CN102364012A - Method for expanding existing large-span truss - Google Patents

Method for expanding existing large-span truss Download PDF

Info

Publication number
CN102364012A
CN102364012A CN2011101372347A CN201110137234A CN102364012A CN 102364012 A CN102364012 A CN 102364012A CN 2011101372347 A CN2011101372347 A CN 2011101372347A CN 201110137234 A CN201110137234 A CN 201110137234A CN 102364012 A CN102364012 A CN 102364012A
Authority
CN
China
Prior art keywords
truss
bracing frame
slippage
span
load
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN2011101372347A
Other languages
Chinese (zh)
Other versions
CN102364012B (en
Inventor
吴伟杰
刘中华
洪国松
李建洪
高良
郑雪祥
胡向萍
黄利顺
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Zhejiang Jinggong Steel Structure Group Co Ltd
Original Assignee
Zhejiang Jinggong Steel Structure Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Zhejiang Jinggong Steel Structure Co., Ltd. filed Critical Zhejiang Jinggong Steel Structure Co., Ltd.
Priority to CN 201110137234 priority Critical patent/CN102364012B/en
Publication of CN102364012A publication Critical patent/CN102364012A/en
Application granted granted Critical
Publication of CN102364012B publication Critical patent/CN102364012B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Abstract

The invention provides a method for expanding an existing large-span truss. The method comprises the following steps of: erecting a support frame below the existing main truss, jacking a midspan truss upwards, cutting the truss, and safely transferring all dead weight of the truss onto the support frame on the lower part and a slippage steel beam; and arranging a hydraulic crawler at a heel, making the cut truss slip by a required distance according to the slippage design requirement, arranging the truss which is required to be expanded after slipping outwards at a high altitude, and detaching the support frame and slippage facilities below the main truss. In the method, the existing large-span truss is directly expanded by cutting and slipping, so that the entire construction period is greatly shortened, and a large amount of labor force is saved. The existing truss is fully reused, so that the consumption of a large amount of steel is lowered, and resources are recycled. Factors in various aspects are fully considered in the design, so that the safety performance is high, and the quality is reliable. The construction safety is ensured, and severe accidents are avoided.

