Method for splicing full-welded steel truss girder of suspension bridge based on local dynamic adjustment of secondary constant load

Abstract

The present application relates to the technical field of steel truss girder splicing of suspension bridge, and particularly relates to a full-welded steel truss girder splicing method of suspension bridge based on local dynamic adjustment of secondary dead load. The construction method comprises the following steps: S1: based on the bridge line shape of the main girder, determining the local loading area and load intensity for making the first batch of set length segments conform to the bridge line shape of the main girder; S2: loading equivalent load in the corresponding area to make the line shape of the set length segments conform to the bridge line shape of the main girder, and then welding and constructing; S3: determining the local loading area and load intensity for making the next batch of set length segments conform to the bridge line shape of the main girder, loading equivalent load in the corresponding area to make the set length segments conform to the bridge line shape of the main girder, and then welding and constructing; S4: repeating the step S3 until the splicing construction between all main girder segments of the suspension bridge is completed. The method can solve the problem of too large equivalent load application amount and increased temporary measure cost caused by the method of eliminating the overall negative bending moment of the steel girder at one time in the prior art.

Description

Technical Field

[0001] This invention relates to the field of steel truss splicing technology for all-welded suspension bridges, and specifically to a method for splicing all-welded steel truss girders for suspension bridges based on local dynamic adjustment of secondary constant load. Background Technology

[0002] In the completed state, the dead load of the main girder, including the structural self-weight and the secondary dead load, is transferred to the main cable by the suspenders. The main girder does not bear the overall bending moment; it can be considered that the main girder is in a stress-free state in the completed state.

[0003] During the construction phase, the manufacturing alignment of the main girder adopts the design alignment of the completed bridge. The main girder is manufactured in segments in the factory, transported to the bridge site, erected, and installed until the bridge is completed. The construction objective is to meet the requirements of the ideal completed bridge design, where the main girder does not bear the overall bending moment, also known as the main girder has no additional bending moment, and the structural components have no additional stress; the main girder alignment meets the requirements.

[0004] In the history of suspension bridge development, truss structure is a common stiffening girder structure for suspension bridges. In terms of the structural relationship between the truss and the bridge deck system, there are two structural forms.

[0005] One type involves riveting or bolting the steel truss girder segments together, separating the bridge deck system from the truss structure. This stiffened girder structure is used in bridges such as the Golden Gate Bridge in the United States, the Akashi Kaikyo Bridge in Japan, and the Baling River Bridge in my country. During bridge construction, the steel truss girders are erected first, and the bridge deck system is installed after the truss girders are joined. The connection between the steel truss girder segments is completed during the erection process; riveting or bolting ensures that the steel girder segments are connected according to the manufacturing alignment, thus ensuring the overall alignment of the steel truss girder bridge. The bridge deck system is simply supported on the truss, ensuring that it does not participate in the overall load-bearing.

[0006] Secondly, there are plate girder composite stiffening girders that integrate the steel truss girder with the bridge deck system into a single structure. This type of stiffening girder structure is used in recently constructed long-span suspension bridges in my country, such as the Qingshuihe Bridge. The bridge deck system generally adopts an orthotropic steel bridge deck structure, welded to the chords of the steel truss girder, serving as both the bridge deck's traffic structure and truss horizontal bracing, participating in the primary load-bearing system. The stiffening girder segments are assembled at the assembly site and then hoisted and installed as whole segments. The connections between plate girder composite stiffening girder segments can be divided into bolted-welded composite and fully welded types, the difference being whether the truss members are connected by bolts or by welding. For bolted-welded composite stiffening girders, during segment hoisting construction, the advantages of bolted connections are fully utilized, and rigid connections (including bolting between truss members and welding between bridge deck systems) are made as appropriate based on changes in the main girder's alignment. This approach also basically ensures that the steel girder segments are connected according to the manufacturing alignment, thus ensuring the final bridge alignment of the steel truss girder.

[0007] For fully welded plate girder composite stiffening girders, the lack of convenient high-strength bolt connections makes it impossible to achieve rigid connections between steel beam segments during the continuous beam erection process where the beam alignment changes. The general approach is to first erect the steel beams until closure, then apply a secondary dead load equivalent to the main beam's shape on the entire bridge deck to adjust the main beam alignment to the completed bridge state. Welding between the steel beam segments is then carried out in this state, completing the connections according to the manufacturing alignment to ensure the final bridge alignment. Water bags or sandbags are commonly used as secondary dead load equivalents; for example, the Yangsigang Yangtze River Bridge used water bags as a secondary dead load equivalent.

[0008] However, the method of applying the equivalent load of the second-phase dead load to the entire bridge to eliminate the overall negative bending moment of the steel beam at once, and then carrying out the welding construction of the welds between the steel beam segments, results in too much equivalent load application, which increases the cost of temporary measures. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a method for splicing steel truss girders of suspension bridges with local dynamic adjustment of the second-phase dead load. This method can solve the problems of excessive equivalent load application and increased cost of temporary measures caused by the existing method of eliminating the overall negative bending moment of the steel beam at one time and then welding the steel beam segments.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for splicing fully welded steel truss girders for suspension bridges based on local dynamic adjustment of secondary dead load, including: S1: Based on the main girder bridge alignment, determine the local loading area and load intensity that make the first batch of set length segments conform to the main girder bridge alignment; S2: Based on the local loading area and load intensity, apply an equivalent load to the corresponding area of ​​the main beam to make the alignment of the set length segment conform to the bridge alignment of the main beam, and carry out welding construction of the set length segment. S3: Based on the main beam bridge alignment, determine the local loading area and load intensity of the next batch of set length segments outside the set length segment to conform to the main beam bridge alignment, apply an equivalent load to the corresponding area of ​​the main beam to make the set length segment conform to the main beam bridge alignment, and carry out the welding construction of the set length segment. S4: Repeat step S3 until the splicing construction between all main girder segments of the suspension bridge is completed.

