CN111456454A - Steel net rack construction method - Google Patents

Abstract

The invention relates to a steel truss construction method of a large-span reticulated shell structure, which further improves the assembly quality and the construction progress. The method comprises the steps of firstly installing a G1 shaft middle support steel structure project, starting a roof net rack starting span from a gable position, forming a stable structure system after the gable starting net rack is completed, enabling the overall strength, rigidity and stability of the starting net rack to meet requirements, then respectively folding the starting net rack from two sides to the G1 shaft middle support direction, carrying out construction on the rest part of the net rack by a crane matched small unit high-altitude bulk method, and pushing the net rack from the n shaft to the 1 shaft until the installation of a main net rack is finished. The method improves the assembling precision of the net rack, the construction quality of the net rack and the whole construction speed, ensures the safety of the structure under the construction working condition, and is worthy of popularization and application.

Description

Steel net rack construction method

Technical Field

The invention relates to a steel net rack construction method, in particular to a steel net rack installation construction method of a large-span reticulated shell structure.

Background

The assembly engineering quantity of the field net rack is large, the assembly quality and speed directly influence the construction progress of the whole steel net rack, in addition, for the net rack with larger span, the starting difficulty is higher, and the integral strength, rigidity and stability of the starting net rack and the integral bearing capacity and rigidity stability of the net rack support frame are very critical.

In the traditional construction method, when the net rack starts, one end of the net rack generally faces to two ends or the middle of the net rack faces to two ends, and the method has low installation and positioning accuracy and has certain influence on the forming of the upper net rack; the traditional construction method is to expand and assemble the bearing from two sides to establish a stress system, and the stress system of the method is easy to exceed the design range and is not beneficial to the accurate forming of the net rack; the traditional construction method adopts single-side folding, the condition that the large-span construction is not consistent with the design is easy to occur, the construction safety is further influenced, and a pulling and fixing measure is required to be adopted in time during the single-side folding, so that the construction process is complex.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a steel truss construction method of a large-span reticulated shell structure, so as to further improve the assembly quality and the construction progress.

In order to solve the technical problems, the invention adopts the technical scheme that:

a steel truss construction method comprises the following steps:

s1: firstly, mounting a support steel structure in the middle of a G1 shaft in the mounting sequence of mounting n-3 shaft steel columns to 3 shaft steel columns;

s2: starting the construction of the net rack,

taking an n-axis intersection A axis and a W axis near a gable as starting unit areas, and mounting a gable bottom unit by using a support and a temporary support of the gable;

secondly, hoisting the 1 st section of unit net rack and the 1 st' section of unit net rack on two sides of the gable in place, and then hoisting two roof net racks corresponding to the unit net racks in place;

step three, after the gable 1 st section unit net rack and the 1' st section unit net rack are hoisted in place, the crane does not loosen the hook, the net racks are observed by a theodolite and a leveling instrument, after the verticality and the levelness of the gable unit net rack are adjusted, the junction of the gable and the roof net rack is immediately sewed, and wind ropes are pulled inside and outside;

hoisting a2 nd section unit net rack and a second 2 ' section unit net rack of the gable in place, wherein the 2 nd section unit net rack is adjacent to the 1 st section unit net rack, and the second 2 ' section unit net rack is adjacent to the second 1 ' section unit net rack;

step five, respectively connecting the gable section 2 unit net rack and the gable section 2 'unit net rack with the section 1 unit net rack and the gable section 1' unit net rack, observing the net racks by using a theodolite and a leveling instrument, adjusting the verticality and the levelness of the net racks, and pulling the net racks inside and outside to fix the net racks by wind ropes;

step six, repeating the step four and the step five, continuously hoisting the remaining adjacent unit net racks in the middle of the gable in place,

step seven, respectively connecting the hoisted gable unit net racks with the in-place roof net racks on two sides, and pulling the wind ropes inside and outside to fix the wind ropes;

step eight, installing the gable unit net racks row by row upwards, and respectively expanding grids towards the axis A and the axis W to the axis n-3;

step nine, the n-1 to n-axis roof net racks are respectively expanded towards the middle and assembled towards the middle in a step shape;

step ten, when the net rack on the side of the shaft A is expanded to a shaft G1, hoisting the small grid units assembled on the ground to a support seat in the middle of the shaft G1 of the shaft n-3 shaft in place;

step eleven: the grid small unit net rack is connected with the starting cross net rack, so that the middle support and the starting cross net rack are stressed together, and the starting net rack is installed;

and S3, forming a stable structure system after the net rack is started, and performing construction by matching a crane with a small-unit high-altitude bulk loading method on the rest roof net rack, and propelling the roof net rack from the n shaft to the 1 shaft until the main net rack is completely installed.

