Urban sewage pipeline bridge transformation design and construction method

Abstract

The invention relates to the technical field of sewage pipeline bridge transformation, in particular to an urban sewage pipeline bridge transformation design and construction method. Comprising the following steps: evaluating the reconstruction feasibility according to the structural state of the existing sewage pipeline bridge and determining to adopt an aluminum alloy fabricated structure; a 160 * 120 * 10 mm aluminum square tube stand column and a 420 * 130 mm stairway longitudinal beam component are designed, and it is ensured that the length deviation is smaller than or equal to 10 mm, the height deviation is + 4 mm, the connector dislocation is smaller than or equal to 2 mm, and the camber deviation is smaller than or equal to L / 5000 mm. The problem that a sewage pipeline bridge is single in purpose is solved, urban construction is improved through transformation, pedestrian passageways are increased, traffic pressure is relieved, the transformed bridge adopts an aluminum alloy structure, most of the transformed bridge adopts an assembly type technology, the requirement for engineering development is met, and the bridge has the advantages of being environmentally friendly, low-carbon, safe and rapid. A reasonable solution is provided for problems existing in current city reconstruction construction, and the method is worthy of application and popularization.

Description

Technical Field

[0001] The invention relates to the technical field of sewage pipeline bridge reconstruction, and in particular to a design and construction method for urban sewage pipeline bridge reconstruction. Background Art

[0002] Municipal pipeline projects are necessary supporting facilities for urban construction and are the key to the normal operation of cities. When municipal pipelines encounter rivers, they are often built across the river by constructing pipeline bridges. However, sewage pipeline bridges have a single purpose and have partially lost their functions over time.

[0003] At present, the city takes intensive development, green and low-carbon development as its path, insists on "retaining, modifying and demolishing" at the same time, focuses on retaining, utilizing and improving, strengthens repair and renovation, makes up for the shortcomings of the city, pays attention to improving functions and enhancing urban vitality. Therefore, the transformation of the original pipeline bridge is of great significance to the country's energy conservation and green development.

[0004] Based on this, the present invention provides a design and construction method for the reconstruction of an urban sewage pipeline bridge to solve the technical problems raised above. Summary of the invention

[0005] The purpose of the present invention is to provide a design and construction method for urban sewage pipeline bridge reconstruction to solve the problems raised by the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for the reconstruction design and construction of a municipal sewage pipeline bridge is provided, comprising the following steps:

[0008] S1. According to the structural status of the existing sewage pipeline bridge and the needs of urban development, the feasibility of its transformation was evaluated, a multifunctional improvement plan was formulated, a new pedestrian passage was added to relieve traffic pressure, and the aluminum alloy prefabricated structure was determined to be used in combination with the energy conservation and emission reduction goals;

[0009] S2. Design 160*120*10mm aluminum square tube columns and 420*130mm ladder longitudinal beam components to ensure that the length deviation is ≤10mm, the height deviation is +4mm, the interface misalignment is ≤2mm, and the camber deviation is ≤L / 5000mm;

[0010] S3. Build double-row ground-type scaffolding at 200mm on both sides of the original bridge piers, with the horizontal spacing of 1.0m and the vertical spacing of 1.5m, the horizontal bar step distance of 1.8m, the top of the scaffolding is 1.0m higher than the bridge railing, and the horizontal safety net is fully hung every 3 steps. The outer side is set with a dense safety net, and equipped with 45° vertical scissor braces and bridge deck wooden frame boards;

[0011] S4. Build a 3.0×3.0m unloading platform with vertical distance of 1.0m, horizontal distance of 0.75m and step distance of 1.5m. Set vertical scissor braces and dense safety nets on the periphery of the platform, and the spacing of top supporting steel pipes is 500mm;

[0012] S5. Use multi-point support and temporary fixing measures to transport prefabricated components to prevent deformation or collision, and use a level to level the site before construction;

[0013] S6. Install prefabricated components according to the design coordinates, control the three-dimensional coordinate error, keep the bridge body linearly smooth and aligned with the axis, use stainless steel bolts for connection, supplemented by flat washers and spring washers, tighten the nuts until the spring washers are compressed, and complete the main structure assembly;

[0014] S7. Full penetration butt welding is used for load-bearing components, and partial penetration welding is used for non-load-bearing components. After welding, the weld surface is checked for cracks and undercut defects. 100% of Grade I welds are ultrasonically inspected, and 20% of Grade II welds are randomly inspected;

[0015] S8. Perform anodizing treatment on aluminum alloy components with an oxide film thickness of ≥15μm. After the bridge deck is installed, inspect the structural safety and functionality.