[0011] In some alternative schemes, based on the completed bridge alignment of the main girder, the local loading areas and load intensities that ensure the first batch of pre-set length segments conform to the completed bridge alignment of the main girder are determined, including: A finite element model of the bridge is established, and a local area of ​​the main beam in the finite element model is loaded to obtain the line shape of the segment of a set length. When the alignment of the set length segment does not conform to the alignment of the main girder bridge, the loading area and / or loading load are adjusted until the set length segment conforms to the alignment of the main girder bridge, and the local loading area and load intensity on the main girder at this time are obtained.

[0012] In some alternative schemes, the main cable force in the bridge finite element model is determined based on the secondary dead load of the main beam, and the main cable alignment is calculated using the segmented catenary theory.

[0013] In some alternative solutions, the method of applying an equivalent load to the corresponding region of the main girder based on the local loading area and load intensity, so that the alignment of the set length segment conforms to the completed bridge alignment of the main girder, includes: Based on the local loading area and load intensity, an equivalent load is initially applied to the corresponding area, and the linear shape of the segment with a set length is obtained. When the alignment of the set length segment does not conform to the alignment of the corresponding area of ​​the main girder completed bridge alignment, the local loading area and / or load intensity are adjusted according to the difference between the alignment of the set length segment and the alignment of the corresponding area of ​​the main girder completed bridge alignment, until the alignment of the set length segment conforms to the main girder completed bridge alignment.

[0014] In some alternative solutions, when applying an equivalent load to the local loading area corresponding to the next batch of predetermined length segments, so that the predetermined length segments conform to the main girder bridge alignment: Obtain the overlapping and non-overlapping areas of the local loading area that makes the previous batch of set length segments conform to the main girder bridge alignment and the local loading area of ​​the next batch of set length segments conform to the main girder bridge alignment. The equivalent load of the non-overlapping area in the local loading region of the previous batch of set length segments conforming to the main girder bridge alignment is moved to the non-overlapping area in the local loading region of the next batch of set length segments conforming to the main girder bridge alignment, and adaptive increases or decreases are made to make the set length segments conform to the main girder bridge alignment.

[0015] In some alternative solutions, when determining the local loading area and load intensity that makes the first batch of set-length segments conform to the bridge alignment of the main girder, the set-length segment in the middle of the main girder is selected.

[0016] In some alternative schemes, when determining the local loading area and load intensity of the next set length segment outside the set length segment to conform to the main beam bridge alignment, the set length segments on both sides of the already welded set length segment are selected simultaneously for alignment adjustment and welding construction.

[0017] In some alternative solutions, after ensuring that the segments of the set length conform to the bridge alignment of the main beam, and before carrying out the welding construction of the segments of the set length, the misalignment adjustment work between the segments of the set length is also carried out.

[0018] In some alternative solutions, prior to step S1, a step of determining the predetermined length segment is included, comprising: Based on the total number of welds, the welding construction period requirements, and the welding operation process requirements, determine the total number of welding batches, the number of construction sections in each batch, and the number of welds in each construction section. The number of construction segments of a set length for each batch is determined based on the number of construction sections in each batch. The number of main beam segments for each specified length segment is determined based on the number of welds in each construction section.

[0019] In some alternative solutions, when multiple construction sections are loaded simultaneously in one batch based on welding construction schedule requirements, the loading parameters are adjusted and calculated according to the number of construction sections loaded simultaneously.

[0020] Compared with existing technologies, the advantages of this invention are as follows: By determining the local loading area and load intensity that makes each batch of set-length segments conform to the bridge alignment of the main girder, and applying equivalent loads to the corresponding areas, only the negative bending moment of the set-length segments is offset, so that the relative alignment between the set-length segments is consistent with the bridge alignment of the main girder. At this time, welding is performed on the splice joints between the set-length segments to complete the rigid connection. In this way, local dynamic loading is applied in batches, and the welding construction of the weld joints between the steel truss girder segments is completed one by one. It is possible to complete the stress-free connection between the steel truss girder segments under the condition of eliminating the additional bending moment of the stiffening girder, realize the control of the bridge alignment of the main girder design, and the cost is far lower than the equivalent load application method of one-time full uniform load. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart of the method for splicing all-welded steel truss girders of a suspension bridge based on local dynamic adjustment of the second-phase dead load in an embodiment of the present invention; Figure 2 This is a diagram showing the loading range and bending moment of the main beam in the first round of loading in this embodiment of the invention. Figure 3 This is a diagram showing the loading range and main beam bending moment in the second round of loading in this embodiment of the invention. Figure 4This is a diagram showing the loading range and bending moment of the main beam in the third round of loading in this embodiment of the invention. Figure 5 This is a diagram showing the loading range and main beam bending moment in the fourth round of loading in this embodiment of the invention. Figure 6 This is a diagram showing the loading range and main beam bending moment in the fifth round of loading in this embodiment of the invention. Figure 7 This is a diagram showing the loading range and main beam bending moment in the sixth round of loading in this embodiment of the invention. Figure 8 This is a diagram showing the loading range and main beam bending moment in the 7th loading cycle of this invention. Figure 9 This is a diagram showing the loading range and main beam bending moment in the 8th loading cycle of this invention. Figure 10 This is a diagram showing the loading range and main beam bending moment in the 9th loading cycle of this invention. Figure 11 This is a diagram showing the loading range and bending moment of the main beam in the 10th loading cycle of this invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0025] For long-span suspension bridges, the structural response under uniformly distributed load corresponds to the overall vertical stiffness of the bridge, dominated by the elastic stiffness of the main cable, while the bending stiffness of the main girder is negligible. Under uniformly distributed load in a localized continuous area, the structural response corresponds to the localized vertical stiffness, dominated by the gravitational stiffness of the main cable. The shorter the localized continuous loading area, the greater the influence of the bending stiffness of the main girder, and the smaller the influence of the gravitational stiffness of the main cable. Uniformly distributed load across the entire bridge is a special case for suspension bridges, as it does not reflect the gravitational stiffness of the main cable. Under localized continuous loading, the main cable deflects downwards in the loaded area and upwards in the unloaded area. The deformation of the main cable achieves force equilibrium, and the deformation exhibits nonlinearity, reflecting the essential characteristics of a suspension bridge.

