Construction method for reconstructing steel truss arch bridge by using existing bridge

Abstract

The application relates to a construction method for reconstructing a steel truss arch bridge by using an existing bridge, which comprises the following steps: after the completion of the closure of the side span steel truss arch, the lower support, the side beam, the upper support and the end section of the main span steel truss arch are sequentially erected from bottom to top on the side of the side span steel truss arch close to the main span; after the erection of the bridge deck support with the overhanging cantilever on the deck of the old bridge, the section of the middle beam is erected to the closure opening through the overhanging cantilever, the section is positioned, the closure of the beam is completed; the middle section of the main span steel truss arch is erected on the upper support and the bridge deck support, and the closure of the main span steel truss arch is completed; the temporary wind brace is installed, the sling is installed, the upper support and the bridge deck support are removed, the sling is tensioned, and the lower support is removed; the deck of the old bridge is cut and the cross beam is installed according to the sequence from the middle span to the side span, and the bridge deck is installed. The application has the advantages of ensuring the installation stability of the arch beam, improving the construction efficiency and reducing the construction cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bridge engineering, and in particular to a construction method for reconstructing a steel truss arch bridge by using an existing bridge. BACKGROUND

[0002] In the regulation project of inland waterway, the cross-waterway bridge must meet the clearance dimension requirements (navigation net width, net height) of waterway planning. The bridge that does not meet the requirements must be reconstructed. The existing inland bridge is mostly a multi-span bridge, and the bridge pier arranged in the river will affect the navigation capacity of the inland river. To solve this problem, the existing solution is to remove the original multi-span bridge with bridge pier in the river and to build a single-span bridge at the position of the old bridge. This reconstruction method often involves road relocation. In particular, the railway bridge and the track transportation bridge that do not meet the requirements cannot be reconstructed due to the difficulty in relocation, the huge cost of reconstruction, the difficulty in bearing the social negative impact, and other reasons, which directly leads to the failure of the waterway to implement the planning level and even affects the overall benefit of the inland waterway network.

[0003] The applicant previously applied for a Chinese patent with the publication number CN109137656B, which discloses a conversion construction method for reconstructing a highway without interrupting traffic, including local area closure construction in multiple stages. The present application uses a method of alternating construction of half of the road surface to realize conversion while the road is open to traffic. A temporary road is constructed for construction access repair, and the start and end points of the temporary road are connected to the original highway for transition. When the temporary road is ready for traffic, the right half of the original highway is partially occupied to convert the right half of the original highway to the temporary road. The original highway two-way passing lane is closed, and the original highway conversion section central separation belt is quickly removed to convert the left half of the original highway to the temporary road, overcoming the problem of traffic interruption in the traditional construction scheme.

[0004] During the construction process using the above method, the applicant found that the new bridge construction needs to wait until the right half of the original highway (old bridge) is completely removed. In the new bridge construction process, a construction trestle needs to be pre-erected to ensure a navigation height of 5m under the construction trestle, and then the new bridge components such as steel truss arch, tie beam, cross beam, and deck system are installed by using the floating crane installation method. In this construction method, the old bridge cannot assist the construction of the new bridge at all, which does not comply with the green, environmentally friendly, and economical construction concept. Moreover, there are many limitations for using the floating crane, the navigation capacity of most inland waterways cannot meet the entry of the floating crane, and the whole section transportation of the steel arch rib cannot be met. When using the floating crane, the river occupation time is long, and the construction efficiency is not high. Therefore, the reconstruction method by using the floating crane is not suitable for the reconstruction of the inland waterway with small navigation capacity.

[0005] Chinese Patent No. CN110042757B discloses a method for synchronous installation of the arch beam of a three-main-truss steel truss arch bridge, including the following steps: S1, after the closure of the side spans of the steel truss arch, the brackets beside the main piers are released, and the fixed supports at the temporary piers are released; the main pier supports are longitudinally offset and then locked; S2, the beam erection equipment on the arch moves forward, and the main span steel truss arch is cantilevered; at the same time, flexible hangers are installed and tensioned; S3, during the synchronous erection of the arch beam, a cable-stayed tower is installed above the upper chord node of the steel truss beam at the top of the main pier; S4, the arch beam erection equipment ...4, during the synchronous erection of the arch beam, a cable-stayed tower is installed above the upper chord node of the steel truss beam at the top of the main pier; at the same time, the main span steel truss arch is erected. The girder erection equipment continues to move forward to erect the arch ribs, tie beams, and bridge deck. According to the erection progress and the stress level of each member under the maximum cantilever state of the steel truss arch, multiple layers of suspension cables are hung and tensioned in sequence. S5, after the steel truss girder is erected to the closure position, the longitudinal displacement of the main pier top is slightly adjusted to achieve the closure of the main span arch ribs. S6, the longitudinal displacement of the main pier top and the cable tension of the suspension tower are slightly adjusted to open the tie beam closure to the design length, completing the closure of the main span tie beam. S7, the cable tension is gradually released, the suspension tower is dismantled, and the girder erection equipment is withdrawn to achieve the designed bridge state of the steel truss arch.