Description

A kind of existing large-span truss enlargement method
Technical field
The present invention relates to the building structure construction technical field, particularly a kind of existing large-span truss enlargement method.
Background technology
In recent years, along with the economic development of country, the name of the country living standard improves; Go out administrative staff's increase; The large-scale public place that domestic part has been built can not satisfy the present stage visitors flowrate, such as railway terminal, sports palace, hospital or the like, especially railway transport capacity.Simultaneously along with the increase of the construction dynamics of the input of country to infrastructure, particularly railway station, this will have station with regard to exigence more and more and extend.
The method of tradition enlarging generally all is the building that reserve part can be reused; Just all the other most of awning truss are all removed; Thoroughly rebuild then; Traditional handicraft not only needs the very long construction period, has strengthened the input of fund simultaneously, and this mode that wastes time and energy can't satisfy the demand of current society.
So the inventor proposes a kind of enlargement method that existing awning truss band is carried cutting back integral slipping, not only practices thrift total time of construction, and can former awning truss recycling can be practiced thrift a large amount of steel.
But certain time limit because original station has come into operation exists complicated internal force in the awning chord member of truss.Existing large-span truss band carries the cutting technique complicacy; Because its distortion, stress have synergistic effect and repeatability in cutting process; Cutting scheme also will be avoided cutting the unexpected release of improper generation internal force, and make the truss integral unstability except the force request that satisfies structure.Also to guarantee that the preceding truss internal force of each cutting is minimum through optimizing cutting sequence.Also to truss be carried out the predeformation measure simultaneously, guarantee that the absolute altitude of main couple cutting finishing back each point can adhere to specification.The above content of truss is that existing large-span truss band carries the key technology in the cutting process.Therefore, when having the cutting of above-mentioned similar structures, how to optimize cutting sequence, improve the efficient of cutting, and how distortion to control, become crucial problem.
Summary of the invention
The object of the present invention is to provide a kind of existing large-span truss enlargement method, design safety is reliable, and cutting arrangement is reasonable; Frictional force in the slipping is less; Reduced the slippage equipment requirements, it is reasonable to unload sequence arrangement simultaneously, effectively control structure distortion; Intersect less with the civil engineering operation, give full play to the effectiveness of stepped unloading.
The present invention realizes through following technical measures: a kind of existing large-span truss enlargement method specifically comprises the steps:
(1) below existing main couple, set up bracing frame, with jack on bracing frame with the span centre truss certain distance of jacking that makes progress, this moment, outside suspension column internal force was minimum, the truss fractional load is transferred on the bracing frame simultaneously;
(2) after the span centre truss made progress jacking, according to finite element method (fem) analysis, outside suspension column chord member internal force was very little, adopted the magnetic force cutting machine with outside suspension column chord member and the cutting of suspension column web member, placed the slippage girder steel simultaneously at the suspension column place;
(3) analyze the little rod member of span centre truss internal force through finite element analysis software, and with its cutting;
(4) analyze the little rod member of all the other internal force in the span centre truss once more through finite element analysis software, and with its cutting, through repeatedly repeating, cut off fully until the span centre truss, this moment, the load transfer of span centre truss was to the bracing frame of bottom;
(5) the inboard suspension column chord member of cutting, truss all cut and finished this moment, and truss is conducted oneself with dignity whole safe transfers on lower support frame and slippage girder steel;
(6) hydraulic pressure creep machine is installed at the suspension column place, according to slippage designing requirement slippage required separation distance, and suspension column is welded fixing truss under the cutting;
(7) adopt mobile crane, the truss of required enlarging after high-altitude benefit dress slippage is gone out;
(8) carry out unloaded operation, remove the bracing frame and the slippage facility of main couple below.
The present invention can be further perfect through following mode:
Described bracing frame is to set up firm foundation with mechanical model; Utilization MADIS software for calculation designs, and the load of considering during design comprises the influence of horizontal wind load that aerodynamic force that dead load, live load, wind load, train cross produces, geological process, support settlement, vibration effect that train crosses, top truss sliding construction process influence and the bracing frame resistance to overturning buckling analysis to the bracing frame system.
Described wind load:
KN/
Wherein ;
Be blast, get 0.45kN/m 2 Be the pulsation enhancement coefficient, Be the pulsation influence coefficient, Be the ratio of mode factor and height variation factor of wind pressure;
Consider wind action on column, picking and placeing big coefficient is 1.1, and then line load is: 2.73 * 1.1 * 0.377=1.13KN/, wherein 0.377 is the pipe diameter.
Said horizontal wind load, consideration train, cross train and produce Pneumatic pressure and aerodynamic suction through out-of-date blast with 300km/h; Because aerodynamic suction and the suffered shearing of bracing frame are in the opposite direction; Favourable to calculating bracing frame, so do not consider aerodynamic suction, only consider the Pneumatic pressure effect; According to relevant regulations, the maximum height that the horizontal gas dynamic pressure acts on the track top is 5m, and has or not the existence of platform shed, needs to consider multiply by 1.5 the coefficient that stops; The train center line that crosses of speed per hour 350KN is 5 meters apart from the member Edge Distance, and the horizontal gas dynamic pressure that then produces is 0.72KN/ ㎡, then calculates wind reference pressure and is:
According to the geometric properties of bracing frame, can calculate bracing frame vertical rod below the 5m height width that keeps out the wind and be:
Then crossing train to the wind load that the bracing frame column produces is:
q=0.595*1.08*1*1=0.642KN/m。
Consider to strengthen load action when support frame as described above calculates, comparatively conservative safety degree more than needed be set, guarantee the safety in work progress of support system and steel structural roof, during calculating, consider following load combination:
①1.35D+0.98L
②1.2D+1.4L
③1.2D+1.4L+0.84W
④1.2D+0.98L+1.4W
⑤1.2D+1.4Δ
⑥1.2(D+0.5L)±1.3Eh
⑦1.0D+1.4L
⑧1.0D+1.4L+0.84W
⑨1.0D+0.98L+1.4W
⑩1.0(D+0.5L)±1.3Eh
Wherein, D represents dead load, and L represents live load, and W represents common wind load and crosses the wind load that train aerodynamic-force produces, and Eh represents horizontal earthquake action, and Δ is represented the support settlement effect.
To put in order truss structure modeling in MADIS software before the said main couple jacking earlier, respectively with main couple make progress jacking 10mm, 20mm and 30mm, suspension column internal force minimum jacking distance in the outside when drawing upwards jacking with the jacking that makes progress of span centre truss, changes step 2 over to then.
Suspension column in the said step 2 is made as initiatively point of slippage, and being erected at the bracing frame place after the span centre truss cuts off is that slippage is followed a little; Initiatively the some place comprises and lays the subgrade case that fixes on the ground, is arranged in initiatively put the slippage girder steel, be installed in the active slipping mechanism of initiatively putting slippage girder steel upper support truss and be fixed on and initiatively put on the slippage girder steel, the hydraulic pressure creep machine that the promotion truss moves on the subgrade case; Follow and a little comprise a slippage girder steel of following that is arranged on the bracing frame, be installed in the slipping mechanism of following of following a slippage girder steel upper support truss.
Describedly initiatively put the slippage girder steel and lay one deck corrosion resistant plate with some slippage girder steel upper surface.