[0026] For long-span suspension bridges, the construction sequence is as follows: first, erect the main cable; then, erect the steel beams; finally, construct the guardrails, bridge deck pavement, and other bridge deck facilities. Traffic is opened only after the bridge has passed inspection. The manufacturing, transportation, and installation methods of the steel beams should be determined based on the bridge site environment. In cases with favorable transportation conditions, such as some large bridges, the steel beams are manufactured, transported, and installed in whole sections at the steel beam factory. For long-span suspension bridges, the steel beams are generally installed from the mid-span towards the main tower, with temporary connections between beam sections to transfer the internal forces between the chords. When the steel beams are erected, because the second phase of construction has not yet begun and the second phase dead load has not been applied, the steel beams flex upwards, and the entire steel beam bears a negative bending moment. The temporary connections of the upper chord bear tension, and the temporary connections of the lower chord bear compression. The overall negative bending moment of the steel beam originates from the second phase dead load. After the second phase dead load is implemented, the main cable and main beam return to the designed bridge alignment, and the overall bending moment of the steel beam is zero. Before the second phase of permanent load construction, the steel beams were subjected to negative bending moments, which caused the relative alignment between the steel beams to differ from the designed bridge state.

[0027] Before the steel truss segments are installed and the second phase of dead load construction begins, the overall shape of the steel truss is an upward deflection curve, equivalent to the deformation of the structure when the second phase of dead load is removed from the completed bridge. At this time, the steel truss is subjected to a negative bending moment, with the upper chord under tension and the lower chord under compression. The greater the second phase of dead load, the greater the upward deflection deformation of the steel truss and the greater the bending moment it bears.

[0028] If the joints between steel beam segments are welded directly without any pretreatment, the overall bending moment will still exist within the steel beams in the completed bridge state after the second phase of dead load construction, which is inconsistent with the designed bridge state. The traditional approach is to apply an equivalent load to all steel beam segments of the entire bridge to eliminate the overall negative bending moment of the steel beams at once, and then carry out the welding construction between the steel beam segments. This approach involves too much equivalent load.

[0029] Because the all-welded steel truss girder lacks high-strength bolts, rigid connections between segments cannot be made using high-strength bolts or drift pins during steel girder erection. Therefore, rigid connections between steel girder segments are not feasible. Applying two constant substitute loads to the entire bridge would be too labor-intensive.

[0030] This patent proposes a method for applying two constant equivalent loads locally and welding steel beam splices in batches. The key parameters of this method are the total number of welding batches, the number of welds per batch, the loading length of each equivalent load, and the load weight per unit length. First, based on the total number of welds, the welding construction period requirements, and the welding process requirements, the total number of welding batches and the number of welds per batch are determined. Then, a finite element model is used to determine the loading length of each equivalent load and the load weight per unit length. The finite element model calculation principle is that under each batch of equivalent load conditions, the main beam alignment corresponding to the welds to be welded in the current batch is consistent with the completed bridge alignment. At this point, the overall bending moment of the main beam is zero, and the axial forces of the upper and lower chords of the truss are zero.

[0031] The main girder is manufactured with the designed bridge alignment. Temporary connectors are used between the steel girder segments after the main girder is erected. Since the second phase of construction has not yet commenced, the main girder as a whole is subjected to a negative bending moment M after erection. 1x The upper chord is under tension, and the lower chord is under compression; the tension or compression is transmitted through temporary connectors. The loading length for the Nth batch is L. N The load intensity is q, which produces a positive bending moment M on the main beam. 2x The upper chord is under compression, and the lower chord is under tension. The purpose of the Nth batch of loading is to increase the length L... N The total bending moment (M) is satisfied within the range. 1x +M 2x When the value is zero, the axial forces on the upper and lower chords of the truss are zero. N Within the range, the alignment of several main beam segments is consistent with the designed bridge alignment. Under this condition, welding construction is carried out on the splice joints of the steel beam segments within the range to complete the rigid connection between the steel beam segments.

