A construction method for a large-span steel box girder over a subway station

Abstract

The present application relates to a method for constructing a large-span steel box girder over a subway station, a hoisting scheme in which the additional stress on the area over the station after simulating and calculating the hoisting segments is less than the bearing capacity of the foundation of the area over the station; the hoisting scheme includes the number of assembling bracket components and steel box girder segments above the area over the station, and the installation area of ​​the assembling bracket components over the area over the station; the assembling bracket components include steel pipe brackets and strip foundations; the assembling bracket components are arranged on the installation area over the area over the station according to the hoisting scheme, and then the crane performs hoisting outside the area over the station; the strip foundation increases the contact area with the ground and disperses the compressive stress, and the weight and length of each hoisting segment are reduced by simulating and calculating the number of assembling bracket components and segments in advance, thereby effectively reducing the compressive stress of the steel beam on the subway roof during actual construction, solving the problem that the large-span steel box girder over the subway station roof cannot be implemented due to excessive load, and reducing engineering costs.

Description

Technical Field

[0001] The present application relates to the technical field of bridge construction, and in particular to a construction method for a large-span steel box girder that spans a subway station. Background Art

[0002] At present, for bridges across existing urban subway stations, due to consideration of the load conditions on the station roof, horizontal traction and jacking construction, longitudinal traction and jacking construction or general lifting and hoisting are generally adopted.

[0003] However, for the construction of steel box girders with large spans, variable cross-sections and curved surfaces located at the intersection of major traffic arteries, between the east and west subway entrances and exits:

[0004] (1) Conventional on-site hoisting cannot meet the requirements within the scope of the subway station. At the same time, the subway roof is covered with thin soil, which will cause significant deformation of the station subway roof and pose a greater safety risk to the subway.

[0005] (2) The longitudinal and transverse traction and pushing technology is adopted. The east and west sides of the bridge construction section are the entrances and exits of the subway station. The inside of the subway station entrance is a busy road, and the outside of the subway entrance is a construction area. There is no site or platform for transverse sliding.

[0006] (3) The longitudinal jacking process is adopted. The cross section of the bridge span shows a nonlinear change in the thickness of the beam at the pier to the mid-span beam. At the same time, the longitudinal slope of the steel box girder in this span is very large, the pier of the previous box girder is low, and the oblique and horizontal thrust settings are complex and difficult to control. In addition, the construction method generally adopted for the steel box girder or concrete box girder directly above the subway is jacking. The load transmitted to the subway roof by using general steel pipe temporary piers or disc brackets cannot meet the requirement of less than or equal to 20kpa, which will cause large deformation of the subway roof and cause great social harm. Summary of the invention

[0007] The embodiment of the present application provides a method for constructing a large-span steel box girder over a subway station, so as to solve the problem in the related art that when constructing a large-span steel box girder with a variable cross-section and variable curvature located at the intersection of major traffic arteries, between the east and west subway entrances and exits, temporary piers are set up, resulting in a large load on the station roof, deformation of the station subway roof and safety risks.

[0008] In a first aspect, a method for constructing a large-span steel box girder over a subway station is provided, comprising:

[0009] A lifting scheme is simulated and calculated that the additional stress on the upper station area after the lifting segment is less than the foundation bearing capacity of the upper station area; the lifting scheme includes the number of assembly bracket components and steel box girder segments on the upper station area, and the installation area of ​​the assembly bracket components corresponding to the upper station area; the assembly bracket components include steel pipe brackets and strip foundations arranged above and below; the lifting scheme is simulated and calculated that the additional stress on the upper station area after the lifting segment is less than the foundation bearing capacity of the upper station area, specifically including the following steps:

[0010] Set the initial number of the segments and the initial number of assembling bracket components, as well as the initial installation area of ​​the assembling bracket components corresponding to the upper station area; calculate the additional stress of each assembling bracket component on the upper station area after the corresponding segment is hoisted; determine whether the additional stress of each assembling bracket component on the upper station area is less than the foundation bearing capacity of the upper station area; if not, adjust the number of segments, the number of assembling bracket components and the installation area, and then update the number of segments, the number of assembling bracket components and the installation area; recalculate the additional stress of each assembling bracket component on the upper station area after the segment is hoisted according to the updated number of segments, the number of assembling bracket components and the installation area, and determine again whether the additional stress is less than the foundation bearing capacity of the upper station area; if so, use the initial number of segments and the initial number of assembling bracket components, as well as the initial installation area of ​​the assembling bracket components corresponding to the upper station area as the hoisting plan;

[0011] According to the hoisting scheme, an assembly bracket assembly is arranged in the installation area above the station area;

[0012] According to the lifting scheme, the segment is lifted onto the assembly bracket assembly by using a crane outside the upper station area.

[0013] In some embodiments, the hoisting scheme also includes the height of the strip foundation and the elevation of the adjustment pipe on the top of the steel pipe support;

[0014] When the additional stress of the assembled bracket components on the upper station area is greater than or equal to the foundation bearing capacity of the upper station area, in addition to adjusting the number of segments, the number of assembled bracket components and the installation area, it is also necessary to adjust the height of the strip foundation and the elevation of the adjusting pipe on the top of the steel pipe bracket to obtain a new lifting plan.