Preferably, the G1 shaft middle support steel structure comprises an upper section of lattice column, a lower section of lattice column and a truss girder, and the upper section of lattice column and the lower section of lattice column are independently assembled on the ground; the construction method comprises the following steps:

firstly, hoisting an n-3 shaft lower section lattice column, adjusting the verticality of a steel column, and connecting the steel column with the ground through a column bottom plate and foundation bolts;

hoisting an upper section of lattice column of the n-3 shaft, temporarily connecting the upper section of lattice column with a lower section of lattice column through a process connection lug plate, setting a cable rope to fix a steel column, correcting the verticality of the steel column, and welding and connecting the steel column through carbon dioxide arc welding;

step three and step four, respectively repeating step one and step two to hoist the n-5 shaft lattice column;

hoisting the truss girder in the middle of the n-5 shaft to the n-3 shaft, and splicing the truss girder and the upper section of latticed column into a whole by using an installation bolt;

and step six, mounting the latticed columns and the truss girders of the rest part of the n-5 to 3 shafts until the whole middle support is mounted.

Preferably, the high-altitude bulk method construction method in step S3 includes the steps of:

step one, a lower chord plane net rack is installed,

installing the support of the first span in place, aligning the axis and the central line of the support, and aligning the elevation by using a level gauge; installing a first span lower chord ball and a first span lower chord rod to form a longitudinal plane grid; mounting a web member and an upper chord ball of the first bay, and then mounting an upper chord member of the first bay;

step two, installing an upper chord inverted triangular grid,

the second unit of the net rack is assembled by adopting a continuous installation method, each small assembly unit for installing the net rack is formed by a triangular pyramid which is assembled on the ground, and the small assembly unit comprises an upper chord ball, an upper chord and two web diagonal rods;

firstly installing a lower chord from the support, and simultaneously installing a lower chord from the first span of the lower chord to form a first square grid, screwing a first node ball in, and sealing the first grid of the lower chord;

installing an inverted triangular pyramid, hanging the small splicing unit into the field, supporting the two diagonal rods on the lower chord ball, tensioning the upper chord rod above the lower chord ball to enable the upper chord rod to gradually approach the installed upper chord ball and screw in the upper chord ball; then the diagonal rods are screwed into the lower chord ball holes and tightened, and the other diagonal rod can be temporarily left empty; continuously installing a lower chord ball and a rod, screwing one rod into an original lower chord ball screw hole, connecting and screwing one ball with the other oblique rod at the front edge of installation, installing the transverse lower chord in place, and screwing two ends of the transverse lower chord ball into the balls to form a second grid seal of the lower chord;

the small splicing units are continuously installed according to the process, and the longitudinal upper chord is installed between the two inverted triangular cones to connect the two inverted triangular cones into a whole. Gradually advancing, installing a longitudinal upper chord member when each group of inverted triangular cones are installed, screwing in two ends of the upper chord member by using bolts, and enabling the upper chord of the net rack to form a closed square grid; the net frames are gradually arranged on the support to form a series of longitudinal inverted triangular pyramid net frames;

step three, installing a lower chord regular triangular grid

After the net rack is provided with the inverted triangular pyramid grid, the regular triangular pyramid grid is arranged, the lower chord ball and the rod are arranged, and the rod is screwed into the bolt hole of the support in a ball-rod mode of the lower chord ball and the lower chord rod; installing a transverse lower chord to enable the ball and the rod to form a closed square grid; or a ball-two-rod form is adopted, namely the lower chord ball and two mutually vertical lower chords are simultaneously installed to form a closed square grid;

installing a side inclined web member, positioning a single rod in place and screwing in;

continuously installing the other side diagonal web member, and screwing the lower chord ball and the upper chord ball into two sides of the diagonal web member to complete a group of right triangular pyramid grids; gradually installing towards one side until the support is reached;

after finishing one regular triangular pyramid, installing and checking the dimension error of the upper chord square grid, gradually adjusting and fastening the bolt;

and step four, mounting a support.

The construction method of the large-span steel net rack provided by the invention comprises the steps of firstly installing a G1 shaft middle support steel structure project, starting a roof net rack starting span from a gable position, forming a stable structure system after the gable starting net rack is finished, meeting the requirements on the overall strength, rigidity and stability of the starting net rack, and then respectively folding the starting net rack from two sides to the G1 shaft middle support direction, thereby being beneficial to improving the construction quality and the construction speed of the net rack on the whole. The rest part of the net racks are constructed by a crane matched small unit high-altitude bulk loading method, and are pushed from the n shaft to the 1 shaft until the main net rack is completely installed, so that the assembling precision of the net racks is improved.

