Technology for non-support suspended splicing of urban viaduct

Abstract

The invention discloses a support-free suspension splicing process for an urban viaduct, and belongs to the technical field of large-span variable-cross-section viaduct steel box girder installing.According to the structural composition characteristics of the urban viaduct steel box girder, all sections of the viaduct are divided and deepened, the steel box girder is divided in a longitudinal segmentation length positioning mode and divided according to box chambers in the transverse direction, and the steel box girder is fixed and spliced in the middle of the viaduct; and establishing a viaduct model and performing checking calculation, and performing calculation and checking on parts with concentrated stress or weak components in the structure in the process of simulating splicing of each section of the steel box girder. According to the invention, reliable and stable implementation of the whole suspended splicing process is ensured, and meanwhile, the adopted elevation and stress monitoring device provides accurate data for quality control and stress monitoring in the suspended splicing process, so that the quality and safety of the suspended splicing process are ensured.

Description

Technical Field

[0001] The invention relates to a process for supporting-free cantilever assembly of urban viaducts, and belongs to the technical field of installation of steel box girders of large-span and variable-section viaducts. Background Art

[0002] As the scale of urban development grows, the roads in urban construction become more and more complex and taller. In order to ease the traffic pressure in some areas of the city and improve the efficiency of transportation, there are more and more high-span urban viaduct projects, so the installation processes of urban viaducts are also varied. For example, the municipal viaduct located above the urban rail transit station cannot be equipped with temporary supports and other facilities under the bridge, so the installation process of "tubular support + crane lifting" cannot be adopted; and the steel box girder structure of the viaduct is designed as a height and width section of unequal diameter, and the construction difficulty of the "assembly at both ends + top push and close" process is relatively large, and it is not conducive to the quality control of the entire top push process; if the "bridge side assembly + lateral sliding" process is adopted, the conditions of the buildings on one side of the road on the site cannot meet the construction conditions.

[0003] Temporary supports and other facilities are set up above urban rail transit stations to build viaducts. The bearing capacity of the supports will have a great impact and hidden dangers on the rail transit running below, so the viaduct must be installed without supports. There are many kinds of processes for viaduct installation without supports, such as the more familiar "retaining the tower after retaining + cantilevered hoisting" process, which allows the steel box girder to be smoothly installed without supports. However, according to the above process, there are cyclic disassembly and installation of ropes, tensioning anchor cables, and retaining lifting ears after welding, which are cumbersome, time-consuming, and risky. Although the erected tower can retain the steel box girder at the front cantilever to prevent the front box girder from deflecting and causing structural deformation, the tower used in the process is generally more than 30 meters high. If it is constructed in an open field, the on-site conditions are completely acceptable, but it is located in an urban traffic fortress, with a busy traffic road on one side and a building on the other side. The 30-meter-high tower will bring serious safety hazards to all roads and buildings covered in the stress area. Therefore, the "retaining towers and hanging assembly" process cannot be used for the installation of urban viaducts without brackets. In view of the installation and construction of urban viaduct steel box girders under the above conditions, we analyzed the structural characteristics of the viaduct itself and the on-site road environment and bridge location conditions, and designed a "no bracket hanging assembly" process for the installation of urban viaducts under special circumstances. Summary of the invention

[0004] The main purpose of the present invention is to solve the technical problem of assembling urban viaducts without any backup. During the installation of urban viaducts that cross underground buildings and are located at traffic fortresses, in order to avoid damage to underground buildings during construction and reduce the impact on surrounding buildings and road traffic, a rapid installation process for viaduct steel box girders without supports is proposed.

[0005] The purpose of the present invention can be achieved by adopting the following technical solutions:

[0006] A process for cantilevering urban viaducts without supports, comprising the following steps:

[0007] Step 1: According to the structural characteristics of the steel box girder of the urban viaduct, the sections of the viaduct are divided and deepened, and the steel box girder is divided into longitudinal sections by length and transversely by box chambers;

[0008] Step 2: Establish a viaduct model and perform calculations to simulate the assembly process of each segment of the steel box girder, and perform calculations and checks on the parts of the structure where stress is concentrated or components are weak;

[0009] Step 3: Before the steel box girder of the middle span viaduct is formally suspended, the erection, assembly and welding process of the side span steel box girder is completed, the assembly bracket of the side span steel box girder is removed, the side span steel box girder is completely lowered on the spherical bearing on the top of the pier, and the connection and fixation of the spherical bearing and the bottom plate of the side span steel box girder are completed;

[0010] Step 4: According to the station design drawing and the on-site conditions, draw the building edge line of the underground rail transit station on the ground below the middle span steel box girder bridge, then level the site between the cordon and the adjacent buildings, arrange crawler cranes, and then hoist the components for the steel box girder suspension assembly onto the bridge deck;