[0015] In some embodiments, calculating the additional stress of each assembled bracket assembly on the upper cross station area after the segment is hoisted includes the following steps:

[0016] Establish a geometric model of the assembled bracket assembly, and obtain the deadweight of the segment and the assembled bracket assembly;

[0017] Applying a first load combination to the geometric model, and combining the deadweight of the segment and the deadweight of the assembled support assembly to calculate the support reaction force of the assembled support assembly after the segment is hoisted;

[0018] Obtain the length and width of the strip foundation, the pressure diffusion angle of the strip foundation, and the distance from the bottom surface of the foundation in the upper cross station area to the weak underlying layer;

[0019] Based on the additional stress calculation formula, and in combination with the support reaction, the length and width of the strip foundation, the pressure diffusion angle of the strip foundation, and the distance from the bottom surface of the foundation of the upper station area to the weak underlying layer, the additional stress of the assembled bracket assembly on the upper station area after the lifting segment is calculated.

[0020] In some embodiments, the additional stress calculation formula is:

[0021] ;

[0022] Wherein, B is the width of the strip foundation ground; is the ground length of the strip foundation; Pk is the support reaction of the assembled bracket assembly after the segment is hoisted; Pc is the self-weight pressure value of the soil at the bottom of the foundation; z is the distance from the bottom of the foundation to the weak underlying layer; θ is the pressure diffusion angle of the strip foundation, and is the additional stress.

[0023] In some embodiments, after establishing the geometric model of the assembled support assembly, before calculating the support reaction force of the assembled support assembly after the segment is hoisted, the following steps are also included:

[0024] Applying a second load combination to the geometric model, and combining the deadweight of the segment and the deadweight of the assembled bracket assembly to calculate the bracket strength of the assembled bracket assembly after the segment is hoisted;

[0025] Determine whether the support strength is greater than the design value;

[0026] If it is greater than, the step of calculating the support reaction force of the assembled bracket assembly after the segment is hoisted is performed;

[0027] Otherwise, the size of the assembled bracket assembly is changed, and then the geometric model is adjusted with the new size; a second load combination is applied to the new geometric model, the bracket strength of the assembled bracket assembly after the segment is hoisted is recalculated, and then the step of determining whether the bracket strength is greater than the design value is returned;

[0028] The first load combination = 1.0 × dead load + 1.0 × construction load + 1.0 × wind load;

[0029] The second load combination = 1.2 × dead load + 1.4 × construction load + 1.1 × wind load;

[0030] The dead load includes the dead weight of the assembled support assembly, the construction load includes the dead weight of the segment, the dead weight of the construction personnel, and the dead weight of the lifting equipment, and the wind load includes the segment wind load and the assembled support assembly wind load.

[0031] In some embodiments, an assembly bracket assembly is provided on the installation area above the station area, specifically comprising the following steps:

[0032] Determine the center and vertical and horizontal cross line positions of each strip foundation according to the bridge centerline pile and horizontal point to calibrate the position of the strip foundation corresponding to the installation area on the upper span station area;

[0033] Dig a cushion trench in the corresponding installation area, and then install the strip foundation;

[0034] The steel pipe support is installed after all strip foundations are installed.

[0035] In some embodiments, before the segment is hoisted by a crane outside the upper station area, after the assembly bracket assembly is set in the installation area of ​​the upper station area according to the hoisting plan, the adjustment pipe is adjusted according to the elevation of the adjustment pipe at the top of the steel pipe support (1) in the hoisting plan.

[0036] In some embodiments, when the segments are hoisted by a crane outside the upper station area, the segments are hoisted sequentially according to the extension direction of the centerline of the bridge.

[0037] In some embodiments, after all segments are hoisted, the annular seams between the segments are welded, and the bridge deck accessories are hoisted and welded.

[0038] The beneficial effects of the technical solution provided by this application include:

[0039] The embodiment of the present application provides a method for constructing a large-span steel box girder over a subway station. The method comprises a hoisting scheme in which the additional stress on the area over the station after hoisting is calculated to be less than the bearing capacity of the foundation of the area over the station. The hoisting scheme comprises an assembly bracket assembly and the number of steel box girder segments above the area over the station, and an installation area of ​​the assembly bracket assembly over the area over the station. The assembly bracket assembly comprises steel pipe brackets and strip foundations arranged above and below. The assembly bracket assembly is arranged on the installation area over the station according to the hoisting scheme. The segments are hoisted on the assembly bracket assembly by a crane outside the station according to the hoisting scheme. Through the above steps, the strip foundation is used to increase the contact area with the ground to disperse the compressive stress. The weight and length of each hoisting segment are reduced by pre-simulating and calculating the number of assembly bracket assemblies and segments, thereby effectively reducing the compressive stress of the steel beam on the subway roof during actual construction, solving the problem that the large-span steel box girder over the subway station roof is too heavy to be implemented, and at the same time greatly reducing the engineering cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 A schematic diagram of a scenario for application construction provided in an embodiment of the present application;

[0042] Figure 2 A schematic diagram of the assembled bracket assembly and segments provided in an embodiment of the present application in the upper span station area;

[0043] Figure 3 A schematic diagram of a segment suspended on an assembled bracket assembly provided in an embodiment of the present application;

[0044] Figure 4 A schematic diagram of the structure of the assembled bracket assembly provided in an embodiment of the present application;

[0045] Figure 5 A rendering of the wind load calculation for the assembled bracket assembly provided in the embodiment of the present application;

[0046] Figure 6 The displacement deformation of the assembled bracket assembly provided in the embodiment of the present application when fully loaded;

[0047] Figure 7 A schematic diagram of the general process of the construction method of a large-span steel box girder across a subway station provided in an embodiment of the present application.