[0016] Preferably, the implementation steps of step S2 are:

[0017] S2.1. Based on BIM modeling software, design 160*120*10mm aluminum square tube columns and 420*130mm ladder longitudinal beam components. The nodes are connected by bolts, and a 20mm width expansion joint is reserved. Output the processing drawings, and mark the tolerance requirements of length deviation ≤10mm and height deviation +4mm;

[0018] S2.2. Complete aluminum alloy cutting, drilling and surface pretreatment in the CNC machining center, pre-assemble the components on the fetal membrane according to the design drawings, use a total station to detect interface misalignment ≤ 2mm, camber deviation ≤ L / 5000mm, and rework unqualified parts;

[0019] S2.3. Recheck the dimensions of components with a three-dimensional coordinate measuring machine, spray them with a scratch-resistant protective film after acceptance, classify and package them according to transport units, and fix them with customized steel frames to avoid deformation during transportation.

[0020] Preferably, the implementation steps of step S3 are:

[0021] S3.1. Clear the debris around the pier, compact the ground, lay 50mm thick steel plates as the base of the poles, and lay out the lines 200mm on both sides of the pier to ensure that the horizontal spacing of the double rows of poles is 1.0m and the vertical spacing is 1.5m;

[0022] S3.2. Install horizontal bars layer by layer at a step distance of 1.8m, set vertical and horizontal sweeping bars 200mm from the ground, set a 45° vertical scissor brace for every 7 vertical bars, and add a 60° scissor brace for every 5 vertical bars below the bridge deck, and use an adjustable top support to tighten against the bridge deck;

[0023] S3.3. The outside of the scaffolding is fully hung with a flame-retardant dense mesh safety net, a horizontal safety net is laid every 3 steps, a double-layer protection net is added at the height of the bridge deck, the bridge deck is fully covered with 50mm thick wooden frame boards, and 200mm high footboards are set on the edges.

[0024] Preferably, the implementation steps of step S4 are:

[0025] S4.1. Level the site below the bridge, cast a C20 concrete cushion layer with a thickness of 150 mm, embed anchor bolts, and set up poles in a range of 3.0×3.0 m, with a longitudinal distance of 1.0 m, a horizontal distance of 0.75 m, and a step distance of 1.5 m;

[0026] S4.2. Support system optimization

[0027] The top supporting steel pipes are arranged at a spacing of 500mm and fixed with double fasteners. Continuous vertical scissor braces are set on the three sides of the platform and connected to the vertical poles through rotating fasteners to enhance the overall stability.

[0028] S4.3. Designate a special storage area for steel bars, aluminum alloy components, and welding equipment, and set a storage area of ​​≤1.5t / m 2 Load limit signs are installed, a 1.2m high protective railing is added to the outside of the platform, and a "overloading is strictly prohibited" warning sign is hung.

[0029] Preferably, the implementation steps of step S5 are:

[0030] S5.1. Plan the transportation route, avoid the sections with height and weight restrictions, use low-bed trailers, place rubber cushions between the components and the vehicle body, and use nylon straps to fix multiple points with a spacing of ≤2m to prevent side sliding;

[0031] S5.2. Use a level to measure the elevation of the area within 50m around the bridge site, fill the local sunken area with graded sand and gravel and compact it, and control the flatness error within ±5mm;

[0032] S5.3. Components should be stacked in order of installation, with sleepers at the bottom spaced ≤1.5m apart. Check that the breaking force of the lifting rigging is ≥5 times the weight of the component. Set up a warning area and arrange dedicated signal workers for command.