[0006] The aforementioned construction method achieves simultaneous installation of the arch and beams by sequentially closing the side spans towards the main span. This method is not limited by the navigation capacity of inland waterways and avoids the drawbacks of the previous floating crane installation method. However, the beam-erecting equipment used travels directly on top of the steel truss arch and installs the arch beams, which can easily affect the stability of the arch beam installation. Considering the load-bearing capacity during bridge construction, additional suspenders need to be installed and tensioned, and then removed after bridge construction is completed. This construction method not only places high demands on the load-bearing capacity of the steel truss arch but also increases the material and labor costs for suspenders, etc. Furthermore, the existing bridge still cannot provide auxiliary support for the construction of the new bridge, and needs improvement. Summary of the Invention

[0007] The problem this invention aims to solve is to provide a construction method for reconstructing steel truss arch bridges using existing bridges, addressing the aforementioned shortcomings of existing technologies. This method utilizes the old bridge (existing bridge) as a construction platform, employing techniques such as temporary fixing with tie beam hooks, constructing scaffolding using the old bridge and tie beams, building the steel truss arch and wind bracing using the scaffolding, and simultaneous dismantling and construction of crossbeams. It adopts an in-situ hoisting and beam-first-arch-later construction method to construct a new arch bridge. This method solves the problems of existing bridges not being able to assist in the construction of new bridges in the reconstruction of inland river bridges, and the high load-bearing capacity requirements of steel truss arch bridges. It has the advantages of ensuring the installation stability of the arch beams, improving construction efficiency, and reducing construction costs. It conforms to the green, environmentally friendly, economical construction concept and is suitable for the construction of large-span steel truss arch bridges.

[0008] The above-mentioned objective of this invention is achieved through the following technical solutions:

[0009] A construction method for converting an existing bridge into a steel truss arch bridge includes the following steps:

[0010] S1 collects the bridge as-built drawings and bridge inspection reports of the old bridge, and assesses the load-bearing capacity reduction parameters of the old bridge due to the increase in service life;

[0011] S2 uses finite element analysis software to establish a joint model of the old bridge and the steel truss arch bridge, simulates the construction steps of S6~S9, the loading sequence of the steel truss arch bridge components, the changes in boundary conditions, and analyzes the deformation of the old bridge during the installation of the supports, closure of the steel truss arch, and closure of the tie beam in S6~S9.

[0012] Based on the analysis results of S2, S3 presets the positions of the lower support, upper support, and bridge deck support so that the old bridge can meet the preset stress requirements under the steps of S6 to S9.

[0013] For the complex structural nodes of the old bridge, S4 uses finite element analysis software to perform solid element analysis, and proposes control measures for the deformation of key structural parts based on the analysis results of S2, so as to ensure that the local stress of the old bridge meets the preset stress requirements.

[0014] S5 uses finite element analysis software to simulate the stress changes during the construction steps of S10 and the removal of the old bridge sections, so that the old bridge after the segment removal meets the preset stress requirements when installing the crossbeams.

[0015] After the S6 side span steel truss arch is closed, the lower support, side tie beam, upper support, and end segment of the main span steel truss arch are erected sequentially from bottom to top on the side of the side span steel truss arch near the main span.

[0016] After S7 erected a bridge deck support with cantilevered arms on the old bridge deck, the segments of the tie beam were erected to the closure joint through the cantilevered arms, and the segments were adjusted to complete the closure of the tie beam.

[0017] S8 erects the middle segment of the main span steel truss arch on the upper support and the bridge deck support to complete the closure of the main span steel truss arch;

[0018] Install temporary wind braces on S9, install slings, remove the upper support and bridge deck support, tension the slings, and remove the lower support;

[0019] S10 follows the sequence from the middle span to the side spans, segmentally cutting off the old bridge deck and installing crossbeams, and installing the bridge deck system.