In the construction method, double L types are symmetrically and accurately positioned from two ends of a gable to the middle of the gable for starting and installation (the processing precision of a rod piece is within +/-1 mm), the assembly and the connection are realized, the accurate installation and the positioning of the latticed shell are facilitated through multipoint positioning, the rod piece is timely and multipoint adjusted in the process, the installation precision is improved, a foundation is laid for forming an upper net rack, the grid small-unit net rack at the first support is connected with a starting cross-net rack, the middle support and the starting cross-net rack are stressed together to form a stable structure system, the molding of the latticed shell is ensured, the safety of the structure under the construction working condition is also ensured, the single-arch latticed shell bilateral folding process is adopted, the grid at the middle support and the installed latticed shell establish a stress system, the control and stress conversion of the molding of the latticed shell are facilitated, the establishment of a middle positioning fulcrum reduces corresponding measures which are established for ensuring the stability of the structure system in the construction process, the.

Drawings

Fig. 1 is a plan view of the steel net cage according to the present invention.

Fig. 2 is an elevation view of the steel structure of the mid-span support.

Fig. 3-13 are schematic views of the steps of installation and construction of the net rack of the present invention.

Fig. 14 is a schematic sectional view of the steel net cage according to the present invention after completion.

Detailed Description

The invention further illustrates the claimed solution by a relatively specific example.

The steel structure subsection described in this embodiment is composed of two sub projects, namely: roofing barrel casing net rack structure project and middle support steel structure project.

The grid structure is in a quadrangular pyramid double-layer three-center cylindrical surface latticed shell structure, multipoint supporting is carried out on the periphery of a lower chord and a support in the middle, the seismic intensity is 8 degrees, an earthquake is designed for a second group, the field belongs to the class III, the defense class is the class C, the structural design life is 50 years, a bolt-sphere connection mode is adopted, the external dimension of the grid is 175m × 162m, the external dimension of the grid is 56.167 m, the highest point of the upper chord of the grid is 56.167 m, the top elevation of an embedded part is +8 m, the horizontal projection area of the grid is 28350, the expansion area of the grid (including the gable area) is about 53000 square meters.

As shown in fig. 1. The main technical parameters are (unit: meter):

the anticorrosion requirement is as follows: 1. all steel products need to be subjected to sand blasting for rust removal, and the quality grade of the rust removal reaches Sa2.5 grade specified in the Steel product surface rust grade and the rust removal grade before coating (GB/T8923). 2. After rust removal, the net rack rod piece is welded and coated with two dry paint films of epoxy zinc-rich primer, two dry paint films of epoxy mica iron intermediate paint and polyurethane finish paint, wherein the thicknesses of the two dry paint films are 80 mu m, and the color of the primary dry paint film of the polyurethane finish paint is 80 mu m.

Middle support steel structure project division:

1. summarizing, the steel structure of the middle bracket is positioned on a G1 shaft (between the G shaft and an H shaft), and the steel frame system (see figure 2) consists of six lattice columns of 3 shafts, 6 shafts, 10 shafts, 14 shafts, 18 shafts and 20 shafts and truss girders, and the main technical parameters are (unit: meter):

the anticorrosion requirement is as follows: 1. all steel products need to be subjected to sand blasting for rust removal, and the quality grade of the rust removal reaches Sa2.5 grade specified in the Steel product surface rust grade and the rust removal grade before coating (GB/T8923). 2. After rust removal, the thickness of two dry paint films of the welded ball-coated epoxy zinc-rich primer of the net rack rod piece is 80 mu m, the thickness of two dry paint films of the epoxy mica iron intermediate paint is 160 mu m, and the thickness of one dry paint film of the polyurethane finish paint is 80 mu m.

The overall construction sequence is as follows:

the overall sequence of the engineering construction is as follows: firstly, installing a G1 shaft middle support steel structure project, wherein the installation sequence is as follows: and (4) mounting the 20-shaft steel column → 3-shaft steel column in the direction. The roof truss starts to span from the 23-axis gable position. The installation sequence of the net rack is as follows: and (5) installing a 23-shaft starting gable net rack → installing a 23-1-shaft net rack roof.

Firstly, mounting a middle support steel structure:

the middle support steel structure comprises lattice columns and truss girders, the total weight of the structure is 754.187 tons, and the weight of the heaviest lattice column is 83.6 tons; the truss girder has the maximum span of 31.6 meters and the weight of 53 tons, the frame girder and the secondary girder are composed of H-shaped steel, the oblique web members and the support rods are composed of ¢ 219 × 16 round steel tubes, and the material is Q345B. The middle size of the cross section is 5m by 5m, and after the whole body is hoisted, the height of the top surfaces of the steel beams and the columns is 42.339 m.