[0048] In the figure: 1. Steel pipe support; 2. Strip foundation. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0050] It should be understood that:

[0051] For the construction of steel box girders with large spans, variable cross-sections and variable curves located at the intersection of major traffic arteries, between the east and west subway entrances and exits, please refer to the specific application scenarios. Figure 1As shown, the middle span of the second section of the left line of the bridge longitudinally crosses the subway station. The longitudinal length of the subway station is 66m, the horizontal width is 58m, and the middle span of the second section above is 82m. The entire span crosses the main body of the subway station. The thickness of the subway roof is 60cm, and the covering soil is 1.6m. The west side is a busy avenue, including Figure 1 The mark S is the bridge section to be erected over the subway station, and the mark T is the subway station. The conventional construction methods include the following three:

[0052] (1) Conventional on-site hoisting cannot meet the requirements within the scope of the subway station. At the same time, the subway roof is covered with thin soil, which will cause significant deformation of the station subway roof and pose a greater safety risk to the subway.

[0053] (2) The longitudinal and transverse traction and pushing technology is adopted. The east and west sides of the bridge construction section are the entrances and exits of the subway station. The inside of the subway station entrance is a busy road, and the outside of the subway entrance is a military management area. There is no site or platform for transverse sliding.

[0054] (3) The longitudinal jacking process is adopted. The cross section of the bridge span shows a nonlinear change in the thickness of the beam at the pier to the mid-span beam. At the same time, the longitudinal slope of the steel box girder in this span is very large, the pier of the previous box girder is low, and the oblique and horizontal thrust settings are complex and difficult to control. In addition, the construction method generally adopted for the steel box girder or concrete box girder directly above the subway is jacking. The load transmitted to the subway roof by using general steel pipe temporary piers or disc brackets cannot meet the requirement of less than or equal to 20kpa, which will cause large deformation of the subway roof and cause great social harm.

[0055] In summary, it is more appropriate to use a method of hoisting combined with temporary piers for construction. However, due to the temporary piers, the load on the station roof is relatively large, and there are problems of deformation and safety risks on the station subway roof. Therefore, the embodiment of the present application provides a method for constructing a large-span steel box girder across a subway station, thereby realizing the erection of scaffolding and the lifting and hoisting of steel box girders in areas where the soil cover on the station roof is relatively thin.

[0056] See also Figure 2-Figure 6 , a construction method for a large-span steel box girder over a subway station, comprising:

[0057] Step 100, simulate and calculate the hoisting scheme in which the additional stress on the upper station area after the hoisting segment is less than the foundation bearing capacity of the upper station area; the hoisting scheme includes the number of assembly bracket components and steel box girder segments on the upper station area, and the installation area of ​​the assembly bracket components corresponding to the upper station area; the assembly bracket components include a steel pipe bracket 1 and a strip foundation 2 arranged above and below; the assembly bracket components can refer to Figure 2 and attached Figure 3 Structures shown; sections can be found at Figure 2 Mark X in the .

[0058] Step 200: Arrange the assembly bracket assembly on the installation area of ​​the upper span station area according to the lifting plan;

[0059] Step 300: hoist the segment onto the assembly bracket assembly using a crane outside the upper station area according to the hoisting plan.

[0060] Through the above steps, the strip foundation 2 is used to increase the contact area with the ground to disperse the compressive stress. The number of assembly bracket components and segments is calculated by pre-simulation, and the weight and length of each lifting segment are reduced, which effectively reduces the compressive stress of the steel beam on the subway roof during actual construction. In addition, due to the advance analysis and calculation, the number of assembly bracket components and segments obtained can avoid actual construction adjustments, eliminate risks in advance, and solve the problem of large-span steel box girders across the subway station roof being too heavy to be implemented, while greatly reducing engineering costs.

[0061] It can also be understood as dividing the steel box girder into sections so that the weight loaded on the corresponding assembly bracket components is reduced, so that the load of each assembly bracket component on the subway station roof will not exceed the bearing capacity of the foundation, thereby avoiding deformation and safety risks of the station subway roof.