[0020] Furthermore, in S1 to S5, the finite element analysis software is Midas Civil software.

[0021] Furthermore, in S6, approach bridges are pre-installed at both ends of the old bridge deck, then piles are driven and temporary supports are erected. Then, in the order from the lower chord of the arch rib to the upper chord of the arch rib, multiple segments of the side span steel truss arch are erected on the temporary supports to complete the closure of the side span steel truss arch.

[0022] Furthermore, in S6, the side tie beam is erected on the top of the lower support on the side closer to the old bridge deck, and the lower support is erected on the top of the side tie beam and the lower support on the side away from the old bridge deck.

[0023] Furthermore, in S7, multiple segments of the central tie beam are temporarily fixed by the lower steel wire rope of the cantilever as a hook, so as to adjust the segment position and connect the whole during the temporary fixing process of the central tie beam and the side tie beam. After the tie beam is closed, the connection between the cantilever and the central tie beam is released.

[0024] Furthermore, in S8, following the order from the side span to the middle span, the lower chords of the arch ribs of multiple middle segments of the main span steel truss arch are first erected symmetrically on the upper support and the bridge deck support, and then the upper chords of the arch ribs of multiple middle segments of the main span steel truss arch are erected symmetrically on the lower chords of the arch ribs, thus completing the closure of the main span steel truss arch.

[0025] Furthermore, in S6~S8, a stiffening rib is pre-installed on the web of the segments of the side span steel truss arch and the main span steel truss arch, and a stiffening rib is installed on the top and bottom plates. Two stiffening ribs are installed on the web of the segments of the side tie beam and the middle tie beam, and a stiffening rib is installed on the top and bottom plates.

[0026] Furthermore, in S9, multiple temporary wind braces are symmetrically installed between the main span steel truss arches on both sides of the arch bridge in sequence from the middle span to the side spans.

[0027] Furthermore, in S10, steel rails are laid on the tie beam in advance, and a sliding trolley for transporting the crossbeam is installed on the steel rails.

[0028] Furthermore, in S10, the bridge deck beams and tie beams of the old bridge are pre-connected with steel connecting rods, and then the bridge deck of the old bridge is cut off segmentally.

[0029] Furthermore, in S10, the old bridge deck is cut off in segments of 2-4m each, symmetrically, from the middle of the span to the side spans. After each segment of the old bridge deck is cut off, a crossbeam is installed.

[0030] In summary, the beneficial technical effects of the present invention are as follows:

[0031] This invention utilizes an existing bridge as a construction platform. Based on technologies such as temporary fixing with tie beam hooks, construction scaffolding using the existing bridge and tie beams, steel truss arch and wind bracing using the construction scaffolding, and simultaneous dismantling and construction of crossbeams, it constructs a new arch bridge using in-situ hoisting and a beam-first-arch-later construction method. This not only allows the use of the existing bridge as a passageway for traffic control and construction, ensuring road access and improving overall construction efficiency during reconstruction and expansion, but also solves the problem of unifying traffic control and schedule requirements in complex external environments, shortening the construction period. Furthermore, it allows the old bridge to be demolished using the newly constructed arch bridge, ensuring the stability of the arch beam installation, improving construction efficiency, and reducing construction costs. It conforms to the green, environmentally friendly, economical and cost-effective construction concept and is suitable for the construction of large-span steel truss arch bridges.

[0032] During the construction of the new arch bridge, with a structural importance coefficient of 0.9, can the load-bearing capacity of the old bridge meet the construction requirements? Can the strength, stiffness, and stability of each support meet the construction requirements? Can the hoisting space meet the requirements?

[0033] The tie beam temporary fixing technology of the present invention uses an outward cantilever as a hook to temporarily fix multiple segments of the tie beam at the same time, which facilitates segment adjustment and overall connection during the temporary fixing process of the tie beam, thereby improving the connection efficiency and quality of the tie beam. In addition, steel connecting rods are used to firmly connect the old bridge body to the tie beams of the new bridge on both sides. Before the corresponding bridge deck beams of the old bridge are demolished, they are gradually removed, thereby improving the stability of the old bridge during the demolition process.

[0034] The construction scaffolding technology of the present invention, which utilizes the old bridge and tie beams, can connect the reconstruction ideas of installing the old bridge to the bridge deck scaffolding, installing the bridge deck scaffolding to the tie beams, installing the tie beams to the superstructure scaffolding, installing the superstructure scaffolding and bridge deck scaffolding to the main span steel truss arch, and installing the tie beams to the old bridge demolition and crossbeam installation. In other words, it can complete the reconstruction scheme of building a new arch bridge using the old bridge and demolishing the old bridge using the arch bridge.

