A steel truss bridge construction method without support

Abstract

A method for constructing steel truss bridges without scaffolding is disclosed. This method involves erecting a ground-based assembly jig on the construction site. Each segment of the steel truss bridge is transported from the processing plant to the construction site, where it is welded, riveted, and assembled using the ground-based jig. After assembly on the ground, the steel truss bridge is erected on the piers using a double-crane lifting method. This method eliminates the need for traditional high-altitude support structures, significantly reducing construction time and costs while greatly improving safety. Furthermore, the ground-based bolting and welding of the steel truss bridge segments facilitates measurement and adjustment of the bridge's assembly linearity, reducing construction difficulty and significantly improving efficiency and quality.

Description

Technical Field

[0001] This invention relates to the field of steel truss bridge construction technology, and specifically to a method for constructing steel truss bridges without supports. Background Technology

[0002] Steel truss bridges are a major structural form for highway or railway bridges, typically with long spans. Due to transportation limitations imposed by highways, railways, and waterways, the steel truss bridge structure needs to be divided into several beam segments for easier transport. Therefore, the current on-site construction method for steel truss bridges involves transporting these segments from a processing plant to the construction site, where they are then assembled using high-altitude bolting and welding techniques to complete the overall structure. However, because high-altitude support frames need to be erected before on-site construction and assembly is required, there are issues such as long construction periods, high costs, and high risks associated with working at heights. Furthermore, high-altitude operations present numerous challenges, including significant construction difficulties and challenges in quality control. Therefore, these issues require further solutions and improvements. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, this invention discloses a method for constructing steel truss bridges without supports. The method involves setting up a ground assembly jig on the construction site, transporting each beam segment of the steel truss bridge from the processing plant to the construction site, and welding, riveting, and assembling the beam segments on the ground assembly jig. After the steel truss bridge is assembled on the ground, it is erected on the bridge piers by lifting it with two cranes.

[0004] To achieve the aforementioned objective, the present invention employs the following technical solution: a method for constructing steel truss bridges without supports. The method involves leveling the site and erecting a ground assembly frame. Each segment of the steel truss bridge is transported from the processing plant to the construction site, where welding and riveting are performed on the ground assembly frame to complete the ground assembly of the steel truss bridge. Then, the steel truss bridge is erected on the piers using a double-crane lifting method. This construction method solves many problems inherent in traditional steel truss bridge construction methods, such as long construction time, high cost, high risk of high-altitude construction, high construction difficulty, and difficulty in controlling construction quality.

[0005] Furthermore, the on-site ground assembly frame is a completely new structure, adopting a standardized modular design with reusability. Compared to traditional high-altitude support frames, it has the advantages of shorter construction period and lower cost. The on-site ground assembly frame includes a base plate, adjustable brackets, support distribution beams, and support columns. The base plate is laid flat on the assembly site ground, the adjustable brackets are fixedly mounted on the base plate, the support distribution beams are fixedly mounted on top of the adjustable brackets, and the support columns are fixedly mounted on top of the support distribution beams. Each beam segment of the steel truss bridge is mounted on top of the support columns, allowing construction personnel to complete the welding, bolting, and assembly of each beam segment of the steel truss bridge on the construction site ground. Because the assembly of the steel truss bridge is carried out on the ground, the construction work is safer, and the measurement, adjustment, and control of various parameters of the steel truss bridge during construction are more convenient, greatly reducing construction difficulty, improving construction efficiency, and ensuring good control of construction quality.

[0006] Furthermore, the method for assembling the ground-based jig on-site is as follows:

[0007] S1. On-site ground assembly frame construction: The assembly area is pre-leveled at the construction site and repeatedly compacted with a vibratory roller 6-8 times. Then, a 600*600mm thick 50mm pad is laid flat on the compacted ground according to the design position. Adjustable supports are temporarily placed on the pads, and the support distribution beams are fixedly placed on top of the adjustable supports. The support columns are fixedly placed on top of the support distribution beams, completing the initial construction of the on-site ground assembly frame. There are two support distribution beams. The parallelism of the two support distribution beams is adjusted, and then the adjustable supports are fixedly connected to the upper part of the pads.