[0062] In some preferred embodiments, the specific steps of step 100 are:

[0063] Step 1001, setting the initial number of segments and the initial number of assembly bracket components, and the initial installation area of ​​the assembly bracket components corresponding to the upper span station area;

[0064] Step 1002, calculating the additional stress of each assembled bracket assembly on the upper cross station area after the segment is hoisted;

[0065] Step 1003, determining whether the additional stress of all assembled bracket components on the upper station area is less than the foundation bearing capacity of the upper station area;

[0066] Step 1004: If not, adjust the number of segments, the number of assembly bracket components and the installation area, and then update the number of segments, the number of assembly bracket components and the installation area; recalculate the additional stress of each assembly bracket component on the upper station area after the segment is hoisted according to the updated number of segments, the number of assembly bracket components and the installation area, and again determine whether the additional stress is less than the foundation bearing capacity of the upper station area;

[0067] Step 1005: If yes, the initial number of segments and the initial number of assembly bracket components, as well as the initial installation area of ​​the assembly bracket components corresponding to the upper span station area are used as the lifting plan.

[0068] When making the above adjustments, you can first adjust the number of segments separately for calculation, or you can first adjust the number of assembled bracket components and the installation area separately. The installation area includes the spacing distance between two adjacent assembled bracket components; you can also adjust the number of segments, the number of assembled bracket components and the installation area at the same time; as long as the requirements are met.

[0069] Furthermore, in the above step 1004, the hoisting scheme also includes the height of the strip foundation 2 and the elevation of the adjustment pipe on the top of the steel pipe support 1;

[0070] When the additional stress of the assembled bracket components on the upper station area is greater than or equal to the foundation bearing capacity of the upper station area, in addition to adjusting the number of segments, the number of assembled bracket components and the installation area, it is also necessary to adjust the height of the strip foundation 2 and the elevation of the adjusting pipe on the top of the steel pipe bracket 1 to obtain a new lifting plan.

[0071] The elevation of the bottom of the composite corresponding segment is achieved during hoisting, and then the elevation of the adjusting pipe on the top of the steel pipe support 1 is set to ensure that the hoisted segment is consistent with the linear shape of the bridge.

[0072] In some preferred embodiments, step 1002, calculating the additional stress of an assembled bracket assembly on the upper cross station area after the segment is hoisted, includes the following steps:

[0073] Step 10021, establishing a geometric model of the assembled support assembly, and obtaining the deadweight of the segment and the deadweight of the assembled support assembly;

[0074] Step 10022: applying a first load combination to the geometric model, and combining the deadweight of the segment and the deadweight of the assembled support assembly to calculate the support reaction force of the assembled support assembly after the segment is hoisted;

[0075] Step 10023, obtaining the length and width of the strip foundation 2, the pressure diffusion angle of the strip foundation 2, and the distance from the bottom surface of the foundation of the upper cross station area to the weak underlying layer;

[0076] Step 10024, based on the additional stress calculation formula, and in combination with the support reaction force, the length and width of the strip foundation 2, the pressure diffusion angle of the strip foundation 2, and the distance from the bottom surface of the foundation of the upper station area to the weak underlying layer, calculate the additional stress of the assembled bracket assembly on the upper station area after the segment is hoisted.

[0077] The additional stress calculation formula is: ;

[0078] Wherein, B is the width of the ground of strip foundation 2; is the ground length of strip foundation 2; Pk is the support reaction force of the assembled bracket assembly after the segment is hoisted; Pc is the self-weight pressure value of the soil at the bottom of the foundation; z is the distance from the bottom of the foundation to the weak underlying layer; θ is the pressure diffusion angle of strip foundation 2, For additional stress.

[0079] Furthermore, between step 10021 and step 10022, the following steps are also included:

[0080] Applying a second load combination to the geometric model and combining the deadweight of the segment and the deadweight of the assembled bracket assembly to calculate the bracket strength of the assembled bracket assembly after the segment is hoisted;

[0081] Determine whether the support strength is greater than the design value;

[0082] If it is greater than, the step of calculating the support reaction force of the assembled bracket assembly after the segment is hoisted is performed;

[0083] Otherwise, change the size of the assembled bracket component, and then adjust the geometric model with the new size; apply the second load combination to the new geometric model, recalculate the bracket strength of the assembled bracket component after the lifting segment, and then return to the step of determining whether the bracket strength is greater than the design value.

[0084] The first load combination above = 1.0 × dead load + 1.0 × construction load + 1.0 × wind load;

[0085] The second load combination = 1.2 × dead load + 1.4 × construction load + 1.1 × wind load;

[0086] The dead load includes the dead weight of the assembled support assembly, the construction load includes the dead weight of the segment, the dead weight of the construction personnel, and the dead weight of the lifting equipment, and the wind load includes the segment wind load and the assembled support assembly wind load.

[0087] The specific calculation provides an embodiment, including:

[0088] Using the software Midas Civil 2020, the model is then built according to the size and material of the assembled bracket components; different load combinations are then applied; you can refer to the relevant attached Figure 5 and 6 , the content displayed.

[0089] The loads include:

[0090] Constant load, load generated by the self-weight of the assembled bracket components, gravity acceleration g=9.8m / s2

[0091] The construction loads generated by the deadweight of the segment, construction workers, and machinery during hoisting are live loads. It is known that the heaviest steel beam segment hoisted on the assembled bracket assembly is 52 tons, and each segment uses 4 adjustment tubes as fulcrums. Therefore, the vertical construction load Fv = the node load converted from the steel beam hoisting, 13t, including human and machine loads.