Described active slipping mechanism comprises the support that supports the truss of treating slippage with to follow slipping mechanism identical, and the polyfluortetraethylene plate that pastes in the support bottom surface, is used on corrosion resistant plate, sliding.
At first with the calculating of whole bracing frame truss after carrying out the bracing frame complete removal in the finite element analysis software, draw every Pin main couple span centre degree of disturbing maximum value in the said step 8; Then with jack on the bracing frame with upwards jacking slightly of main couple, jacking gets final product to being about to break away from bracing frame;
First truss structure is unloaded, and the height of unloading is that aforementioned calculation degree of disturbing is peaked half the; Then with the unloading of second truss structure, it is peaked half that the height of unloading is similarly aforementioned calculation degree of disturbing; It is peaked half that first truss structure is unloaded degree of disturbing again, and at this moment, first truss structure is all completions of discharge, and the bracing frame below it can complete removal;
It is peaked half that the 3rd truss structure is begun to unload degree of disturbing; At this moment; It is peaked half that the 3rd truss structure and the 4th truss structure absolute altitude differ degree of disturbing; The 3rd truss structure is consistent with the second truss structure absolute altitude, and it is peaked half that second truss structure and the first truss structure absolute altitude differ degree of disturbing, and absolute altitude is stepped between each truss structure;
It is peaked half that second truss structure is unloaded degree of disturbing again, and at this moment, second truss structure is all completions of discharge, and the bracing frame below it also can complete removal; Then with the 4th truss structure also according to aforesaid way unloading, repeat above-mentioned steps, unload every truss structure is stepped, until whole truss completions of discharge.
After adopting such scheme, the present invention has many beneficial effects:
1, the present invention directly to existing large-span truss cut, the enlarging mode of slippage, rather than existing truss removed reconstruction, thus the whole construction duration shorten dramatically, saved great amount of manpower.
2, the present invention utilizes existing truss fully again, only needs to replenish the truss part of welding enlarging distance, has saved the consumption of great deal of steel, and resource is able to recycling, meets requirements of the times energy-conservation in the current society.
3, the design of bracing frame has taken into full account the factor of various aspects among the present invention, and security performance is high, reliable in quality.In cutting and the slipping, it is thorough that each details is all considered simultaneously, ensured the safety of construction, and generation avoids a nasty accident.
4, the present invention proposes a kind of stair-stepping truss mode, and civil engineering unit can be earlier descend the step construction to the truss that has unloaded, and can accomplish that civil engineering and steel work unloaded operation carry out synchronously, has further practiced thrift the overall duration of site operation.And, confirm structure unloading flow process through unloading is optimized in proper order, adopt finite element analysis software; Structure unloading overall process is carried out simulation analysis; And before the truss unloading, confirm the predeformation value of structure, guarantee that the levelness after the structure unloading is accomplished meets design requirement.The equipment that stepped unloading drops into respect to synchronous unloading is few, improves comprehensive benefit.
Description of drawings
Fig. 1 is the structural representation of step 1 in the preferred embodiment of the present invention;
Fig. 2 is the structural representation of step 2 in the preferred embodiment of the present invention;
Fig. 3 is the structural representation of step 3 in the preferred embodiment of the present invention;
Fig. 4 is the structural representation of step 4 in the preferred embodiment of the present invention;
Fig. 5 is the structural representation of step 5 in the preferred embodiment of the present invention;
Fig. 6 is the structural representation of step 6 in the preferred embodiment of the present invention;
Fig. 7 is the structural representation of step 7 in the preferred embodiment of the present invention;
Fig. 8 is an existing large-span truss schematic top plan view of the present invention
Fig. 9 is the schematic top plan view behind the existing large-span truss slippage certain distance of the present invention;
Figure 10 is the schematic top plan view that existing large-span truss of the present invention is mended the dress main couple;
Figure 11 is the schematic perspective view of bracing frame in the preferred embodiment of the present invention;
Figure 12 be preferred embodiment slippage of the present invention initiatively put follow a little with slippage in the Sliding Structures sketch map.
The specific embodiment
In conjunction with accompanying drawing, preferred embodiment of the present invention is explained further details.
In the present embodiment reconstruction to the large-scale awning truss in railway terminal, its building span 64.6m as shown in Figure 1, spring of arch 19.5m, length 545m.The awning structure adopts is just putting leg-of-mutton three limb lattice truss, about 2.5 meters of the truss leg length of side, the high 4.5m of triangular truss, maximum caliber 550mm.Main couple totally 26 Pin along its length, truss Pin is apart from 22m.Roofing is a color steel sheet, and furred ceiling adopts the aluminium sheet furred ceiling.The main platform clear span is 10.5 meters, does not satisfy instructions for use, the main platform clear span is expanded as 15 meters, and former truss span is 64.6m, and the enlarging back is 69.1m at present.
Employing the present invention technology, job practices specifically comprises the steps:
One, bracing frame 2 is built
Bracing frame 2 is to set up firm foundation with mechanical model, and utilization MADIS software for calculation designs.The load that will consider during design comprises the influence of horizontal wind load that aerodynamic force that dead load, live load, wind load, train cross produces, geological process, support settlement, vibration effect that train crosses, top truss sliding construction process influence and the bracing frame resistance to overturning buckling analysis to the bracing frame system.
The dead load that bracing frame 2 receives is considered dead load multiplier 1.0, roofing dead load 0.8KN/ ㎡ during calculating.Side fixed end bracing frame bears vertical force 315KN, bears horizontal shear 180KN to the inside.The slippage end structure is 404KN to the axial pressure of bracing frame, considers that friction factor is 0.05 between sliding rail and the roof system, and then the kinetic force of friction during the roof system slippage is 20.2KN.
Live load is mainly considered bracing frame 2 top operators' load, when calculating bracing frame, needs to consider the construction live load of bracing frame top 3.5KN/ ㎡.
Wind load, Blast is got 0.45kN/m 2, wind load comprises and acting directly on the bracing frame 2 have according to " GBJ135-90 " GBJ135-2004 4.2.9 bar:
Wind load:
KN/
Consider wind action on column, picking and placeing big coefficient is 1.1, and then line load is:
2.73×1.1×0.377=1.13KN/
Because in this engineering construction process, adjacent tracks is still normally used, thus need the consideration train with 300km/h through out-of-date blast.According to the relevant regulations of " 300~350 kilometers passenger dedicated railway line designs of newly-built speed per hour temporary provisions " (No. [2007] 47, iron construction) file, train is calculated as follows through the blast that produces:
Cross train and produce Pneumatic pressure and aerodynamic suction, favourable because aerodynamic suction and bracing frame 2 suffered shearings are in the opposite direction to calculating bracing frame 2, so do not consider aerodynamic suction, only consider the Pneumatic pressure effect.According to relevant regulations, the maximum height that the horizontal gas dynamic pressure acts on the track top is 5m, and has or not the existence of platform shed, needs to consider multiply by 1.5 the coefficient that stops.Table look-up and can get, the train center line that crosses of speed per hour 350KN is 5 meters apart from the member Edge Distance, and the horizontal gas dynamic pressure that then produces is 0.72KN/ ㎡, then calculates wind reference pressure and is:
According to the geometric properties of bracing frame 2, can calculate bracing frame 2 vertical rods below the 5m height width that keeps out the wind and be:
Then crossing train to the wind load that bracing frame 2 columns produce is:
q=0.595*1.08*1*1=0.642KN/m。
In view of this engineering is the railway station, in the transformation process, still to guarantee normal operation, so its safety is extremely important, need to consider the influence of geological process.According to the relevant design data, the design parameters of seismic design is: seismic fortification intensity 7 degree, the basic earthquake acceleration 0.10g of design, earthquake is divided into groups second group, site category II class.
