Bridge steel truss mounting method

Abstract

The invention relates to the technical field of bridge construction, and discloses a bridge steel truss mounting method which at least comprises the following steps: S1, modular prefabrication and pre-assembly; s2, on-site integral welding; s3, configuring a hoisting system; s4, multi-lifting-point collaborative lifting is carried out; and S5, accurate positioning and fixing are carried out. According to the bridge steel truss mounting method, through high-precision prefabrication and on-site rapid assembly, the on-site operation time is shortened, all links are closely connected, the construction efficiency is improved, the construction period is effectively shortened, the engineering cost is reduced, the high-altitude operation amount is reduced, the risk of construction personnel working in a complex high-altitude environment is reduced, multi-lifting-point balanced lifting and real-time monitoring adjustment are achieved, and the construction efficiency is improved. The steel truss is ensured to be installed stably, and safety accidents caused by structural instability are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge construction, and particularly to a method for installing a bridge steel truss. Background Technique

[0002] A steel truss refers to a truss made of steel. In industrial and civil buildings, roof structures, crane beams, bridges, and hydraulic gates, etc., steel trusses are commonly used as the main load-bearing members. Various types of tower structures, such as mast towers, television towers, and transmission line towers, etc., commonly use space steel trusses composed of three-sided, four-sided, or multi-sided plane trusses. In bridge construction, due to its good mechanical properties, high strength-to-weight ratio, and excellent spanning ability, the steel truss structure is widely used in the construction of various large bridges.

[0003] Traditional steel truss installation methods generally adopt the methods of high-altitude bulk assembly and welding. Construction workers need to work in a complex high-altitude environment, with a high potential for safety accidents. Moreover, due to the complex construction site conditions, it is difficult to accurately control the positions and angles of each component during the segmented hoisting process, resulting in poor overall structural accuracy. Therefore, a method for installing a bridge steel truss is needed. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for installing a bridge steel truss to solve the problems raised in the above background technique.

[0005] To solve the above technical problems, the present invention is solved through the following technical solutions: A method for installing a bridge steel truss includes the following steps: S1. Modular prefabrication and pre-assembly; S2. On-site integral welding; S3. Hoisting system configuration; S4. Multi-lifting point coordinated lifting; S5. Precise positioning and fixing.

[0006] Preferably, the specific method in the step S1, modular prefabrication and pre-assembly is as follows; S1-1. Divide the steel truss into standard segments with a length of 16m - 20m, complete the welding in the factory and reserve the butt flanges; S1-2. Set up a rigid jig in the prefabrication yard, complete the pre-assembly of 3 - 5 segments to form a hoisting unit with a length of 20m - 50m; S1-3. Set up temporary reinforcement gusset plates at the flange connection.

[0007] Preferably, the specific method in the step S2, on-site integral welding is as follows; S2-1. Build an adjustable assembly platform at the bridge site, with the platform bearing capacity ≥ 200t and the flatness error ≤ 3mm / m; S2-2: Adopt the welding sequence from the mid-span to both ends. First, weld the lower chord, then the web members, and finally the upper chord; S2-3: After each 10m welding section is completed, apply a pre-tightening force of 50kN - 100kN using a hydraulic jack to eliminate welding deformation.

[0008] Preferably, the specific method in step S3, the hoisting system configuration steps, is as follows; S3-1: The lateral spacing of the double floating cranes is the width of the truss plus 10m, and the longitudinal front-back offset ≤ 5m. After anchoring and positioning, use a depth sounder to recheck the water depth to ensure that the draft allowance ≥ 1m; S3-2: Adopt a lifting system composed of four floating cranes. The main lifting points are arranged at the 1 / 4 span of the steel truss, and the spacing of the auxiliary lifting points is 8m - 12m.

[0009] Preferably, the specific method in step S4, the multi-lifting point coordinated lifting steps, is as follows; S4-1: Each lifting point is equipped with a mechanical synchronous controller, and the speed synchronization is achieved through the linkage of the gearbox; S4-2: During the lifting process, pause every 2m of ascent. Use a laser alignment instrument to detect the levelness. When the deviation > 5mm, correct the deviation by adjusting the length of the wire rope of the corresponding lifting point.