[0092] Wind load is based on the "Highway Bridge Wind Resistance Design Code" JTG / T 3360-01-2018

[0093] Local wind speed V=27.7m / s;

[0094] Segmental lateral wind load: FH1=0.5×1.25×(1.49×0.84×1.02×1×0.86×27.7)2×1.8×1.9=2KN / m, which is converted into a maximum node load of FHJ1=2×14 / 4=7KN;

[0095] Segmental longitudinal bridge wind load: FH2=7×0.25=1.8KN;

[0096] Wind load of assembled bracket components: Fh1 = 0.5 × 1.25 × (1.49 × 0.84 × 1.02 × 1 × 0.86 × 27.7) 2 × 0.6 × 0.478 = 168 N / m;

[0097] According to the General Specifications for Highway Bridge and Culvert Design, the wind load partial coefficient is 1.1 and the combined value coefficient is 0.75. Figure 5 shown.

[0098] Combine the loads and calculate the strength of the components using the load combination = 1.2 × constant load + 1.4 × construction load + 1.1 × wind load; calculate the stiffness and support reaction of the components using the standard combination = 1.0 × constant load + 1.0 × construction load + 1.0 × wind load; the support feet of the assembled bracket components are fully constrained by displacement; calculate the strength, stiffness, and displacement deformation of the bracket; the calculation of displacement deformation is as follows Figure 6 shown.

[0099] The above steps can ensure the construction effect of the assembled bracket components in actual construction, ensure construction safety, and calculate additional stress on the basis of ensuring construction safety.

[0100] In some preferred embodiments, this case does not exclude the scheme of using a crane for lifting in the upper station area. At this time, it is necessary to calculate whether the additional stress of the crane after lifting is greater than the bearing capacity of the foundation. If it is greater, the above lifting is performed outside the upper station area.

[0101] To calculate whether the additional stress of the crane after hoisting is greater than the bearing capacity of the foundation, refer to the following steps:

[0102] It is known that a 200t truck crane weighs 55t, with a counterweight of 70t, G0=55+70=125t, the maximum lifting weight (including lifting equipment) G1=50t, the maximum lifting radius R=14m, the outrigger spacing a=9.1m, b=8.3m, θ is the boom plane angle, and the boom rotation center, outrigger center, and vehicle center of gravity are approximately the same point.

[0103] According to the moment balance, the reaction force of each leg is calculated as follows:

[0104] F 1M +

[0105] F 2M -

[0106] F 3M +

[0107] F 4M -

[0108] The dynamic load coefficient of hoisting is 1.2. According to calculation, the maximum support reaction force occurs when θ=50°.

[0109] F1= 1×G0 / 4+1.2×G1 / 4+1.2×F 1M =114.7t.

[0110] F2 = 1×G0 / 4+1.2×G1 / 4+1.2×F 2M =92.4t.

[0111] F3 = 1×G0 / 4+1.2×G1 / 4+1.2×F 3M =114.7t.

[0112] F4= 1×G0 / 4+1.2×G1 / 4+1.2×F 4M =92.4t.

[0113] At this time, the maximum support reaction force is 114.7t.

[0114] There is a 2.2m×2m pad under each leg. Therefore, the (Pk) plane load g=114.7 / 4.4=26.1t / m2=261kpa.

[0115] Additional stress at 2.7m below the foundation:

[0116]

[0117] Where: b, l---width and length of rectangular foundation or strip foundation ground (m)

[0118] Pk---The average pressure value at the bottom of the foundation corresponding to the standard combination of actions (kPa)

[0119] Pc---The self-weight pressure value of the soil at the bottom of the foundation corresponding to the standard combination of actions (kPa)

[0120] z---the distance from the bottom of the foundation to the weak underlying layer (m)

[0121] θ---pressure diffusion angle of cushion (material), take 23°

[0122] ---Distance from the bottom of the foundation to the weak underlying layer (m)

[0123]

[0124]

[0125] Since there is a subway station 2.7m below the foundation, the bearing capacity of the foundation shall not be greater than 20kPa, and the calculated Pz=59.6kPa>20kPa, so the steel box girder hoisted by the truck crane above the station does not meet the requirements.

[0126] In some preferred embodiments, an assembly bracket assembly is provided on the installation area of ​​the upper cross station area, specifically comprising the following steps:

[0127] Determine the center and vertical and horizontal cross line positions of each strip foundation 2 according to the bridge centerline pile and horizontal point to calibrate the position of the installation area of ​​the strip foundation 2 corresponding to the upper span station area;

[0128] Dig a cushion groove in the corresponding installation area, and then install the strip foundation 2;

[0129] After all strip foundations 2 are installed, install the steel pipe support 1. Strip foundation 2 adopts multiple length and width dimensions such as 7000mm×1800mm×600mm, 4300mm×1800mm×600mm, etc., with a thickness of 600mm. The support concrete foundation adopts C30 concrete with double-layer bidirectional reinforcement. Taking into account the principles of green construction, material saving, land saving, energy saving, water saving, and environmental protection, the principle of on-site prefabrication and recycling is adopted. After the use of this project is completed, it can be dragged to other similar projects of the company for use. According to the cross lines of the on-site lofting, the prefabricated strip foundation 2 is positioned and installed. Before installation, the flatness of the ground is inspected and accepted, and those that do not meet the requirements are processed to ensure that the strip foundation is closely attached to the base; after hoisting, the four corners of the strip foundation are reviewed and accepted. The next step of construction can be carried out after the acceptance is completed. The main structure of the steel pipe support 1 is made of Q235 steel pipes, and the top is welded with double rows of 40a steel and steel pipes. The cross sections of each load-bearing steel pipe and the connection system on the side are connected with C16 channel steel to enhance the overall stability of the structure. Figure 3 and Figure 4 shown.