This engineering original structure came into operation 3 years, can think that the foundation settlement on track foundation, platform basis tends towards stability, in work progress, big variation can not take place.The foundation settlement that 30mm takes place than unfavorable position bracing frame 2 bearings is got in full consideration content to retain sovereignty over a part of the country during calculating, calculates.
Because the vibration that train crosses act as low frequency vibration, its frequency and support system and steel awning basic cycle difference are bigger, covibration can not take place, so do not consider the vibration effect that train crosses in this calculating.
Consider to strengthen load action during calculating, comparatively conservative safety degree more than needed is set, guarantee the safety in work progress of support system and steel structural roof.During calculating, consider following load combination:
①1.35D+0.98L
②1.2D+1.4L
③1.2D+1.4L+0.84W
④1.2D+0.98L+1.4W
⑤1.2D+1.4Δ
⑥1.2(D+0.5L)±1.3Eh
⑦1.0D+1.4L
⑧1.0D+1.4L+0.84W
⑨1.0D+0.98L+1.4W
⑩1.0(D+0.5L)±1.3Eh
Wherein, D represents dead load, and L represents live load, and W represents wind load (comprise wind load and cross the wind load that train aerodynamic-force produces), and Eh represents horizontal earthquake action, and Δ is represented the support settlement effect.
When the steel work main couple cut off, as yet not during the state of slippage because sedimentation takes place on the basis of intermediate support beam 2, this place bracing frame 2 directly bears roof system deadweight effect simultaneously, this moment, the rod member stress of bracing frame system was maximum, was out of shape also maximum.Be the stability of checking computations bracing frame system, choose this state and carry out buckling analysis.Buckling analysis considers that 1.0 dead loads+1.0 mobile load states calculate.
Bracing frame 2 specifications are 2m * 3.5m in the present embodiment, and every joint highly is 2m, and bracing frame 2 columns are Φ 377 * 16 steel pipes, and straight web member and diagonal web member all adopt Φ 180 * 12 steel pipes, and the rod member material all adopts Q235B, design strength f=215N/mm2.
In conjunction with Fig. 1 and Figure 11 in order to prevent that bracing frame 2 is in loading process; Prevent that from there is the phenomenon of differential settlement in bracing frame 2; Position in that bracing frame 2 is installed as setting up subgrade case on platform and the track for a train basis, firmly is connected subgrade case with platform through i iron 25.In order to ensure the destruction that track for a train and sleeper do not receive upper support shelf 2, before setting up, track for a train and sleeper are all removed.Subgrade case itself is parts commonly used in the building trade, is to adopt i iron to be welded, and at i iron upper and lower surfaces welding steel, i iron is wrapped process.
It on the subgrade case 21 supporting frame 22.Supporting frame 22 comprises some columns 23 and plurality of cross bars 24.Between column 23, be fixedly connected with level or oblique welding, form whole supporting frame 22 through cross bar 24.When whole supporting frame 22 was fixed on subgrade case 21, the foot of column 23 all should be placed in the subgrade case 21 each i iron infall in length and breadth, strengthened the ability to bear of supporting frame 22.
The outer heel post 23 of supporting frame 22, just near the column of original train protection canopy 10, the distance that should keep greater than 100mm with train protection canopy 10 guarantees that the distortion of supporting frame 22 does not influence train protection canopy 10.Supporting frame 22 corresponding slippage truss places are provided with slippage girder steel 40.
The bracing frame force analysis
1, the truss slipping is to the influence of bracing frame
1. do not begin the preceding dead load state of slippage after analyzing cutting, draw X under the standard combination, Y, Z direction displacement isogram (X is a glide direction, the longitudinal direction between each truss structure of Y, Z bracing frame sedimentation direction) through software.In the present embodiment, do not begin the deformation values less (X maximum displacement 7.3mm, Y maximum displacement 1.95mm, Z maximum displacement 75mm) of bracing frame system under the slip state, the requirement of related specifications is satisfied in the support system distortion, also satisfies the needs of construction precision.In addition, the stress and the stress ratio situation of output support system: support system maximum stress ratio be 0.7,0.7 1.0, practical so the design safety of this bracing frame system is reliable, can satisfy the needs of this project construction.
2. slide onto the bracing frame centre position, the dead load effect is maximum to the moment of flexure of the vertical force generation of sliding rail beam, these state slippage girder steel 40 stressed maximums; Under the dead load effect, analyze the deformation values (X maximum displacement 5.33mm, the Y maximum displacement 1.51mm that draw the bracing frame system; Z maximum displacement 77mm), the maximum stress ratio is 0.679, and is visible by The above results; Support system maximum stress ratio is 0.679 < < 1.0; So the design safety of this bracing frame system is reliable, practical, can satisfy the needs of this project construction.
When 3. moving to bracing frame center, left side, the dead load effect is maximum to the moment of flexure of the vertical force generation of sliding rail beam, under this state; Sliding rail beam 40 stressed maximums under the dead load effect, are analyzed deformation values (the X maximum displacement 5.52mm that draws the bracing frame system; Y maximum displacement 1.52mm, Z maximum displacement 87mm), the maximum stress ratio is 0.661; Visible by The above results, 0.661 1.0, so the design safety of this bracing frame system is reliable; Practical, can satisfy the needs of this project construction.
4. the conclusion analyzed of work progress
Visible by the aforementioned calculation analysis, in the sliding construction process, the distortion of bracing frame system is less, and all directions are out of shape all less than 6mm, and the rigidity aspect satisfies construction requirement.In each construction state, support system rod member stress ratio is 0.7 to the maximum, and rod member intensity also satisfies related request.So above computational analysis shows that the design safety of this bracing frame system is reliable, and is practical.
2, support system stability analysis
Can know by above calculating, when the steel structural roof truss cut off, as yet not during the state of slippage because sedimentation takes place on the basis of intermediate support beam, this place bracing frame directly bears roof system deadweight effect simultaneously, this moment, the rod member stress of bracing frame system was maximum, was out of shape also maximum.Be the stability of checking computations bracing frame system, choose this state and carry out buckling analysis.
Buckling analysis considers that 1.0 dead loads+1.0 mobile load states calculate, first buckling mode (the flexing factor 62.59), second buckling mode (the flexing factor 62.65), the 3rd buckling mode (the flexing factor 62.91).Visible by The above results; Under 1.0 dead loads+1.0 mobile load effects, the flexing factor minimum of bracing frame system is 62.59, promptly under 62.59 times of 1.0 dead load+1.0 mobile load effect; Flexing could take place in the bracing frame system; This shows that the resistance to overturning of bracing frame system is very high, in work progress, be difficult to take place the flexing unstability.
Two,, 50 tons jack 11 is set, on the bracing frame top with the main couple 1 certain distance of jacking upwards like Fig. 2.
Because this engineering has been moved 5 years; Main couple 1 is under the dead load effect; Span centre degree of disturbing is bigger, and after main couple 1 cutting, the absolute altitude of truss can adhere to specification; To guarantee also simultaneously that internal force is minimum in the truss cutting process, therefore before cutting, need to adopt large-scale finite element analysis software to carry out the computational analysis in the cutting process.
In computation model, adopt bearing forced displacement 10mm, 20mm and 30mm respectively, compare analysis respectively, when finding to make progress jacking 30mm, main couple suspension column 30 place's internal force are minimum, and the therefore definite main couple 1 upwards numerical value of jacking is 30mm.
Three, as shown in Figure 3; After adopting the magnetic force cutting machine that outside suspension column chord member 3 and 4 cuttings of suspension column web member are finished; In order to ensure the stability of truss suspension column, at truss suspension column 30 place's mounting slip girder steels 5, slippage girder steel 5 is connected with truss suspension column 30 original structures; Attachment rail beam on slippage girder steel 5 can make things convenient for the installation of hydraulic pressure creep machine 12 simultaneously.