[0035] The present invention utilizes the construction scaffolding to build a steel truss arch and temporary wind bracing technology to prevent the steel truss beam segments from shifting and becoming unstable after installation. Temporary wind bracing is installed between the two steel truss beams, and the support points of the temporary wind bracing can rest on the old bridge deck and the construction scaffolding, ensuring the stability of the steel truss beam after installation.

[0036] The present invention's technology of dismantling and building crossbeams simultaneously involves dismantling the old bridge while symmetrically regressing to both sides to install new crossbeams. During this process, the remaining bridge deck is used as a working platform and transportation channel for crossbeam installation, avoiding the need to erect additional construction platforms and improving construction efficiency. Attached Figure Description

[0037] Figure 1 This is a flowchart of the construction method provided in Embodiment 1 of the present invention;

[0038] Figure 2 This is a schematic diagram of the steel truss arch bridge newly constructed using the construction method of Example 1 of this invention;

[0039] Figure 3 This is a calculation and analysis model diagram of the old bridge for construction steps S1 to S5 of Embodiment 1 of the present invention;

[0040] Figure 4 This is a diagram showing the overall calculation and analysis results of the old bridge in construction steps S1 to S5 of Embodiment 1 of the present invention; wherein, in Figure (a), from top to bottom, are Mn(Min), rMn(Min), rMn(Max), Mn(Max), and in Figure (a), from top to bottom, are Sig-ALW(Max), Sig-TMAX(Max), Sig-TMAX(Min), and Sig-ALW(Min);

[0041] Figure 5 This is a partial analysis model diagram of the old bridge in construction steps S1 to S5 of Embodiment 1 of the present invention;

[0042] Figure 6 This is a partial analysis model diagram of the steel truss arch bridge in construction steps S1 to S5 of Embodiment 1 of the present invention;

[0043] Figure 7 This is a schematic diagram of construction steps S603~S609 of Embodiment 2 of the present invention;

[0044] Figure 8 This is a schematic diagram of construction steps S610~S611 in Embodiment 2 of the present invention;

[0045] Figure 9 This is a schematic diagram of construction step S71 in Embodiment 3 of the present invention;

[0046] Figure 10 This is a schematic diagram of construction step S72 in Embodiment 3 of the present invention;

[0047] Figure 11 This is a schematic diagram of construction steps S81~S82 of Embodiment 4 of the present invention;

[0048] Figure 12 This is a schematic diagram of construction steps S83~S84 of Embodiment 4 of the present invention;

[0049] Figure 13 This is a schematic diagram of construction step S91 in Embodiment 5 of the present invention;

[0050] Figure 14 This is a schematic diagram of construction step S92 in Embodiment 5 of the present invention;

[0051] Figure 15 This is a schematic diagram of construction step S101 in Embodiment 6 of the present invention;

[0052] Figure 16 This is a schematic diagram of construction step S102 in Embodiment 6 of the present invention;

[0053] Figure 17 This is a schematic diagram of construction step S103 in Embodiment 6 of the present invention. Detailed Implementation

[0054] To make the technical means, creative features, objectives and effects of this invention clearer and easier to understand, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0055] Example 1: Refer to Figures 1-6 This invention discloses a construction method for converting an existing bridge into a steel truss arch bridge, comprising the following steps:

[0056] S1 collects the bridge as-built drawings and bridge inspection reports of the old bridge, and assesses the load-bearing capacity reduction parameters of the old bridge due to the increase in service life;

[0057] S2 uses finite element analysis software to establish a joint model of the old bridge and the steel truss arch bridge, simulates the construction steps of S6~S9, the loading sequence of the steel truss arch bridge components, the changes in boundary conditions, and analyzes the deformation of the old bridge during the installation of the supports, the closure of the steel truss arch, and the closure of the tie beam in S6~S9.

[0058] Based on the analysis results of S2, S3 pre-determines the positions of the lower support, upper support, and bridge deck support so that the old bridge can meet the pre-determined stress requirements in steps S6 to S9.

[0059] For the complex structural nodes of the old bridge, S4 uses finite element analysis software to perform solid element analysis, and proposes control measures for the deformation of key structural parts based on the analysis results of S2, so as to ensure that the local stress of the old bridge meets the preset stress requirements.