[0008] S2. Adjustment of the on-site ground assembly jig: The height of all adjustable supports is measured using a laser level. During adjustment, there is a 1-2mm height difference between the adjustable supports located on the same support distribution beam, and the height of the adjustable support in the middle of the same support distribution beam is greater than the height of the adjustable supports on both sides, so that the support distribution beam has an upward convex arc. This adjustment method of the on-site ground assembly jig is to prevent the adjustable support located in the middle of the same support distribution beam from having a smaller bearing capacity in the early stage, which would lead to uneven settlement of the steel truss bridge during the later assembly operation, resulting in poor alignment control of the steel truss bridge after assembly.

[0009] S3. Settlement Adjustment of On-site Ground Assembly Frame: Each beam segment of the steel truss bridge is hoisted onto the support columns of the ground assembly frame one by one, and its position is adjusted. The frame is then left to stand for 3-5 days. During this period, the height of the adjustable supports is measured every twelve hours using a laser level. If any change in the height of an adjustable support is detected, it is adjusted promptly to ensure that the height of all adjustable supports remains consistent, and that the two supporting distribution beams are at the same height and horizontal. Although a three-day standing period is required before assembling the steel truss bridge using the on-site ground assembly frame to allow the settlement of the frame to stabilize, this significantly reduces the construction period compared to the approximately fifteen days required for traditional high-altitude support frame construction, including the construction of pipe pile holes, cast-in-place piles (including the abutment), and the erection of the high-altitude support frame.

[0010] S4. Adjustment of height difference between beam segments of steel truss bridge: After the settlement of the on-site ground assembly jig has stabilized, hydraulic jacks are used to lift each beam segment. By setting shims on the support columns, the height difference between each beam segment of the steel truss bridge is adjusted. This height difference is used to control the pre-deformation of the steel truss bridge after ground assembly, ensuring that the alignment of the completed steel truss bridge meets the required control alignment.

[0011] Preferably, at certain construction sites, if the foundation soil is soft soil such as silty soil or collapsible loess, and the load-bearing capacity is insufficient, a partial replacement layer method is adopted at the location where the pad is placed on the site. The original foundation soil layer is replaced with a well-graded crushed stone and clay mixture. The area of ​​the partial replacement layer is 1.5-2 times the area of ​​the pad, and the depth is not less than 0.5m. After the replacement layer is filled, it is compacted 6-8 times with a vibratory roller to ensure the settlement stability of the on-site assembly frame.

[0012] Furthermore, before the two cranes officially lift the bridge, a pre-lift test must be conducted. The pre-lift test will assess the stability of the cranes. Then, the steel truss bridge will be re-set on the adjusted simulated pier support on the ground assembly jig, and the bridge deck deflection will be tested.

[0013] Furthermore, the actual lifting weight of each crane must not exceed 70-80% of the crane's nominal maximum lifting weight.

[0014] Furthermore, after the steel truss bridge is hoisted onto the piers and positioned according to the design requirements, it must first be pre-fixed before the hoisting hooks can be detached to ensure the safety of the steel truss bridge's fixed construction and erection.

[0015] Due to the adoption of the above-described technical solution, the present invention has the following beneficial effects: The present invention discloses a method for constructing steel truss bridges without supports. This method involves erecting a ground assembly jig on the construction site. Each beam segment of the steel truss bridge is transported from the processing plant to the construction site, and then welded, riveted, and assembled on the ground assembly jig. After the steel truss bridge is assembled on the ground, it is erected on the piers using a double-crane lifting method. This method eliminates the traditional process of erecting high-altitude support frames, thus significantly reducing the construction period and cost, and greatly improving construction safety. Furthermore, when bolting and welding the beam segments of the steel truss bridge on the ground, it is more convenient to measure and adjust the assembly linearity of the steel truss bridge, reducing construction difficulty and significantly improving construction efficiency and quality. Attached Figure Description

[0016] Figure 1 A schematic diagram of the on-site assembly of a steel truss bridge;

[0017] Figure 2 This is a schematic diagram of a steel truss bridge double-machine lifting construction.

[0018] Figure 3 This is a schematic diagram of the on-site ground assembly frame structure;

[0019] Figure 4 This is a partially enlarged schematic diagram of the on-site ground assembly jig structure;

[0020] Figure 5 This is a schematic diagram of the adjustable bracket.

[0021] Figure 6 This is an exploded view of the adjustable support structure.

[0022] Figure 7 This is a schematic diagram of the bracket's appearance.