[0010] Preferably, the specific method in step S5, the precise positioning and fixing steps, is as follows; S5-1: Switch to the fine-tuning mode when it is 1m away from the design elevation, and the hoisting speed is reduced to 0.2m / min; S5-2: Use wedge-shaped positioning blocks to achieve millimeter-level alignment. First, insert temporary pin shafts and then complete the final tightening of high-strength bolts.

[0011] Preferably, in step S1-3, the thickness of the reinforcing gusset plate is 1.2 times the thickness of the base material.

[0012] Preferably, in step S2-2, the lower chord is butt-welded with a weld height of 8mm and a speed of 300mm / min. The web members are fillet-welded at an inclined angle with a weld height of 12mm and a preheating temperature of 120℃. The upper chord is cover-plate welded using the sectional backstep welding method, and the length of each section ≤ 500mm.

[0013] Preferably, in step S3-2, the main lifting points are composed of four groups of φ100mm wire ropes, equipped with rotating shackles. The auxiliary lifting points are composed of eight groups of φ50mm chain slings, equipped with self-locking devices. The lifting lugs are double-sided welded to the truss gusset plate, and the weld leg height ≥ 12mm.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. Through high-precision prefabrication and rapid on-site assembly, the present invention reduces the on-site operation time. Each link is closely connected, improving the construction efficiency, effectively shortening the construction period, and reducing the project cost; 2. Reduce the amount of work at height, lower the risk of construction workers operating in complex high-altitude environments, use multi-hoisting points for balanced lifting and real-time monitoring and adjustment to ensure the smooth installation of the steel truss, and avoid safety accidents caused by structural instability; 3. Conduct strict quality inspections on precast segments, precisely control on-site assembly and positioning, achieve an installation accuracy of the steel truss of ±3 mm, use high-strength connection methods to ensure the structural stability, and extend the service life of the bridge. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a flow schematic diagram of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] Unless otherwise clearly specified in the context, nouns without a quantifier and nouns modified by "the" include singular and plural referents.

[0017] As used in the specification and claims, the terms "comprising", "including", "having", "may", "containing" and their variants refer to open transitional phrases, terms or words that require the presence of the specified component / step and allow the presence of other components / steps. However, such description should also be interpreted as describing the composition or method as "consisting of" and "substantially consisting of" the listed components / steps, which allows only the presence of the specified components / steps and any inevitable impurities that may result therefrom, and excludes other components / steps.

[0018] The numerical values in the specification and claims of the present application should be understood to include the same numerical values when reduced to the same number of significant figures and numerical values that differ from the said values by less than the experimental error of the conventional measurement techniques used to determine the said values of the type described in the present application.

[0019] All ranges disclosed herein include the indicated endpoints and can be combined independently (for example, the range of "2 grams to 10 grams" includes the endpoints 2 grams and 10 grams, and all intermediate values).

[0020] The terms "about" and "approximate" can be used to include any numerical value that can vary without changing the basic function of the value. When used with a range, "about" and "approximate" also disclose the range defined by the absolute values of the two endpoints. For example, "about 2 to about 4" also discloses the range of "2 to 4". Generally, the terms "about" and "approximate" can refer to ±10% of the indicated number. However, for temperature, the term "about" means ±1°C.

[0021] Unless otherwise clearly specified, the percentage of an element should be considered as the weight percentage of the said alloy.

[0022] This disclosure may relate to the temperature of certain method steps. It should be noted that these indicators generally refer to the temperature set by a heat source (such as a furnace), rather than necessarily the temperature that the heated material must reach.

[0023] A method for installing a bridge steel truss includes the following steps: S1. Modular prefabrication and pre-assembly; S1-1. Divide the steel truss into standard segments with a length of 16m - 20m, complete welding in the factory and reserve butt flanges, prefabricate using high-precision factory equipment to ensure the dimensional accuracy of the segments and welding quality, and reduce the difficulty of on-site operations; S1-2. Set up a rigid jig in the prefabrication yard, complete the pre-assembly of 3 - 5 segments to form a hoisting unit with a length of 20m - 50m, and use the rigid constraint of the jig to control the overall shape and dimensional accuracy; S1-3. Set up temporary reinforcement gusset plates at the flange connection, and the plate thickness of the reinforcement gusset plates is 1.2 times the thickness of the base material. Utilize the strong bending and shear resistance of the reinforcement gusset plates to enhance the stability of the hoisting unit during transportation and subsequent operations and avoid deformation.