[0130] In some preferred embodiments, the step 400 is also included, before the segment is hoisted by a crane outside the upper station area, after the assembly bracket assembly is set in the installation area of ​​the upper station area according to the hoisting scheme, the adjustment pipe is adjusted according to the elevation of the adjustment pipe at the top of the steel pipe bracket (1) in the hoisting scheme. After the adjustment is completed, when the segment is hoisted by a crane outside the upper station area, the segments are hoisted in sequence according to the extension direction of the center line of the bridge; the advantage of this is to ensure that the linear shape of multiple segments is the same as the designed linear shape of the bridge, avoid the problem that the cross section of the bridge span presents a nonlinear change in the thickness of the beam at the pier to the mid-span beam caused by the top-pushing construction, and at the same time, the longitudinal slope of the steel box girder of this span is very large, the pier of the previous box girder is low, and the oblique and horizontal thrust settings are complex and difficult to control.

[0131] Step 500: After all segments are hoisted, the annular seams between the segments are welded, and the bridge deck accessories are hoisted and welded.

[0132] The welding operation is:

[0133] (1) Bridge construction preparation

[0134] a. According to the total amount of welding projects on the bridge and the construction progress requirements, a welding power supply with a capacity of 200KVA is configured on each hoisting welding work surface.

[0135] b. Before construction, hoist and debug the power distribution equipment, welding equipment, ventilation and dust removal equipment, windproof scaffolding required for CO2 welding, rust removal equipment, gouging tools, flame cutting tools, waterproof and moisture-proof equipment, welding material drying box, high-strength bolt cutting and other necessary construction equipment and tools, and appoint full-time maintenance management personnel.

[0136] c. Set up a temporary working platform and edge protection before construction.

[0137] d. Purchase welding materials for construction in advance and carry out re-inspection.

[0138] e. Establish and improve the post responsibility system, safety system, power supply system, ventilation and dust removal system and other rules and regulations on bridge construction, set up power safety notices and power safety facilities on the bridge, and implement various systems to the responsible persons to ensure construction safety.

[0139] (2) Specific operations of on-site welding

[0140] a. Before welding, carefully check whether the size of the breach is qualified, and remove water, rust, oil stains in the breach, as well as welding slag, spatter and dirt outside the positioning weld.

[0141] b. After welding, carefully remove defects such as spatter, weld bead, undercut, surface pores, lack of fusion, cracks, etc. on the weld.

[0142] c. Welding sequence

[0143] During on-site welding, a detailed welding sequence is arranged according to the hoisting sequence. Taking the main line hoisting as an example, the welding sequence of each weld in the main bridge hoisting process is analyzed. Temporary welding adopts the code plate connection, the code plate is welded firmly, and the code plate is provided with a welding hole. After welding, the welding nodules should be polished to ensure that the bridge deck steel plate is flat and clean.

[0144] Step 1: Hoist the middle box girder block, first complete the longitudinal seam welding of the top plate and the bottom plate at the same time, and then complete the welding of the middle web plate.

[0145] The second step: hoist the cantilever blocks on both sides. The cantilever blocks on both sides can be constructed simultaneously according to the on-site construction personnel and equipment conditions. First, complete the longitudinal seam welding of the top plate and the bottom plate on both sides, and then complete the welding of the middle web plate.

[0146] Step 3: Complete the circumferential seam welding. When welding the circumferential seam, first weld the top plate and bottom plate welds, in the order from the middle to the sides; then weld the web position welds on both sides, in the principle of bottom to top.

[0147] Step 4: Complete the welding of the patch parts.

[0148] d. Welding method

[0149] e. Use submerged arc automatic welding as much as possible, that is, use C02 gas shielded semi-automatic welding for the base and submerged arc automatic welding for the cover.

[0150] f. The on-site welding sequence should be formulated based on the principle of welding long welds first and short welds later, and welding welds with large deposits first and welds with small deposits later.

[0151] g. Connection welds at the bridge section construction site: first weld the transverse butt welds of the top and bottom plates, then weld the butt welds of the web plates, and finally weld the welds of the patching section.

[0152] h. During welding, the product test plate should be welded according to the requirements of the supervision engineer and the relevant process files. The thickness, rolling direction and groove size of the product test plate should be consistent with the joint it represents, and the same process method and parameters should be used for welding at the same time. The product test plate should be marked and can only be removed and transferred to the test department for sampling and testing after being accepted by the supervision engineer.