[0032] The main girder of a suspension bridge can be considered as a continuous beam with multi-point elastic support under the cable system. According to the stress characteristics of a continuous beam, L... N >L N That is, the loading length should be greater than the total bending moment (M). 1x +M 2x The control length is zero. The mid-span bending moment of the simply supported beam is 1 / 8qL. 2 As can be seen, the loading length L N The load intensity q is interrelated and can be determined through iterative calculation. Loading length L N The larger the value, the more positive bending moment M is generated on the main beam. 2x The gentler the slope over a longer range, the better it can satisfy the total bending moment (M). 1x +M 2x The requirement is that L is zero; but L N A larger equivalent load also means a greater workload for equivalent load construction, therefore optimization is needed. The equivalent load should be kept as small as possible while still meeting the moment control requirements within the welding length range. Furthermore, considering the ease of application of the equivalent load, the loading length L of each loading cycle should also be... N Basically the same.

[0033] As can be seen from the above description, the main beam, once erected, is subjected to a negative bending moment M. 1x The load distribution is within the entire length of the main girder; the bending moment of the main girder during each loading is M within a certain segment range. 2x Satisfying the total bending moment (M) 1x +M 2xThe requirement of zero welding speed was used to create welding conditions where the main girder alignment within the specified range corresponded to the completed bridge alignment. Through several rounds of local loading, welding of all joints across the entire bridge was achieved. The welding of all joints was completed in N rounds, with no necessary sequential relationship between the rounds. For example, two work faces could be started symmetrically from mid-span towards their respective main towers, or two additional work faces could be added simultaneously at the quarter-span and three-quarter-span. However, due to the nonlinear deformation of the main cable of the suspension bridge, the bending moments of the main girder under simultaneous loading in each round interfered with each other, requiring adjustments to the loading parameters based on the number of simultaneously loaded work faces.

[0034] This invention fully utilizes the aforementioned structural deformation characteristics of suspension bridges. The entire bridge is subjected to a single, full-scale application of the secondary dead load equivalent to the previous load, which is then transformed into multiple rounds of segmented, locally applied dynamic equivalent loads. The application of these locally applied equivalent loads is coordinated with the welding construction between the steel beam segments within the corresponding ranges. The welding construction between the steel beam segments of the entire bridge is completed gradually in multiple rounds. The steel beam welding schedule is subject to the overall construction schedule, and the range of application of the locally applied equivalent loads should meet the requirements for the number of welding work surfaces on the steel truss beams.

[0035] Based on the above analysis, such as Figure 1 As shown, this application proposes a method for splicing fully welded steel truss girders of suspension bridges based on local dynamic adjustment of secondary dead load, including the following steps: S1: Based on the main girder's completed bridge alignment, determine the local loading area and load intensity that make the first batch of set-length segments conform to the main girder's completed bridge alignment.

[0036] In some optional embodiments, step S1 includes: S11: Establish a finite element model of the bridge, load a local area of ​​the main beam in the finite element model of the bridge, and obtain the line shape of the segment of a set length.

[0037] In this embodiment, the main cable force in the bridge finite element model is determined based on the secondary dead load of the main girder, and the final bridge alignment of the main cable is calculated using the segmented catenary theory. The final bridge alignment of the main girder is determined based on the bridge deck design alignment.

[0038] In addition, the set length segment is also selected based on actual needs. For example, in this case, the set length segment is determined to be 3 segments for the first time.

[0039] In some optional embodiments, before step S1, a step of determining the set length segments for each batch is included, including: determining the total number of welding batches, the number of construction segments in each batch, and the number of welds in each construction segment based on the total number of welds, the welding construction period requirements, and the welding operation process requirements; determining the number of set length segments in each batch based on the number of construction segments in each batch; and determining the number of main beam segments in each set length segment based on the number of welds in each construction segment.

[0040] For example, if the construction period is tight, the number of length segments set for each batch of construction can be reasonably adjusted, and multiple construction work surfaces can be set up at the same time to shorten the construction period.

[0041] S12: When the alignment of the set length segment does not conform to the alignment of the main girder bridge, adjust the loading area and / or the loading load until the set length segment conforms to the alignment of the main girder bridge, and obtain the local loading area and load intensity on the main girder at this time.

[0042] Here, the statement that the alignment of the set-length segment does not conform to the alignment of the main girder bridge means that the alignment of the main girder after loading the set-length segment in the bridge finite element model does not conform to the alignment of the set-length segment region corresponding to the alignment of the main girder bridge.

[0043] During adjustment, the local loading area and / or load intensity on the main beam can be adjusted to ultimately obtain the local loading area and load intensity that make the set length segment conform to the bridge alignment of the main beam.

[0044] S2: Based on the local loading area and load intensity, apply an equivalent load to the corresponding area of ​​the main beam to make the alignment of the set length segment conform to the bridge alignment of the main beam, and carry out welding construction of the set length segment.

[0045] In this embodiment, based on the local loading area and load intensity, an equivalent load is applied to the corresponding area of ​​the main girder to make the alignment of the set length segment conform to the final bridge alignment of the main girder, including: A: Based on the local loading area and load intensity, an equivalent load is initially applied to the corresponding area, and the linear shape of the segment with a set length is obtained.

[0046] After initially applying an equivalent load to the corresponding area based on the local loading area and load intensity, the actual alignment of the segment of a set length in the main beam is obtained by measurement.