Four, combine Fig. 4, the cutting of main couple chord member 6 and web member 7.After the chord member cutting of the suspension column outside finishes; Adopt finite element analysis software to analyze, find that span centre upper chord 6 and web member 7 internal force are minimum, begin cutting cutting span centre upper chord 6 and web member 7; Begin to cut span centre lower chord 8 (two) then, cut inboard suspension column chord member 9 (two) at last.
Five, referring to Fig. 5, main couple 1 slippage.After main couple 1 all cut and finishes, its load was all transferred on the lower support frame system.Suspension column 30 places arrange hydraulic pressure creep machine 12, with truss 1 along the certain distance of station one side slip.Slippage 13 truss structures for the first time, slippage weight is about 1300 tons, after slippage for the first time finishes, 13 truss structures of slippage symmetry again, slippage weight is about 1300 tons, adds up to the slippage gross weight to be about 2600 tons.
Six, like Fig. 6, the truss after the dress slippage is gone out is mended in the high-altitude.
After truss 1 slippage puts in place, can set about carrying out the benefit bar installation of truss 1, filling a vacancy of truss 1 interlude adopts mobile crane mode in bulk to install, and undertaken by the order of web member behind the first chord member.When the truss suspension column is installed, should be in advance suspension column be placed on the stone bolt on cushion cap basis temporary fixed, treats after the truss slippage puts in place suspension column to be mentioned, dock welding with chord member of truss, and fix, so that be in the milk from now in the spot welding of heel slab underlay upper padding plate.The truss that is connected with station adopts whole hanging method to install, and near the platform truss, carries out assembly unit earlier before installing, and installs with mobile crane then.
Seven, shown in Figure 7, remove the bracing frame and the slippage facility of main couple below.The main couple slippage finishes, and after the agent structure installation, need carry out the integral body unloading to established main structure.50 tons of mobile cranes of field by using are removed bracing frame.
The dismounting mode is also different with traditional approach, adopts stepped unloading manner.In conjunction with Fig. 8~Figure 10, at first with the calculating of whole bracing frame truss after carrying out the bracing frame complete removal in the finite element analysis software, drawing every Pin main couple span centre degree of disturbing maximum value is 40mm.Then with jack on the bracing frame with upwards jacking slightly of main couple, jacking gets final product to being about to break away from bracing frame.
Behind first truss structure 1a unloading 20mm, can be with second truss structure 2a unloading 20mm; Then the first truss structure 1a is unloaded 20mm again, at this moment, the first truss structure 1a all completions of discharge, the bracing frame 11 of its below can complete removal.
The 3rd truss structure 3a is begun to unload 20mm, and at this moment, the 3rd Pin 3a and the 4th truss structure 4a absolute altitude differ 20mm; The 3rd Pin 3a is consistent with the second truss structure 2a absolute altitude; The second truss structure 2a and the first truss structure 1a absolute altitude differ 20mm, and absolute altitude is stepped between each truss structure, all differs 20mm.
The second truss structure 2a is unloaded 20mm again, at this moment, the second truss structure 2a all completions of discharge, the bracing frame of its below also can complete removal; Then the 4th truss structure 4a is also unloaded according to aforesaid way, repeat above-mentioned steps, until whole truss completions of discharge.Adopt finite element analysis, each truss structure is when support displacement 20mm, and maximum distortion 42mm, maximum stress ratio are 0.265 much smaller than 1, and it is safe and reliable therefore unloading according to this scheme.
What also need propose here is that in the present invention, the suspension column place is provided with hydraulic pressure creep machine 12 as slippage active point, and on bracing frame, supports the slippage truss, is to follow a little as slippage.For reducing the frictional force in the slippage, the Sliding Structures that adopts in the present embodiment is referring to Fig. 1 and Figure 12.
Initiatively putting 30 places comprises subgrade case 31, initiatively puts slippage girder steel 5, initiatively slipping mechanism 32, hydraulic pressure creep machine 12.
Subgrade case 31 is laid and is fixed on platform, on subgrade case 31, arranges and initiatively puts slippage girder steel 5, and what initiatively put 5 employings of slippage girder steel is i iron, lays one deck corrosion resistant plate 33 at the upper surface of i iron.Initiatively slipping mechanism 32 is erected at and initiatively puts on the slippage girder steel 5; Initiatively slipping mechanism 32 mainly is directly to contact with treating mobile main couple 1 suspension column 30; Mainly comprise and support the support 34 of waiting to move main couple 1 suspension column 30, the bottom surface of support 34 is the plane, and pastes one deck polyfluortetraethylene plate 35.Polyfluortetraethylene plate 35 fits tightly with above-mentioned corrosion resistant plate 33 and contacts.Hydraulic pressure creep machine 12 is fixed on initiatively to be put on the slippage girder steel 5, and its application point connection is simultaneously waited to move main couple 1, promotes this and waits to move main couple 1 slippage.
Follow a slippage girder steel 40 and initiatively to put slippage girder steel 5 structures identical, following slipping mechanism is to support main couple lower chord 8, and structure is identical with active slipping mechanism 32 structures, does not do being repeated in this description.When slippage, corrosion resistant plate 33 and the friction between the polyfluortetraethylene plate 35 in this structure are little, have guaranteed smooth and easy, the safety of slippage, simultaneously the driving arrangement power requirement are reduced significantly, and the choice is big.
Because the complexity of job site condition; Only depend on the simulation analysis of finite element ideal model; Be difficult to the many invisible factor that simulated field exists, therefore also in work progress, displacement structure, internal force carried out timely monitor, to obtain structure actual distortion and stressing conditions.
A. deformation monitoring: whether the main couple deformation values is consistent with desirable calculated value in the monitoring work progress; The preparatory arch value of actual measurement deformation values in each cutting process and Theoretical Calculation is compared; So that take corresponding measure to come the control structure distortion, accomplish engineering construction smoothly.
B. stress monitoring: large-span truss has additivity and repeatability in cutting process, use stress monitoring
Among the present invention, the chord member of large-span truss is with when carrying cutting, structure has inconsistent phenomenon in incision, and we will be provided with jack the absolute altitude of truss is adjusted below the main couple chord member.After truss all cuts and finishes, all loads will be delivered on the bracing frame and slippage girder steel of below.
Because the particularity of truss, large-span truss is in the different cutting stages, and its distortion has synergistic effect and repeatability, so the present invention also adopts finite element analysis software, the structure cuts overall process is carried out simulation analysis, thereby confirm the predeformation value of structure.The value size of the predeformation value of structure is closely related with the cutting flow process, because in the different cutting stages, the rigidity of structure self, stress have very big difference, the malformation distribution situation also has marked change.Therefore, the predeformation value of structure must be confirmed according to the distortion situation of structure in the cutting flow process.After accomplishing the cutting of span centre truss lower chord, truss can push the bracing frame of bottom under the deadweight effect, thereby can make the absolute altitude of cutting back truss be lower than design elevation; Therefore; After main couple cutting finishes, at the bracing frame top jack is set, with the truss certain distance of jacking that makes progress.
In the main couple cutting process; Structure has been carried out the monitoring of distortion and internal force, obtained structure actual distortion and stressing conditions, when guaranteeing in the cutting process safety of structure; Field actual measurement results and simulation calculation result compare, the accuracy of check work progress simulation analysis.More than the monitoring content is through whole construction course.