[0153] i. The circumferential seam between beam sections is a transverse butt weld, which is the main force-transmitting weld and requires 100% penetration and 100% nondestructive testing. Due to the poor construction conditions on the bridge and the large weld constraint, experienced welders with high welding skills should be selected from qualified welders for welding.

[0154] j. The ambient temperature for welding on bridges should be above 5°C, the relative humidity should not exceed 80%, and the wind force should not exceed level 5. If welding is carried out in the open air or on rainy days, effective wind, rain and moisture protection measures should be taken.

[0155] k. Position welding can be done by manual welding or CO2 gas shielded welding. When position welding is performed, the relevant provisions of the bridge connection welding process shall be followed. When cracks or other serious defects occur in the position welding, the cause should be found out first, then the defects should be removed and additional position welding should be performed.

[0156] l. Before welding, thoroughly check the misalignment, gap and groove size of the interface.

[0157] m. Before welding, use a grinding wheel to remove the rust on the surface. The removal range is 50mm on both sides of the weld. Welding must be done within 24 hours after rust removal to prevent the joint from rusting or being contaminated again. Otherwise, welding should be done after rust removal.

[0158] When using CO2 gas shielded welding in a steel box, the welder must wear a protective mask and must be equipped with ventilation and safety facilities to prevent the CO generated during welding from affecting the welder's safety.

[0159] It should be noted in this application that the above crane has a slewing radius of 46 meters and a boom length of 60 meters. Under this condition, the maximum lifting capacity is 30 tons, and segment 8 weighs about 26 tons to meet the requirements of the lifting span.

[0160] The beneficial effects are:

[0161] 1. Effectively control the hoisting weight of single-segment steel box girders, reduce the hoisting of single-segment steel box girders, reduce the reaction force of the crane and steel beams on the roof of the subway station, ensure that the steel box girders are installed under the allowable stress range, and ensure the installation quality of the steel beams.

[0162] 2. Effectively decompose the compressive stress of temporary piers on the roof, increase the number of temporary piers, reduce the spacing between temporary piers, and set up expanded strip foundations under the temporary piers to further decompose and reduce the impact on the roof of the subway station.

[0163] 3. High safety: Increasing the number of sections is conducive to reducing the lifting weight, helping to narrow the lifting range, reducing the impact on the travel of surrounding residents and road traffic, and further improving safety.

[0164] 4. Reduce costs and protect the environment. The use of horizontal top-pushing requires a larger site, and the surrounding trees and forests require the relocation of seedlings. The top-pushing cost is relatively high. By using this method, the cost is effectively reduced, while protecting the surrounding ecological environment and reducing the project cost.

[0165] With the national urban renewal process, under the influence of the existing surrounding environment (subway, integrated pipe gallery, surrounding buildings, box culverts, underground pipelines, underground squares and other underground space structures), reliable construction measures are taken to minimize the impact on the surrounding environment.

[0166] Practical application cases:

[0167] The subway is buried shallowly about 1.5m, and 75% of the mid-span brackets fall in the subway workshop section, an area of ​​about 62m long. If the construction is not careful, the deformation of the top plate will exceed the standard, which will cause the subway to stop operating. The impact and loss are immeasurable. In view of this situation, the left second steel box girder is hoisted by adding prefabricated strip foundations, increasing the bracket spacing ("full-house style"), and increasing the number of steel box girder segments. This directly avoids the influence of thin soil cover on the subway top plate, load sensitivity, and large load span, effectively simplifies the operation procedures of steel box girder hoisting, improves hoisting efficiency and quality, and completes the bridge pile steel box girder hoisting construction task one month ahead of schedule. According to monitoring, the deformation stress of the subway top plate remained within the allowable range during the construction of the left second joint, and no alarm occurred. The project quality was commended by the owner and the supervision unit. At the same time, this technology uses prefabricated strip foundations, which are green, environmentally friendly, reusable, and resource-saving.

[0168] In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0169] It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0170] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied for herein.

Claims

1. A method for constructing a large-span steel box girder over a subway station, characterized in that: It includes: The simulation calculated the hoisting scheme in which the additional stress on the upper station area after the hoisting segment is less than the foundation bearing capacity of the upper station area; The lifting scheme includes the number of assembled bracket components and steel box beam segments on the upper station area, and the installation area of ​​the assembled bracket components corresponding to the upper station area; the assembled bracket components include steel pipe brackets (1) and strip foundations (2) arranged above and below; and the lifting scheme is simulated and calculated to obtain a lifting scheme in which the additional stress on the upper station area after the segments are lifted is less than the bearing capacity of the foundation of the upper station area, specifically including the following steps: Set the initial number of the segments and the initial number of assembling bracket components, as well as the initial installation area of ​​the assembling bracket components corresponding to the upper station area; calculate the additional stress of each assembling bracket component on the upper station area after the corresponding segment is hoisted; determine whether the additional stress of each assembling bracket component on the upper station area is less than the foundation bearing capacity of the upper station area; if not, adjust the number of segments, the number of assembling bracket components and the installation area, and then update the number of segments, the number of assembling bracket components and the installation area; recalculate the additional stress of each assembling bracket component on the upper station area after the segment is hoisted according to the updated number of segments, the number of assembling bracket components and the installation area, and determine again whether the additional stress is less than the foundation bearing capacity of the upper station area; if so, use the initial number of segments and the initial number of assembling bracket components, as well as the initial installation area of ​​the assembling bracket components corresponding to the upper station area as the hoisting plan; According to the hoisting scheme, an assembly bracket assembly is arranged in the installation area above the station area; According to the lifting scheme, the segment is lifted onto the assembly bracket assembly by using a crane outside the upper station area.

