rods, and then a quadrangular pyramid with one ball, two windings and two abdominal rods;

S20202. Support the two inclined web bars on the lower chord ball, and tighten the upper chord rod above, so that the upper chord rod is gradually approached to the installed upper chord ball (push cone), screwed in, adjusted and tightened;

S20203. During the installation of the grid, check whether the axis of the grid is deviated from the axis of the building foundation at any time, and adjust it at any time;

S20204. Check the overall deflection of the grid frame, strictly control the size of the upper and lower chords of the grid frame, and ensure that each bolt is tightened in place;

S20205. Check the subsidence of each temporary fulcrum at any time during the installation process of the grid frame. If there is a drop, reinforce it in time.

Among them, the mesh frame adopts the steel mesh frame, as shown in the attached drawings 3-9, the assembly process of the steel mesh frame is as follows:

(1) Position the temporary support point of the first lower chord grid on the ground;

(2) Complete the assembly of the first mesh lower chord on the temporary support point;

(3) Assemble a top chord ball and the web frame web bar connected to it into a whole and assemble the lower chord unit installed in place into an integral structure;

(4), assemble the lower chord member of the next cell grid;

(5), assemble a top chord ball and the web frame web rod connected to it and a top chord rod on one side into a whole and the installed bottom chord unit into an overall structure;

(6), repeat steps (4) and step (5) to continue the assembling of the remaining grid members;

(7), until the entire structure is assembled.

S3. Arrange the jacking point and install the jacking device; in the process of determining the position of the jacking device, ensure that the force of each node ball is uniform during the jacking process, and set the steel plate support at the bottom of the jacking device to avoid the jacking device. The pressure on the support surface is too large, as shown in Figure 10;

When the jacking device is on the concrete structure surface, set the support point at the position of the concrete column and beam, and determine whether it needs to be reinforced by checking calculation;

When the support point is not placed at the main beam, make a reserved hole in the floor in advance and deal with the ground, as shown in Figure 11. At the same time, check the bearing capacity of the ground to ensure that the ground subsidence does not affect the construction quality and Safety, and then put the jacking device on the ground through the reserved hole.

S4, quality and safety inspection; the details are as follows: before the grid frame is lifted, the quality and safety inspection of the assembled grid needs to be carried out. Review. In terms of safety, focus on checking the position of the jacking devices, such as jacks, cable wind ropes, computer monitoring and control systems, etc. In addition, it is also necessary to pay attention to whether other facilities hinder the lifting of the grid frame and whether the grid frame is separated from other structures.

S5. Test jacking; the details are as follows: Before the grid frame is jacked up, detailed technical and safety disclosures shall be made to all construction personnel, and the first jacking shall be started after the on-site equipment is checked correctly. Each jacking power unit starts to lift synchronously under the unified command, and the jacking control is coordinated by the wired network computer. The height of the test jacking is controlled at about 500mm, so that the assembled grid can be separated from the support point and be in a suspended state.

S6. Formal jacking: After the test jacking is completed, check in time to determine whether there is any problem. If the indicators are normal, the formal jacking can be directly carried out. The formal jacking is the same as the test jacking operation method; the details are as follows:

S601. Use a total station to review the elevation and deformation of different azimuth points of the grid frame, and the allowable deviation of each elevation point is determined according to the construction check calculation of the grid frame;

S602. Pause for about 1.5m each time of jacking up, check the deviation of each point of the grid frame, and lift the grid frame to the predetermined elevation in stages and fix it;

S603. After being jacked up to a predetermined elevation and fixed, check the overall displacement and torsional deviation of the grid frame; when there is a large deviation, use the concrete structure as the tension point, and adjust the grid through the reverse chain;

S604. When the height is increased, the lower bracket is stressed. When the piston rod is fully extended, a support bracket is added. After the relevant bolts are tightened, the piston rod is retracted, and the upper bracket is stressed. When the piston rod is fully retracted, the lower bracket is retracted to the previous one. Move the cross bar (stressed bar) upward at the place where it can bear the force, and the horizontal bar should correspond to the position of the stress beam of the lower bracket;

S605. When dismantling, the upper bracket is stressed, the piston rod is retracted to no force, and the horizontal rod (stressed rod) is moved down. The horizontal rod should correspond to the position of the stressed beam of the lower bracket. Move the frame to the next support frame, so that the lower bracket is stressed, the upper bracket is not stressed, and a section of the support frame is removed. The lifting, installation, installation and conversion process of the jacking frame are shown in Figures 12 and 13.