[0011] Step 5: Position and install fixed hinges above the corresponding position of the web plate of the H4 segment of the side span steel box girder, and install a set of corresponding movable hinges on the upper plane of the G4 segment steel box girder to be hoisted. The hinges are fixed to the top plate of the steel box girder, and triangular ribs are added to the side of each set of hinges to fix them to the top plate;

[0012] Step 6: Arrange the measurement points according to the new pre-camber drawing calculated previously, mark the measurement points at the four corner positions of the G4 steel box girder segment to be hoisted, then use the crawler crane to lift the steel box girder segment off the ground, measure the relative elevations between the four groups of measurement points in the hoisted state, and calculate the absolute height difference between each group of measurement points. Adjust the relative elevations of the four corner positions of the steel box girder by adding or removing horseshoe shackles at each rope end;

[0013] Step 7: According to the principle of staggered top and bottom webs of the divided steel box girder segments, the top plate of the G4 steel box girder segment needs to be pressed on the webs of the H4 segment of the side span steel box girder. The G4 steel box girder segment is lifted to the top of the installation position by a crawler crane to complete the pin insertion process;

[0014] Step 8: Secondary measure the absolute elevation values ​​of the four groups of measurement and control points of the G4 steel box girder segment, and compare them with the design elevation values ​​of the steel box girder under this process to clarify the elevation deviation values ​​of each measurement and control point;

[0015] Step 9: Arrange multiple sets of tooling devices on the top plate between the G4 steel box girder segment and the side span steel box girder H4 segment. The arranged tooling devices are fully welded to the top plate of the steel box girder, and a T-type yard plate is used to connect the top and bottom web plates;

[0016] Step 10: Establish a network of elevation settlement observation points from the steel box girder segment to the side span steel box girder K4 segment on the bridge deck. After the installation of the stacking plate and tooling between the G4 steel box girder segment and the side span steel box girder H4 segment, conduct the first elevation settlement observation of the G4 steel box girder segment and the side span steel box girder H4 segment before the formal welding operation. Then, conduct the welding operation of the G4 steel box girder and the side span steel box girder H4 segment in the order of web plate, bottom plate, top plate, embedded U rib and T rib, and I rib.

[0017] Step 11: Perform 100% non-destructive testing on the top and bottom web butt welds between the G4 steel box girder and the H4 segment of the side span steel box girder, and perform 50% non-destructive testing on the welds between the embedded U ribs and the T ribs and I ribs. The butt welds are confirmed to be qualified by non-destructive testing, and stress monitoring devices are arranged on the top plate, bottom plate, and web plate in the web position area to provide stress monitoring data for the subsequent crawler crane hook release process;

[0018] Step 12: Before the crawler crane releases the hook, the elevation and stress measurement and control points are arranged in place, and the elevation of the cantilever end of the G4 segment steel box girder, the elevation of the outermost K4 segment of the side span, and the stress values ​​of the G4 steel box girder segment and the H4 segment steel box girder of the side span steel box girder corresponding to the crawler crane lifting weight after each reduction are made;

[0019] Step 13: After the installation of the G4 steel box girder segment is completed, except for the special H-shaped steel fixture, the other temporary facilities such as the code plate and the folding leaf are removed. Then, according to the principle of from far to near, the G5 steel box girder segment is suspended and assembled. According to the process of step 4 to step 12, the positioning, measurement, assembly, welding, flaw detection, monitoring, and hook loosening operations are carried out in sequence. At the same time, in order to ensure the transverse slope of the G5 steel box girder segment and the G4 segment steel box girder after they are in place, multiple sets of H-shaped steel fixtures are arranged on the top plates of the G5 steel box girder segment and the G4 steel box girder segment;

[0020] Step 14: After the installation of the G5 steel box girder segment is completed, re-measure the elevation of the cantilever end of the G4 steel box girder, and at the same time observe the elevation of the cantilever end of the G5 steel box girder segment and the elevation of the K4 segment at the outermost end of the side span. Since the G3 steel box girder segment is close to the front of the crane, it is necessary to consider in advance whether the G3 steel box girder segment to be hoisted will affect the boom operation of the crawler crane. Then, perform the cantilever assembly and installation of the G3 steel box girder segment in the order of steps 4 to 13, and perform the operations of positioning, measuring, assembling, welding, flaw detection, monitoring, and hook loosening. At this point, the cantilever assembly operations of the three groups of main box chambers of the G3 steel box girder segment, the G4 steel box girder segment, and the G5 steel box girder segment are completed;

[0021] Step 15: The cantilever assembly of the E steel box girder segment on the other side of the viaduct is carried out in the order of Steps 4 to 14, and the operations are carried out in accordance with the procedures of positioning, measuring, assembling, welding, flaw detection, monitoring, and hook loosening;

[0022] Step 16: Re-measure the net distances L1 to Ln between the cantilever ends of the steel box girders of the E and G segments, and cut and trim the lengths of the top and bottom webs of the steel box girders of the integrated segment F based on the distances. Since both ends of the top plate of the F segment extend out of the webs, the crawler crane first lifts the steel box girder to the top of the bridge, and then performs the operations of positioning, assembly, welding, flaw detection, and hook loosening in sequence from top to bottom;

[0023] Step 17: The assembly sequence of the main box chamber of the closing section F steel box girder is F4-F5-F3. The remaining cantilever steel structures of the viaduct EFG segment are hoisted synchronously and symmetrically to achieve the purpose of rapid installation of the urban viaduct steel box girder without support.