[0024] S2. On-site integral welding; S2-1. Build an adjustable assembly platform at the bridge site, with the platform bearing capacity ≥ 200t and the flatness error ≤ 3mm / m, to provide stable support for the steel truss, ensure the fixed position of the structure during welding, and reduce welding errors caused by platform deformation; S2-2. Adopt a welding sequence from the mid-span to both ends. First weld the lower chord, then the web members, and finally the upper chord. The lower chord is butt-welded with a weld height of 8mm and a speed of 300mm / min. The web members are fillet-welded with a weld height of 12mm and a preheating temperature of 120°C. The upper chord cover plate is welded using the step-back welding method, with each section length ≤ 500mm, and welded from the mid-span to both ends. Utilize the symmetry of the structure to evenly distribute the welding stress and reduce the overall deformation; S2-3. After each 10m welding section is completed, apply a pre-tightening force of 50kN - 100kN using a hydraulic jack to eliminate welding deformation.

[0025] S3. Hoisting system configuration; S3-1. The lateral spacing of the double floating cranes is the width of the truss plus 10m, and the longitudinal front-back offset ≤ 5m, ensuring that the floating cranes have sufficient working space during operation and can lift in a coordinated and stable manner. After anchoring and positioning, use a depth sounder to check the water depth to ensure that the draft allowance ≥ 1m to avoid capsizing due to insufficient draft; S3-2. A lifting system is formed by four floating cranes. The main lifting points are arranged at the 1 / 4 span of the steel truss, and the distance between the auxiliary lifting points is 8m - 12m. The main lifting points are composed of four groups of φ100mm steel wire ropes, equipped with rotating shackles. The auxiliary lifting points are composed of eight groups of φ50mm chain slings, equipped with self-locking devices. The lifting lugs are double-sided welded to the truss gusset plate, and the weld leg height is ≥12mm. The mechanical principle is used to make the bending moment distribution of the steel truss more reasonable during lifting. The auxiliary lifting points are evenly arranged to adjust the attitude and ensure the overall force balance.

[0026] S4. Multiple lifting points cooperate to lift. S4-1. Each lifting point is equipped with a mechanical synchronous controller. The speed synchronization is achieved through the linkage of the gearbox. Using the accuracy of mechanical transmission, ensure that the lifting speeds of all lifting points are the same, and avoid uneven stress on the steel truss caused by speed differences. S4-2. During the lifting process, pause every 2m of ascent. Use a laser alignment instrument to detect the levelness. When the deviation > 5mm, correct the deviation by adjusting the length of the steel wire rope of the corresponding lifting point.

[0027] S5. Precise positioning and fixation. S5-1. When it is 1m away from the design elevation, switch to the fine-tuning mode, and the lifting speed is reduced to 0.2m / min to reduce the influence of inertia and facilitate precise position control. S5-2. Use wedge-shaped positioning blocks to achieve millimeter-level alignment. First insert the temporary pin and then complete the final tightening of the high-strength bolts. Utilize the high pre-tightening force and shear and tensile properties of the high-strength bolts to ensure a firm connection.