Among them, the lifting process is as follows:

①. After the construction of the concrete structure is completed, install the jacking bracket according to the plane position of the jacking point;

②. The internal grid of the stand is assembled on the ground. After the overall assembly of the grid is completed, the size and welding quality of the grid must be self-checked. After it is correct, the lifting work can be carried out. When the height meets the next grid pairing, the lifting is stopped, and the grids are assembled and welded;

③. Start to lift, lift to 3.5m, and extend the rod outward;

④. After the installation of the rod is completed, continue to lift 7.1m and extend the rod outward;

⑤ After the installation of the rod is completed, continue to lift 9.4m and extend the rod outward. At the same time, the number and position of jacking points are adjusted;

⑥. Repeat steps ①-⑤. After jacking up to the position above 20.6m of the support, install the support, and drop the jacking frame to make the support stress; after the support is stressed and the structure is stable, use a car to hoist. Overhang part of the mesh frame until the mesh frame is complete.

S7. External expansion assembly and cyclic promotion; the details are as follows:

S701. When the grid frame is lifted to the set height and can meet the requirements of the grid frame's expansion and assembly, stop lifting;

S702, expand and assemble the assembled micro-grid unit by hoisting; at the same time, according to the expansion size, add a lifting device according to the position determined by calculation in time;

S703. After the external expansion assembly and the installation of the jacking device are completed, try jacking again to ensure that the jacking devices installed in the front and rear are synchronized;

S704. During the process of expanding and assembling and cyclic jacking, pay attention to the installation and adjustment of cable wind ropes and knotted wire ropes; when jacking up to a height of 3 meters, in order to ensure the overall stability, add inclined supports to the jacking equipment; When jacking up to a height of 10 meters, the cable wind rope is used. The angle of the cable wind rope is not less than 30 degrees. The arrangement position is the four corners of the jacking truss. There are connecting plates on the standard section of the jacking frame to connect the steel support or the cable wind rope. Figure 14 shows.

S8. Lift in place and dock the support; the details are as follows:

S801. The grid frame is expanded and assembled to a predetermined range, and the jacking is stopped after it is jacked up to the support height;

S802. Review and adjust the height, displacement and torsional deviation of the grid frame, and complete the embedding work of the support rods after the adjustment is in place; at the same time, carry out the installation and elevation adjustment of the support to ensure the quality of the connection between the grid frame and the support;

S803 , after the grid frame is dropped and the support is stressed, the remaining cantilever node balls and rods are assembled until the grid frame is completely assembled.

S9. Uninstall synchronously; the details are as follows:

S901. Measure the elevation of the node in the middle of the grid before unloading;

S902. Under the control of the computer, the jacking device is lowered synchronously by 10mm each time, observe whether the jacking device is separated from the grid frame, and measure the elevation change of the middle node of the grid frame until the jacking device is completely separated from the grid frame;

S10, remove the jacking device, and the installation is completed. details as follows:

S1001. After removing the two sections of the jacking device, use a crane to hoist the remaining support frame as a whole and place it on the ground;

S1002. Dismantle on the ground, stack them neatly, and transport them off-site.

The environmental protection measures are as follows:

1) During the assembling process of the grid frame, the welding operation surface should be well ventilated and replaced to prevent the harm of smoke and dust to the operators;

2) Closed and container management should be carried out when spraying paint on the grid to prevent air pollution. The amount of paint thinner should be strictly controlled, and the remaining part should be recycled in time to prevent secondary pollution;

3) The roads entering and leaving the construction site should be cleaned and sprinkled in time, and the tires and body of the transport vehicle should be cleaned before leaving the site;

4) The components should be stored in partitions according to the type and installation order, and should be flat, padded, dry, and free of water to prevent the material from rusting.

Specific implementation cases:

1) The jacking process was adopted in the Beijing University of Chemical Technology Gymnasium project to avoid the erection of full-scale scaffolding and save the cost of measures. It is estimated that the cost is saved by 950,000 yuan. The installation of the jacking process can reduce the investment of large crawler cranes. Only one 25t crawler crane is put into the project site, and the cost of reducing the mechanical shift is estimated to be 250,000 yuan.

2) The Nanning Real Estate Service Building project avoids the erection of full-scale scaffolding, saving 80,000 yuan in the rental fee of scaffolding steel pipes, and 10,000 yuan in erection and dismantling costs. The total saving of scaffolding measures is 90,000 yuan. The construction period is shortened by 25 days, the cost of each machine shift is 2,000 yuan, and there are 3 machines per day, reducing the total cost of mechanical shifts by 150,000 yuan. And achieved good social benefits.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features thereof can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention. scope.