[0024] Optionally, in step one, the middle box chamber includes two webs and a top and bottom plate, and the side box chambers are composed of at least one set of webs.

[0025] Optionally, in step five, a fixed hinge and a movable hinge are combined into a set of hinge devices, and the pin hole diameters of the two hinges should be consistent and their relative positions in space should correspond to each other.

[0026] Optionally, in step seven, the crawler crane lifts the G4 steel box girder segment to just above the installation position and puts it into position from top to bottom. After the pin holes of the fixed hinge and the movable hinge coincide with each other, the crawler crane stops the steel box girder from descending and then inserts the pin between the two sets of hinges.

[0027] Optionally, in step nine, the added tooling is close to the web and avoids the position of the butt weld, and the top plate welding under the tooling needs to be completed before the tooling is arranged.

[0028] Optionally, in step ten, a settlement observation network is established to carry out welding operations on the G4 and H4 segment steel box girders in the order of web plate - bottom plate - top plate - embedded U rib and T rib, I rib.

[0029] Optionally, in step eleven, the non-destructive testing is specifically to grind the 80-120 mm area on both sides of the top, bottom and web welds after the welding of the G4 steel box girder segment and the H4 steel box girder segment is completed, and to perform non-destructive testing of the welds 18 to 30 hours after the welding is completed.

[0030] Optionally, the hook loosening is to reduce the load of the lifting weight M displayed by the crawler crane weighing instrument step by step by M / 5 each time, and monitor the corresponding elevation and stress every time the lifting weight is reduced by M / 5, and the hook can be loosened only after the crawler crane's lifting load is reduced and stabilized without abnormalities.

[0031] Optionally, the hinge group is composed of a fixed hinge and a movable hinge, a gap of 5 to 15 mm is reserved below the front arc segment, and the hinge group is welded in an area close to the web.

[0032] Optionally, the tooling device is a double-jointed H440×300 steel device.

[0033] Beneficial technical effects of the present invention:

[0034] (1) The present invention can be applied to the case where temporary supports cannot be arranged below the steel box girder bridge site, mobile cranes cannot be arranged on one side of the bridge site, and the bridge structure itself is relatively unique and not suitable for horizontal and vertical jacking processes. Instead, a support-free suspension assembly process is adopted. Compared with the traditional "support + crane" process, the time and cost of support foundation arrangement and installation and removal are saved; compared with the "assembly on one side of the bridge site + horizontal and vertical jacking" process, the jacking movement of the steel box girder weighing thousands of tons is avoided, the construction process is reduced, and the safety factor is improved; at the same time, the time for disassembly and installation of the jacking support and the high cost of the jacking process are reduced;

[0035] (2) The aerial docking and assembly technology mentioned in the process of suspended assembly uses a hinge group that can not only quickly and safely complete the aerial assembly of larger components, but also plays a role in preliminary positioning, effectively controlling the quality of the entire aerial assembly and greatly improving the quality control level of the suspended assembly process;

[0036] (3) The box chamber of the middle section steel box girder, i.e. the first section steel box girder, uses H-shaped steel fixtures during the cantilever assembly process, which effectively enhances the interface strength of the weak points of the cantilever assembly section, ensuring the reliable and stable implementation of the entire cantilever assembly process. At the same time, the elevation and stress monitoring devices used provide accurate data for quality control and stress monitoring during the cantilever assembly process, ensuring the quality and safety of the cantilever assembly process;

[0037] (4) The transverse H-shaped steel fixtures used in the segmental steel box beam box chambers on both sides, i.e. the second or third segmental steel box beams during the cantilever assembly process, effectively ensure the transverse slope, rigidity and stability of the entire cantilever segment steel box beam structure;

[0038] (5) The large longitudinal and transverse spans and reasonable segmentation of the bridge steel structure provide suitable conditions for the subsequent single-segment cantilever assembly of the steel box girder, which not only achieves safe and reliable lifting of the structure, but also reduces the number of segments to be cantilevered. That is, after the E and G segments on both sides are cantilevered, the F segment can be closed, which shortens the required cantilever assembly time and reduces the risk of aerial operations during the cantilever assembly operation. DETAILED DESCRIPTION

[0039] In order to make the technical solution of the present invention more clear and specific to those skilled in the art, the present invention is further described in detail below in conjunction with embodiments, but the embodiments of the present invention are not limited thereto.

