Expressway crossing steel box girder dragging erection construction method

Abstract

The method comprises the following steps that S1, preparation work and buttress installation are conducted, specifically, a dragging buttress, a glide way buttress, a welding platform buttress and a beam falling buttress are erected on the two sides of a highway, the glide way buttress is installed at the position of a medial strip, and a bailey truss, a slide way carrier roller, a beam falling jack, a transverse position adjusting device and a dragging mechanism are arranged at the tops of the buttresses; the construction method disclosed by the invention is suitable for the special conditions of erection, high construction difficulty and the like under the condition that large-span steel beams span river water surfaces, expressways, railways and the like under the condition that passing cannot be interrupted, and the construction difficulty is high, so that the manufacturing precision and the welding quality of each part of the steel structure are ensured, and complex processing procedures are arranged to be completed in a factory; on-site assembling, splicing and welding work can be simplified, and the precision and welding quality of the steel box girder are improved.

Description

Technical Field

[0001] The invention relates to the technical field of steel box girder dragging method erection, in particular to a construction method for erecting a steel box girder across a highway by dragging method. Background Art

[0002] In recent years, the scale of my country's expressways has continued to expand, and new expressways and existing roads will inevitably form intersection conflicts. When the construction of new and old roads intersect, it is necessary to choose to pass over the existing expressway. This not only requires ensuring the safety of new road construction, but also properly solving the impact of road construction on existing roads.

[0003] The Tianyong section of the Yinbai Expressway (G69) is the Tianshuibao-Qingcheng-Yonghe Expressway, and is an important section of the Yinchuan-Baise National Expressway (G69). During construction, the project needs to cross the G22 Qinglan Expressway. In order to ensure the safe operation of the expressway and prevent bridge construction from damaging highway equipment and affecting normal traffic operations, it is a major technical challenge.

[0004] In general, traditional solutions may increase construction costs due to factors such as long construction period, complex project management, and large investment in manpower and equipment. The splicing and welding work carried out under on-site conditions is affected by weather and environmental factors, and it is difficult to ensure the same manufacturing accuracy and welding quality as in-factory processing. It requires a lot of manpower and equipment investment, and the construction efficiency is low. Due to construction restrictions, it may take longer to complete the construction and splicing of the bridge. This will prolong the impact on the surrounding environment and traffic during the construction period, and increase construction costs and the complexity of project management.

[0005] In summary, it is necessary to propose a method of erecting steel box girders across highways by dragging them to solve the above problems. Summary of the invention

[0006] The object of the present invention is to provide a method for erecting a steel box girder across a highway by dragging, so as to solve the problems raised in the above-mentioned background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The method for erecting a steel box girder across a highway by dragging and pulling includes the following steps:

[0009] S1. Preparation and installation of piers: Build piers for towing, gliding path piers, welding platform piers and beam-dropping piers on both sides of the expressway, install gliding path piers at the central median, and set up Bailey frames, slideway rollers, beam-dropping jacks, lateral position adjustment devices and tractor mechanisms on the top of the piers;

[0010] S2. Installation and splicing of steel box girders: A 60t, 33m span, 17m lifting height gantry crane is used to hoist the steel box girders onto temporary supports. First, both ends of the steel box girders are erected. Each segment of the steel box girders is longitudinally divided into 35 small segments. A 60t disassembled gantry crane is used to hoist each small segment from the construction site below the bridge axis and install it on the welded piers at both ends. Each small segment is assembled into an integral traction segment, and the welding of the traction segment beam is completed on the support;

[0011] S3. Towing installation of the middle span: The length of the middle towing beam is 72m, from the 11th section to the 25th section, a total of 15 small sections, and the towing method is used to carry out two towing to achieve the crossing of the expressway. After towing, it is supported on the temporary supports on both sides of the 8th and 9th piers, and the beam is dropped and positioned as the reference section;

[0012] S4. Gantry crane installation on both sides: Gantry cranes are used for the steel box beam spans on both sides, and the beams of 10 small sections on the left and right are welded into a whole;

[0013] S5. Overall dismantling: After the three spans of the bridge have passed the welding test, four 500t hydraulic cylinders are used to lift the entire bridge, adjust the gap between the support and the bottom of the beam and the support reaction force, remove the pads on each temporary pier, and drop the beam into place to achieve the conversion of the entire bridge system. After the conversion is completed, remove the supports and temporary piers under the bridge, and repaint. When the piers in the central isolation zone are removed and repainted, in order to ensure safety, warning signs are set up for a short period of time during the dismantling process and traffic control is implemented.

[0014] Preferably, in step S2, the steel box girder is divided into several sections and manufactured before leaving the factory. After being hoisted on site, the sections are welded into a bridge. The steel box girder portion is located within the vertical curve. To ensure the linear shape of the steel girder after the bridge is completed, a pre-arch is set on the mid-span steel girder. At the same time, it is noted that the vertical linear shape of the steel girder includes a design curve and a pre-arch curve. The manufacturing should be carried out according to the superimposed curve of the two parts.

[0015] Preferably, the step S2 of temporary support foundation processing and temporary support fabrication and installation comprises the following steps:

[0016] S2.1.1. Arrangement of temporary supports: 13 sets of temporary supports are arranged on each of the left and right sides of the main line bridge;

[0017] S2.1.2. Design of temporary supports. Calculate the stress of each set of temporary supports according to the layout of temporary supports and the load of the whole bridge. The foundation of each set of temporary supports is excavated from the hard original soil layer. According to the geological exploration report, the soil strength of the hard clay layer reaches 0.15Mpa. The soil that does not meet the strength requirements must be replaced with rough stone so that each foundation can withstand a stress of 510t. Each set of temporary supports is designed to be composed of eight steel pipes larger than Φ426×6. The steel pipes of each column are connected and used as scissor braces with Φ159×6 steel pipes;

[0018] S2.1.3. A sliding device is provided between the top of the temporary support column and the steel box beam, and a guiding device is provided at both ends;

[0019] S2.1.4. Bailey frames are installed on the top brackets of temporary supports, and a set of welding platforms is set between each set of temporary supports;

[0020] S2.1.5. All welding platforms and temporary supports are connected as a whole with steel sections to form a complete assembled large platform.

[0021] Preferably, the installation steps of the sliding device and the guiding device in step S2.3 are as follows:

[0022] S2.1.3.1. According to the arrangement position of the support, the length of the traction segment beam and the installation position, slideways are arranged on the top surface of each temporary pier to be loaded and the central isolation segment support pier. The slideways are arranged on the bottom of the beam under the pressure of the two outer webs of the steel box beam. Three rows are arranged on the left and right of the single beam. At the same time, due to the downward deflection of the traction head of the steel box cantilever, the height of the roller assembly can be adjusted during the actual installation;

[0023] S2.1.3.2. The slideway is welded from two I-beams. A stainless steel plate and a polytetrafluoroethylene pad are also provided on the upper surface of the slideway to allow the beam body and the polytetrafluoroethylene pad to slide between the stainless steel plate. Since the weight of the intermediate segment beam is about 450t, the slideway and the bottom of the steel box beam are padded with a polytetrafluoroethylene pad. The theoretical friction coefficient is about 0.1. It can be seen that its traction force is 45t. Considering that static friction must be overcome before starting the towing, a certain safety factor is taken. A 100-ton hydraulic traction machine is used for towing, and 5 Φ21.5 steel strands are used as towing steel wires to reduce the friction during towing;

[0024] S2.1.3.3. In order to ensure the lateral displacement and installation alignment of the steel box girder when it is dragged, transverse fine-tuning supports are welded and fixed on each temporary pier to provide jack support reaction force during fine-tuning, and at the same time play a certain limiting role when the steel box girder is dragged and deflected.