[0033] Preferably, the implementation steps of step S6 are:

[0034] S6.1. Use a total station to mark the axis control points on the bridge piers and verify that the coordinate error is ≤2mm. When installing the first section of the column, use a jack to fine-tune the level and the verticality deviation is ≤1 / 1000;

[0035] S6.2. Install components in the order of "from bottom to top, primary first and secondary later", use stainless steel bolts for connection, and use matching flat washers and spring washers. Tighten with a torque wrench twice, initially tightening to 50% torque and finally tightening until the spring washers are flattened;

[0036] S6.3. After assembling every three sections, use a laser collimator to detect the bridge line shape, adjust the interface gap to ≤1mm, and ensure that the center axis offset is ≤3mm.

[0037] Preferably, the implementation steps of step S7 are:

[0038] S7.1. TIG welding is used for load-bearing components and MIG welding is used for non-load-bearing components. Before welding, the groove is cleaned with acetone to remove the oxide layer;

[0039] S7.2. Immediately after welding, knock off the welding slag and check whether the weld surface is smooth, free of cracks, and the undercut depth is ≤ 0.5 mm. Use a weld gauge to measure the weld leg height.

[0040] S7.3. 100% of the Grade I welds shall be ultrasonically inspected according to GB / T11345 standard, and 20% of the Grade II welds shall be randomly selected. If defects are found, they shall be removed by carbon arc gouging and then re-welded. Only after passing the re-inspection can the next process be entered.

[0041] Preferably, the implementation steps of step S8 are:

[0042] S8.1. Immerse the aluminum alloy component in a 15% sulfuric acid electrolyte, apply a voltage of 12V, and oxidize for 30 minutes to form an AA15 grade oxide film with an average thickness of ≥15μm and a local thickness of ≥12μm;

[0043] S8.2. Spray 80μm thick epoxy resin primer, lay glass fiber cloth, and then apply polyurethane topcoat with a total thickness of ≥1.2mm. The closed water test is passed after 24 hours without leakage;

[0044] S8.3. Carry out 1.2 times load test, vibration test and pedestrian traffic simulation, and the acceptance report shall cover structural safety, anti-corrosion performance and traffic comfort indicators.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The present invention solves the single purpose of sewage pipeline bridges, transforms and improves urban construction, increases pedestrian passages, and relieves traffic pressure. The transformed bridge adopts an aluminum alloy structure, and most of it adopts assembly technology, which is suitable for the needs of engineering development. Its green, low-carbon, safe and fast characteristics provide a reasonable solution to the current problems in urban transformation and construction, and it is worthy of promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic diagram of the structure of the reserved expansion joint of the bridge deck in the urban sewage pipeline bridge reconstruction design and construction method of the present invention;

[0048] Figure 2 This is a cross-sectional diagram of the bridge deck reconstruction according to the urban sewage pipeline bridge reconstruction design and construction method of the present invention.

[0049] Legend:

[0050] 1. Bridge deck; 2. Expansion joint; 3. Aluminum square tube; 4. Connecting plate; 5. M16 stainless steel bolts; 6. Vertical rod; 7. Handrail; 8. Longitudinal beam. DETAILED DESCRIPTION

[0051] The following will be combined with 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.

[0052] Example 1, please refer to Figure 1 to Figure 2 The present invention proposes a method for the reconstruction design and construction of a municipal sewage pipeline bridge, which specifically includes the following steps:

[0053] S1. According to the structural status of the existing sewage pipeline bridge and the needs of urban development, the feasibility of its transformation was evaluated, a multifunctional improvement plan was formulated, a new pedestrian passage was added to relieve traffic pressure, and the aluminum alloy prefabricated structure was determined to be used in combination with the energy conservation and emission reduction goals;

[0054] Conduct field surveys of existing sewage pipeline bridges, use 3D laser scanning technology to obtain bridge geometry data, detect concrete cracking, steel corrosion, foundation settlement damage, and record key structural parameters, including span, bridge deck width, and load capacity;

[0055] Combined with the traffic flow data provided by the urban planning department and the results of the resident survey, it is clear that the width of the pedestrian passage (≥2.5m) needs to be increased, and the demand for pipeline expansion is evaluated simultaneously. According to the green and low-carbon policy, it is determined to use aluminum alloy prefabricated structures and formulate energy-saving and emission reduction indicators;