1. Lattice column hoist

(1) General overview of the Structure

There are six lattice columns, namely: the number of the column is No. 1-6, each column comprises four □ 700x 16 box-shaped columns, oblique web members and other members, the length of the column is 24.353 meters, and the elevation of the top of the column is 42.395 meters. The total weight is about 83.6 tons. The processing and transportation are divided into two sections in a processing plant, and the two sections are spliced on a construction site.

(2) Selection of hoisting equipment

According to the construction site, the weight of the component, the lifting height and the condition of the field operation surface, the lattice column is a steel column, and an upper section and a lower section of independent ground are adopted for splicing;

the lower section post contains spare parts such as stand, little crossbeam, column brace, oblique web member, and the piecing together into holistic lattice post makes it to form a stable geometry invariance component, and the post is long 12.22 meters, and the dead weight is about 42 tons, and the capital elevation is: 32.22 m, hoisting integrally; and hoisting the lower section column from the ground to the installation position by adopting a QAY350 type truck crane.

The upper section column and the lower section column comprise upright columns, small cross beams, column braces, diagonal web members and other parts, and are spliced into an integral lattice column, and the top elevation of the column is 42.339 m; the hoisting of the upper section column can meet the requirement by adopting a 500-ton truck crane.

The maximum part weight making up the lattice column is 7.062 tons. And the assembly platform is manufactured on site, and the height is 1.5. And (3) assembling the components on the ground by adopting a 50-ton automobile crane.

Lattice column hoisting process: preparation work before hoisting → field leveling, rolling → bed-jig manufacturing → inspection levelness → lattice column transportation → steel column on-site assembling → connecting plate bolt positioning → inspection perpendicularity → steel column butt welding → secondary inspection of steel column perpendicularity → position elevation retest → integral hoisting → fixing → inspection of steel column perpendicularity → foundation bolt tightening → welding → quality inspection, acceptance and acceptance → secondary casting.

2. Truss girder

(1) The structure is characterized in that: the truss girder of this embodiment is a steel girder, and the maximum span is 31.6 meters, and the space truss system that comprises HN700X300X13X24, HW400X400X13X21 main, secondary beam and HW 250X 9X 14, phi 219X 16 web members, oblique web members, the total weight is 754.187 tons. The maximum span is 31.6 meters, the length of the longest truss beam is 24.228 meters, the weight of the whole truss beam is about 53 tons, and the installation height (the upper surface of the truss beam) is about 42.339 meters.

(2) Selection of hoisting equipment

Two creep 300K type truck cranes are selected for hoisting operation by the hoisting equipment for site structure construction.

The truss girder comprises a primary girder, a secondary girder, a diagonal web member and the like, is integrally assembled and welded on the ground to form a stable geometric invariant, and can enter an integral hoisting stage after flaw detection is qualified and paint is coated.

Hoisting the truss girder: preparation work before hoisting → field leveling, rolling → jig frame making → levelness inspection → steel beam transportation → steel beam on-site assembling → high-strength bolt preliminary screwing → steel beam deflection inspection → high-strength bolt re-screwing → steel beam joint reinforcement → high-strength bolt final screwing → position elevation re-measurement → integral hoisting → fixation → steel beam verticality inspection → preliminary screwing → final screwing → welding → quality inspection and acceptance.

3. Steel column and steel beam hoisting

After the steel column and the steel beam enter the site, lifting lugs are arranged on the steel column side plate and the steel beam upper wing plate, and the position is confirmed through calculation.

And selecting a site in a construction site for splicing the lattice column and the main truss beam. And leveling, rolling and hardening the ground, then making a jig frame, and building a brick foundation under the jig frame. The elevation of the top surface of the jig frame is plus 1.50 meters, so that overhead welding is facilitated. The bed-jig is composed of 4H-shaped steels with the length of 7 meters and the length of 200X 200, and every two H-shaped steels support one section of steel beam and column. 4H-shaped steel must be on same horizontal plane, check with the level appearance, if uneven with backing plate pad to the level to guarantee same horizontal plane.

The steel column and the steel beam are spliced on the ground and cannot be directly placed at the splicing position, secondary transportation is needed, the steel column and the beam component are lifted to the upper surface of the finished jig frame by 25 tons of steam, and the levelness (verticality) of the steel beam is measured by a level gauge. The steel beam ground splicing adopts 10.9-grade large hexagon head high-strength bolts (M30 x 115) for connection, and the installation of the high-strength bolts is strictly carried out according to the requirements of GB 50205-2001 'acceptance criteria for construction quality of steel structure engineering'.