[0025] Preferably, in step S1, the Bailey frame is used to splice the steel box girders in the air and to strengthen the stability between the temporary supports. The Bailey frame is composed of two rows of 1500 mm high Bailey sheets connected by 900 mm wide lattices.

[0026] Preferably, the welding process of the drag segment beam in step S2 comprises the following steps:

[0027] S2.2.1. The components shall be brought to the construction site strictly according to the assembly sequence on site. They shall be unloaded immediately upon arrival and directly hoisted to the assembly site for assembly. The 4m wide steel box beam shall be first assembled on the ground into an 8m wide steel box beam and then hoisted as a whole onto the towing assembly platform for assembly;

[0028] S2.2.2. Lift the steel box beam onto the assembly platform, use a 20t hydraulic jack to adjust the gap size of the interface to control it between 5 and 10mm, and use instruments to check whether the center line, elevation, curvature and camber of the two spliced ​​steel box beams meet the requirements of the drawings;

[0029] S2.2.3. After adjustment, use riding plates to weld firmly, and then weld. Use high-temperature ceramic pads to stick to the bottom of the weld on the top and bottom plates, use CO2 gas shielded welding to prime, and submerged arc automatic welding to cover. The two webs are directly welded by CO2 gas shielded welding or manual welding. After the welds are qualified by non-destructive testing, grind the welds at the longitudinal ribs on the top and bottom plates, connect the longitudinal ribs of the two steel box girders with longitudinal ribs, and finally weld the longitudinal ribs on the webs, the longitudinal ribs on the cantilever and the guard plate. The transverse butt welds of the top, bottom, webs and longitudinal ribs must meet the Class I weld standards.

[0030] S2.2.4. Hoist the first section of the component assembled on the ground onto the towing platform, with one end mounted on the pier slideway and the other end mounted on the Bailey frame. At this time, there is a 640mm space between the Bailey frame and the bottom of the beam. Use a temporary small bracket to pad it, and use a temporary small bracket and a jack to level the elevation of the interface with the second section of the component. Hoist the second section of the component into place and assemble it with the first section. When assembling on the column top platform, ensure that each section of the component has four fixed stress points, and at the same time, lay movable stress points for adjustment;

[0031] S2.2.5. Lift the anti-collision guardrail on the top plate into place, adjust it and weld it securely.

[0032] Preferably, the step S3 of dragging the steel box girder comprises the following steps:

[0033] S3.1. Preparation before hauling: After the hauling segment steel box girder is assembled and welded and inspected and qualified, the lifting lugs for hauling and the ends of the hauling beam are welded and reinforced to make the beam in the condition before hauling;

[0034] S3.2. Towing the steel box girder across the highway, the length of the steel box girder to be towed reaches 56m. When towing, at each roller assembly, the segmental steel box girder moves 16m across the highway. When the front end of the steel box girder reaches the pier of the central isolation belt, fix the support points at each pier to ensure that the steel box girder and the support are completely fixed as a whole to eliminate the influence of wind force in non-operating conditions;

[0035] S3.3. Drag the other half of the steel box girder on the same side according to step S3.2, and carry out the preliminary preparation work for both sides simultaneously;

[0036] S3.4. Close the left lane of the expressway for traffic and carry out preparations for the next stage of hauling. The entire hauling process and control shall be carried out in accordance with the hauling procedure of the first stage. The segmental steel box girder shall continue to move forward for about 20m from the first stage hauling position to the designed horizontal position. After the single span is hauled into place and fixed, the other half of the segmental steel box girder shall be hauled into place and fixed. The hauling of the main span of the entire main line bridge shall be completed, and all temporary facilities set on the road surface except the central isolation belt pier shall be removed;

[0037] S3.5. Hydraulic cylinders and jacks are used on temporary supports of some piers to fine-tune the absolute spatial coordinates of the segmental beams. The absolute coordinate data are given by the computer simulation design drawings. The spatial coordinates are monitored and calibrated by a total station. The calibration points are located on the corresponding top plates at the intersection of the two outer webs and the partitions. The longitudinal spacing of the calibration points is 4m and they are marked during assembly.

[0038] Preferably, the step S1 adopts a bracket erection method, the remaining small segment beams on both sides are relatively small, and the maximum segment weight is 50t. The gantry cranes on both sides can directly hoist the steel box beam into place for assembly, positioning and welding.

[0039] Preferably, a group of Bailey frames consisting of two rows of 1500mm high Bailey sheets connected by 450mm wide lattices are arranged on the top of the middle column of the temporary support.

[0040] Preferably, after the first stage of hauling in step S3.3 is completed, various temporary facilities for closing the left span are removed to open traffic, and then the next stage of hauling is started, and four 16M sections are extended again at the tail of the steel box girder to reach a length of 72m.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows: the construction method of the present invention is suitable for the erection of large-span steel beams across rivers, highways, railways and other places where traffic cannot be interrupted, and highways and railways in special cases where the construction is difficult, while ensuring the manufacturing accuracy and welding quality of various components of the steel structure and arranging the complex processing procedures to be completed in the factory, it can simplify the on-site assembly and welding work, improve the accuracy and welding quality of the steel box beam, and the steel box beam assembly area and the beam drop area can be constructed separately, which is conducive to the unified arrangement of construction period requirements, and during the erection and dragging of the steel beam, the construction and personal safety are guaranteed, and the hidden dangers of traffic safety in the erection of the steel beam within the scope involved are eradicated. At the same time, the successful use of the dragging sliding device shortens the construction period, saves equipment investment, reduces a large number of steel pipe supports, and has strong economy and technical promotion. Therefore, the construction cost is low, less machinery and equipment and labor are required, and the work efficiency is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A flow chart of the construction method of the dragging method for erecting a steel box girder across a highway according to the present invention;

[0043] Figure 2 The engineering drawing of the construction method of the steel box girder dragging method across the expressway of the present invention;

[0044] Figure 3 It is a schematic diagram of temporary support arrangement of the present invention;

[0045] Figure 4 A schematic diagram of a temporary support of the present invention;

[0046] Figure 5 It is the layout diagram of the gantry crane and track of the present invention;

[0047] Figure 6 It is a schematic diagram of the guide and slide device of the present invention;

[0048] Figure 7 It is a schematic diagram of the planar layout of the Bailey frame of the present invention;

[0049] Figure 8 It is a schematic diagram of the layout of the towing slideway of the present invention; DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] Example 1

[0052] See also Figure 1 and Figure 2 The method for erecting a steel box girder across a highway by dragging and pulling includes the following steps:

[0053] S1. Preparation and installation of piers: Build piers for towing, gliding path piers, welding platform piers and beam-dropping piers on both sides of the expressway, install gliding path piers at the central median, and set up Bailey frames, slideway rollers, beam-dropping jacks, lateral position adjustment devices and tractor mechanisms on the top of the piers;

[0054] S2. Installation and splicing of steel box girders: A 60t, 33m span, 17m lifting height gantry crane is used to hoist the steel box girders onto temporary supports. First, both ends of the steel box girders are erected. Each segment of the steel box girders is longitudinally divided into 35 small segments. A 60t disassembled gantry crane is used to hoist each small segment from the construction site below the bridge axis and install it on the welded piers at both ends. Each small segment is assembled into an integral traction segment, and the welding of the traction segment beam is completed on the support;

[0055] S3. Towing installation of the middle span: The length of the middle towing beam is 72m, from the 11th section to the 25th section, a total of 15 small sections, and the towing method is used to carry out two towing to achieve the crossing of the expressway. After towing, it is supported on the temporary supports on both sides of the 8th and 9th piers, and the beam is dropped and positioned as the reference section;

[0056] S4. Gantry crane installation on both sides: Gantry cranes are used for the steel box beam spans on both sides, and the beams of 10 small sections on the left and right are welded into a whole;

[0057] S5. Overall dismantling: After the three spans of the bridge have passed the welding test, four 500t hydraulic cylinders are used to lift the entire bridge, adjust the gap between the support and the bottom of the beam and the support reaction force, remove the pads on each temporary pier, and drop the beam into place to achieve the conversion of the entire bridge system. After the conversion is completed, remove the supports and temporary piers under the bridge, and repaint. When the piers in the central isolation zone are removed and repainted, in order to ensure safety, warning signs are set up for a short period of time during the dismantling process and traffic control is implemented.

[0058] In this embodiment, it should be noted that in step S2, the steel box girder is divided into several sections and manufactured before leaving the factory. After being hoisted on site, the sections are welded into a bridge. The steel box girder portion is located within the vertical curve. In order to ensure the linear shape of the steel beam after the bridge is completed, a pre-arch is set on the mid-span steel beam. At the same time, it should be noted that the vertical linear shape of the steel beam includes two parts, the design curve and the pre-arch curve. The manufacturing should be carried out according to the superimposed curve of the two parts.

[0059] In this embodiment, it should be noted that step S2 of temporary support foundation processing and temporary support fabrication and installation includes the following steps:

[0060] S2.1.1. Arrangement of temporary supports: 13 sets of temporary supports are arranged on each of the left and right sides of the main line bridge;

[0061] S2.1.2. Design of temporary supports. Calculate the stress of each set of temporary supports according to the layout of temporary supports and the load of the whole bridge. The foundation of each set of temporary supports is excavated from the hard original soil layer. According to the geological exploration report, the soil strength of the hard clay layer reaches 0.15Mpa. The soil that does not meet the strength requirements must be replaced with rough stone so that each foundation can withstand a stress of 510t. Each set of temporary supports is designed to be composed of eight steel pipes larger than Φ426×6. The steel pipes of each column are connected and used as scissor braces with Φ159×6 steel pipes;

[0062] S2.1.3. A sliding device is provided between the top of the temporary support column and the steel box beam, and a guiding device is provided at both ends;

[0063] S2.1.4. Bailey frames are installed on the top brackets of temporary supports, and a set of welding platforms is set between each set of temporary supports;

[0064] S2.1.5. All welding platforms and temporary supports are connected as a whole with steel sections to form a complete assembled large platform.

[0065] In this embodiment, it should be noted that the installation steps of the sliding device and the guiding device in step S2.3 are as follows:

[0066] S2.1.3.1. According to the arrangement position of the support, the length of the traction segment beam and the installation position, slideways are arranged on the top surface of each temporary pier to be loaded and the central isolation segment support pier. The slideways are arranged on the bottom of the beam under the pressure of the two outer webs of the steel box beam. Three rows are arranged on the left and right of the single beam. At the same time, due to the downward deflection of the traction head of the steel box cantilever, the height of the roller assembly can be adjusted during the actual installation;

[0067] S2.1.3.2. The slideway is welded from two I-beams. A stainless steel plate and a polytetrafluoroethylene pad are also provided on the upper surface of the slideway to allow the beam body and the polytetrafluoroethylene pad to slide between the stainless steel plate. Since the weight of the intermediate segment beam is about 450t, the slideway and the bottom of the steel box beam are padded with a polytetrafluoroethylene pad. The theoretical friction coefficient is about 0.1. It can be seen that its traction force is 45t. Considering that static friction must be overcome before starting the towing, a certain safety factor is taken. A 100-ton hydraulic traction machine is used for towing, and 5 Φ21.5 steel strands are used as towing steel wires to reduce the friction during towing;

[0068] S2.1.3.3. In order to ensure the lateral displacement and installation alignment of the steel box girder when it is dragged, transverse fine-tuning supports are welded and fixed on each temporary pier to provide jack support reaction force during fine-tuning, and at the same time play a certain limiting role when the steel box girder is dragged and deflected.

[0069] In this embodiment, it should be noted that the Bailey frame in step S1 is used to splice the steel box girders in the air and to strengthen the stability between the temporary supports. The Bailey frame is composed of two rows of 1500 mm high Bailey sheets connected by 900 mm wide lattices.

[0070] In this embodiment, it should be noted that the welding process of the drag segment beam in step S2 includes the following steps:

[0071] S2.2.1. The components shall be brought to the construction site strictly according to the assembly sequence on site. They shall be unloaded immediately upon arrival and directly hoisted to the assembly site for assembly. The 4m wide steel box beam shall be first assembled on the ground into an 8m wide steel box beam and then hoisted as a whole onto the towing assembly platform for assembly;

[0072] S2.2.2. Lift the steel box beam onto the assembly platform, use a 20t hydraulic jack to adjust the gap size of the interface to control it between 5 and 10mm, and use instruments to check whether the center line, elevation, curvature and camber of the two spliced ​​steel box beams meet the requirements of the drawings;

[0073] S2.2.3. After adjustment, use riding plates to weld firmly, and then weld. Use high-temperature ceramic pads to stick to the bottom of the weld on the top and bottom plates, use CO2 gas shielded welding to prime, and submerged arc automatic welding to cover. The two webs are directly welded by CO2 gas shielded welding or manual welding. After the welds are qualified by non-destructive testing, grind the welds at the longitudinal ribs on the top and bottom plates, connect the longitudinal ribs of the two steel box girders with longitudinal ribs, and finally weld the longitudinal ribs on the webs, the longitudinal ribs on the cantilever and the guard plate. The transverse butt welds of the top, bottom, webs and longitudinal ribs must meet the Class I weld standards.