[0023] In the diagram: 1. On-site ground assembly frame; 1.1, Pad; 1.2, Adjustable bracket; 1.2.1, Bracket base; 1.2.1.1, Support sleeve; 1.2.1.1.1, Anti-rotation pin groove; 1.2.1.2.1, Magnetic seat hole; 1.2.1.2, Support base; 1.2.1.3, Sleeve flange; 1.2.2, Lead screw; 1.2.2.1, Anti-rotation pin; 1.2.2.2, Anti-rotation bolt; 1.2.3, Adjusting nut; 1.2.4, Top plate; 1.2.5, Pressure block; 1.2.6, Magnetic seat; 1.2.7, Bolt; 1.3, Support distribution beam; 1.4, Support column; 1.5, Connecting sleeve; 2. Steel truss bridge; 3. Crane; 4. Pier. Detailed Implementation

[0024] The present invention will be explained in detail through the following embodiments. The purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention. Example

[0025] A method for constructing a steel truss bridge without scaffolding involves leveling the site and erecting a ground assembly frame 1. Each segment of the steel truss bridge is transported from the processing plant to the construction site, where welding and riveting are performed on the ground assembly frame 1 to assemble the steel truss bridge 2. The steel truss bridge 2 is then erected on the piers 4 using a double crane 3 lifting method.

[0026] In the scaffold-free construction method for this steel truss bridge, a ground-assembled jig 1 is used. The ground-assembled jig 1 includes: a base plate 1.1, an adjustable bracket 1.2, a support distribution beam 1.3, and support columns 1.4. For details, please refer to the appendix of the instruction manual. Figure 3-7 The pad 1.1 is made of 600*600mm thick structural steel plate; the adjustable bracket 1.2 includes a bracket base 1.2.1, a lead screw 1.2.2, an adjusting nut 1.2.3, a top plate 1.2.4, and a pressure block 1.2.5; the bracket base 1.2.1 includes a cylindrical support sleeve 1.2.1.1, with a channel steel support base 1.2.1.2 welded to the bottom, and four reinforcements are welded between the support sleeve 1.2.1.1 and the support base 1.2.1.2. The bottom of the reinforcing rib and support base 1.2.1.2 is symmetrically provided with magnetic seat holes 1.2.1.2.1; the top of the support sleeve 1.2.1.1 is welded with a circular support flange, and the end face of the support flange is provided with several radial oil storage grooves; the side wall of the support sleeve 1.2.1.1 is symmetrically provided with through anti-rotation pin grooves 1.2.1.1.1; the lead screw 1.2.2 is provided with an anti-rotation pin hole near its lower end, and the lead screw 1.2.2 is movably set in the circular hole of the support base 1.2.1, and fixed in the anti-rotation pin hole. An anti-rotation pin 1.2.2.1 is provided, extending into the anti-rotation pin groove 1.2.1.1.1 of the support base 1.2.1; an adjusting nut 1.2.3 is movably mounted on the lead screw 1.2.2, located at the top of the support base 1.2.1, with its bottom surface contacting the upper end face of the support flange. Both the upper and lower end faces of the adjusting nut 1.2.3 are provided with radial oil reservoirs. Lubricating grease is applied to the oil reservoir between the support flange and the contact surface of the adjusting nut 1.2.3. The adjusting nut 1.2... .3 Six pry bar holes are evenly distributed on the outer circumference; the top of the lead screw 1.2.2 is provided with a support plate, and the top plate 1.2.4 is fixedly set on the support plate at the top of the lead screw 1.2.2 and is fixedly connected by welding; the top plate 1.2.4 is provided with connecting bolt holes, and the pressure block 1.2.5 is movably connected to the top surface of the top plate 1.2.4 by bolts; the adjustable bracket 1.2 is used with a magnetic base 1.2.6, which is cylindrical, with a clamping ring on the outer circumference and a rotating knob on the top;

[0027] The supporting distribution beam 1.3 is made of double-section I-beam profile, and several connecting bolt holes are provided on both the upper and lower plates; the supporting column 1.4 includes the supporting column body and the supporting column pad. The supporting column body is fixedly installed in the middle of the upper part of the adjusting column pad. The supporting column pad has four connecting through holes evenly distributed around the axis of the supporting column body.