[0047] B: When the alignment of the set length segment does not conform to the alignment of the corresponding area of ​​the main girder completed bridge alignment, adjust the local loading area and / or load intensity according to the difference between the alignment of the set length segment and the alignment of the corresponding area of ​​the main girder completed bridge alignment, until the alignment of the set length segment conforms to the main girder completed bridge alignment.

[0048] In this embodiment, after obtaining the actual alignment of a segment of a set length in the main beam, the actual alignment of the segment of the set length is compared with the alignment of the corresponding area of ​​the main beam's completed bridge alignment. When the two do not match, the local loading area and / or load intensity are adjusted according to the difference between the actual alignment of the segment of the set length and the alignment of the corresponding area of ​​the main beam's completed bridge alignment, until the alignment of the segment of the set length conforms to the main beam's completed bridge alignment.

[0049] S3: Based on the main girder's completed bridge alignment, determine the local loading area and load intensity that will make the next batch of designated length segments outside the designated length segment conform to the main girder's completed bridge alignment. Apply an equivalent load to the corresponding area of ​​the main girder to make the designated length segments conform to the main girder's completed bridge alignment, and then carry out the welding construction of the designated length segments.

[0050] In some optional embodiments, when an equivalent load is applied to the local loading area corresponding to the next batch of predetermined length segments, so that the predetermined length segments conform to the completed bridge alignment of the main girder: A: Obtain the overlapping and non-overlapping areas of the local loading area that makes the previous batch of set length segments conform to the main girder bridge alignment and the local loading area of ​​the next batch of set length segments conform to the main girder bridge alignment.

[0051] B: Move the equivalent load of the non-overlapping area in the local loading area of ​​the previous batch of set length segments that conforms to the main girder bridge alignment to the non-overlapping area in the local loading area of ​​the next batch of set length segments that conforms to the main girder bridge alignment, and make adaptive additions or subtractions to make the set length segments conform to the main girder bridge alignment.

[0052] When the local loading area corresponding to the previous batch of set length segments overlaps with the local loading area of ​​the next batch of set length segments that conforms to the main girder bridge alignment, the load in the non-overlapping area can be moved only and adjusted accordingly to achieve loading of the local loading area corresponding to the next batch of set length segments, so that the alignment of the set length segments conforms to the main girder bridge alignment.

[0053] In this example, when determining the local loading area and load intensity that make the first batch of set-length segments conform to the bridge alignment of the main girder, the set-length segment in the middle of the main girder is selected.

[0054] Therefore, in this scheme, loading is applied to a local area of ​​the main beam in the bridge finite element model. The loading is applied to a local area corresponding to a selected segment of length in the middle of the main beam. The range of this local area can be smaller or larger than the segment of length in the middle of the main beam, depending on the actual needs.

[0055] Based on the requirements for the number of welded joints in a single round of steel beam welding construction, the loading area, load intensity, and loading rounds were calculated using a finite element model. The stiffening girder of the suspension bridge is an elastically supported continuous beam. Generally, the loading area should be larger than the beam segment where the welded joint is located; the bending moment of the stiffening girder should be continuously distributed within the loading area, with the optimal state being that the average bending moment of the target welded joint area is close to zero. A larger loading area and a higher load intensity mean more equipment and counterweights are required, leading to higher implementation costs. Based on these calculation and implementation considerations, the loading round arrangement parameters were optimized through iterative calculations in the finite element model.

[0056] The welding of steel beams occupies the critical path time of the entire bridge, necessitating control over the overall welding period of the splice joints. After completing the welding of the designated length segments in the middle of the main beam, welding proceeds symmetrically towards each bridge tower, establishing two welding zones. This means simultaneously defining welding zones for two designated length segments on either side of the main beam, with two work teams working concurrently in each zone. For ease of implementation, the length of the local loading zones in each cycle is essentially the same, meaning the differences between the local loading zones are only within the designated range, and the load intensity variation remains within the designated range, without significant changes.

[0057] In this example, when determining the local loading area and load intensity that make the next batch of set-length segments outside the set-length segment conform to the main beam bridge alignment, set-length segments on both sides of the already welded set-length segments are selected simultaneously for alignment adjustment and welding construction.

[0058] In addition, in some optional embodiments, after the set length segments conform to the main beam bridge alignment, before the welding construction of the set length segments, the misalignment adjustment work between the segments in the set length segments is also carried out.

[0059] In this example, the equivalent load is applied by filling the water bag with water.

[0060] S4: Repeat step S3 until the splicing construction between all main girder segments of the suspension bridge is completed.

[0061] In some optional embodiments, when multiple construction sections are loaded simultaneously in one batch based on the welding construction period requirements, the loading parameters are adjusted and calculated according to the number of construction sections loaded simultaneously.

[0062] For example, in this case, a working face is first constructed from the mid-span, corresponding to the construction section (the same below). Then, starting from the already constructed working face at the mid-span, two working faces are constructed symmetrically towards their respective main towers. When the construction period is tight, two more working faces are added simultaneously at the quarter-span and three-quarter-span. However, due to the influence of the nonlinear deformation of the main cable of the suspension bridge, the bending moments of the main girder under simultaneous loading in each round interfere with each other, requiring the loading parameters to be recalculated and corrected based on the number of construction sections under simultaneous loading.