Claims (10)

1. an existing large-span truss enlargement method is characterized in that: comprise the steps:
The first step, below existing main couple, set up bracing frame, with jack on bracing frame with the span centre truss certain distance of jacking that makes progress, this moment, outside suspension column internal force was minimum, the truss fractional load is transferred on the bracing frame simultaneously;
Second step, span centre truss make progress after the jacking, and according to finite element method (fem) analysis, outside suspension column chord member internal force is very little, adopt the magnetic force cutting machine with outside suspension column chord member and the cutting of suspension column web member, place the slippage girder steel simultaneously at the suspension column place;
The 3rd step, analyze the little rod member of span centre truss internal force through finite element analysis software, and with its cutting;
The 4th step, analyze the little rod member of all the other internal force in the span centre truss once more through finite element analysis software, and with its cutting, through repeatedly repeating, cut off fully until the span centre truss, this moment, the load transfer of span centre truss was to the bracing frame of bottom;
The 5th step, the inboard suspension column chord member of cutting, truss all cut and finished this moment, and truss is conducted oneself with dignity whole safe transfers on lower support frame and slippage girder steel;
The 6th step, hydraulic pressure creep machine is installed, according to slippage designing requirement slippage required separation distance, and suspension column is welded fixing truss under the cutting at the suspension column place;
The 7th step, employing mobile crane, the truss of required enlarging after high-altitude benefit dress slippage is gone out;
The 8th goes on foot, carries out unloaded operation, removes the bracing frame and the slippage facility of main couple below.
2. a kind of existing large-span truss enlargement method as claimed in claim 1; It is characterized in that: bracing frame is to set up firm foundation with mechanical model in described the 1st step; Utilization MADIS software for calculation designs, and the load of considering during design comprises the influence of horizontal wind load that aerodynamic force that dead load, live load, wind load, train cross produces, geological process, support settlement, vibration effect that train crosses, top truss sliding construction process influence and the bracing frame resistance to overturning buckling analysis to the bracing frame system.
3. a kind of existing large-span truss enlargement method as claimed in claim 2 is characterized in that: described wind load:
KN/
Wherein ;
Be blast, get 0.45kN/m 2 Be the pulsation enhancement coefficient, Be the pulsation influence coefficient, Be the ratio of mode factor and height variation factor of wind pressure;
Consider wind action on column, picking and placeing big coefficient is 1.1, and then line load is: 2.73 * 1.1 * 0.377=1.13KN/, wherein 0.377 is the pipe diameter.
4. a kind of existing large-span truss enlargement method as claimed in claim 2; It is characterized in that: said horizontal wind load, consideration train, cross train and produce Pneumatic pressure and aerodynamic suction through out-of-date blast with 300km/h; Because aerodynamic suction and the suffered shearing of bracing frame are in the opposite direction; Favourable to calculating bracing frame, so do not consider aerodynamic suction, only consider the Pneumatic pressure effect; According to relevant regulations, the maximum height that the horizontal gas dynamic pressure acts on the track top is 5m, and has or not the existence of platform shed, needs to consider multiply by 1.5 the coefficient that stops; The train center line that crosses of speed per hour 350KN is 5 meters apart from the member Edge Distance, and the horizontal gas dynamic pressure that then produces is 0.72KN/ ㎡, then calculates wind reference pressure and is:
According to the geometric properties of bracing frame, can calculate bracing frame vertical rod below the 5m height width that keeps out the wind and be:
Then crossing train to the wind load that the bracing frame column produces is:
q=0.595*1.08*1*1=0.642KN/m。
5. a kind of existing large-span truss enlargement method as claimed in claim 1; It is characterized in that: consider to strengthen load action when support frame as described above calculates, comparatively conservative safety degree more than needed is set; Guarantee the safety in work progress of support system and steel structural roof; During calculating, consider following load combination:
①1.35D+0.98L
②1.2D+1.4L
③1.2D+1.4L+0.84W
④1.2D+0.98L+1.4W
⑤1.2D+1.4Δ
⑥1.2(D+0.5L)±1.3Eh
⑦1.0D+1.4L
⑧1.0D+1.4L+0.84W
⑨1.0D+0.98L+1.4W
⑩1.0(D+0.5L)±1.3Eh
Wherein, D represents dead load, and L represents live load, and W represents common wind load and crosses the wind load that train aerodynamic-force produces, and Eh represents horizontal earthquake action, and Δ is represented the support settlement effect.
6. a kind of existing large-span truss enlargement method as claimed in claim 1; It is characterized in that: will put in order truss structure modeling in MADIS software before the said main couple jacking earlier; Respectively with main couple make progress jacking 10mm, 20mm and 30mm; Suspension column internal force minimum jacking distance in the outside when drawing upwards jacking with the jacking that makes progress of span centre truss, changes step 2 over to then.
7. a kind of existing large-span truss enlargement method as claimed in claim 1 is characterized in that: the suspension column in the said step 2 is made as initiatively point of slippage, and being erected at the bracing frame place after the span centre truss cuts off is that slippage is followed a little; Initiatively the some place comprises and lays the subgrade case that fixes on the ground, is arranged in initiatively put the slippage girder steel, be installed in the active slipping mechanism of initiatively putting slippage girder steel upper support truss and be fixed on and initiatively put on the slippage girder steel, the hydraulic pressure creep machine that the promotion truss moves on the subgrade case; Follow and a little comprise a slippage girder steel of following that is arranged on the bracing frame, be installed in the slipping mechanism of following of following a slippage girder steel upper support truss.
8. a kind of existing large-span truss enlargement method as claimed in claim 7 is characterized in that: describedly initiatively put the slippage girder steel and follow a some slippage girder steel upper surface and lay one deck corrosion resistant plate.
9. a kind of existing large-span truss enlargement method as claimed in claim 7; It is characterized in that: described active slipping mechanism is with to follow slipping mechanism identical; Comprise the support that supports the truss of treating slippage, and the polyfluortetraethylene plate that pastes in the support bottom surface, is used on corrosion resistant plate, sliding.
10. a kind of existing large-span truss enlargement method as claimed in claim 1; It is characterized in that: at first with the calculating of whole bracing frame truss after carrying out the bracing frame complete removal in the finite element analysis software, draw every Pin main couple span centre degree of disturbing maximum value in the said step 8; Then with jack on the bracing frame with upwards jacking slightly of main couple, jacking gets final product to being about to break away from bracing frame;
First truss structure is unloaded, and the height of unloading is that aforementioned calculation degree of disturbing is peaked half the; Then with the unloading of second truss structure, it is peaked half that the height of unloading is similarly aforementioned calculation degree of disturbing; It is peaked half that first truss structure is unloaded degree of disturbing again, and at this moment, first truss structure is all completions of discharge, and the bracing frame below it can complete removal;
It is peaked half that the 3rd truss structure is begun to unload degree of disturbing; At this moment; It is peaked half that the 3rd truss structure and the 4th truss structure absolute altitude differ degree of disturbing; The 3rd truss structure is consistent with the second truss structure absolute altitude, and it is peaked half that second truss structure and the first truss structure absolute altitude differ degree of disturbing, and absolute altitude is stepped between each truss structure;
It is peaked half that second truss structure is unloaded degree of disturbing again, and at this moment, second truss structure is all completions of discharge, and the bracing frame below it also can complete removal; Then with the 4th truss structure also according to aforesaid way unloading, repeat above-mentioned steps, unload every truss structure is stepped, until whole truss completions of discharge.
CN 201110137234 2011-05-26 2011-05-26 Method for expanding existing large-span truss Active CN102364012B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN 201110137234 CN102364012B (en) 2011-05-26 2011-05-26 Method for expanding existing large-span truss