[0028] Specific steps: Divide the steel truss into standard segments with a length of 15m-20m, complete welding in the factory and reserve docking flanges, use the factory's high-precision equipment for prefabrication to ensure segment size accuracy and welding quality, reduce the difficulty of on-site operations, set up a rigid tire frame in the prefabrication yard, complete the pre-assembly of 3-5 segments, and form a 20m-50m hoisting unit. Use the rigid constraints of the tire frame to control the overall shape and size accuracy. Set up temporary reinforcement truss plates at the flange connection. The thickness of the reinforcement truss plates is 1.2 times the thickness of the parent material. Use the strong bending and shear resistance of the reinforcement truss plates to enhance the stability of the hoisting unit during transportation and subsequent operations and avoid deformation. Build an adjustable assembly platform at the bridge position with a platform bearing capacity of ≥200t , flatness error ≤3mm / m, provide stable support for steel trusses, ensure that the structural position is fixed during welding, reduce welding errors caused by platform deformation, adopt welding sequence from mid-span to both ends, first weld the lower chord and then the web, and finally weld the upper chord, butt welding of lower chord, welding height 8mm, speed 300mm / min, web bevel welding, welding height 12mm, preheating temperature 120℃, upper chord cover welding, segmented back welding method, each section length ≤500mm, welding from mid-span to both ends, using the symmetry of the structure to evenly distribute welding stress and reduce overall deformation, after completing each 10m welding section, use hydraulic jack to apply 50kN-100kN preload to eliminate welding deformation, double floating crane horizontal The spacing is the truss width plus 10m, and the longitudinal front and rear offset is ≤5m, which ensures that the floating crane maintains sufficient working space during operation and can coordinate stable lifting. After anchoring and positioning, the depth sounder verifies the water depth to ensure that the draft depth margin is ≥1m to avoid capsizing due to insufficient draft. Four floating cranes are used to form a lifting system. The main lifting point is arranged at 1 / 4 of the span of the steel truss. The auxiliary lifting point spacing is 8m-12m. The main lifting point consists of four groups of φ100mm steel wire ropes with rotating shackles. The auxiliary lifting point consists of eight groups of φ50mm chain rigging with self-locking devices. The lifting lugs are double-sided welded to the truss node plate, and the weld foot height is ≥12mm. The mechanical principle is used to make the bending moment distribution of the steel truss more reasonable during lifting, and the auxiliary lifting points are evenly arranged for Adjust the posture to ensure the overall force balance. Each lifting point is equipped with a mechanical synchronous controller. The speed synchronization is achieved through the linkage of the gear box. The accuracy of mechanical transmission is used to ensure the consistency of the lifting speed of each lifting point to avoid uneven force on the steel truss due to speed differences. During the lifting process, pause every 2m and use a laser line projector to detect the horizontality. When the deviation is greater than 5mm, adjust the length of the wire rope at the corresponding lifting point to correct it. When it is 1m away from the design elevation, switch to the fine-tuning mode and the lifting speed is reduced to 0.2m / min to reduce the influence of inertia and facilitate precise control of the position. Wedge-shaped positioning blocks are used to achieve millimeter-level alignment. First insert the temporary pin shaft and then complete the final tightening of the high-strength bolts. The high preload force and shear and tensile properties of the high-strength bolts are used to ensure a firm connection. Embodiment 1:

[0029] In a certain plain area, a highway bridge with a span of 300m needs to be built, adopting a steel truss structure. The total weight of the steel truss is about 2500t; S1. Modular prefabrication and pre-assembly; S1-1. Divide the steel truss into 15 standard segments with a length of 16m, complete welding in the factory and reserve docking flanges; S1-2. Set up a rigid jig in the prefabrication yard, complete the pre-assembly of 5 segments to form a 50m hoisting unit; S1-3. Set up temporary reinforcement gusset plates at the flange joints. The thickness of the gusset plates is 1.2 times the thickness of the base material.

[0030] S2. On-site integral welding; S2-1. Build an adjustable assembly platform at the bridge site. The bearing capacity of the platform is 300t, and the flatness error is 2mm / m; S2-2. Adopt a welding sequence from the mid-span to both ends. First, weld the lower chord members, butt welding, weld height 8mm, speed 300mm / min, then weld the web members, fillet welding, weld height 12mm, preheating temperature 120°C, and finally weld the upper chord members, using the segmental backstep welding method, with each segment length of 400mm; S2-3. After each 10m welding section is completed, apply an 80kN pre-tightening force using a hydraulic jack to eliminate welding deformation.