[0040] This embodiment provides a process for supporting a suspended urban viaduct without support, comprising the following steps:

[0041] Step 1: According to the structural composition characteristics of the steel box girder of the urban viaduct, as well as the on-site environment and conditions, the sections of the viaduct are divided and deepened. The longitudinal section length of the steel box girder is set at 18 meters, and it is divided horizontally according to the box chamber. The middle box chamber is composed of two webs and main components such as the top and bottom plates. The side box chambers are composed of at least one group of webs to avoid serious deformation of the structure itself due to insufficient rigidity during the manufacture and installation of the steel structure. The segment length of the steel structure bridge is 18 meters and the number of webs contained in each structure is clarified. On the one hand, it is conducive to the subsequent cantilever hoisting of the middle span part, reducing the number of cantilever sections and shortening the operation time; on the other hand, under the premise of ensuring the strength of the structure, the order of the subsequent cantilever assembly is clarified to ensure that the safety requirements of the site are met.

[0042] Step 2: Establish a viaduct model and perform verification calculations. During the assembly process of each segment of the steel box girder, calculate and verify the parts of the structure where stress is concentrated or the components are weak. According to the calculations, the steel plate at the bottom of the steel box girder is reinforced or thickened to ensure that the structural strength and stability meet the requirements. At the same time, the pre-arch distribution value of the steel box girder under this process is recalculated, and reliable re-verification calculations are performed. Finally, the pre-arch values ​​of each segment of the complete viaduct during the assembly process are compiled. The feasibility of the cantilever assembly process and the monitoring and measurement data during the subsequent installation process are verified, providing theoretical support for the cantilever assembly of steel box girders, reinforcing the weak parts of the structure, and providing basis support for the elevation control of the steel box girder during the subsequent installation process.

[0043] Step 3: Before the steel box girder of the middle span viaduct is formally suspended, the erection, assembly and welding process of the ABCD segment between piers 27-28 and the HIJK segment between piers 29-30 are completed, the assembly bracket of the side span steel box girder is removed, and the side span steel box girder is completely dropped on the spherical bearing on the top of the pier to complete the force system conversion of the side span steel box girder, ensuring that the spherical bearing bears the overall weight of the side span steel box girder, and then the connection and fixation of the spherical bearing and the bottom plate of the side span steel box girder are completed to ensure that the steel box girder is fixed reliably. The steel box girders of the side spans on both sides are installed first and dropped on the spherical bearings above the piers. On the one hand, the steel box girders of the side spans on both sides are used as weights to offset the overturning of the EG segment during the suspension process, and on the other hand, the permanent piers are used as support points, which is more stable and reliable than using temporary steel bracket structures.

[0044] Step 4: According to the station design and the on-site conditions, draw the building edge line of the underground rail transit station on the ground below the middle span steel box girder bridge, and arrange eye-catching cordon lines and warning signs. Then level the site between the cordon line and the adjacent buildings, and arrange crawler cranes. Then hoist the double-jointed H440×300 reinforced I-beams, steel structure stress monitoring devices, special extended yard plates, fixed hinges and other components used for the steel box girder suspension assembly to the bridge deck.

[0045] Step 5: Position weld a fixed hinge above the corresponding position of the web of the H4 segment of the side span steel box girder, and weld a corresponding set of movable hinges on the upper plane of the G4 segment steel box girder to be hoisted. A fixed hinge and a movable hinge are combined into a set of hinge devices. The pin hole diameters of the two hinges should be straight, and the relative positions in space should correspond to each other. At the same time, a 10mm gap is cut below the head of the hinge to ensure that the hinge group has sufficient rotation area. The hinge is fully welded and fixed to the top plate of the steel box girder, and a triangular rib plate is added to the side of each set of hinges and fully welded to the top plate to ensure that the hinge group is fixed reliably. The hinge group arranged consists of a fixed hinge and a movable hinge. A 10mm gap is reserved below the front arc segment, and the hinge group is welded near the web position area, which is very conducive to the subsequent docking and assembly of the steel box girder in the air, and improves the efficiency of aerial assembly.

[0046] Step 6: Arrange the measurement points according to the new pre-camber drawing calculated previously, mark the 1~4# measurement points at the four groups of corner positions of the G4 steel box girder segment to be hoisted, and then use the crawler crane to lift the steel box girder segment 300~500mm off the ground, measure the relative elevation between the four groups of measurement points in the hoisting state, and calculate the absolute height difference between each group of measurement points. Adjust the relative elevation of the four corner positions of the steel box girder by adding or removing the horseshoe-shaped shackles at each rope end. The height difference value should be 10~20mm larger than the absolute elevation difference after the G4 steel box girder segment is in place, so as to facilitate the later adjustment of the G4 steel box girder segment. Adjusting the relative elevation and height difference of the G4 segment steel box girder solves the problem of the relative elevation difference between the large and small mileage sides of the G4 segment steel box girder during the subsequent aerial docking assembly, which is conducive to the later adjustment of the G4 steel box girder segment and reduces the difficulty of the subsequent aerial assembly of the steel box girder.