Claims (10)

1. The construction method for externally expanding, splicing and integrally jacking the large-span net rack is characterized by comprising the following steps of:

assembling and jacking: assembling the net rack on the ground, installing a jacking bracket when the net rack is assembled to the position of the stand, and stopping jacking when the net rack is jacked by the jacking bracket to a set height to meet the assembly of the next grid;

symmetrically expanding and assembling: after the jacking operation is stopped, symmetrically expanding and assembling the completed space rigidity units from the center of the net rack, so that the net rack continuously extends to the periphery;

adjusting the number and the positions of jacking points: when the net rack is expanded and spliced outwards, the number and the positions of the jacking points of the net rack are adjusted according to the calculation result;

unloading and dismantling: repeatedly assemble and jacking, the symmetry expands outward and assembles and adjust jacking point quantity and position, after the rack rises to above the position of structure elevation, the rack is accomplished the back and is inlayed the post top member, uninstallation and demolish jacking device, and the rack construction is accomplished.

2. The large-span net rack outward-expanding splicing integral jacking construction method according to claim 1, characterized in that the construction method comprises the following specific process flows:

s1, preparation before construction;

s2, assembling net racks;

s3, arranging jacking points, and installing a jacking device;

s4, quality and safety inspection;

s5, trial jacking;

s6, formally jacking;

s7, outward expanding assembly and circular lifting;

s8, lifting to the right and butting the support;

s9, synchronous unloading;

and S10, removing the jacking device, and finishing the installation.

3. The large-span net rack externally-expanding, assembling and integral jacking construction method according to claim 2, wherein the preparation before construction in the step S1 is as follows:

s101, counting the net rack materials which have entered the field, respectively stacking balls and rods in a classified manner, and checking the processing sizes of the balls and the rods;

s102, cleaning up sundries stacked on site to ensure smooth construction;

s103, calculating the number and the positions of the jacking frames by using MIDAS according to the site condition and the structure appearance, and performing stress and deformation accounting; after the net rack is checked and calculated, if the super-stress rod is found, temporary reinforcement is carried out, namely, the outer side of the rod piece is reinforced by a clamp;

s104, releasing the mounting position of the jacking frame and the projection position of part of the lower chord ball according to the position of the scheme, and positioning the position of the lower chord ball with the concrete structure at the position of the column beam;

s105, checking jacking equipment to ensure that the equipment runs normally in the jacking process;

s106, checking the foundation of the jacking equipment, wherein the foundation should have enough strength.

4. The large-span net rack outward-expanding assembling integral jacking construction method according to claim 2, wherein the net rack assembling in the step S2 is as follows:

s201, installing a lower chord plane net rack, and specifically comprising:

s20101, centering a column axis and a center line, rechecking elevation by using a level gauge, and correcting errors;

s20102, forming a longitudinal plane grid by a lower chord ball and a rod in the central area of the installation net rack; arranging temporary supporting points to ensure the equality of the lower string ball; finding out the slope bottom on the temporary pivot when an arching requirement exists;

s20103, mounting web members and an upper chord ball between first units, wherein a first cone is a small unit with one ball and four web members, and is screwed and fixed with a lower chord ball after being in place;

s20104, starting the second cone to be a triangular cone which is firstly provided with a ball, a chord and two web members, then filling the other two web members, and gradually circularly installing the net rack of the first unit;

s20105, checking the net rack, the grid size and the longitudinal size and rise of the net rack; meanwhile, the position of the net rack is checked, and if the net rack is in and out, the position and the height of the temporary fulcrum are adjusted to calibrate the positioning size of the net rack;

s202, installing an upper chord inverted triangular grid, and specifically comprising:

s20201, starting from the side span, firstly forming a triangular pyramid of the first sphere-first upper chord second web member, and then forming a quadrangular pyramid of the first sphere-second upper chord second web member;

s20202, supporting the two diagonal web members on the lower chord ball, and tensioning the upper chord member above to enable the upper chord member to be gradually close to the mounted upper chord ball to be screwed, adjusted and fastened;

s20203, in the installation process of the net rack, whether the axis of the net rack deviates from the axis of the building foundation is checked at any time, and the adjustment is carried out at any time;

s20204, checking the integral deflection of the net rack, strictly controlling the sizes of the upper chord and the lower chord of the net rack, and ensuring that each bolt is screwed in place;

s20205, the net rack is inspected at any time in the installation process for the sinking condition of each temporary supporting point, and if the sinking condition exists, the net rack is reinforced in time.

5. The large-span net rack outward-expanding assembling integral jacking construction method according to claim 4, wherein the net rack is a steel net rack, and the assembling process of the steel net rack is as follows:

(1) positioning a first lower chord grid temporary supporting point on the ground;

(2) assembling the first grid lower chord member on the temporary supporting point;

(3) assembling an upper chord ball and a net rack web member connected with the upper chord ball into a whole and assembling a lower chord unit in place into an integral structure;

(4) assembling a lower chord member of the next unit grid frame;

(5) assembling an upper chord ball, a net rack web member connected with the upper chord ball and an upper chord member on one side into a whole and assembling a lower chord unit in place into an integral structure;

(6) repeating the step (4) and the step (5) to continue assembling the other grid components;

(7) and assembling the whole structure.