[0031] S3. Hoisting system configuration; S3-1. Select two large floating cranes. The transverse distance between the two floating cranes is the width of the truss plus 10m, and the longitudinal front and rear dislocation is 3m. After anchoring and positioning, use a depth sounder to check the water depth, and the draft is 1.2m; S3-2. Adopt a lifting system composed of four floating cranes. The main lifting points are arranged at the 1 / 4 span of the steel truss, and the distance between the auxiliary lifting points is 10m. The main lifting points are composed of four groups of φ100mm steel wire ropes, equipped with rotating shackles. The auxiliary lifting points are composed of eight groups of φ50mm chain slings, equipped with self-locking devices. The lifting lugs are double-sided welded to the truss gusset plates, and the fillet weld height is 12mm.

[0032] S4. Multi-lifting point coordinated lifting; S4-1. Configure mechanical synchronous controllers for each lifting point, and achieve speed synchronization through gearbox linkage; S4-2. Pause every 2m during the lifting process, and use a laser alignment instrument to detect the levelness. There was once a deviation of 6mm during construction, and the deviation was corrected by adjusting the length of the steel wire ropes at the corresponding lifting points.

[0033] S5. Precise positioning and fixation; S5-1. Switch to the fine-tuning mode when it is 1m away from the design elevation, and the hoisting speed is reduced to 0.2m / min; S5-2. Achieve millimeter-level alignment by using wedge-shaped positioning blocks. First, insert temporary pin shafts and then complete the final tightening of high-strength bolts.

[0034] Specific steps: Divide the steel truss into 15 standard segments with a length of 16 m. Complete welding in the factory and reserve butt flanges. Set up a rigid jig in the prefabrication yard and complete the pre-assembly of 5 segments to form a 50-m hoisting unit. Set up temporary reinforcement gusset plates at the flange joints. The thickness of the reinforcement gusset plates is 1.2 times the thickness of the base material. Build an adjustable assembly platform at the bridge site. The bearing capacity of the platform is 300 t, and the flatness error is 2 mm / m. Adopt a welding sequence from the mid-span to both ends. First, weld the lower chord members by butt welding with a weld height of 8 mm and a speed of 300 mm / min. Then, weld the web members by fillet welding with a weld height of 12 mm and a preheating temperature of 120 °C. Finally, weld the upper chord members by using the segmental backstep welding method with each segment having a length of 400 mm. After each 10-m welding segment is completed, apply a pre-tightening force of 80 kN with a hydraulic jack to eliminate welding deformation. Select two large floating cranes. The lateral distance between the two floating cranes is the width of the truss plus 10 m, and the longitudinal front-back dislocation is 3 m. After anchoring and positioning, use a depth sounder to check the water depth with a draft of 1.2 m. Adopt a lifting system composed of four floating cranes. The main lifting points are arranged at the 1 / 4 span of the steel truss, and the distance between the auxiliary lifting points is 10 m. The main lifting points are composed of four groups of φ100-mm steel wire ropes with rotating shackles. The auxiliary lifting points are composed of eight groups of φ50-mm chain slings with self-locking devices. The lifting lugs are welded to the truss gusset plates on both sides with a weld leg height of 12 mm. Each lifting point is equipped with a mechanical synchronous controller to achieve speed synchronization through the linkage of the gearbox. During the lifting process, pause every 2 m of ascent and use a laser alignment instrument to detect the levelness. During construction, there was once a deviation of 6 mm, which was corrected by adjusting the length of the steel wire ropes at the corresponding lifting points. When the elevation is 1 m from the design elevation, switch to the fine-tuning mode with the lifting speed reduced to 0.2 m / min. Achieve millimeter-level alignment by using wedge-shaped positioning blocks. First, insert temporary pin shafts and then complete the final tightening of high-strength bolts. The installation accuracy of the steel truss is controlled within ±3 mm, meeting the design requirements. The entire installation process was smooth without any safety accidents. The installation period was 10 days ahead of the original plan, greatly improving the construction efficiency. Example 2:

[0035] Build a 200-m-span railway bridge in a mountainous canyon. The total weight of the steel truss is 1800 t, and the construction site is narrow and the terrain is complex. S1. Modular prefabrication and pre-assembly; S1-1. Divide the steel truss into 10 standard segments with a length of 18 m. Complete welding in the factory and reserve butt flanges; S1-2. Set up a rigid jig in the prefabrication yard and complete the pre-assembly of 3 segments to form a 36-m - 54-m hoisting unit; S1-3. Set up temporary reinforcement gusset plates at the flange joints. The thickness of the reinforcement gusset plates is 1.2 times the thickness of the base material.