[0047] Step 7: According to the principle of dislocation of the top and bottom webs of the divided steel box girder segments, the top plate of the G4 steel box girder segment needs to be pressed on the webs of the H4 segment. Therefore, the crawler crane is needed to lift the G4 steel box girder segment to the top of the installation position, and then it can be put in place from top to bottom. After the pin holes of the fixed hinge and the movable hinge coincide, the crawler crane stops the steel box girder from descending, and then inserts the φ50×100mm pin between the two groups of hinges. Note that the front end of the φ50×100mm pin should be processed into a chamfered shape to facilitate the rapid completion of the pin insertion process. After the steel box girder is in place, the pin of the hinge group is first inserted, which can quickly complete the aerial positioning of the steel box girder, and at the same time facilitate the subsequent position adjustment of the G4 steel box girder segment, and it is safe and reliable.

[0048] Step 8: Measure the absolute elevation values ​​of the four groups of control points of the G4 steel box girder segment for the second time, and compare them with the design elevation values ​​of the steel box girder under this process to clarify the elevation deviation values ​​of each control point. Since the measurement on one side was done before, the deviation value produced in this measurement is small, and the G4 and H4 segments have been fixed with hinges, so the elevation of the cantilever end is mainly adjusted. The cantilever end of the G4 steel box girder segment is adjusted by the crawler crane to be slightly larger than the calculated elevation value by 10 to 20 mm, so as to offset the deflection of the cantilever end of the suspended segment steel box girder due to its own gravity after the subsequent crawler crane is unhooked, to avoid large inelastic deformation, and at the same time, properly trim the gap, staggered mouth, and groove of the suspended G4 segment and H4 segment to ensure the docking quality between the structures.

[0049] Step 9: Two sets of double-joined H440×300 steel devices are arranged in the area above the corresponding web position on the top plate between the G4 and H4 segment steel box girders. The material of the tooling is Q345qD, which is consistent with the material of the bridge plate. The length of a single set of steel is L=2 meters, with an internal 12mm rear rib plate and a spacing of 500m; the arranged double-joined H440×300 steel devices are fully welded to the top plate of the steel box girder. The added tooling is that the double-joined I-beam should be as close to the web as possible and avoid the position of the butt weld to facilitate the assembly of the steel box girder, and the top plate welding under the tooling must be completed before the tooling is arranged. The top and bottom webs are butt-jointed with a special extended version of the T-type code plate, which is made of 14mm steel plate, with a size of 16×200×500 and a spacing of 300mm. Arrange two sets of double H440×300 steel devices and extended T-type yard plates to increase the cross-sectional bending strength between the G4 and H4 segments. Compared with the traditional "I"-shaped yard plates, it is more stable and reliable, avoiding fractures due to excessive stress at the cross section, which can cause serious consequences. At the same time, the materials of the selected steel and yard plates are consistent with those of the steel box beam, ensuring the welding quality of the structure and avoiding affecting the quality of the steel box beam parent material.

[0050] Step 10: Establish an elevation settlement observation point network for the G4-K4 segment on the bridge deck to facilitate elevation control during the subsequent installation process. After the installation of the code plate and tooling between the G4 and H4 segment steel box girders, conduct the first elevation settlement observation of the G4-K4 segment steel box girders before the formal welding operation. The establishment of a settlement observation network can effectively control the elevation of the steel box girder of the entire cantilever segment. The welding operations of the G4 and H4 segment steel box girders are carried out in the order of web plate - bottom plate - top plate - embedded U ribs and T ribs, I ribs, which can effectively avoid local stress concentration during welding. Since the welding operation lasts for 24 to 30 hours, the lifting weight changes of the crawler crane are monitored synchronously during the welding process. If an abnormality occurs, the operation will be stopped in time and the operation can only be continued after the cause is found.

[0051] Step 11: To ensure the welding quality and the safety and reliability of the hoisting process, 100% non-destructive testing is performed on the top and bottom web butt welds between the G4 and H4 segmental steel box girders, and 50% non-destructive testing is performed on the welds between the embedded U ribs and the T ribs and I ribs. Specifically, after the welding of the G4 and H4 segmental steel box girders is completed, the 100mm area on both sides of the top, bottom and web welds is polished, and the welds are non-destructively tested 24 hours after the welding is completed. Only after the non-destructive testing of the butt welds is confirmed to be qualified, stress monitoring devices can be arranged on the top plate, bottom plate and web in the web position area to provide stress monitoring data for the subsequent crawler crane unhooking process. The G4 and H4 sections are the weakest positions of the entire structure. Non-destructive testing and uniform stress monitoring are performed on the welds at the connection, which can effectively control the stress changes in the weak areas of the top plate of the steel box girder. In the case of excessive stress, effective measures such as reinforcement and secondary suspension can be taken in time to avoid serious problems such as bending and deformation of the structure.