The steel column and steel beam mounting process comprises the following steps:

the first step is as follows: firstly, hoisting a latticed column at the lower section of a No. 6 column (20-shaft), popping a column center line on a steel column side plate, and correcting the size of the center line to ensure that the size of the center line is within an error range. After the steel column is hoisted to the elevation position, the two theodolites are used for aligning the steel column from two directions at 90 degrees, the verticality of the steel column is adjusted by utilizing the leveling bolt, the steel column is inserted into the column bottom plate by using the wedge iron after the verification is finished, the steel column is fixed by spot welding, and the nut on the foundation bolt is screwed.

The second step is that: hoisting 20 shaft upper section lattice columns, temporarily connecting the lower sections with the technical connection lug plates, arranging cable ropes to fix the steel columns, correcting the verticality of the steel columns, and welding and connecting the steel columns by carbon dioxide arc welding.

The third step and the fourth step: according to the first step and the second step, 18-shaft latticed columns (No. 5 columns) are hoisted.

The fifth step: and hoisting the truss girder between 18-20 shafts. Eight workers (also called observers) stand by on the operating platforms at the beam column connecting portions on the 18-axis and 20-axis shafts, respectively. After the steel beam is lifted, four workers control the position of the steel beam by using a cable rope on the ground, after the steel beam is lifted to a designed position and is in place, eight workers on the steel column quickly splice the beam column into a whole by using mounting bolts, and after all bolt holes are aligned to be correct, the beam column nodes are immediately connected by using high-strength bolts. At the moment, the middle support No. 5 column, the middle support No. 6 column and the truss girder steel structure form a stable geometric invariant system.

And a sixth step: and according to the first step to the fifth step, mounting the steel structure from the No. 4 column (14 shaft) to the No. 1 column (3 shaft) until the whole middle support steel structure is hoisted. Four electric welders then performed the welding of the steel structure joints.

The installation sequence is as follows: and (3) sequentially mounting the main frame beams from the 20-shaft-18-shaft steel column → 18-shaft-14-shaft steel column → 14-shaft-10-shaft steel column → 10-shaft-6-shaft steel column → 6-shaft-3-shaft steel column until the mounting is finished.

Second, net rack installation

The starting net rack spans from the 23-axis gable part, is respectively folded from the W-axis direction and the A-axis direction to the G1-axis middle support direction, and adopts a mounting method of small piece hoisting high-altitude bulk loading. After the gable starting net rack is finished, a stable structure system is formed, the rest part of net racks are subjected to construction by matching a crane with a small unit high-altitude bulk method, and the net racks are pushed from the 23 shaft to the 1 shaft until the main net rack is completely installed.

In order to ensure the stability of the net rack in the installation process, firstly, the unconnected parts of the gable net racks close to the A axis and the W axis are connected by the technical steel pipes, and after the whole starting cross-net rack is installed, the whole starting cross-net rack is dismantled; secondly, because this engineering rack structure supports for interior chord support, and rack outer chord adopts interim steel pipe to support, along with the continuous rising of rack, the installation of both sides shell rack is the stairstepping.

The starting net rack construction method comprises the following steps:

the first step is as follows: and the positions of the axis line of 23, which are crossed with the W axis and the A axis, are used as starting unit areas, and a gable bottom unit is installed by utilizing a support and a temporary support of a gable. (as shown in FIG. 3)

The second step is that: after the net rack of the small unit in the first step of the gable is in place, the crane does not loosen the hook, and then the net racks of the W-axis and A-axis roof parts corresponding to the net rack are hoisted in place. (as shown in fig. 4).

And thirdly, after the small unit net racks in the first step and the second step of the gable are in place, the crane does not loosen the hook, the net racks are observed by using a theodolite and a leveling instrument, the verticality and the levelness of the small unit net racks of the gable are adjusted, the joints of the gable and the net rack of the roof are sewn immediately (as shown in figures 5 and 6), wind-holding ropes are pulled inside and outside, and at the moment, the small net rack units at the positions where the 23 axes are crossed with the W axis and the A axis form an L-shaped stable geometric invariant system.

The fourth step: and hoisting net rack units of the sections 2 and 2 'of the gable in place (the net rack units adjacent to the sections 1 and 1' respectively, as shown in fig. 7).

The fifth step: and respectively connecting the net racks of the 2 sections and the 2 'sections of the gable with the net racks of the 1 section and the 1' section. The net rack is observed by a theodolite and a level gauge, and the verticality and the levelness of the net rack are adjusted. The wind rope is pulled inside and outside to be fixed, the crane slowly releases the hook, the change of the net rack is observed, and the wind rope is pulled inside and outside. (as shown in fig. 8).

And a sixth step: and repeating the fourth step and the fifth step to continuously hoist the next adjacent unit net racks (3 sections and 3' sections) in the middle of the gable wall to be in place. (as shown in fig. 9).