[0074] S2.2.4. Hoist the first section of the component assembled on the ground onto the towing platform, with one end mounted on the pier slideway and the other end mounted on the Bailey frame. At this time, there is a 640mm space between the Bailey frame and the bottom of the beam. Use a temporary small bracket to pad it, and use a temporary small bracket and a jack to level the elevation of the interface with the second section of the component. Hoist the second section of the component into place and assemble it with the first section. When assembling on the column top platform, ensure that each section of the component has four fixed stress points, and at the same time, lay movable stress points for adjustment;

[0075] S2.2.5. Lift the anti-collision guardrail on the top plate into place, adjust it and weld it securely.

[0076] In this embodiment, it should be noted that step S3 of dragging the steel box girder includes the following steps:

[0077] S3.1. Preparation before hauling: After the hauling segment steel box girder is assembled and welded and inspected and qualified, the lifting lugs for hauling and the ends of the hauling beam are welded and reinforced to make the beam in the condition before hauling;

[0078] S3.2. Towing the steel box girder across the highway, the length of the steel box girder to be towed reaches 56m. When towing, at each roller assembly, the segmental steel box girder moves 16m across the highway. When the front end of the steel box girder reaches the pier of the central isolation belt, fix the support points at each pier to ensure that the steel box girder and the support are completely fixed as a whole to eliminate the influence of wind force in non-operating conditions;

[0079] S3.3. Drag the other half of the steel box girder on the same side according to step S3.2, and carry out the preliminary preparation work for both sides simultaneously;

[0080] S3.4. Close the left lane of the expressway for traffic and carry out preparations for the next stage of hauling. The entire hauling process and control shall be carried out in accordance with the hauling procedure of the first stage. The segmental steel box girder shall continue to move forward for about 20m from the first stage hauling position to the designed horizontal position. After the single span is hauled into place and fixed, the other half of the segmental steel box girder shall be hauled into place and fixed. The hauling of the main span of the entire main line bridge shall be completed, and all temporary facilities set on the road surface except the central isolation belt pier shall be removed;

[0081] S3.5. Hydraulic cylinders and jacks are used on temporary supports of some piers to fine-tune the absolute spatial coordinates of the segmental beams. The absolute coordinate data are given by the computer simulation design drawings. The spatial coordinates are monitored and calibrated by a total station. The calibration points are located on the corresponding top plates at the intersection of the two outer webs and the partitions. The longitudinal spacing of the calibration points is 4m and they are marked during assembly.

[0082] In this embodiment, it should be noted that step S1 adopts the bracket erection method, the remaining small segment beams on both sides are relatively small, and the maximum segment weighs 50t. The gantry cranes on both sides can directly hoist the steel box beam into place for assembly, positioning and welding.

[0083] In this embodiment, it should be noted that a group of Bailey frames consisting of two rows of 1500mm high Bailey sheets connected by 450mm wide lattices are arranged on the top of the middle column of the temporary support.

[0084] In this embodiment, it should be noted that after the first stage of towing in step S3.3 is completed, various temporary facilities for closing the left span are removed to open traffic and enter the next stage of towing, where the tail of the steel box girder is extended by four sections of 16M again to reach a length of 72m.

[0085] Example 2

[0086] See also Figures 1 to 8 The present invention is applied in the step-by-step construction of the dragging and scaffolding across the G22 Qinglan Expressway and the TY14 contract section of the Tianyong section of the Yinchuan-Baise Expressway (G69), specifically, including the following steps:

[0087] 1. Process principle

[0088] The erection of the steel box girder of the main line bridge is carried out by two methods: one-way dragging and supporting beam erection;

[0089] The middle span of the steel box girder was dragged twice using the dragging method to achieve the span across the highway;

[0090] First, set up traction piers, slideway piers, welding platform piers, beam drop piers, etc. on both sides of the expressway, install the slideway piers at the central dividing strip, and place Bailey frames, slideway rollers, beam drop jacks, lateral position adjustment devices, tractor mechanisms, etc. on the top of each pier;

[0091] The steel box girders on both sides are hoisted onto temporary supports by 60t gantry cranes;

[0092] The steel box girder segments (divided into 35 processing sub-segments longitudinally) were hoisted and installed on the welding piers at both ends from the construction site below the bridge axis by a 60t dismantling gantry crane on site, assembled into integral traction segments, and the welding of the traction segment beams was completed on the brackets;

[0093] The middle dragging beam is 72m long (from the 11th section to the 25th section, a total of 15 sections). After dragging across the highway twice, it is supported on temporary supports on both sides of piers 8 and 9 and positioned as a reference section. Then, the gantry cranes on both sides are directly used to weld the span segment beams on both sides (10 sections on each side). The main line bridge dragging schematic diagram is shown as follows: Figure 2 As shown;

[0094] 2. Construction process and operation points

[0095] (1) Steel box girder production

[0096] The steel box girder is manufactured in several sections and then welded into a bridge after being hoisted on site;

[0097] The steel box girder is located in the vertical curve. To ensure the linear shape of the steel girder after the bridge is completed, the mid-span steel girder is set with a pre-camber. At the same time, it should be noted that the vertical linear shape of the steel girder includes the design curve and the pre-camber curve. Therefore, the factory should manufacture according to the superimposed curve of the two parts.

[0098] (2) Transportation of steel box beams

[0099] Due to the geographical location of G22 Qinglan Expressway, the production of steel box girders is divided into in-plant cutting, processing grooves and assembly welding of plate units, and segment assembly welding. According to the progress of the project, a dedicated person in the factory is responsible for directing the transportation time, transportation volume and required formation, loading, confirmation and delivery of hoisting, bundling and reinforcement, and completing the handover procedures such as shipping batches, batches, quantities and arrival time requirements at the construction site;

[0100] Considering the damage to components during transportation, packing and wooden wedges are used for isolation during stacking to prevent deformation during transportation;

[0101] (3) Temporary support foundation treatment and temporary support fabrication and installation

[0102] ① Arrangement of temporary supports

[0103] There are 13 sets of temporary supports on each of the left and right sides of the main bridge (of which the 6th and 8th sets are movable trolleys). The layout of temporary supports for the main bridge is shown in Figure 3 ;

[0104] ② Design of temporary support

[0105] According to the arrangement of temporary supports and the load of the whole bridge, the force of each set of temporary supports can be calculated;

[0106] The foundation of each set of temporary supports is excavated to reveal the hard original soil layer. According to the geological survey report, the soil strength of the hard clay layer reaches 0.15Mpa. If the soil does not meet the strength requirements, it must be replaced with rough stone;

[0107] Each foundation can bear a load of 510t;

[0108] Each set of temporary supports is designed to consist of eight steel pipes larger than Φ426×6;

[0109] The Φ159×6 steel pipes between the steel pipes of each column are connected and used as scissor braces. Figure 4 ;

[0110] A sliding device is set between the top of the temporary support column and the steel box beam, and a guiding device is set at both ends; a Bailey frame is installed on the top bracket of the temporary support; a set of welding platforms is set between each set of temporary supports; all welding platforms and temporary supports are connected as a whole with steel sections, thus forming a complete assembly platform;

[0111] (4) Gantry crane installation

[0112] ① Gantry crane selection;

[0113] The maximum weight of the steel box girder delivered by the manufacturer is about 35t, so a 60t, 33m span, and 17m lifting height gantry crane was selected;

[0114] ② Arrangement of gantry crane;