[0052] Step 12: Before the crawler crane releases the hook, the elevation and stress measurement and control points must be arranged in place, and the elevation of the cantilever end of the G4 segment steel box girder, the elevation of the K4 segment at the outermost end of the side span, and the stress values ​​of the G4 and H4 segment steel box girders corresponding to each reduction in the crawler crane lifting weight must be done. According to the rules of the suspension process, the weight is reduced, the elevation is small, and the stress increases. The lifting weight M displayed by the crawler crane weighing instrument is gradually reduced by M / 5 each time. The corresponding elevation and stress are monitored every time the lifting weight is reduced by M / 5. After each crawler crane lifting load is reduced, it is stabilized for 5 minutes to ensure that there is no abnormality before the hook can be released. It can more effectively monitor whether the stress changes at the section and the elevation value of the cantilever end meet the design requirements. It is necessary to pay close attention to the stress changes to avoid increasing the difficulty of elevation adjustment and reinforcement at the section when the steel box girder elevation does not meet the requirements.

[0053] Step 13: After the installation of the G4 segment steel box girder is completed, the temporary facilities such as the code plates and folding sheets are removed except for the special H-shaped steel fixtures; then, the G5 segment steel box girder is suspended and assembled according to the principle of from far to near, and the operations such as positioning, measurement, assembly, welding, flaw detection, monitoring, and hook loosening are carried out in sequence according to the processes of steps 4 to 12. At the same time, in order to ensure the transverse slope of the G5 and G4 steel box girders after they are in place, two sets of special H-shaped steel fixtures are arranged on the top plates of the G5 and G4 steel box girders.

[0054] Step 14: After the installation of the G5 segment is completed, re-measure the elevation of the G4 cantilever end, and observe the elevation of the G5 cantilever end and the elevation of the K4 segment at the outermost end of the side span at the same time. Only after ensuring that there is no abnormality can the G3 segment steel box girder be suspended. Since the G3 segment is close to the front of the crane, it is necessary to consider in advance whether the G3 segment to be suspended will affect the crawler crane boom operation. Then, the G3 segment suspension installation is carried out in the order of steps 4 to 13, and the operations are carried out according to the procedures of positioning, measuring, assembling, welding, flaw detection, monitoring, and hook loosening. At this point, the suspension operation of the three main box chambers of the G segment is completed, which effectively ensures the overall stability of the steel box girder structure and provides favorable conditions for the subsequent closing of the mid-span steel box girder and the hoisting of the other side. After completing the G4 segment, the G5 segment is suspended, which is more in line with the actual hoisting conditions on site. Otherwise, the G5 segment steel box girder cannot be hoisted after the G3 segment steel box girder suspension in step 14 is completed. At the same time, the addition of transverse H-shaped steel tooling is more conducive to ensuring the transverse slope, stiffness and stability of the entire cantilever section steel box girder structure.

[0055] Step 15: The cantilever assembly of the 3~5# steel box girders of the E section on the other side of the viaduct is carried out in the order of steps 4 to 14, and the spatial positions are relatively symmetrical, and the operations are carried out according to the procedures of positioning, measuring, assembling, welding, flaw detection, monitoring, and hook loosening. In order to improve the installation efficiency of the steel box girders of urban viaducts, the 3~5# steel box girders of the E and G sections can be cantilevered and assembled simultaneously as needed, which will increase the construction efficiency of the viaduct by 50% and speed up the installation progress of the cantilevered steel box girders.

[0056] Step 16: Re-measure the net distance L1~Ln between the cantilever ends of the steel box girders of the E and G segments, and cut and trim the length of the top and bottom webs connected to the steel box girders of the closing segment F based on this, so as to avoid the subsequent failure to proceed normally. Since both ends of the top plate of the F segment extend out of the web by 200m, the crawler crane first lifts the steel box girder to the top of the bridge, and then performs the operations of positioning, assembly, welding, flaw detection, and hook loosening in sequence from top to bottom. The difference from the traditional process of positioning, hook loosening, assembly, welding, flaw detection, etc. of the steel box girder optimizes the installation sequence of the entire bridge; at the same time, the synchronous and symmetrical lifting process is adopted to achieve the rapid installation effect of the steel box girder of the urban viaduct without a support. The most important stage of the steel box girder suspension assembly process - the closing of the steel box girder of the middle span F segment, clarifies the size of the closing section, the temperature requirements during the closing period, and the lifting process of the closing section, which is more conducive to the orderly and reliable construction of the closing section.

[0057] Step 17: The assembly sequence of the main box chamber of the steel box girder in the closing section F is F4-F5-F3. It is necessary to consider that all steel box girders are assembled and welded without supports. Therefore, the steel box girders can be unhooked only after welding is completed to avoid local deformation of the structure. In order to improve the installation efficiency of the steel box girders of the urban viaduct, the remaining cantilever steel structures of the EFG segment of the viaduct can be hoisted synchronously and symmetrically to achieve the purpose of rapid installation of the steel box girders of the urban viaduct without supports.