[0028] The method for assembling the ground assembly frame 1 on site is as follows:

[0029] S1. Construction of the on-site ground assembly frame 1: The assembly area is pre-leveled at the construction site and repeatedly compacted eight times with a vibratory roller. Then, a 600*600mm, 50mm thick pad 1.1 is laid flat on the compacted ground according to the design position. The adjustable bracket 1.2 is temporarily placed on the pad 1.1, and the magnetic seat 1.2.6 is placed in the magnetic seat hole 2.1.2.1. The support distribution beam 1.3 is fixedly placed on top of the adjustable bracket 1.2. The position of the adjustable bracket 1.2 is adjusted, and then the bolts of the pressure block 1.2.5 are tightened to make the support distribution beam... The supporting beam 1.3 is fixedly connected to the top of the adjustable bracket 1.2; several support columns 1.4 are set according to actual needs. The support columns 1.4 are fixedly set on the top of the supporting distribution beam 1.3 and fixedly connected to the supporting distribution beam 1.3 by bolts, thus completing the initial construction of the ground assembly frame 1 on the construction site; there are two supporting distribution beams 1.3. Adjust the parallelism of the two supporting distribution beams 1.3, and then rotate the rotation knob of the magnetic seat 1.2.6. By rotating the clamping ring of the magnetic seat 1.2.6, the adjustable bracket 1.2 is fixedly connected to the pad 1.1.

[0030] S2. Adjustment of the on-site ground assembly jig 1: Measure the height of all adjustable supports 1.2 using a laser level; when there is a difference in the height of the adjustable supports 1.2, insert a pry bar into the pry bar hole of the adjusting nut 1.2.3, and rotate the adjusting nut 1.2.3 to raise and lower the lead screw 1.2.2; during adjustment, there should be a height difference of 1-2mm between the top plates 1.2.4 of the adjustable supports 1.2 located on the same support distribution beam 1.3, and the height of the top plate 1.2.4 of the adjustable support 1.2 located in the middle of the same support distribution beam 1.3 should be greater than the height of the top plates 1.2.4 of the adjustable supports 1.2 on both sides; after adjustment, the support distribution beam 1.3 should have a slightly upward convex arc.

[0031] S3. Settlement adjustment of the ground assembly jig 1: Each beam segment of the steel truss bridge is hoisted onto the support column 1.4 of the ground assembly jig, and its position is adjusted. It is left to stand for three days. During this period, the height of the adjustable support 1.2 is measured every twelve hours with a laser level. If the height of the top plate 1.2.4 of the adjustable support 1.2 changes, the adjusting nut 1.2.3 is adjusted in time by rotating the pry bar. Finally, the height of all adjustable supports 1.2 is kept consistent, and the two support distribution beams 1.3 are at the same height and in a horizontal state.

[0032] S4. Adjustment of the height difference between each beam segment of steel truss bridge 2: After the settlement of the ground assembly jig 1 on site tends to stabilize, hydraulic jacks are used to lift each beam segment. By setting shims on the support column 1.4, the height difference between each beam segment of steel truss bridge 2 is adjusted to control the pre-deformation of steel truss bridge 2 after ground assembly.

[0033] The steel truss bridge beams are assembled on the ground assembly jig 1. During the assembly process, the height of the adjustable bracket 1.2 is dynamically monitored using a laser level. When the height of the adjustable bracket 1.2 changes by more than 2.0 mm, the height of the adjustable bracket 1.2 is adjusted by rotating the adjusting nut 1.2.3 with a pry bar to keep it within the set range.

[0034] After the steel truss bridge is assembled on the ground, it will be hoisted as a whole by two cranes 3. When selecting cranes, the actual lifting weight of crane 3 should be calculated. The actual lifting weight of each crane 3 should not exceed 70% of the nominal maximum lifting weight of crane 3. For example, if the total lifting weight of steel truss bridge 2 is 400 tons and the actual lifting weight of each crane 3 is 200 tons, then a crane with a lifting capacity of 286 tons should be selected based on 70% of the nominal maximum lifting weight of crane 3. Finally, a crane with a maximum nominal lifting weight of 300 tons should be selected. Before the two cranes 3 are officially lifted, a pre-lifting test must be carried out. The stability of crane 3 is tested in the pre-lifting test. Then, steel truss bridge 2 is reset on the adjusted on-site ground assembly jig 1, and the bridge deck deflection is tested. After the test is qualified, steel truss bridge 2 is hoisted onto the bridge pier 4 by two cranes 3 and adjusted into place according to the design requirements. Pre-fixation is carried out first, and then the lifting hooks can be detached before the formal fixing construction of steel truss bridge is carried out.