[0056] Prepare a technical report on the renovation plan, including content on function improvement, structural optimization and environmental impact assessment, organize an expert review meeting, focus on demonstrating the compatibility of pedestrian access and pipeline loads, the durability of aluminum alloy materials, and finally determine the implementation plan;

[0057] S2. Design 160*120*10mm aluminum square tube columns and 420*130mm ladder longitudinal beam components to ensure that the length deviation is ≤10mm, the height deviation is +4mm, the interface misalignment is ≤2mm, and the camber deviation is ≤L / 5000mm;

[0058] In this embodiment, it should be noted that the implementation steps of step S2 are:

[0059] S2.1. Based on BIM modeling software, design 160*120*10mm aluminum square tube columns and 420*130mm ladder longitudinal beam components, and use bolts to connect the nodes;

[0060] See also Figure 1 , the two bridge decks 1 reserve a 20mm wide expansion joint 2 structure, output the processing drawings, and mark the tolerance requirements for length deviation ≤10mm and height deviation +4mm;

[0061] S2.2. Complete aluminum alloy cutting, drilling and surface pretreatment in the CNC machining center, pre-assemble the components on the fetal membrane according to the design drawings, use a total station to detect interface misalignment ≤ 2mm, camber deviation ≤ L / 5000mm, and rework unqualified parts;

[0062] S2.3. Re-check the dimensions of components with a three-dimensional coordinate measuring machine, spray anti-scratch protective film after acceptance, classify and package according to transport units, and fix them with customized steel frames to avoid deformation during transportation;

[0063] S3. Build double-row ground-type scaffolding at 200mm on both sides of the original bridge piers, with the horizontal spacing of 1.0m and the vertical spacing of 1.5m, the horizontal bar step distance of 1.8m, the top of the scaffolding is 1.0m higher than the bridge railing, and the horizontal safety net is fully hung every 3 steps. The outer side is set with a dense safety net, and equipped with 45° vertical scissor braces and bridge deck wooden frame boards;

[0064] In this embodiment, it should be noted that the implementation steps of step S3 are:

[0065] S3.1. Clear the debris around the pier, compact the ground, lay 50mm thick steel plates as the base of the poles, and lay out the lines 200mm on both sides of the pier to ensure that the horizontal spacing of the double rows of poles is 1.0m and the vertical spacing is 1.5m;

[0066] S3.2. Install horizontal bars layer by layer at a step distance of 1.8m, set vertical and horizontal sweeping bars 200mm from the ground, set a 45° vertical scissor brace for every 7 vertical bars, and add a 60° scissor brace for every 5 vertical bars below the bridge deck, and use an adjustable top support to tighten against the bridge deck;

[0067] S3.3. The outside of the scaffolding is fully hung with a flame-retardant dense mesh safety net, and a horizontal safety net is laid every 3 steps. A double-layer protective net is added at the bridge deck height. The bridge deck is fully covered with 50mm thick wooden frame boards, and 200mm high footboards are set at the edges;

[0068] S4. Build a 3.0×3.0m unloading platform with vertical distance of 1.0m, horizontal distance of 0.75m and step distance of 1.5m. Set vertical scissor braces and dense safety nets on the periphery of the platform, and the spacing of top supporting steel pipes is 500mm;

[0069] In this embodiment, it should be noted that the implementation steps of step S4 are:

[0070] S4.1. Level the site below the bridge, cast a C20 concrete cushion layer with a thickness of 150 mm, embed anchor bolts, and set up poles in a range of 3.0×3.0 m, with a longitudinal distance of 1.0 m, a horizontal distance of 0.75 m, and a step distance of 1.5 m;

[0071] S4.2. The top supporting steel pipes are arranged at a spacing of 500 mm and fixed with double fasteners. Continuous vertical scissor braces are set on the three sides of the platform and connected to the vertical poles with rotating fasteners to enhance the overall stability;

[0072] S4.3. Designate a special storage area for steel bars, aluminum alloy components, and welding equipment, and set a storage area of ​​≤1.5t / m 2 Load limit signs, 1.2m high guardrails are added to the periphery of the platform, and a "Strictly No Overloading" warning sign is hung;