[0058] In summary, in this embodiment, according to the process for the suspension splicing of urban viaduct without support in this embodiment, the suspension splicing technology without support proposed in the present invention is greatly different from the traditional "suspending splicing without support + retaining the tower after buckling" technology. The latter needs to arrange the traction system such as the sleeve, lock, lifting device, and lifting lug, which is relatively complicated and risky to operate in practice. Especially for the bridge in the present invention located in the complex traffic environment area of ​​the urban area, the installation and use of the tower will bring great safety hazards to the surrounding traffic and life. Therefore, the suspension splicing process without support can be applied to the installation of urban viaducts with complex bridge environment and harsh conditions. Therefore, compared with the traditional suspension splicing steel box girder process with retaining the tower after buckling, it is more suitable for the installation of urban viaducts in complex environments. Compared with the "support method" process in the industry, this process can complete the installation in the "supportless" state, so the scope of application is wider. At the same time, compared with the "pushing method", this process can realize the assembly of the bridge without support, which greatly saves the investment funds of the support and pushing equipment, and is safer and more reliable.

[0059] The above description is only a further embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the scope disclosed by the present invention, which belong to the protection scope of the present invention.

Claims

1. A process for cantilever assembly of urban viaduct without support, characterized in that: The steps include: Step 1: According to the structural characteristics of the steel box girder of the urban viaduct, the sections of the viaduct are divided and deepened, and the steel box girder is divided into longitudinal sections by length and transversely by box chambers; Step 2: Establish a viaduct model and perform calculations to simulate the assembly process of each segment of the steel box girder, and perform calculations and checks on the parts of the structure where stress is concentrated or components are weak; Step 3: Before the steel box girder of the middle span viaduct is formally suspended, the erection, assembly and welding process of the side span steel box girder is completed, the assembly bracket of the side span steel box girder is removed, the side span steel box girder is completely lowered on the spherical bearing on the top of the pier, and the connection and fixation of the spherical bearing and the bottom plate of the side span steel box girder are completed; Step 4: According to the station design drawing and the on-site conditions, draw the building edge line of the underground rail transit station on the ground below the middle span steel box girder bridge, then level the site between the cordon and the adjacent buildings, arrange crawler cranes, and then hoist the components for the steel box girder suspension assembly onto the bridge deck; Step 5: Position and install fixed hinges above the corresponding position of the web plate of the H4 segment of the side span steel box girder, and install a set of corresponding movable hinges on the upper plane of the G4 segment steel box girder to be hoisted. The hinges are fixed to the top plate of the steel box girder, and triangular ribs are added to the side of each set of hinges to fix them to the top plate; Step 6: Arrange the measurement points according to the new pre-camber drawing calculated previously, mark the measurement points at the four corner positions of the G4 steel box girder segment to be hoisted, then use the crawler crane to lift the steel box girder segment off the ground, measure the relative elevations between the four groups of measurement points in the hoisted state, and calculate the absolute height difference between each group of measurement points. Adjust the relative elevations of the four corner positions of the steel box girder by adding or removing horseshoe shackles at each rope end; Step 7: According to the principle of staggered top and bottom webs of the divided steel box girder segments, the top plate of the G4 steel box girder segment needs to be pressed on the webs of the H4 segment of the side span steel box girder. The G4 steel box girder segment is lifted to the top of the installation position by a crawler crane to complete the pin insertion process; Step 8: Secondary measure the absolute elevation values ​​of the four groups of measurement and control points of the G4 steel box girder segment, and compare them with the design elevation values ​​of the steel box girder under this process to clarify the elevation deviation values ​​of each measurement and control point; Step 9: Arrange multiple sets of tooling devices on the top plate between the G4 steel box girder segment and the side span steel box girder H4 segment. The arranged tooling devices are fully welded to the top plate of the steel box girder, and a T-type yard plate is used to connect the top and bottom web plates; Step 10: Establish a network of elevation settlement observation points from the steel box girder segment to the side span steel box girder K4 segment on the bridge deck. After the installation of the stacking plate and tooling between the G4 steel box girder segment and the side span steel box girder H4 segment, conduct the first elevation settlement observation of the G4 steel box girder segment and the side span steel box girder H4 segment before the formal welding operation. Then, conduct the welding operation of the G4 steel box girder and the side span steel box girder H4 segment in the order of web plate, bottom plate, top plate, embedded U rib and T rib, and I rib. Step 11: Perform 100% non-destructive testing on the top and bottom web butt welds between the G4 steel box girder and the H4 segment of the side span steel box girder, and perform 50% non-destructive testing on the welds between the embedded U ribs and the T ribs and I ribs. The butt welds are confirmed to be qualified by non-destructive testing, and stress monitoring devices are arranged on the top plate, bottom plate, and web plate in the web position area to provide stress monitoring data for the subsequent crawler crane hook release process; Step 12: Before the crawler crane releases the hook, the elevation and stress measurement and control points are arranged in place, and the elevation of the cantilever end of the G4 segment steel box girder, the elevation of the outermost K4 segment of the side span, and the stress values ​​of the G4 steel box girder segment and the H4 segment steel box girder of the side span steel box girder corresponding to the crawler crane lifting weight after each reduction are made; Step 13: After the installation of the G4 steel box girder segment is completed, except for the special H-shaped steel fixture, the other temporary facilities such as the code plate and the folding leaf are removed. Then, according to the principle of from far to near, the G5 steel box girder segment is suspended and assembled. According to the process of step 4 to step 12, the positioning, measurement, assembly, welding, flaw detection, monitoring, and hook loosening operations are carried out in sequence. At the same time, in order to ensure the transverse slope of the G5 steel box girder segment and the G4 segment steel box girder after they are in place, multiple sets of H-shaped steel fixtures are arranged on the top plates of the G5 steel box girder segment and the G4 steel box girder segment; Step 14: After the installation of the G5 steel box girder segment is completed, re-measure the elevation of the cantilever end of the G4 steel box girder, and at the same time observe the elevation of the cantilever end of the G5 steel box girder segment and the elevation of the K4 segment at the outermost end of the side span. Since the G3 steel box girder segment is close to the front of the crane, it is necessary to consider in advance whether the G3 steel box girder segment to be hoisted will affect the boom operation of the crawler crane. Then, perform the cantilever assembly and installation of the G3 steel box girder segment in the order of steps 4 to 13, and perform the operations of positioning, measuring, assembling, welding, flaw detection, monitoring, and hook loosening. At this point, the cantilever assembly operations of the three groups of main box chambers of the G3 steel box girder segment, the G4 steel box girder segment, and the G5 steel box girder segment are completed; Step 15: The cantilever assembly of the E steel box girder segment on the other side of the viaduct is carried out in the order of Steps 4 to 14, and the operations are carried out in accordance with the procedures of positioning, measuring, assembling, welding, flaw detection, monitoring, and hook loosening; Step 16: Re-measure the net distances L1 to Ln between the cantilever ends of the steel box girders of the E and G segments, and cut and trim the lengths of the top and bottom webs of the steel box girders of the integrated segment F based on the distances. Since both ends of the top plate of the F segment extend out of the webs, the crawler crane first lifts the steel box girder to the top of the bridge, and then performs the operations of positioning, assembly, welding, flaw detection, and hook loosening in sequence from top to bottom; Step 17: The assembly sequence of the main box chamber of the closing section F steel box girder is F4-F5-F3. The remaining cantilever steel structures of the viaduct EFG segment are hoisted synchronously and symmetrically to achieve the purpose of rapid installation of the urban viaduct steel box girder without support.