The seventh step: the suspended gable net rack is respectively connected with the well-positioned net rack, and the wind ropes are pulled well inside and outside to be fixed. (as shown in fig. 10).

So far, the whole gable wall, the W shaft and the A shaft form a U-shaped stable geometric invariant system.

Eighth step: on the basis of the installation method, the gable net racks are installed upwards row by row. The A axis and the W axis respectively extend 2 x4 grids towards the 20 axes, the 22-23 axis roof net racks respectively extend towards the middle, and the roof net racks are assembled towards the middle in a step shape (as shown in figure 11).

The ninth step: the net frame is in a step shape along the longitudinal direction and continuously expands from the W axis to the middle according to the rows.

The tenth step: when the A-axis net rack is expanded to the G1Z axis, 3X 3 grid small units assembled on the ground are hoisted to the middle support seat of the 20 axis G1 axis to be in place. (as shown in fig. 12).

The eleventh step: the crane does not loose the hook, and then the 3x 3 grid small unit net rack is connected with the starting cross net rack, so that the middle support and the starting cross net rack are stressed together to form a stable geometric invariant system. And at this moment, the starting net rack is installed completely and is continuously installed in a row by row mode towards the direction of the 1 axis. (as shown in fig. 13).

The method of the bulk net rack comprises the following steps:

(1) installing lower chord plane net rack

Installing the support of the first span in place, aligning the axis and the central line of the support, and aligning the elevation by using a level gauge; and installing a first span lower chord ball and a first span lower chord rod to form a longitudinal plane grid. Arranging temporary pivot points, ensuring the parallelism of the lower chord, and finding out the slope bottom on the temporary pivot points if arching is required. After the small unit of the web member and the upper chord ball, generally a ball and a two-web member, between the first span and the upper chord ball are installed in place, the small unit and the lower chord ball are screwed and fixed. And installing an upper chord between the first spans to control the size of the grid. Note that the depth of screwing affects the down-deflection of the entire rack, which is checked by quality inspectors and well-controlled in size.

And checking the sizes of the net rack and the grids, and checking the longitudinal size and the rise size of the net rack. If the net rack is in or out, the height position of the temporary fulcrum can be adjusted to control the size of the net rack.

(2) Mounting upper chord inverted triangle mesh

And the second unit of the net rack is assembled by adopting a continuous installation method. Each small splicing unit for installing the net rack is formed by a triangular pyramid, the triangular pyramid is spliced on the ground, and each small splicing unit comprises an upper chord ball, an upper chord and two web diagonal rods; the small splicing triangular cone is spliced on the ground, the fastening degree of the bolts of the net rack is controlled during splicing, and an effective small splicing unit can be formed as long as the progress of the bolts is in place on the premise that the machining size is not deviated. When assembling, effectively control bolt fastening degree, reduce accumulative error just can.

A lower chord is installed from a support, the quality of threads is checked, screw holes and threads are cleaned and then screwed in, a lower chord is also installed from the first span of the lower chord to form a first square grid, a first node ball is screwed in, and the first grid of the lower chord is closed.

Installing an inverted triangular pyramid, and hoisting a ball three-rod small unit (namely a small splicing unit consisting of an upper chord ball, an upper chord rod and two web diagonal rods) into the site. And supporting the two inclined rods on the lower chord ball, and tensioning the upper chord rod above to enable the upper chord rod to gradually approach the installed upper chord ball and be screwed in. Then the diagonal rod is screwed into the lower string ball hole and tightened, and the other diagonal rod can be temporarily left empty. The installation of the lower chord ball and rod continues (second grid, lower chord ball is a ball-rod). One rod is screwed into the screw hole of the original lower chord ball, one ball is connected and screwed with the other oblique rod at the front installation edge, the transverse lower chord (the second rod) is installed in place, and the two ends of the transverse lower chord are respectively screwed with the balls to form a second grid seal of the lower chord.

And continuously installing a ball three-rod inverted triangular cone according to the process, and installing a longitudinal upper chord between the two inverted triangular cones to connect the inverted triangular cones into a whole. And gradually advancing, installing a longitudinal upper chord member when each group of inverted triangular cones are installed, screwing in the two ends of the upper chord member by using bolts, and enabling the upper chord of the net rack to form a closed square grid.

After being gradually installed on the support, the support forms a series of longitudinal inverted triangular pyramid net racks. And (4) checking the longitudinal size, the flexibility of the net rack and the stress condition of each supporting point.