2. The method for constructing a large-span steel box girder across a subway station as claimed in claim 1, characterized in that: The lifting scheme also includes the height of the strip foundation (2) and the elevation of the adjustment pipe on the top of the steel pipe support (1); When the additional stress of the assembled bracket components on the upper station area is greater than or equal to the foundation bearing capacity of the upper station area, in addition to adjusting the number of segments, the number of assembled bracket components and the installation area, it is also necessary to adjust the height of the strip foundation (2) and the elevation of the adjustment pipe on the top of the steel pipe bracket (1) to obtain a new lifting plan.

3. The method for constructing a large-span steel box girder across a subway station as claimed in claim 1, characterized in that: Calculate the additional stress of each assembly bracket component on the upper span station area after the segment is hoisted, including the following steps: Establish a geometric model of the assembled bracket assembly, and obtain the deadweight of the segment and the assembled bracket assembly; Applying a first load combination to the geometric model, and combining the deadweight of the segment and the deadweight of the assembled support assembly to calculate the support reaction force of the assembled support assembly after the segment is hoisted; Obtain the length and width of the strip foundation (2), the pressure diffusion angle of the strip foundation (2), and the distance from the bottom surface of the foundation in the upper cross station area to the weak underlying layer; Based on the additional stress calculation formula, and in combination with the support reaction force, the length and width of the strip foundation (2), the pressure diffusion angle of the strip foundation (2), and the distance from the bottom surface of the foundation of the upper station area to the weak underlying layer, the additional stress of the assembled bracket assembly on the upper station area after the segment is hoisted is calculated.

4. The method for constructing a large-span steel box girder across a subway station as claimed in claim 3, characterized in that: The additional stress calculation formula is: ; Where B is the width of the strip foundation (2) ground surface; is the ground length of the strip foundation (2); Pk is the support reaction force of the assembled bracket assembly after the segment is hoisted; Pc is the self-weight pressure value of the soil at the bottom of the foundation; z is the distance from the bottom of the foundation to the weak underlying layer; θ is the pressure diffusion angle of the strip foundation (2), For additional stress.

5. The method for constructing a large-span steel box girder across a subway station as claimed in claim 3, characterized in that: After the geometric model of the assembled support assembly is established, the following steps are also included before the support reaction force of the assembled support assembly after the segment is hoisted: Applying a second load combination to the geometric model, and combining the deadweight of the segment and the deadweight of the assembled bracket assembly to calculate the bracket strength of the assembled bracket assembly after the segment is hoisted; Determine whether the support strength is greater than the design value; If it is greater than, the step of calculating the support reaction force of the assembled bracket assembly after the segment is hoisted is performed; Otherwise, the size of the assembled bracket assembly is changed, and then the geometric model is adjusted with the new size; a second load combination is applied to the new geometric model, the bracket strength of the assembled bracket assembly after the segment is hoisted is recalculated, and then the step of determining whether the bracket strength is greater than the design value is returned; The first load combination = 1.0 × dead load + 1.0 × construction load + 1.0 × wind load; The second load combination = 1.2 × dead load + 1.4 × construction load + 1.1 × wind load; The dead load includes the dead weight of the assembled support assembly, the construction load includes the dead weight of the segment, the dead weight of the construction personnel, and the dead weight of the lifting equipment, and the wind load includes the segment wind load and the assembled support assembly wind load.

6. The method for constructing a large-span steel box girder across a subway station as claimed in claim 2, characterized in that: Arranging an assembly bracket assembly on the installation area of ​​the upper span station area specifically includes the following steps: Determine the center and vertical and horizontal cross line positions of each strip foundation (2) according to the bridge centerline pile and the horizontal point, so as to calibrate the position of the installation area of ​​the strip foundation (2) corresponding to the upper span station area; Dig a cushion trench in the corresponding installation area and then install the strip foundation (2); After all strip foundations (2) are installed, the steel pipe support (1) is installed.

7. The method for constructing a large-span steel box girder across a subway station as claimed in claim 6, characterized in that: Before the segment is hoisted by a crane outside the upper station area, after the assembly bracket assembly is set in the installation area of ​​the upper station area according to the hoisting plan, the adjustment pipe is adjusted according to the elevation of the adjustment pipe at the top of the steel pipe support (1) in the hoisting plan.

8. The method for constructing a large-span steel box girder across a subway station as claimed in claim 7, characterized in that: When using a crane to lift segments outside the upper station area, the segments are lifted sequentially in the extension direction of the bridge centerline.

9. The method for constructing a large-span steel box girder over a subway station as claimed in claim 8, characterized in that: After all segments are hoisted, the annular seams between segments are welded, and the bridge deck accessories are hoisted and welded.

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