[0035] In some construction sites, if the foundation soil is soft soil such as silty soil or collapsible loess, and the load-bearing capacity is insufficient, a partial replacement layer method is adopted at the 1.1 position of the pad on the site. The original foundation soil layer is replaced with a well-graded crushed stone and clay mixture. The area of ​​the partial replacement layer is twice the area of ​​the pad, and the depth is 1.0m. After the replacement layer is filled, it is compacted 8 times with a vibratory roller to ensure the settlement stability of the assembly frame on the site.

[0036] The parts of this invention not described in detail are prior art.

Claims

1. A method for constructing steel truss bridges without scaffolding, characterized in that: The construction site is leveled, and a ground assembly frame (1) is erected. Each beam segment of the steel truss bridge is transported from the processing plant to the construction site. Welding and riveting of each beam segment of the steel truss bridge are carried out on the ground assembly frame (1) to complete the assembly of the steel truss bridge (2). The steel truss bridge (2) is erected on the pier (4) by lifting with two cranes (3). The ground assembly frame (1) includes a pad (1.1), an adjustable bracket (1.2), a support distribution beam (1.3), and a support column (1.4). The pad (1.1) is laid flat on the ground of the assembly site. The adjustable bracket (1.2) is fixedly set on the pad (1.1). The support distribution beam (1.3) is fixedly set on the top of the adjustable bracket (1.2). The support column (1.4) is fixed on the top of the support distribution beam (1.3). The method of erecting the ground assembly frame (1) is as follows: S1. Construction of the on-site ground assembly frame (1): The assembly site is pre-leveled at the construction site and repeatedly compacted with a vibratory roller. Then, the pad (1.1) is laid flat on the compacted ground according to the design position, and the adjustable bracket (1.2) is temporarily set on the pad (1.1). The support distribution beam (1.3) is fixedly set on the top of the adjustable bracket (1.2). The support column (1.4) is fixedly set on the top of the support distribution beam (1.3) to complete the initial construction of the on-site ground assembly frame (1). There are two support distribution beams (1.3). The parallelism of the two support distribution beams (1.3) is adjusted, and then the adjustable bracket (1.2) is fixedly connected to the upper part of the pad (1.1). S2. Adjustment of the on-site ground assembly jig (1): Measure the height of all adjustable supports (1.2) using a laser level; during adjustment, there is a height difference of 1-2mm between the adjustable supports (1.2) located on the same support distribution beam (1.3), and the height of the adjustable support (1.2) located in the middle of the same support distribution beam (1.3) is greater than the height of the adjustable supports (1.2) on both sides, so that the support distribution beam (1.3) has an upward bulging arc; S3. Settlement adjustment of the ground assembly frame (1): Each beam segment of the steel truss bridge is hoisted onto the support column (1.4) of the ground assembly frame and its position is adjusted. The frame is left to stand for 3-5 days. During this period, the height of the adjustable support (1.2) is measured with a laser level every twelve hours. If the height of the adjustable support (1.2) changes, it is adjusted in time to ensure that the height of all adjustable supports (1.2) is consistent and that the two support distribution beams (1.3) are at the same height and in a horizontal state. S4. Adjustment of height difference between beam segments of steel truss bridge (2): By setting shims on the support column (1.4), the height difference between beam segments of steel truss bridge (2) is adjusted to control the pre-deformation of steel truss bridge (2) after ground assembly.

2. The method for constructing steel truss bridges without supports according to claim 1, characterized in that: The location where the pad (1.1) is placed on the ground is adopted by the partial replacement pad method, which replaces the original foundation soil layer with a well-graded crushed stone and clay mixture; the area of ​​the partial replacement pad is 1.5-2 times the area of ​​the pad, and the depth is not less than 0.5m; after the replacement pad is filled, it is compacted by a vibratory roller.

3. The method for constructing steel truss bridges without supports according to claim 1, characterized in that: Before the double crane (3) is officially lifted, a pre-lifting test must be carried out; the stability of the crane is tested in the pre-lifting test, and then the steel truss bridge (2) is reset on the adjusted on-site ground assembly frame (1) for bridge deck deflection test.

4. The method for constructing steel truss bridges without supports according to claim 1, characterized in that: The actual lifting weight of each crane (3) shall not exceed 70-80% of the nominal maximum lifting weight of the crane (3).

5. The method for constructing steel truss bridges without supports according to claim 1, characterized in that: After the steel truss bridge (2) is hoisted into place, it must be pre-fixed before the hoisting hook can be detached.

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