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN 201110137234 CN102364012B (en) 2011-05-26 2011-05-26 Method for expanding existing large-span truss

Publications (2)

Publication Number Publication Date
CN102364012A true CN102364012A (en) 2012-02-29
CN102364012B CN102364012B (en) 2013-07-31

Family

ID=45690603

Family Applications (1)

Application Number Title Priority Date Filing Date
CN 201110137234 Active CN102364012B (en) 2011-05-26 2011-05-26 Method for expanding existing large-span truss

Country Status (1)

Country Link
CN (1) CN102364012B (en)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102852338A (en) * 2012-03-26 2013-01-02 上海通用金属结构工程有限公司 Large-span roof displacement unloading construction method
CN104989114A (en) * 2015-07-15 2015-10-21 上海绿地建设(集团)有限公司 Sliding construction device and method for large-span arc-shaped roof
CN105528483A (en) * 2015-12-07 2016-04-27 北京市政建设集团有限责任公司 Inclined truss stability checking method
CN107165420A (en) * 2017-06-12 2017-09-15 南通四建集团有限公司 The method of integrated Mechatronic Systems hydraulic pressure lift integral installation in steel structural roof rack
CN109607399A (en) * 2018-12-12 2019-04-12 中国三冶集团有限公司 A kind of hoisting for installing roof rack
CN110374200A (en) * 2019-07-25 2019-10-25 中亿丰建设集团股份有限公司 Large span rigidity unevenly mixes rack high altitude bulk method
CN110781627A (en) * 2019-11-01 2020-02-11 友联船厂(蛇口)有限公司 Simulation analysis cutting method for self-elevating drilling platform deformed pile leg
CN112727134A (en) * 2020-12-10 2021-04-30 中铁五局集团建筑工程有限责任公司 Construction method for rebuilding and expanding main structure of existing overhead operation subway station building

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH08270227A (en) * 1995-03-30 1996-10-15 Nippon Steel Corp Repair method for existing roof truss having large span
JPH1144104A (en) * 1997-07-28 1999-02-16 Shimizu Corp Demolition method of dome roof
CN2440891Y (en) * 2000-08-16 2001-08-01 广州市鲁班建筑防水补强专业公司 Lower railing mechanism for horizontal movement of construction
JP2004027756A (en) * 2002-06-28 2004-01-29 Sekisui House Ltd Extension construction method for roof truss
JP2004044082A (en) * 2002-06-28 2004-02-12 Sekisui House Ltd Extension working method of roof truss
CN101280630A (en) * 2008-05-20 2008-10-08 冯贵法 Network frame house cap integral lifting construction method

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH08270227A (en) * 1995-03-30 1996-10-15 Nippon Steel Corp Repair method for existing roof truss having large span
JPH1144104A (en) * 1997-07-28 1999-02-16 Shimizu Corp Demolition method of dome roof
CN2440891Y (en) * 2000-08-16 2001-08-01 广州市鲁班建筑防水补强专业公司 Lower railing mechanism for horizontal movement of construction
JP2004027756A (en) * 2002-06-28 2004-01-29 Sekisui House Ltd Extension construction method for roof truss
JP2004044082A (en) * 2002-06-28 2004-02-12 Sekisui House Ltd Extension working method of roof truss
CN101280630A (en) * 2008-05-20 2008-10-08 冯贵法 Network frame house cap integral lifting construction method

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
彭成均;李成义;邵茂;郭福乐: "国家博物馆改扩建工程超大面积钢桁架施工技术", 《第三届全国钢结构工程技术交流会论文集》 *
徐联明;王煦: "深圳机场扩建航站楼屋盖钢桁架滑移施工", 《施工技术》 *