[0115] Two 60t gantry cranes are installed between piers 7 and 8 and between piers 9 and 11 of the main line bridge. Figure 5 ;

[0116] (5) Slide and guide device design

[0117] According to the arrangement position of the support, the length of the dragging segment beam and the installation position, slideways are arranged on the top surface of each temporary pier and the central isolation section support pier. The slideways are arranged on the bottom of the two outer webs of the steel box beam, and three rows are arranged on the left and right of the single beam. At the same time, due to the downward deflection of the dragging head of the steel box cantilever, the height of the roller assembly can be adjusted during the actual installation;

[0118] The slideway is made of two I-beams welded together, and a stainless steel plate and a polytetrafluoroethylene pad are also arranged on the upper surface of the slideway, so that the beam body and the polytetrafluoroethylene pad slide between the stainless steel plate to reduce the friction during dragging;

[0119] In order to ensure the lateral displacement and installation alignment of the steel box girder during dragging, the transverse fine-tuning supports are welded and fixed on each temporary pier, which are mainly used to provide the jack support reaction force during fine-tuning, and also play a certain limiting role when the steel box girder is dragged and deflected;

[0120] The guide device adopts rolling bearing;

[0121] The schematic diagram of the guide and slide device is as follows Figure 6 :

[0122] (6) Traction device

[0123] Since the weight of the middle segment beam is about 450t (including guardrail), the slideway and the bottom of the steel box beam are padded with polytetrafluoroethylene pads, and the theoretical friction coefficient is about 0.1, it can be known that its traction force is 45t;

[0124] Considering that static friction must be overcome before starting the towing, and taking a certain safety factor, a 100-ton hydraulic traction machine is used for towing;

[0125] Use 5 Φ21.5 steel strands as traction wires;

[0126] (7) Laying out of slideways and Bailey racks

[0127] ① A full-length Bailey frame is set up between piers 7 and 8# to splice steel box girders in the air;

[0128] A set of Bailey frames is set on the top of the columns on both sides of each temporary support. This set of Bailey frames consists of two rows of 1500mm high Bailey sheets connected by 900mm wide lattices; a set of Bailey frames is set on the top of the middle column of the temporary support. It consists of two rows of 1500mm high Bailey sheets connected by 450mm wide lattices;

[0129] ② Bailey frames are set up between piers 9 and 10 to splice steel box girders in the air and strengthen the stability between temporary supports;

[0130] The Bailey frames are connected by pins instead of welding;

[0131] The Bailey frame and the steel column are connected with bolts;

[0132] An operating platform is set up with scaffolding at the temporary support between two connected sets of Bailey frames;

[0133] ③ A group of Bailey frames is set on the top brackets of the columns on both sides of each temporary support between piers 9 and 10#. This group of Bailey frames consists of two rows of 1500mm high Bailey pieces connected by 900mm wide lattices; a group of Bailey frames is set on the top of the middle column of the temporary support, which consists of two rows of 1500mm high Bailey pieces connected by 450mm wide lattices;

[0134] Bailey frame layout diagram Figure 7 :

[0135] ④ The middle column of 9# pier is the stress bearing part of the dragging beam. The dragging beam is 5 meters long. An additional column is set at the bottom of the dragging beam. The foundation treatment is the same as that of the temporary pier. The foundation of this column is 3m×3m, with reinforcement Φ12mm@10cm×10cm, and poured with 60cm thick C30 concrete;

[0136] according to Figure 8 Arrange the drag slide;

[0137] (8) Lifting, assembly and welding

[0138] ① The components shall be brought to the construction site strictly according to the assembly sequence on site, unloaded immediately upon arrival, and directly hoisted to the assembly site for assembly;

[0139] The 4m wide steel box beam is first assembled on the ground into an 8m wide steel box beam and then hoisted as a whole into the towing assembly platform for assembly;

[0140] ②Hang the steel box girder into the assembly platform and use a 20t hydraulic jack to adjust the gap size of the interface, which is generally controlled between 5 and 10 mm;

[0141] Use instruments to check whether the center line, elevation, curvature and camber of the two spliced ​​steel box girders meet the requirements of the drawings;

[0142] ③After adjustment, use the riding plate to weld firmly, and then weld;

[0143] The top and bottom plates are pasted with high-temperature ceramic pads on the bottom surface of the weld, and the base is welded with CO2 gas shielded welding, and the cover is welded with submerged arc automatic welding; the two webs are directly welded by CO2 gas shielded welding or manual welding; after the welds are qualified by non-destructive testing, the welds at the longitudinal ribs on the top and bottom plates are smoothed, and the longitudinal ribs of the two steel box girders are connected with the longitudinal ribs; finally, the longitudinal ribs on the webs, the longitudinal ribs on the cantilevers and the guard plates are welded;

[0144] The transverse butt welds of the top plate, bottom plate, web plate and longitudinal ribs must meet the Class I weld standards;

[0145] ④ Place the first section of the component assembled on the ground on the hoisting and dragging platform, with one end mounted on the slideway of pier 9# and the other end mounted on the Bailey frame. At this time, there is about 640mm space between the Bailey frame and the bottom of the beam, which is padded with a temporary small bracket, and the elevation of the interface with the second section of the component is leveled with a temporary small bracket and a jack;

[0146] Lift the second section into place and assemble it with the first section...When assembling the top platform of the column, ensure that each section has four fixed stress points and at the same time, movable stress points for adjustment;

[0147] ⑤ Lift the anti-collision guardrail on the top plate into place, adjust it and weld it firmly;

[0148] (9) Towing steel box beam

[0149] ①Preparation before hauling: After the hauling segment steel box girder (sections 11 to 19, 44m) is assembled and welded and inspected to be qualified, the lifting lugs for hauling and the ends of the hauling beams are welded together to make the beams in the condition before hauling;

[0150] In order to ensure the safety of the main line bridge steel box girder dragging across the expressway, a 12m dragging rehearsal distance was reserved between the front end of the dragging girder and the shoulder of the 9# pier of the expressway as a test dragging section to adjust and verify the overall dragging equipment support, personnel coordination, etc., to ensure absolute safety, reliability and speed when crossing the expressway;

[0151] At this time, the front end of the drag beam should reach the temporary pier on the roadbed slope protection on the side of 9# pier, waiting to officially cross the expressway;

[0152] ② Towing across the expressway: According to the pre-towing approval plan and the road closure time, the road is officially closed, and the right section of the Beijing-Zhuhai Expressway near the 9# pier is in a fully closed state. Warning signs and anti-collision facilities are set up at both ends of the closed section and at the lane change points as required, and a special person is assigned to ensure traffic safety; an on-site commander is appointed; and personnel from various departments are coordinated in a unified manner, including liaison management personnel, towing operators, steel box girder operation process monitoring personnel, support monitoring personnel, temporary pier and roller monitoring personnel, equipment inspection and maintenance personnel, and various auxiliary workers;

[0153] At this time, the length of the steel box girder to be towed reaches 56m. During towing, two people are assigned to each roller assembly to monitor the towing process and feed the slide plate.