[0073] S5. Use multi-point support and temporary fixing measures to transport prefabricated components to prevent deformation or collision, and use a level to level the site before construction;

[0074] In this embodiment, it should be noted that the implementation steps of step S5 are:

[0075] S5.1. Plan the transportation route, avoid the sections with height and weight restrictions, use low-bed trailers, place rubber cushions between the components and the vehicle body, and use nylon straps to fix multiple points with a spacing of ≤2m to prevent side sliding;

[0076] S5.2. Use a level to measure the elevation of the area within 50m around the bridge site, fill the local sunken area with graded sand and gravel and compact it, and control the flatness error within ±5mm;

[0077] S5.3. Components should be stacked in the order of installation, with sleepers at the bottom spaced ≤1.5m apart. Check that the breaking force of the lifting rigging is ≥5 times the weight of the component. Set up a warning area and arrange a full-time signalman for command.

[0078] S6. Install prefabricated components according to the design coordinates, control the three-dimensional coordinate error, keep the bridge body linearly smooth and aligned with the axis, use stainless steel bolts for connection, supplemented by flat washers and spring washers, tighten the nuts until the spring washers are compressed, and complete the main structure assembly;

[0079] In this embodiment, it should be noted that the implementation steps of step S6 are:

[0080] S6.1. Use a total station to mark the axis control points on the bridge piers and verify that the coordinate error is ≤2mm. When installing the first section of the column, use a jack to fine-tune the level and the verticality deviation is ≤1 / 1000;

[0081] S6.2. Install components in the order of "from bottom to top, primary first and secondary later", use stainless steel bolts for connection, and use matching flat washers and spring washers. Tighten with a torque wrench twice, initially tightening to 50% torque and finally tightening until the spring washers are flattened;

[0082] S6.3. After assembling every three sections, use a laser collimator to check the bridge alignment, adjust the interface gap to ≤1mm, and ensure that the center axis offset is ≤3mm;

[0083] See also Figure 2 In this step, the welding structure is set according to the aluminum square tube 3 in the figure, the longitudinal beams 8 on both sides of the aluminum square tube 3 on both sides of the top are installed through the connecting plate 4, and fixed by the M16 stainless steel bolts 5, and the vertical rod 6 is installed on the outside of the longitudinal beam 8, and finally the handrail 7 is fixed on the top of the vertical rod 6;

[0084] S7. Full penetration butt welding is used for load-bearing components, and partial penetration welding is used for non-load-bearing components. After welding, the weld surface is checked for cracks and undercut defects. 100% of Grade I welds are ultrasonically inspected, and 20% of Grade II welds are randomly inspected;

[0085] In this embodiment, it should be noted that the implementation steps of step S7 are:

[0086] S7.1. TIG welding is used for load-bearing components and MIG welding is used for non-load-bearing components. Before welding, the groove is cleaned with acetone to remove the oxide layer;

[0087] S7.2. Immediately after welding, knock off the welding slag and check whether the weld surface is smooth, free of cracks, and the undercut depth is ≤ 0.5 mm. Use a weld gauge to measure the weld leg height.

[0088] S7.3. According to GB / T11345 standard, 100% of the Class I welds shall be ultrasonically inspected, and 20% of the Class II welds shall be randomly selected. If defects are found, they shall be removed by carbon arc gouging and re-welded. Only after passing the re-inspection can the next process be entered;

[0089] S8. Perform anodizing treatment on aluminum alloy components, with the oxide film thickness ≥ 15μm. After the bridge deck is paved, inspect the structural safety and functionality;

[0090] In this embodiment, it should be noted that the implementation steps of step S8 are:

[0091] S8.1. Immerse the aluminum alloy component in a 15% sulfuric acid electrolyte, apply a voltage of 12V, and oxidize for 30 minutes to form an AA15 grade oxide film with an average thickness of ≥15μm and a local thickness of ≥12μm;

[0092] S8.2. Spray 80μm thick epoxy resin primer, lay glass fiber cloth, and then apply polyurethane topcoat with a total thickness of ≥1.2mm. The closed water test is passed after 24 hours without leakage;

[0093] S8.3. Carry out 1.2 times load test, vibration test and pedestrian traffic simulation, and the acceptance report shall cover structural safety, anti-corrosion performance and traffic comfort indicators.