[0063] In summary, before the steel truss segments are installed and the second phase of dead load construction begins, the overall alignment of the steel truss is an upward-deflecting curve, equivalent to the structural deformation when the second phase dead load is removed from the completed bridge. At this time, the steel truss as a whole bears a negative bending moment, with the upper chord under tension and the lower chord under compression. The greater the second phase dead load, the greater the upward deflection of the steel truss, and the greater the bending moment it bears. Current technology, which involves fully distributing the second phase dead load as an equivalent load across the entire bridge, aims to offset the deflection deformation of the steel truss in one go, thereby eliminating the negative bending moment.

[0064] The local dynamic loading method proposed in this invention applies a uniformly distributed load to a small area of ​​the main beam, offsetting only the negative bending moment of a few consecutive steel truss segments. This ensures that the relative alignment between these consecutive steel beams matches the manufacturing alignment. Welding is then performed at the joints of these consecutive steel beams to achieve a rigid connection. Following the direction from mid-span to the main tower, local dynamic loading is applied in stages, sequentially completing the welding of the joints between the steel truss segments. This method enables stress-free connection between steel truss segments while eliminating the additional bending moment of the stiffening girder, achieving bridge alignment control in the main beam design, and at a significantly lower cost than the equivalent load application method using a single, full uniformly distributed load.

[0065] A more specific embodiment is given below: This is a single-span simply supported suspension bridge with a span of 1860m. The stiffening girder is a fully welded plate girder composite steel truss structure, meaning that the main truss members and bridge deck are all welded connections. The entire stiffening girder consists of 69 segments, numbered JD35 at mid-span, decreasing sequentially towards the next mileage, with JD1 at the end. The standard segment length is 27m. There are 68 splices between the 69 stiffening girder segments. The splice between JD35 and JD34 is numbered 34, decreasing sequentially, and the splice between JD2 and JD1 at the end is numbered 1. The secondary dead load design value for the steel truss girder is 107.1kN / m, and the total secondary dead load of the entire bridge is approximately 200MN. Welding of the splices between the segments will be carried out after all segments have been erected.

[0066] If a full equivalent load is applied to the entire bridge at once, a counterweight of 200MN needs to be placed on the bridge deck, which is costly and time-consuming. Furthermore, the long-term presence of a temporary equivalent load on the entire bridge also affects other operations. The suspension bridge fully welded steel truss splicing method based on local dynamic adjustment of the second-phase dead load proposed in this invention can be adopted.

[0067] Using the scheme provided in this application, a finite element model of the bridge in the embodiment was established, and calculation analysis and optimization of local dynamic loading cycles were carried out. The calculation results are shown in Table 1 below. The mid-span mileage of the main beam is 0.0m. The table only shows the calculation results of half of the steel beams in the direction from the mid-span to the smaller mileage. The other half is arranged symmetrically about the mid-span.

[0068] Table 1 Results of local dynamic loading cycles

[0069] The optimized calculation results show that the welding of the bridge steel beam splice joints in the embodiment was completed in ten rounds. The load arrangement for the ten rounds is shown in [reference needed]. Figures 2-11 As shown. The load is symmetrically arranged around the mid-span, with a standard loading length of 144m and a maximum loading weight of 5760kN. Three or four welded joints are used each time. The maximum loading weight accounts for 5.8% of the total dead and permanent weight of the entire bridge.

[0070] Based on the finite element calculation results, Figure 2 The equivalent bending moment diagram for the first loading cycle is shown below. Figure 3 The diagram shows the equivalent bending moment for each symmetrical loading cycle. It can be seen that under each loading cycle, the equivalent bending moment of the stiffening beam in the corresponding welded area of ​​the splice joint is close to 0, thus the axial force of the chord members is close to 0, facilitating the adjustment of the relative alignment of the steel beams on both sides of the splice joint.

[0071] Specifically, such as Figure 2 As shown, the loading length for the first round was 288m, with the area on the lower mileage side ranging from -144m to 0m, and the upper mileage side symmetrically arranged along the mid-span of the main span. The longitudinal load intensity was 21kN / m, with a total load of 3024kN on one side. Loading was achieved by injecting water into water bags, and the load weight was calculated based on the volume of water injected. After loading was completed, welding construction of the steel beam segment joints was organized; joints numbered 32-34 in this round. Figure 2 As can be seen, the bending moment of the steel beam within the welding area is basically zero, so the axial force of the upper and lower chords of the steel truss is also basically zero. The steel beam segments meet the stress-free matching relationship. At this time, it is convenient to take measures to adjust the misalignment and other linear errors between the steel beam segments. Welding can be carried out after the adjustment is completed.

[0072] like Figure 3 As shown, after welding joints 32-34, the second round of loading begins. The second round of loading has a single-sided loading length of 144m, with the area on the lower mileage side ranging from -189m to -45m, and the higher mileage side symmetrically arranged along the mid-span of the main span. The longitudinal load intensity is 40kN / m, with a total single-sided load of 5760kN. From the loading mileage, it can be seen that the loading range of the second round largely overlaps with that of the first round, with only a 45m non-overlapping area. During construction, the 45m water bag from the mid-span portion of the first round can be moved to the 45m area near the main tower in the second round, quickly transferring the load between rounds. After loading is completed, welding of the steel beam segment joints is organized; joints in this round are numbered 29-31. Figure 3 It is evident that the bending moment of the steel beam within the welding area is essentially zero.