2. The process for cantilever assembly of urban viaduct without support according to claim 1 is characterized in that: In step one, the middle box chamber is composed of two webs and a top and bottom plate, and the side boxes are composed of at least one set of webs.

3. The process for cantilever assembly of urban viaduct without support according to claim 1 is characterized in that: In step five, a fixed hinge and a movable hinge are combined into a hinge device. The pin hole diameters of the two hinges should be consistent and their relative positions in space should correspond to each other.

4. The process for cantilever assembly of urban viaduct without support according to claim 1 is characterized in that: In step seven, the crawler crane lifts the G4 steel box girder segment to just above the installation position and puts it in place from top to bottom. After the pin holes of the fixed hinge and the movable hinge coincide with each other, the crawler crane stops the steel box girder from descending and then inserts the pin between the two sets of hinges.

5. The process for cantilever assembly of urban viaduct without support according to claim 1 is characterized in that: In step nine, the added tooling is close to the web and avoids the position of the butt weld, and the top plate welding under the tooling needs to be completed before the tooling is arranged.

6. The process for cantilever assembly of urban viaduct without support according to claim 1 is characterized in that: In step ten, a settlement observation network is established and welding operations of G4 and H4 segmental steel box girders are carried out in the order of web plate - bottom plate - top plate - embedded U rib and T rib, I rib.

7. The process for cantilever assembly of urban viaduct without support according to claim 1 is characterized in that: In step eleven, after the G4 steel box girder segment and the H4 steel box girder segment are welded, the 80-120 mm area on both sides of the top, bottom and web welds is polished, and the non-destructive testing of the weld is performed 18-30 hours after the welding is completed.

8. The process for cantilever assembly of urban viaduct without support according to claim 1 is characterized in that: The hook loosening is to reduce the load of the lifting weight M displayed by the crawler crane weighing instrument step by step by M / 5 each time, and monitor the corresponding elevation and stress every time the lifting weight is reduced by M / 5. After each crawler crane lifting load is reduced and ensured to be stable without abnormalities, the hook can be loosened.

9. The process for cantilever assembly of urban viaduct without support according to claim 1, characterized in that: The hinge group is composed of a fixed hinge and a movable hinge. A gap of 5 to 15 mm is reserved below the front arc segment, and the hinge group is welded in an area close to the web.

10. The process for cantilever assembly of urban viaduct without support according to claim 1, characterized in that: The tooling device is a double-jointed H440×300 steel device.