6. The construction method for the outward-expanding, assembling and integral jacking of the large-span net rack according to claim 2, wherein in the step of determining the position of the jacking device in the step S3, each node ball is uniformly stressed in the jacking process, and a steel plate support is arranged at the bottom of the jacking device;

when the jacking device is arranged on the concrete structure surface, the supporting points are arranged at the concrete columns and the concrete beams, and whether reinforcement is needed or not is determined through checking calculation;

when the supporting point is not placed at the main beam, a reserved hole is made before the floor slab is lifted, the ground is processed, meanwhile, the bearing capacity of the ground is checked, it is ensured that the ground settlement can not affect the construction quality and safety, and then the jacking device penetrates through the reserved hole to stand on the ground.

7. The construction method for the outward-expanding, splicing and integral jacking of the large-span net rack according to claim 1, wherein the formal jacking in the step S6 is as follows:

s601, rechecking the elevations and deformation conditions of different square points of the net rack by using a total station, and determining the allowable deviation of each elevation point according to the construction check calculation of the net rack;

s602, pausing each time of jacking for about 1.5m, checking the deviation of each point of the net rack, jacking the net rack to a preset elevation in times and then fixing;

s603, after the net rack is jacked to a preset elevation and fixed, checking the integral displacement and torsion deviation of the net rack; when large deviation exists, a concrete structure is used as a pulling node, and chain inversion adjustment is carried out;

s604, the lower bracket is stressed when the piston rod is heightened, a section of support frame is added when the piston rod is completely extended out, the piston rod retracts after the related bolt is screwed, the upper bracket is stressed, when the piston rod retracts completely, the lower bracket retracts to a position capable of being stressed, the cross rod is moved upwards, and the position of the cross rod corresponds to that of a stress beam of the lower bracket;

s605, when the upper bracket is stressed during dismantling, the piston rod retracts to be not stressed, the cross rod is moved downwards, the position of the cross rod is corresponding to that of the stress beam of the lower bracket, the piston rod extends out, the lower bracket is moved to the next support frame, the lower bracket is stressed, the upper bracket is not stressed, and a section of support frame is dismantled.

8. The large-span net rack externally-expanding assembling integral jacking construction method according to claim 2, wherein the externally-expanding assembling and cyclic lifting in the step S7 are as follows:

s701, stopping jacking when the net rack is jacked to a set height and the requirement of outward expansion and assembly of the net rack can be met;

s702, carrying out outward expansion assembly on the assembled miniature grid units through hoisting; meanwhile, according to the external expansion size, a jacking device is added at a determined position in time according to calculation;

s703, after the external expansion assembling and jacking devices are installed, performing trial jacking again to ensure that the jacking devices installed front and back are synchronous;

s704, paying attention to installation, adjustment and application of the guy rope and the tied steel wire rope in the processes of outward expanding assembly and circulating jacking; when the lifting device is lifted to the height of 3 m, the inclined support is added to the lifting device to ensure the integral stability; when the lifting is carried out to the height of 10 meters, the guy cables are adopted, the cable-stayed angle of the guy cables is not less than 30 degrees, and the arrangement positions are four corners of the lifting truss.

9. The construction method for the outward-expanding, assembling and integral jacking of the large-span net rack according to claim 2, wherein the lifting in place and the butt joint of the support in the step S8 are as follows:

s801, expanding and assembling the net rack to a preset range, and stopping jacking after jacking to the elevation of the support;

s802, rechecking and adjusting the elevation, the displacement and the torsional deviation of the net rack, and completing the support rod piece embedding work after the adjustment is in place; simultaneously, the installation and elevation adjustment of the support are carried out, so that the butt joint quality of the net rack and the support is ensured;

and S803, after the net rack falls down and the support is stressed, assembling the residual overhanging node balls and the rod pieces until the net rack is completely assembled.

10. The construction method for the outward-expanding, splicing and integral jacking of the large-span net rack according to claim 2, wherein the synchronous unloading in the step S9 is as follows:

s901, measuring the elevation of the middle node of the net rack before unloading;

s902, synchronously descending the jacking device by 10mm each time under the control of a computer, observing whether the jacking device is separated from the net rack, and measuring the elevation change condition of the middle node of the net rack until the jacking device is completely separated from the net rack;

and (S10) removing the jacking device, wherein the installation is completed as follows:

s1001, after the two sections of the jacking devices are disassembled, integrally and horizontally hanging the rest support frames on the ground by using a crane;

s1002, dismantling the steel pipe from the ground, stacking the steel pipe neatly and transporting the steel pipe to the outside of the field.

Images