(3) Mounting lower chord regular triangle mesh

After the net rack is installed with the inverted triangular pyramid grids, the regular triangular pyramid grids are installed. The lower chord ball and rod are installed in a ball-rod style (i.e., lower chord ball and lower chord) with a rod threaded into the support bolt hole. And (5) installing a transverse lower chord to enable the ball and the rod to form a closed square grid, and checking the size. Or a one-ball two-rod form (the lower chord ball and two mutually perpendicular lower chords are simultaneously installed to form a closed square grid) can be adopted.

And a diagonal web member on one side is installed, and the single rod is in place and screwed in, so that the rise of the grid can be conveniently controlled. And continuously installing the inclined web members on the other side, and screwing the lower chord ball and the upper chord ball into the two sides to complete a group of right-angled triangular cone grids. Gradually installed to one side until the support.

After finishing one equilateral triangle cone, installing and checking the dimension error of the upper chord square grid, gradually adjusting and fastening the bolt.

(4) Adjusting and fastening

The net rack is installed by the high-altitude bulk method, and the quality of the net rack is measured and checked at any time. Checking the size and diagonal of the lower chord grid, checking the size and diagonal of the upper chord grid, and checking the longitudinal length, the transverse length and the grid rise of the net rack.

The flexibility of the whole net rack is checked, and the flexibility value can be controlled by adjusting the sizes of the upper chord and the lower chord. The deflection measuring method comprises the following steps: the designer provides the deflection value, and the field technician uses a total station for measurement or uses a steel ruler and a vertical line for measurement and calculation.

The sinking condition of each temporary supporting point is required to be checked at any time in the installation process of the net rack, and if the sinking condition exists, the net rack is required to be reinforced in time to prevent the phenomenon of falling.

After the net rack is checked and adjusted, the net rack high-strength bolt is fastened again. After the net frame high-strength bolt is fastened, the small positioning bolt on the sleeve is screwed and locked.

The bolt ball node net rack is composed of a node ball, a rod piece, a sleeve and a high-strength bolt. The internodal axis dimension is determined by the radius of the two balls, the length of the rod (including the seal plate or cone head) and the length of the two sleeves. The high-strength bolt integrates the bolt ball, the sleeve and the rod piece from the inside. Whether the high-strength bolt is screwed in place or not is judged that the high-strength bolt is fastened in place after the surface of the high-strength bolt is fastened, no gap is formed on the spherical contact surface of the nut and the wrench cannot rotate continuously. If the force is still continuously applied after the fastening, the jackscrew is easy to break.

(5) Mounting bracket

The bracket welding piece on the upper chord ball is screwed in. The slope is found on the support bar member for mounting the roofing sheet.

The unused holes on the bolt ball and the gaps between the bolt and the sleeve and between the bolt and the rod piece are sealed to prevent rainwater leakage.

Claims (3)

1. A steel net rack construction method is characterized by comprising the following steps:

s1: firstly, mounting a support steel structure in the middle of a G1 shaft in the mounting sequence of mounting n-3 shaft steel columns to 3 shaft steel columns;

s2: starting the construction of the net rack,

taking an n-axis intersection A axis and a W axis near a gable as starting unit areas, and mounting a gable bottom unit by using a support and a temporary support of the gable;

secondly, hoisting the 1 st section of unit net rack and the 1 st' section of unit net rack on two sides of the gable in place, and then hoisting two roof net racks corresponding to the unit net racks in place;

step three, after the gable 1 st section unit net rack and the 1' st section unit net rack are hoisted in place, the crane does not loosen the hook, the net racks are observed by a theodolite and a leveling instrument, after the verticality and the levelness of the gable unit net rack are adjusted, the junction of the gable and the roof net rack is immediately sewed, and wind ropes are pulled inside and outside;

hoisting a2 nd section unit net rack and a second 2 ' section unit net rack of the gable in place, wherein the 2 nd section unit net rack is adjacent to the 1 st section unit net rack, and the second 2 ' section unit net rack is adjacent to the second 1 ' section unit net rack;

step five, respectively connecting the gable section 2 unit net rack and the gable section 2 'unit net rack with the section 1 unit net rack and the gable section 1' unit net rack, observing the net racks by using a theodolite and a leveling instrument, adjusting the verticality and the levelness of the net racks, and pulling the net racks inside and outside to fix the net racks by wind ropes;

step six, repeating the step four and the step five, and continuing to hoist the residual adjacent unit net racks in the middle of the gable to be in place;

step seven, respectively connecting the hoisted gable unit net racks with the in-place roof net racks on two sides, and pulling the wind ropes inside and outside to fix the wind ropes;

step eight, installing the gable unit net racks row by row upwards, and respectively expanding grids towards the axis A and the axis W to the axis n-3;

step nine, the n-1 to n-axis roof net racks are respectively expanded towards the middle and assembled towards the middle in a step shape;

step ten, when the net rack on the side of the shaft A is expanded to a shaft G1, hoisting the small grid units assembled on the ground to a support seat in the middle of the shaft G1 of the shaft n-3 shaft in place;

step eleven: the grid small unit net rack is connected with the starting cross net rack, so that the middle support and the starting cross net rack are stressed together, and the starting net rack is installed;

s3: and after the starting net rack is finished, a stable structure system is formed, the rest net racks on the roof are constructed by a crane matched small unit high-altitude bulk loading method, and the net racks are pushed from the n shaft to the 1 shaft until the main net rack is completely installed.