[0094] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0095] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A design and construction method for urban sewage pipeline bridge reconstruction, characterized in that: The following steps are involved: S1. Evaluate the feasibility of the renovation based on the structural status of the existing sewage pipeline bridge and determine the use of aluminum alloy prefabricated structure; S2. Design 160*120*10mm aluminum square tube columns and 420*130mm ladder longitudinal beam components to ensure that the length deviation is ≤10mm, the height deviation is +4mm, the interface misalignment is ≤2mm, and the camber deviation is ≤L / 5000mm; S3. Build double-row ground-type scaffolding at 200mm on both sides of the original bridge piers, with the horizontal spacing of 1.0m and the vertical spacing of 1.5m, the horizontal bar step distance of 1.8m, the top of the scaffolding is 1.0m higher than the bridge railing, and the horizontal safety net is fully hung every 3 steps. The outer side is set with a dense safety net, and equipped with 45° vertical scissor braces and bridge deck wooden frame boards; S4. Build a 3.0×3.0m unloading platform with vertical distance of 1.0m, horizontal distance of 0.75m and step distance of 1.5m. Set vertical scissor braces and dense safety nets on the periphery of the platform, and the spacing of top supporting steel pipes is 500mm; S5. Use multi-point support and temporary fixing measures to transport prefabricated components to prevent deformation or collision, and use a level to level the site before construction; S6. Install prefabricated components according to the design coordinates, control the three-dimensional coordinate error, keep the bridge body linearly smooth and aligned with the axis, use stainless steel bolts for connection, supplemented by flat washers and spring washers, tighten the nuts until the spring washers are compressed, and complete the main structure assembly; S7. Full penetration butt welding is used for load-bearing components, and partial penetration welding is used for non-load-bearing components. After welding, the weld surface is checked for cracks and undercut defects. 100% of Grade I welds are ultrasonically inspected, and 20% of Grade II welds are randomly inspected; S8. Perform anodizing treatment on aluminum alloy components with an oxide film thickness of ≥15μm. After the bridge deck is installed, inspect the structural safety and functionality.

2. A method for the reconstruction design and construction of a municipal sewage pipeline bridge according to claim 1, characterized in that: The implementation steps of step S2 are: S2.

1. Based on BIM modeling software, design 160*120*10mm aluminum square tube columns and 420*130mm ladder longitudinal beam components. The nodes are connected by bolts, and a 20mm width expansion joint is reserved. Output the processing drawings, and mark the tolerance requirements of length deviation ≤10mm and height deviation +4mm; S2.

2. Complete aluminum alloy cutting, drilling and surface pretreatment in the CNC machining center, pre-assemble the components on the fetal membrane according to the design drawings, use a total station to detect interface misalignment ≤ 2mm, camber deviation ≤ L / 5000mm, and rework unqualified parts; S2.

3. Recheck the dimensions of components with a three-dimensional coordinate measuring machine, spray them with a scratch-resistant protective film after acceptance, classify and package them according to transport units, and fix them with customized steel frames to avoid deformation during transportation.

3. The method for designing and constructing a bridge for urban sewage pipeline reconstruction according to claim 2 is characterized in that: The implementation steps of step S3 are: S3.

1. Clear the debris around the pier, compact the ground, lay 50mm thick steel plates as the base of the poles, and lay out the lines 200mm on both sides of the pier to ensure that the horizontal spacing of the double rows of poles is 1.0m and the vertical spacing is 1.5m; S3.

2. Install horizontal bars layer by layer at a step distance of 1.8m, set vertical and horizontal sweeping bars 200mm from the ground, set a 45° vertical scissor brace for every 7 vertical bars, and add a 60° scissor brace for every 5 vertical bars below the bridge deck, and use an adjustable top support to tighten against the bridge deck; S3.

3. The outside of the scaffolding is fully hung with a flame-retardant dense mesh safety net, a horizontal safety net is laid every 3 steps, a double-layer protection net is added at the height of the bridge deck, the bridge deck is fully covered with 50mm thick wooden frame boards, and 200mm high footboards are set on the edges.