[0073] like Figure 4 As shown, in the third round of loading, the weld joints were numbered 26-28. The single-sided loading length in the third round was 144m, with the area on the lower mileage side ranging from -279m to -135m, and the higher mileage side symmetrically arranged along the mid-span of the main span. The longitudinal load intensity was 40kN / m, and the total single-sided load was 5760kN. From the loading mileage, it can be seen that the overlapping area between the third and second round loading ranges is 54m. Figure 4 It is evident that the bending moment of the steel beam within the welded joint area is essentially zero.

[0074] like Figure 5As shown, in the fourth round of loading, the weld joints were numbered 22-25. The single-sided loading length in the fourth round was 144m, with the area on the lower mileage side ranging from -369m to -225m, and the higher mileage side symmetrically arranged along the mid-span of the main span. The longitudinal load intensity was 40kN / m, and the total single-sided load was 5760kN. From the loading mileage, it can be seen that the overlapping area between the fourth and third rounds of loading is 54m. Figure 5 It is evident that the bending moment of the steel beam within the welded joint area is essentially zero.

[0075] like Figure 6 As shown, in the fifth round of loading, the weld joints were numbered 18-21. The single-side loading length in the fifth round was 144m, with the area on the lower mileage side ranging from -477m to -333m, and the higher mileage side symmetrically arranged along the mid-span of the main span. The longitudinal load intensity was 40kN / m, and the total single-side load was 5760kN. From the loading mileage, it can be seen that the loading range of the fifth round overlapped with that of the fourth round by 36m. Figure 6 It is evident that the bending moment of the steel beam within the welded joint area is essentially zero.

[0076] like Figure 7 As shown, in the sixth round of loading, the weld joints were numbered 14-17. The single-sided loading length in the sixth round was 144m, with the area on the lower mileage side ranging from -585m to -441m, and the higher mileage side symmetrically arranged along the mid-span of the main span. The longitudinal load intensity was 40kN / m, and the total single-sided load was 5760kN. From the loading mileage, it can be seen that the loading range of the sixth round overlapped with that of the fifth round by 36m. Figure 7 It is evident that the bending moment of the steel beam within the welded joint area is essentially zero.

[0077] like Figure 8 As shown, in the 7th round of loading, the weld joints were numbered 10-13. The single-sided loading length in the 7th round was 144m, with the area on the lower mileage side ranging from -689.2m to -545.2m, and the higher mileage side symmetrically arranged along the mid-span of the main span. The longitudinal load intensity was 32kN / m, and the total single-sided load was 4608kN. From the loading mileage, it can be seen that the overlapping area between the 7th and 6th round loading ranges is 39.8m. Figure 8 It is evident that the bending moment of the steel beam within the welded joint area is essentially zero.

[0078] like Figure 9As shown, in the 8th round of loading, the weld joints were numbered 7-9. The single-sided loading length in the 8th round was 144m, with the area on the lower mileage side ranging from -774m to -630m, and the higher mileage side symmetrically arranged along the mid-span of the main span. The longitudinal load intensity was 30kN / m, and the total single-sided load was 4320kN. From the loading mileage, it can be seen that the overlapping area between the 8th and 7th round loading ranges is 59.2m. Figure 9 It is evident that the bending moment of the steel beam within the welded joint area is essentially zero.

[0079] like Figure 10 As shown, in the 9th round of loading, the weld joints are numbered 4-6. The single-side loading length in the 9th round is 144m, with the area on the lower mileage side ranging from -873m to -729m, and the higher mileage side symmetrically arranged along the mid-span of the main span. The longitudinal load intensity is 30kN / m, and the total single-side load is 4320kN. From the loading mileage, it can be seen that the loading range of the 9th round overlaps with that of the 8th round by 45m. Figure 10 It is evident that the bending moment of the steel beam within the welded joint area is essentially zero.

[0080] like Figure 11 As shown, in the 10th round of loading, the weld joints were numbered 1-3. The single-sided loading length in the 10th round was 144m, with the area on the lower mileage side ranging from -928.2m to -828m, and the higher mileage side symmetrically arranged along the mid-span of the main span. The longitudinal load intensity was 40kN / m, and the total single-sided load was 4008kN. From the loading mileage, it can be seen that the loading range of the 10th round overlapped with that of the 9th round by 45m. Figure 11 It is evident that the bending moment of the steel beam within the welded joint area is essentially zero.

[0081] Through the above 10 rounds of welding, 34 welds on one side and 68 welds on the whole bridge were completed, realizing the transformation from temporary connection to rigid permanent connection between the stiffening girder segments of the suspension bridge. Thus, the construction of the stiffening girder structure was completed.

[0082] In each welding cycle, an equivalent load of a defined load intensity is applied to the main beam within a locally loaded region that conforms to the bridge's final beam alignment for the corresponding length segments, thus eliminating bending moments present in the main beam. Within this locally loaded region, the bending moments of the steel beams near several splices smaller than the loaded region are essentially zero. At this point, these steel beam segments meet the stress-free alignment matching requirements, meaning their relative alignment is consistent with the final bridge alignment. Welding is then performed at these splices to complete the permanent rigid connection between the steel beams.

[0083] Each loading cycle involves a localized loading area exceeding the length of the steel beam segment within the weld seam range. This ensures that the bending moment of the main beam within the weld seam range of that cycle is essentially zero, achieving the requirement of a stress-free linear rigid connection between steel beam segments. For example, with a loading length of 144m, three weld seams correspond to two standard beam segments of 54m in length, while four weld seams correspond to three standard beam segments of 81m in length. The loading areas of adjacent loading cycles overlap.