2. The steel truss construction method according to claim 1, wherein the G1 shaft middle support steel structure comprises an upper section lattice column, a lower section lattice column and a truss girder, and the upper section lattice column and the lower section lattice column are independently assembled on the ground; the construction method comprises the following steps:

firstly, hoisting an n-3 shaft lower section lattice column, adjusting the verticality of a steel column, and connecting the steel column with the ground through a column bottom plate and foundation bolts;

hoisting an upper section of lattice column of the n-3 shaft, temporarily connecting the upper section of lattice column with a lower section of lattice column through a process connection lug plate, setting a cable rope to fix a steel column, correcting the verticality of the steel column, and welding and connecting the steel column through carbon dioxide arc welding;

step three and step four, respectively repeating step one and step two to hoist the n-5 shaft lattice column;

hoisting the truss girder in the middle of the n-5 shaft to the n-3 shaft, and splicing the truss girder and the upper section of lattice column into a whole by using mounting bolts;

and step six, mounting the latticed columns and the truss girders of the rest part of the n-5 to 3 shafts until the whole middle support is mounted.

3. The steel truss construction method as claimed in claim 1, wherein: the high-altitude bulk method construction method in the step S3 includes the steps of:

step one, a lower chord plane net rack is installed,

installing the support of the first span in place, aligning the axis and the central line of the support, and aligning the elevation by using a level gauge; installing a first span lower chord ball and a first span lower chord rod to form a longitudinal plane grid; mounting a web member and an upper chord ball of the first bay, and then mounting an upper chord member of the first bay;

step two, installing an upper chord inverted triangular grid,

the second unit of the net rack is assembled by adopting a continuous installation method, each small assembly unit for installing the net rack is formed by a triangular pyramid which is assembled on the ground, and the small assembly unit comprises an upper chord ball, an upper chord and two web diagonal rods;

firstly installing a lower chord from the support, and simultaneously installing a lower chord from the first span of the lower chord to form a first square grid, screwing a first node ball in, and sealing the first grid of the lower chord;

installing an inverted triangular pyramid, hanging the small splicing unit into the field, supporting the two diagonal rods on the lower chord ball, tensioning the upper chord rod above the lower chord ball to enable the upper chord rod to gradually approach the installed upper chord ball and screw in the upper chord ball; then the diagonal rods are screwed into the lower chord ball holes and tightened, and the other diagonal rod can be temporarily left empty; continuously installing a lower chord ball and a rod, screwing one rod into an original lower chord ball screw hole, connecting and screwing one ball with the other oblique rod at the front edge of installation, installing the transverse lower chord in place, and screwing two ends of the transverse lower chord ball into the balls to form a second grid seal of the lower chord;

continuously installing the small splicing units according to the process, and installing a longitudinal upper chord between the two inverted triangular cones to connect the two inverted triangular cones into a whole; gradually advancing, installing a longitudinal upper chord member when each group of inverted triangular cones are installed, screwing in two ends of the upper chord member by using bolts, and enabling the upper chord of the net rack to form a closed square grid; the net frames are gradually arranged on the support to form a series of longitudinal inverted triangular pyramid net frames;

step three, installing a lower chord regular triangular grid

After the net rack is provided with the inverted triangular pyramid grid, the regular triangular pyramid grid is arranged, the lower chord ball and the rod are arranged, and the rod is screwed into the bolt hole of the support in a ball-rod mode of the lower chord ball and the lower chord rod; installing a transverse lower chord to enable the ball and the rod to form a closed square grid; or a ball-two-rod form is adopted, namely the lower chord ball and two mutually vertical lower chords are simultaneously installed to form a closed square grid;

installing a side inclined web member, positioning a single rod in place and screwing in;

continuously installing the other side diagonal web member, and screwing the lower chord ball and the upper chord ball into two sides of the diagonal web member to complete a group of right triangular pyramid grids; gradually installing towards one side until the support is reached;

after finishing one regular triangular pyramid, installing and checking the dimension error of the upper chord square grid, gradually adjusting and fastening the bolt;

and step four, mounting a support.

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