4. The method for designing and constructing a bridge for urban sewage pipeline reconstruction according to claim 3 is characterized in that: The implementation steps of step S4 are: S4.

1. Level the site below the bridge, cast a C20 concrete cushion layer with a thickness of 150 mm, embed anchor bolts, and set up poles in a range of 3.0×3.0 m, with a longitudinal distance of 1.0 m, a horizontal distance of 0.75 m, and a step distance of 1.5 m; S4.

2. The top supporting steel pipes are arranged at a spacing of 500 mm and fixed with double fasteners. Continuous vertical scissor braces are set on the three sides of the platform and connected to the vertical poles with rotating fasteners to enhance the overall stability; S4.

3. Designate a special storage area for steel bars, aluminum alloy components, and welding equipment, and set a storage area of ​​≤1.5t / m 2 Load limit signs are installed, 1.2m high protective railings are added to the outside of the platform, and a "Strictly No Overloading" warning sign is hung.

5. A method for the reconstruction design and construction of a municipal sewage pipeline bridge according to claim 4, characterized in that: The implementation steps of step S5 are: S5.

1. Plan the transportation route, avoid the sections with height and weight restrictions, use low-bed trailers, place rubber cushions between the components and the vehicle body, and use nylon straps to fix multiple points with a spacing of ≤2m to prevent side sliding; S5.

2. Use a level to measure the elevation of the area within 50m around the bridge site, fill the local sunken area with graded sand and gravel and compact it, and control the flatness error within ±5mm; S5.

3. Components should be stacked in order of installation, with sleepers at the bottom spaced ≤1.5m apart. Check that the breaking force of the lifting rigging is ≥5 times the weight of the component. Set up a warning area and arrange dedicated signal workers for command.

6. A method for the reconstruction design and construction of a municipal sewage pipeline bridge according to claim 5, characterized in that: The implementation steps of step S6 are: S6.

1. Use a total station to mark the axis control points on the bridge piers and verify that the coordinate error is ≤2mm. When installing the first section of the column, use a jack to fine-tune the level and the verticality deviation is ≤1 / 1000; S6.

2. Install components in the order of "from bottom to top, primary first and secondary later", use stainless steel bolts for connection, and use matching flat washers and spring washers. Tighten with a torque wrench twice, initially tightening to 50% torque and finally tightening until the spring washers are flattened; S6.

3. After assembling every three sections, use a laser collimator to detect the bridge line shape, adjust the interface gap to ≤1mm, and ensure that the center axis offset is ≤3mm.

7. A method for the reconstruction design and construction of a municipal sewage pipeline bridge according to claim 6, characterized in that: The implementation steps of step S7 are: S7.

1. TIG welding is used for load-bearing components and MIG welding is used for non-load-bearing components. Before welding, the groove is cleaned with acetone to remove the oxide layer; S7.

2. Immediately after welding, knock off the welding slag and check whether the weld surface is smooth, free of cracks, and the undercut depth is ≤ 0.5 mm. Use a weld gauge to measure the weld leg height. S7.

3. 100% of the Grade I welds shall be ultrasonically inspected according to GB / T11345 standard, and 20% of the Grade II welds shall be randomly selected. If defects are found, they shall be removed by carbon arc gouging and then re-welded. Only after passing the re-inspection can the next process be entered.

8. The method for designing and constructing a bridge for urban sewage pipeline reconstruction according to claim 7 is characterized in that: The implementation steps of step S8 are: S8.

1. Immerse the aluminum alloy component in a 15% sulfuric acid electrolyte, apply a voltage of 12V, and oxidize for 30 minutes to form an AA15 grade oxide film with an average thickness of ≥15μm and a local thickness of ≥12μm; S8.

2. Spray 80μm thick epoxy resin primer, lay glass fiber cloth, and then apply polyurethane topcoat with a total thickness of ≥1.2mm. The closed water test is passed after 24 hours without leakage; S8.

3. Carry out 1.2 times load test, vibration test and pedestrian traffic simulation. The acceptance report covers structural safety, anti-corrosion performance, traffic comfort indicators, and final handover.

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