[0036] S2. Overall on-site welding; S2-1. Build an adjustable assembly platform at the bridge location. The bearing capacity of the platform is 250t, and the flatness error is 3mm / m; S2-2. Adopt the welding sequence from the mid-span to both ends. First, weld the lower chord members by butt welding with a weld height of 8mm and a speed of 300mm / min. Then, weld the web members by fillet welding with a weld height of 12mm and a preheating temperature of 120°C. Finally, weld the upper chord members using the segmental backstep welding method, with each segment length of 400mm; S2-3. After each 10m welding section is completed, apply a pre-tightening force of 60kN using a hydraulic jack to eliminate welding deformation.

[0037] S3. Hoisting system configuration; S3-1. Select a more flexible floating crane. The transverse distance between the two floating cranes is the width of the truss plus 10m, and the longitudinal front-back offset is 3m. After anchor positioning, use a depth sounder to check the water depth, and the draft is 1.2m; S3-2. Adopt a lifting system composed of four floating cranes. The main lifting points are arranged at the 1 / 4 span of the steel truss, and the distance between the auxiliary lifting points is 8m. The main lifting points are composed of four groups of φ100mm steel wire ropes with rotating shackles, and the auxiliary lifting points are composed of eight groups of φ50mm chain slings with self-locking devices. The lifting lugs are double-sided welded to the truss gusset plates with a weld leg height of 12mm.

[0038] S4. Multi-lifting point coordinated lifting; S4-1. Each lifting point is equipped with a mechanical synchronous controller to achieve speed synchronization through gearbox linkage; S4-2. Pause every 2m during the lifting process and use a laser alignment instrument to detect the levelness. During the lifting process, due to the influence of canyon wind, perform multiple levelness detection and deviation correction operations.

[0039] S5. Precise positioning and fixing; S5-1. Switch to the fine-tuning mode when it is 1m away from the design elevation, and the hoisting speed is reduced to 0.2m / min; S5-2. Use wedge-shaped positioning blocks to achieve millimeter-level alignment. First, insert temporary pins and then complete the final tightening of high-strength bolts.

[0040] Specific steps: Divide the steel truss into 10 standard segments with a length of 18 m, complete welding in the factory and reserve butt flanges. Set up a rigid jig in the prefabrication yard, complete the pre-assembly of 3 segments to form a hoisting unit of 36 m - 54 m. Set up temporary reinforcing gusset plates at the flange joints, and the plate thickness of the reinforcing gusset plates is 1.2 times the thickness of the base material. Build an adjustable assembly platform at the bridge site, with a platform bearing capacity of 250 t and a flatness error of 3 mm / m. Adopt a welding sequence from the mid-span to both ends. First, weld the lower chord members, using butt welding with a weld height of 8 mm and a speed of 300 mm / min. Then, weld the web members, using fillet welding with a weld height of 12 mm and a preheating temperature of 120 °C. Finally, weld the upper chord members, using the segmental backstep welding method with each segment having a length of 400 mm. After each 10 m welding section is completed, apply a pre-tightening force of 60 kN using a hydraulic jack to eliminate welding deformation. Select a more flexible floating crane. The transverse distance between the two floating cranes is the width of the truss plus 10 m, and the longitudinal front and rear offset is 3 m. After anchoring and positioning, use a depth sounder to check the water depth, with a draft of 1.2 m. Adopt a lifting system composed of four floating cranes. The main lifting points are arranged at the 1 / 4 span of the steel truss, and the spacing between the auxiliary lifting points is 8 m. The main lifting points are composed of four groups of φ100 mm steel wire ropes, equipped with rotating shackles. The auxiliary lifting points are composed of eight groups of φ50 mm chain slings, equipped with self-locking devices. The lifting lugs are double-sided welded to the truss gusset plates with a weld leg height of 12 mm. Each lifting point is equipped with a mechanical synchronous controller to achieve speed synchronization through gearbox linkage. During the lifting process, pause every 2 m of ascent, and use a laser alignment instrument to detect the levelness. During the lifting process, due to the influence of canyon wind, conduct levelness detection and deviation correction operations multiple times. When it is 1 m away from the design elevation, switch to the fine-tuning mode, and the lifting speed is reduced to 0.2 m / min. Use wedge-shaped positioning blocks to achieve millimeter-level alignment. First, insert temporary pins and then complete the final tightening of high-strength bolts. Successfully overcome the complex mountain terrain and climatic conditions, and the installation accuracy of the steel truss reaches ±2.5 mm, meeting the high-precision requirements of railway bridges. Through reasonable construction organization and technical application, the construction safety and quality are guaranteed.