[0154] At this time, the segmental steel box girder moves 16m across the road, and when the front end of the steel box girder reaches the pier of the central isolation zone;

[0155] Fix the supporting points at each pier to ensure that the steel box girder and the bracket are completely fixed as a whole;

[0156] Eliminate the effects of wind forces in non-operating situations;

[0157] Follow the same steps to drag the other half of the steel box girder on the same side, and the preliminary preparation work is carried out simultaneously on both sides;

[0158] At this time, the first stage of hauling is over, and various temporary facilities blocking the left section of Beijing-Zhuhai Railway are removed to open up traffic and enter the next stage of hauling;

[0159] At the tail of the steel box girder, four sections of 16 meters are extended again;

[0160] Reach 72m in length;

[0161] ③ Close the left lane of the expressway to prepare for the next stage of hauling. The entire hauling process and control will be carried out in accordance with the hauling procedures of the first stage;

[0162] The segmental steel box girder continues to move forward about 20m from the first stage dragging position to the designed horizontal position. After a single span is dragged into place and fixed, the other half of the segmental steel box girder is dragged into place and fixed. The dragging of the main span of the entire main line bridge is completed, and all temporary facilities set on the road surface except the central isolation belt pier are removed;

[0163] ④ Use hydraulic cylinders and jacks to fine-tune the spatial absolute coordinates of the segmental beams on the temporary supports of piers 8 and 9#;

[0164] Its absolute coordinate value data is given by the computer simulation design drawing;

[0165] The monitoring of spatial coordinate values ​​is carried out by total station detection and calibration. The calibration points are located on the corresponding top plates where the two outer webs and the partitions intersect. The longitudinal spacing of the calibration points is 4m and they are marked during assembly.

[0166] The total station measurement is fixed at 7:00-9:00 every morning until the linear size of the bridge deck of the segment is stable, and it is fixed as the spatial position reference size and starting assembly point for the assembly of the remaining small segment beams on both sides;

[0167] (10) Lateral offset adjustment of steel box beam

[0168] The steel box girder has been initially positioned according to the designed position during the dragging process, and lateral deviation will occur during construction;

[0169] In the design of slideway and guide device, the transverse fine-tuning support welded and fixed on each temporary pier has been considered, which is mainly convenient for providing jack support reaction force during fine-tuning, and at the same time plays a certain role in limiting the displacement of steel box girder when it is dragged and deflected. A 20t hydraulic jack is used to correct the transverse deviation problem.

[0170] (11) Assembly of steel box beams on both side spans

[0171] ① The bracket erection method was adopted on both sides of the expressway. The remaining small segment beams on both sides were small in size, with the largest segment weighing 50t, and would not affect the traffic of the expressway. The gantry cranes on both sides could directly hoist the steel box beams into place. Therefore, the gantry cranes were used on the 8# pier side and the 9# pier side to hoist and assemble the small segment beams into place at one time, and then assembled and positioned and welded;

[0172] ② In order to ensure the length of the entire bridge and compensate for the shrinkage of the weld, a certain amount of shrinkage was reserved during processing when splicing the last two segments on piers 7# and 10#. After the overall size was determined, the length was measured and spliced ​​in place;

[0173] (12) Overall drop

[0174] After the three spans of the bridge have passed the welding test, four 500t hydraulic cylinders are used to lift the bridge as a whole, adjust the gap between the support and the bottom of the beam and the support reaction force, remove the pads on the temporary piers, drop the beams into place, and realize the conversion of the entire bridge system;

[0175] After the conversion is completed, the supports and temporary piers under the bridge are removed and repainted;

[0176] When the central isolation belt piers are removed and repainted, in order to ensure safety, warning signs will be set up and traffic control will be implemented for a short period of time during the removal process;

[0177] 3. Materials and equipment (see Table 1)

[0178] Table 1 Equipment and tools list

[0179]

[0180]

[0181] 4. Quality Control

[0182] This technical construction shall comply with the following specifications and standards:

[0183] "Technical Specifications for Highway Bridge Construction" (JTJ041-89),

[0184] Municipal Bridge Engineering Quality Assessment Standard (CJJ2-90),

[0185] "Code for Acceptance of Construction Quality of Steel Structure Engineering" (GB50205-2001),

[0186] 《Rust level and rust removal level of steel surface before painting》

[0187] "Dimensions of Steel Welds" (GB10854-89),

[0188] "Building Steel Structure Welding Code" (JGJ81-2002),

[0189] "Basic types and dimensions of manual arc welding joints" (GB985),

[0190] "Basic types and dimensions of submerged arc automatic welding joints" (GB986);

[0191] Quality measures:

[0192] Strictly control each construction process, implement "three-process" management, construct according to the construction plan and construction technical measures, strictly implement the construction acceptance specifications and design standards, and ensure the design quality requirements;

[0193] Before welding the steel box girder, all weld ends and both sides of the weld, the weld groove cutting surface, and the welded steel surface should be polished and cleaned of any impurities such as scale, rust, moisture, paint, etc. that may hinder welding within the specified range, and the metallic luster should be exposed;

[0194] If the weld seam after assembly and cleaning is not welded in time, and the weld seam area is rusted again or has moisture and rust due to climate or other reasons, the weld seam area should be cleaned again before welding;

[0195] For open-air construction, measures must be taken to prevent wind and rain, such as baffles and awnings;

[0196] Control the quality of welding rods, check and confirm whether the test reports and factory certificates of materials are complete and valid;

[0197] Check the purity of various welding gases and various test data;

[0198] For the process report and report confirmation of typical welding nodes, simulated on-site process tests are conducted for different materials, different welding forms and different welding conditions, parameters are formulated and test reports are provided;

[0199] A dedicated person is responsible for the repair and maintenance of the welding machine to ensure the performance of the welding machine during operation and strengthen the supervision and management before, during and after welding.

[0200] Quality inspection after welding: First, the welding team conducts self-inspection of the weld quality and makes records according to the requirements of the design drawings;

[0201] On the basis of the team's self-inspection, full-time personnel will conduct special inspections and keep records. Finally, ultrasonic or magnetic particle inspections will be performed on the welds according to the requirements of the owner and the design.

[0202] V. Safety Measures

[0203] Safety training is carried out for personnel entering the site, safety briefing is carried out before construction, and reminders are given before the shift;

[0204] When entering the site, you must wear a safety helmet, work clothes, non-slip shoes, and safety belts when going to heights;

[0205] Before lifting, simulated lifting should be carried out and forced lifting is not allowed;

[0206] The lifting must be directed by a qualified crane operator, and no illegal operations or safety production operating procedures shall be violated;

[0207] A safe operating platform is set up on the top of the temporary support, with safety railings and a straight ladder with a protective cover leading to the ground;

[0208] When welding inside a steel box girder, use an induced draft fan to extract the smoke inside the girder to prevent accidents;

[0209] The wing plates on both sides of the steel box girder are welded with a movable inverted hanging basket. The hanging basket must be set firmly and fixed firmly. At the same time, the safety belt rope must be led out from the steel box girder.