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102852338A (en) * 2012-03-26 2013-01-02 上海通用金属结构工程有限公司 Large-span roof displacement unloading construction method
CN102852338B (en) * 2012-03-26 2015-09-09 上海通用金属结构工程有限公司 Long-span roofing displacement method for discharging construction
CN104989114A (en) * 2015-07-15 2015-10-21 上海绿地建设(集团)有限公司 Sliding construction device and method for large-span arc-shaped roof
CN105528483A (en) * 2015-12-07 2016-04-27 北京市政建设集团有限责任公司 Inclined truss stability checking method
CN105528483B (en) * 2015-12-07 2018-07-06 北京市政建设集团有限责任公司 A kind of inclination truss stability checking method
CN107165420A (en) * 2017-06-12 2017-09-15 南通四建集团有限公司 The method of integrated Mechatronic Systems hydraulic pressure lift integral installation in steel structural roof rack
CN109607399A (en) * 2018-12-12 2019-04-12 中国三冶集团有限公司 A kind of hoisting for installing roof rack
CN109607399B (en) * 2018-12-12 2020-02-21 中国三冶集团有限公司 Hoisting process for installing roof net rack
CN110374200A (en) * 2019-07-25 2019-10-25 中亿丰建设集团股份有限公司 Large span rigidity unevenly mixes rack high altitude bulk method
CN110781627A (en) * 2019-11-01 2020-02-11 友联船厂(蛇口)有限公司 Simulation analysis cutting method for self-elevating drilling platform deformed pile leg
CN112727134A (en) * 2020-12-10 2021-04-30 中铁五局集团建筑工程有限责任公司 Construction method for rebuilding and expanding main structure of existing overhead operation subway station building

Also Published As

Publication number Publication date
CN102364012B (en) 2013-07-31

Similar Documents

Publication Publication Date Title
CN102364012B (en) Method for expanding existing large-span truss
CN104141383B (en) A kind of Bailey beam pendent form support system and construction thereof
CN103266573A (en) Self-anchored suspension bridge steel box girder three-slideway synchronous jacking construction method
CN202227476U (en) High-altitude large-span overhung corridor-type reinforced concrete structure
CN103114681B (en) High-altitude long-span reinforced concrete beam treat pouring structure
CN106088660B (en) A kind of building up station platform widens the construction method of reconstruction structure system
CN104005338A (en) Three-directional temporary tower and girder consolidation structure of large-span cable-stayed bridge
CN102392536A (en) Construction method for long-span hanging vestibule type template support system
CN105970811A (en) Construction technology for elevated bridge with large-span spatial 3D-surface fish-bellied box steel structure
CN106702909A (en) Integral swiveling structure for double-body steel box girder and construction method thereof
CN203947771U (en) A kind of Bailey beam pendent form support system
CN206428595U (en) A kind of mobile platform suitable for the wet seam construction of section assembling box beam
CN202544854U (en) Lining trolley for subway station
CN103382702B (en) A kind of support of cast-in-situ box girder and building method thereof
CN106284838A (en) A kind of lattice Honeycomb Beam sections and large span lattice girder steel and fabrication and installation method thereof
CN109025281A (en) A kind of construction system and method suitable for business superelevation super-span Atrium Structure
CN104831639A (en) Consolidation and release construction method for 0# blocks of ultra-wide non-uniform continuous beam
CN102691267A (en) High pier construction method for external whole operation platform
CN203145273U (en) Dismountable steel-concrete composite floor
CN102444293B (en) Cutting and slipping method for extension of existing large-span truss structure
CN204780635U (en) Super wide nonprismatic continuous beam 0# piece concreties and relieves construction structures
CN106906750A (en) A kind of multi-functional across railway line swing bridge girder closing construction mould bases and its construction method
CN203393639U (en) Diamond self-anchored hanging basket for road and bridge construction
CN208201663U (en) Continuous rigid frame bridge box beam 0# block is overlapped beam without bracket cast-in-place support
CN110409624A (en) A kind of installation of large scale equipment and main structure be inverse to be made to calculate and construction method

Legal Events

Date Code Title Description
C06 Publication
PB01 Publication
C10 Entry into substantive examination
SE01 Entry into force of request for substantive examination
C53 Correction of patent for invention or patent application
CB03 Change of inventor or designer information

Inventor after: Wu Weijie

Inventor after: Xu Chaoyi

Inventor after: Liu Zhonghua

Inventor after: Hong Guosong

Inventor after: Li Jianhong

Inventor after: Gao Liang

Inventor after: Zheng Xuexiang

Inventor after: Hu Xiangping

Inventor after: Huang Lishun

Inventor before: Wu Weijie

Inventor before: Liu Zhonghua

Inventor before: Hong Guosong

Inventor before: Li Jianhong

Inventor before: Gao Liang

Inventor before: Zheng Xuexiang

Inventor before: Hu Xiangping

Inventor before: Huang Lishun

COR Change of bibliographic data

Free format text: CORRECT: INVENTOR; FROM: WU WEIJIE LIU ZHONGHUA HONG GUOSONG LI JIANHONG GAO LIANG ZHENG XUEXIANG HU XIANGPING HUANG LISHUN TO: WU WEIJIE XU CHAOYI LIU ZHONGHUA HONG GUOSONG LI JIANHONG GAO LIANG ZHENG XUEXIANG HU XIANGPING HUANG LISHUN

C14 Grant of patent or utility model
GR01 Patent grant
C56 Change in the name or address of the patentee

Owner name: ZHEJIANG JINGGONG STEEL STRUCTURE GROUP CO., LTD.

Free format text: FORMER NAME: ZHEJIANG JINGGONG STEEL STRUCTURE CO., LTD.

CP01 Change in the name or title of a patent holder

Address after: 312030 Zhejiang city of Shaoxing province Shaoxing County Keqiao Jianhu Road No. 1587

Patentee after: ZHEJIANG JINGGONG STEEL STRUCTURE GROUP CO., LTD.

Address before: 312030 Zhejiang city of Shaoxing province Shaoxing County Keqiao Jianhu Road No. 1587

Patentee before: Zhejiang Jinggong Steel Structure Co., ltd.