[0041] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A bridge steel truss installation method, characterized in that: The following steps are involved: S1. Modular prefabrication and pre-assembly; S2, on-site overall welding; S3, hoisting system configuration; S4, multi-point coordinated lifting; S5. Accurate positioning and fixation.

2. A bridge steel truss installation method according to claim 1, characterized in that: The specific method in the step S1, modular prefabrication and pre-assembly is as follows; S1-1. Divide the steel truss into standard sections with a length of 16m-20m, complete welding in the factory and reserve butt flanges; S1-2. Set up a rigid frame in the prefabrication yard and complete the pre-assembly of 3-5 segments to form a 20m-50m hoisting unit; S1-3. Temporary reinforcement trusses are installed at flange connections.

3. A bridge steel truss installation method according to claim 1, characterized in that: The specific method in the step S2, on-site integral welding, is as follows; S2-1. Build an adjustable assembly platform at the bridge location, with a platform bearing capacity of ≥200t and a flatness error of ≤3mm / m; S2-2, adopt the welding sequence from the middle of the span to both ends, first weld the lower chord, then the web, and finally the upper chord; S2-3. After completing each 10m welding section, use a hydraulic jack to apply a 50kN-100kN preload to eliminate welding deformation.

4. A bridge steel truss installation method according to claim 1, characterized in that: The specific method in the step S3, the hoisting system configuration step is as follows; S3-1. The horizontal spacing of the double floating cranes is the truss width plus 10m, and the longitudinal front-to-back offset is ≤5m. After anchoring, the depth is checked by the depth sounder to ensure that the draft margin is ≥1m; S3-2, four floating cranes are used to form a lifting system, with the main lifting point arranged at 1 / 4 span of the steel truss and the auxiliary lifting points spaced 8m-12m apart.

5. The method for installing a bridge steel truss according to claim 1, characterized in that: The specific method in the step S4, multi-hanging point coordinated lifting, is as follows: S4-1. Each lifting point is equipped with a mechanical synchronous controller to achieve speed synchronization through gearbox linkage; S4-2. During the lifting process, pause every 2m and use a laser line projector to check the horizontality. If the deviation is greater than 5mm, adjust the length of the wire rope at the corresponding lifting point to correct the deviation.

6. A bridge steel truss installation method according to claim 1, characterized in that: The specific method in the step S5, precise positioning and fixing, is as follows; S5-1, switch to fine-tuning mode when 1m away from the design elevation, and the hoisting speed drops to 0.2m / min; S5-2. Use wedge-shaped positioning blocks to achieve millimeter-level alignment, insert temporary pins first, and then complete the final tightening of high-strength bolts.

7. A bridge steel truss installation method according to claim 2, characterized in that: In the step S1-3, the thickness of the reinforced truss plate is 1.2 times the thickness of the parent material.

8. The method for installing a bridge steel truss according to claim 3, characterized in that: In the step S2-2, the lower chord is butt welded with a weld height of 8 mm and a speed of 300 mm / min, the web is bevel welded with a weld height of 12 mm and a preheating temperature of 120°C, and the upper chord cover is welded with a segmented back-welding method, with each segment length ≤500 mm.

9. A bridge steel truss installation method according to claim 4, characterized in that: In step S3-2, the main lifting point is composed of four groups of φ100mm steel wire ropes equipped with rotating shackles, and the auxiliary lifting point is composed of eight groups of φ50mm chain rigging equipped with self-locking devices. The lifting lugs are double-sided welded to the truss node plate, and the weld foot height is ≥12mm.

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