[0210] During the dragging and pausing of the steel box girder, the stability of the steel support shall be observed and any abnormality shall be promptly reinforced;

[0211] At the same time, construction workers are prohibited from crossing the highway;

[0212] Strengthen the connection with highway management departments, actively invite traffic control departments to hold professional knowledge lectures, and train on-site safety and technical management personnel. All traffic control plans must be approved by the traffic police department before implementation, and must be implemented strictly according to the reported plans;

[0213] Before construction, set up obvious construction and safety signs on the construction section;

[0214] Construction and safety signs are complete, standardized, clear, well-recognized, accurately located, and firmly set up, which can effectively remind and guide drivers through the construction section;

[0215] VI. Environmental Protection Measures

[0216] Actively negotiate and communicate with the Highway Administration and the Road Administration Department to formulate detailed protection plans to maintain the greening, road surface and facilities of the Beijing-Zhuhai Expressway;

[0217] Transplant trees on the slopes and central divider on both sides of the highway, and clear the drainage system in a timely manner; remove the original isolation fence facilities on both sides of the Beijing-Zhuhai Highway, and move them to the corrugated guardrails on both sides of the highway to ensure the closure of the highway and prevent local people and poultry from entering the highway. After completion, restore the original appearance;

[0218] During the steel box girder dragging process, in order to prevent the mobile piers from causing damage to the road surface, steel plates are placed in the vulnerable areas for protection;

[0219] VII. Benefit Analysis

[0220] The construction method of the present invention adopts the dragging construction technology to smoothly and orderly erect the steel box girder across the G22 Qinglan Expressway, making full use of the structural characteristics of the continuous steel box girder itself and the advantages of the supporting equipment. According to calculations, the dragging and erecting speed of the continuous steel box girder can be controlled at more than 0.6m / min, which greatly reduces the pressure on the existing high-speed operation. At the same time, the dragging and erecting construction across the G22 Qinglan Expressway is carried out in steps, which can cancel the auxiliary measures of adding auxiliary piers on the existing highway, greatly reducing the impact of the construction on the safety of highway operation, and providing a reliable decision-making basis and technical indicators for the construction of bridges across highways under similar circumstances in the future. The novel construction method and technology will promote the progress of bridge engineering construction technology, and the social and environmental benefits are obvious;

[0221] Compared with similar bridge erection construction methods, the construction method of the present invention reduces the scope of support foundation treatment and speeds up the construction progress. The steel box girder construction adopts the long-distance steel box girder dragging construction technology across the highway, optimizes the original design and construction plan, speeds up the construction progress, and saves construction costs. The main optimization project saves economic costs of 3.2 million yuan;

[0222] 8. Application Examples

[0223] The Tianyong section of Yinbai Expressway (G69) is the Tianshuibao-Qingcheng-Yonghe Expressway, which is an important section of the Yinchuan-Baise National Expressway (G69). The TY14 section of the Tianyong section has a total of 4 steel box girder bridges, namely K213+364.7 Xihe Road Separated Interchange, K225+862.446 G211 Separated Interchange, MK204+600.0 Vehicle Overpass, AK0+440.0 Vehicle Overpass. The upper structure is constructed with steel box girders, and the lower structure is constructed with column piers, column platforms, and pile foundations. Among them, the K225+862.446 G211 separated interchange needs to cross the G22 Qinglan Expressway, which has high construction technical difficulty and construction safety control requirements;

[0224] The steel box girder construction adopted the long-distance steel box girder dragging construction technology across the expressway, which optimized the original design and construction plan, accelerated the construction progress, and saved construction costs. The main optimization project saved economic costs of 3.2 million yuan;

[0225] During the construction process, the noise level of mechanical equipment is low, which does not affect the lives of surrounding residents. During construction, there is no pollution to the surrounding environment and atmosphere, which complies with relevant national environmental protection standards.

[0226] The structure is stable throughout the entire process, and there is no need for blocking or slowing down, ensuring the safety of existing line construction;

[0227] By optimizing the construction plan, we improved work efficiency, shortened the construction period, received praise from the owner, design and supervision units, established a good corporate image, received widespread attention from the society, and achieved good economic, social, energy-saving and environmental benefits.

[0228] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for erecting a steel box girder across a highway by dragging, characterized in that: The following steps are involved: S1. Preparation and installation of piers: Build piers for towing, gliding path piers, welding platform piers and beam-dropping piers on both sides of the expressway, install gliding path piers at the central median, and set up Bailey frames, slideway rollers, beam-dropping jacks, lateral position adjustment devices and tractor mechanisms on the top of the piers; S2. Installation and splicing of steel box girders: A 60t, 33m span, 17m lifting height gantry crane is used to hoist the steel box girders onto temporary supports. First, both ends of the steel box girders are erected. Each segment of the steel box girders is longitudinally divided into 35 small segments. A 60t disassembled gantry crane is used to hoist each small segment from the construction site below the bridge axis and install it on the welded piers at both ends. Each small segment is assembled into an integral traction segment, and the welding of the traction segment beam is completed on the support; S3. Towing installation of the middle span: The length of the middle towing beam is 72m, from the 11th section to the 25th section, a total of 15 small sections, and the towing method is used to carry out two towing to achieve the crossing of the expressway. After towing, it is supported on the temporary supports on both sides of the 8th and 9th piers, and the beam is dropped and positioned as the reference section; S4. Gantry crane installation on both sides: Gantry cranes are used for the steel box beam spans on both sides, and the beams of 10 small sections on the left and right are welded into a whole; S5. Overall dismantling: After the three spans of the bridge have passed the welding test, four 500t hydraulic cylinders are used to lift the entire bridge, adjust the gap between the support and the bottom of the beam and the support reaction force, remove the pads on each temporary pier, and drop the beam into place to achieve the conversion of the entire bridge system. After the conversion is completed, remove the supports and temporary piers under the bridge, and repaint. When the piers in the central isolation zone are removed and repainted, in order to ensure safety, warning signs are set up for a short period of time during the dismantling process and traffic control is implemented.

2. The method for erecting a steel box girder across a highway by dragging according to claim 1 is characterized in that: In step S2, the steel box girder is divided into several sections for factory manufacturing. After being hoisted on site, the sections are welded into a bridge. The steel box girder part is located in the vertical curve. In order to ensure the linear shape of the steel girder after the bridge is completed, the mid-span steel girder is provided with a pre-camber. At the same time, it is noted that the vertical linear shape of the steel girder includes two parts, the design curve and the pre-camber curve. The manufacturing should be carried out according to the superimposed curve of the two parts.

3. The method for erecting a steel box girder across a highway by dragging according to claim 2 is characterized in that: The step S2 of temporary support foundation processing and temporary support fabrication and installation includes the following steps: S2.1.

1. Arrangement of temporary supports: 13 sets of temporary supports are arranged on each of the left and right sides of the main line bridge; S2.1.

2. Design of temporary supports. Calculate the stress of each set of temporary supports according to the layout of temporary supports and the load of the whole bridge. The foundation of each set of temporary supports is excavated from the hard original soil layer. According to the geological exploration report, the soil strength of the hard clay layer reaches 0.15Mpa. The soil that does not meet the strength requirements must be replaced with rough stone so that each foundation can withstand a stress of 510t. Each set of temporary supports is designed to be composed of eight steel pipes larger than Φ426×6. The steel pipes of each column are connected and used as scissor braces with Φ159×6 steel pipes; S2.1.