[0084] By optimizing the loading length, the local loading area length is the same in the first 9 rounds of this scheme, which facilitates construction organization; the load variation is small, which facilitates the transfer of the load material (such as water bag loading); there is a certain degree of overlap between adjacent loading areas, and the load material in the overlapping area can be reused; 3 or 4 welds are welded each time, which facilitates the organization and implementation of welding construction work.

[0085] In summary, this invention employs symmetrical loading and welding along the mid-span of the main span towards the two main towers, effectively dividing the entire bridge into two working surfaces. If a longer construction period is required, additional loading equipment and working surfaces can be added, allowing subsequent rounds in Table 1 to be carried out earlier. In this case, finite element analysis is needed to verify the length of the loading area, the load intensity, and the number of weld passes at the splice joints. The principle is to ensure that the bending moment of the steel beam within the welded splice joint area is zero.

[0086] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0087] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0088] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for splicing fully welded steel truss girders for suspension bridges based on local dynamic adjustment of secondary dead load, characterized in that, include: S1: Based on the completed bridge alignment of the main girder, determine the local loading area and load intensity that ensures the first batch of segments of a set length conforms to the completed bridge alignment of the main girder, including: A finite element model of the bridge is established, and a local area of ​​the main beam in the finite element model is loaded to obtain the line shape of the segment of a set length. When the alignment of the set length segment does not conform to the alignment of the main beam bridge, the loading area and / or loading load are adjusted until the set length segment conforms to the alignment of the main beam bridge, and the local loading area and load intensity on the main beam at this time are obtained; the main cable force in the bridge finite element model is determined according to the second-stage dead load of the main beam, and the main cable alignment is calculated using the segmented catenary theory; S2: Based on the local loading area and load intensity, apply an equivalent load to the corresponding area of ​​the main girder to make the alignment of the set length segment conform to the completed bridge alignment of the main girder, including: Based on the local loading area and load intensity, an equivalent load is initially applied to the corresponding area, and the linear shape of the segment with a set length is obtained. When the alignment of the set length segment does not conform to the alignment of the corresponding area of ​​the main girder bridge alignment, the local loading area and / or load intensity are adjusted according to the difference between the alignment of the set length segment and the alignment of the corresponding area of ​​the main girder bridge alignment, until the alignment of the set length segment conforms to the main girder bridge alignment. When applying equivalent loads to the local loading areas corresponding to the next batch of segments of a set length, so that the segments of the set length conform to the bridge alignment of the main girder: Obtain the overlapping and non-overlapping areas of the local loading area that makes the previous batch of set length segments conform to the main girder bridge alignment and the local loading area of ​​the next batch of set length segments conform to the main girder bridge alignment. The equivalent load of the non-overlapping area in the local loading area of ​​the previous batch of set length segments conforming to the main girder bridge alignment is moved to the non-overlapping area in the local loading area of ​​the next batch of set length segments conforming to the main girder bridge alignment, and adaptive increases or decreases are made to make the set length segments conform to the main girder bridge alignment. And perform welding construction on the segments of the set length; S3: Based on the main beam bridge alignment, determine the local loading area and load intensity of the next batch of set length segments outside the set length segment to conform to the main beam bridge alignment, apply an equivalent load to the corresponding area of ​​the main beam to make the set length segment conform to the main beam bridge alignment, and carry out the welding construction of the set length segment. S4: Repeat step S3 until the splicing construction between all main girder segments of the suspension bridge is completed.

2. The method for splicing fully welded steel truss girders of suspension bridges based on local dynamic adjustment of secondary dead load as described in claim 1, characterized in that, When determining the local loading area and load intensity that make the first batch of set-length segments conform to the bridge alignment of the main girder, the set-length segment in the middle of the main girder is selected.

3. The method for splicing fully welded steel truss girders of suspension bridges based on local dynamic adjustment of secondary dead load as described in claim 2, characterized in that, When determining the local loading area and load intensity of the next set length segment outside the set length segment to conform to the main beam bridge alignment, the set length segments on both sides of the already welded set length segment are selected simultaneously for alignment adjustment and welding construction.

4. The method for splicing fully welded steel truss girders of suspension bridges based on local dynamic adjustment of secondary dead load as described in claim 1, characterized in that, After ensuring that the segments of a set length conform to the bridge alignment of the main beam, before proceeding with the welding of the segments of the set length, the misalignment adjustment work between the segments of the set length is also carried out.

5. The method for splicing fully welded steel truss girders of suspension bridges based on local dynamic adjustment of secondary dead load as described in claim 1, characterized in that, Before step S1, the method further includes a step of determining the set length segment, including: Based on the total number of welds, the welding construction period requirements, and the welding operation process requirements, determine the total number of welding batches, the number of construction sections in each batch, and the number of welds in each construction section. The number of construction segments of a set length for each batch is determined based on the number of construction sections in each batch. The number of main beam segments for each specified length segment is determined based on the number of welds in each construction section.

6. The method for splicing fully welded steel truss girders of suspension bridges based on local dynamic adjustment of secondary dead load as described in claim 5, characterized in that, When multiple construction sections are loaded simultaneously in one batch based on the welding construction schedule requirements, the loading parameters are adjusted and calculated according to the number of construction sections loaded at the same time.

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