3. A sliding device is provided between the top of the temporary support column and the steel box beam, and a guiding device is provided at both ends; S2.1.

4. Bailey frames are installed on the top brackets of temporary supports, and a set of welding platforms is set between each set of temporary supports; S2.1.

5. All welded platforms and temporary supports are connected as a whole with steel sections to form a complete assembled large platform.

4. The method for erecting a steel box girder across a highway by dragging according to claim 3 is characterized in that ,The installation steps of the sliding device and the guiding device in step S2.3 are as follows: S2.1.3.

1. According to the arrangement position of the support, the length of the traction segment beam and the installation position, slideways are arranged on the top surface of each temporary pier to be loaded and the central isolation segment support pier. The slideways are arranged on the bottom of the beam under the pressure of the two outer webs of the steel box beam. Three rows are arranged on the left and right of the single beam. At the same time, due to the downward deflection of the traction head of the steel box cantilever, the height of the roller assembly can be adjusted during the actual installation; S2.1.3.

2. The slideway is welded from two I-beams. A stainless steel plate and a polytetrafluoroethylene pad are also provided on the upper surface of the slideway to allow the beam body and the polytetrafluoroethylene pad to slide between the stainless steel plate. Since the weight of the intermediate segment beam is about 450t, the slideway and the bottom of the steel box beam are padded with a polytetrafluoroethylene pad. The theoretical friction coefficient is about 0.

1. It can be seen that its traction force is 45t. Considering that static friction must be overcome before starting the towing, a certain safety factor is taken. A 100-ton hydraulic traction machine is used for towing, and 5 Φ21.5 steel strands are used as towing steel wires to reduce the friction during towing; S2.1.3.

3. In order to ensure the lateral displacement and installation alignment of the steel box girder when it is dragged, transverse fine-tuning supports are welded and fixed on each temporary pier to provide jack support reaction force during fine-tuning, and at the same time play a certain limiting role when the steel box girder is dragged and deflected.

5. The method for erecting a steel box girder across a highway by dragging method according to claim 4 is characterized in that: In step S1, the Bailey frame is used to splice the steel box beams in the air and to strengthen the stability between the temporary supports. The Bailey frame is composed of two rows of 1500 mm high Bailey sheets connected by 900 mm wide lattices.

6. The method for erecting a steel box girder across a highway by dragging method according to claim 5 is characterized in that: The welding process of the drag segment beam in step S2 includes the following steps: S2.2.

1. The components shall be brought to the construction site strictly according to the assembly sequence on site. They shall be unloaded immediately upon arrival and directly hoisted to the assembly site for assembly. The 4m wide steel box beam shall be first assembled on the ground into an 8m wide steel box beam and then hoisted as a whole onto the towing assembly platform for assembly; S2.2.

2. Lift the steel box beam onto the assembly platform, use a 20t hydraulic jack to adjust the gap size of the interface to control it between 5 and 10mm, and use instruments to check whether the center line, elevation, curvature and camber of the two spliced ​​steel box beams meet the requirements of the drawings; S2.2.

3. After adjustment, use riding plates to weld firmly, and then weld. Use high-temperature ceramic pads to stick to the bottom of the weld on the top and bottom plates, use CO2 gas shielded welding to prime, and submerged arc automatic welding to cover. The two webs are directly welded by CO2 gas shielded welding or manual welding. After the welds are qualified by non-destructive testing, grind the welds at the longitudinal ribs on the top and bottom plates, connect the longitudinal ribs of the two steel box girders with longitudinal ribs, and finally weld the longitudinal ribs on the webs, the longitudinal ribs on the cantilever and the guard plate. The transverse butt welds of the top, bottom, webs and longitudinal ribs must meet the Class I weld standards. S2.2.

4. Hoist the first section of the component assembled on the ground onto the towing platform, with one end mounted on the pier slideway and the other end mounted on the Bailey frame. At this time, there is a 640mm space between the Bailey frame and the bottom of the beam. Use a temporary small bracket to pad it, and use a temporary small bracket and a jack to level the elevation of the interface with the second section of the component. Hoist the second section of the component into place and assemble it with the first section. When assembling on the column top platform, ensure that each section of the component has four fixed stress points, and at the same time, lay movable stress points for adjustment; S2.2.

5. Lift the anti-collision guardrail on the top plate into place, adjust it and weld it securely.

7. The method for erecting a steel box girder across a highway by dragging according to claim 6 is characterized in that The step S3 of dragging the steel box beam comprises the following steps: S3.

1. Preparation before hauling: After the hauling segment steel box girder is assembled and welded and inspected and qualified, the lifting lugs for hauling and the ends of the hauling beam are welded and reinforced to make the beam in the condition before hauling; S3.

2. Towing the steel box girder across the highway, the length of the steel box girder to be towed reaches 56m. When towing, at each roller assembly, the segmental steel box girder moves 16m across the highway. When the front end of the steel box girder reaches the pier of the central isolation belt, fix the support points at each pier to ensure that the steel box girder and the support are completely fixed as a whole to eliminate the influence of wind force in non-operating conditions; S3.

3. Drag the other half of the steel box girder on the same side according to step S3.2, and carry out the preliminary preparation work for both sides simultaneously; S3.

4. Close the left lane of the expressway for traffic and carry out preparations for the next stage of hauling. The entire hauling process and control shall be carried out in accordance with the hauling procedure of the first stage. The segmental steel box girder shall continue to move forward for about 20m from the first stage hauling position to the designed horizontal position. After the single span is hauled into place and fixed, the other half of the segmental steel box girder shall be hauled into place and fixed. The hauling of the main span of the entire main line bridge shall be completed, and all temporary facilities set on the road surface except the central isolation belt pier shall be removed; S3.

5. Hydraulic cylinders and jacks are used on temporary supports of some piers to fine-tune the absolute spatial coordinates of the segmental beams. The absolute coordinate data are given by the computer simulation design drawings. The spatial coordinates are monitored and calibrated by a total station. The calibration points are located on the corresponding top plates at the intersection of the two outer webs and the partitions. The longitudinal spacing of the calibration points is 4m and they are marked during assembly.

8. The method for erecting a steel box girder across a highway by dragging method according to claim 7 is characterized in that: The step S1 adopts the support erection method. The remaining small segment beams on both sides are relatively small, with the largest segment weighing 50t. The gantry cranes on both sides can directly hoist the steel box beams into place for assembly, positioning and welding.

9. The method for erecting a steel box girder across a highway by dragging method according to claim 8, characterized in that: A group of Bailey frames consisting of two rows of 1500mm high Bailey sheets connected by 450mm wide lattices are arranged on the top of the middle column of the temporary support.

10. The method for erecting a steel box girder across a highway by dragging method according to claim 9, characterized in that: After the first stage of hauling in step S3.3 is completed, various temporary facilities for closing the left span are removed to open the traffic, and then the next stage of hauling is started, where the tail of the steel box girder is extended by another four sections of 16 meters to reach a length of 72 meters.

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