[0060] S5 uses finite element analysis software to simulate the stress changes during the construction steps of S10 and the removal of the old bridge sections, so that the old bridge after the segment removal meets the preset stress requirements when installing the crossbeams.

[0061] After the S6 side span steel truss arch is closed, the lower support, side tie beam, upper support, and end segments of the main span steel truss arch are erected sequentially from bottom to top on the side of the side span steel truss arch closest to the main span; among them,

[0062] One stiffening rib is provided on the web of the segments of the side span steel truss arch and the main span steel truss arch, and one stiffening rib is provided on the top and bottom plates. Two stiffening ribs are provided on the web of the segments of the side tie beam and the middle tie beam, and one stiffening rib is provided on the top and bottom plates.

[0063] Approach bridges are installed at both ends of the old bridge deck in advance, then piles are driven and temporary supports are erected. Then, in the order from the lower chord of the arch rib to the upper chord of the arch rib, multiple segments of the side span steel truss arch are erected on the temporary supports to complete the closure of the side span steel truss arch.

[0064] A lower support is erected on the side of the side span steel truss arch close to the main span. Then, a side tie beam is erected on the top of the lower support on the side close to the old bridge deck. Then, an upper support is erected on the top of the side tie beam and the lower support on the side away from the old bridge deck. Finally, the end segments of the main span steel truss arch are erected on the upper support.

[0065] After erecting a bridge deck support system with cantilevered outwards on the old bridge deck, the S7 bridge uses these cantilevered outwards to support the segments of the central tie beam at the closure joint. The segments are then repositioned to complete the closure of the tie beam.

[0066] A bridge deck support with cantilevered outwards is erected on the old bridge deck. Multiple segments of the central tie beam are temporarily fixed by the steel wire ropes placed under the cantilevered outwards as hooks. This allows for segment adjustment and overall connection during the temporary fixing of the central tie beam and the side tie beam. After the tie beam is closed, the connection between the cantilevered outwards and the central tie beam is released.

[0067] S8 involves erecting the middle segment of the main span steel truss arch on the upper support and bridge deck support to complete the closure of the main span steel truss arch; among which,

[0068] Following the order from the side span to the middle span, the lower chords of the arch ribs of multiple middle segments of the main span steel truss arch are first erected symmetrically on the upper support and the bridge deck support, and then the upper chords of the arch ribs of multiple middle segments of the main span steel truss arch are erected symmetrically on the lower chords of the arch ribs to complete the closure of the main span steel truss arch.

[0069] S9 involved installing temporary wind braces, installing slings, dismantling the upper and deck supports, tensioning the slings, and dismantling the lower supports.

[0070] Multiple temporary wind braces are installed symmetrically between the main span steel truss arches on both sides of the arch bridge, in the order from the middle of the span to the side spans.

[0071] Install the slings, remove the upper support and bridge deck support, tension the slings three times, and remove the lower support.

[0072] S10 follows a sequence from the mid-span to the side spans, segmentally removing the old bridge deck and installing crossbeams, then installing the bridge deck system. Among these steps...

[0073] Steel rails are laid on the tie beam in advance, and a sliding trolley for transporting the crossbeam is installed on the steel rails;

[0074] First, the bridge deck beams and tie beams of the old bridge are connected by steel connecting rods. Then, the bridge deck of the old bridge is cut off in sections of 3m each, symmetrically, from the middle of the span to the side spans. After each section of the old bridge deck is cut, a crossbeam is transported and installed by a sliding trolley.

[0075] Example 2: Refer to Figure 7 and Figure 8 This invention discloses a construction method for converting an existing bridge into a steel truss arch bridge. The difference between this method and Example 1 is that S6 includes...

[0076] The S601 approach bridge will be installed with 9m steel plate girders. The steel plate girders will be manufactured and assembled in pairs. The maximum weight of the side and middle beams of the steel plate girders is 4.5t. A 30t truck crane will be used for lifting, with a rotation radius of 11m, a boom length of 17m, and a rated lifting capacity of 5.8t > 4.5t, which meets the lifting requirements. A steel trestle bridge will be erected for the approach bridge, and a temporary construction passage will be built to connect the entire site. After the approach bridge is installed, the bridge deck will be poured, and after the strength is guaranteed, the side span steel truss girders will be installed.

[0077] S602 piling, erecting temporary supports (supports 1~2).

[0078] The S603 side span steel truss arch GK01 arch rib lower chord and segment have a maximum weight of 54t. A 260t crane is used for single-machine lifting, with a rotation radius of 12m, a boom length of 18m, and a rated lifting capacity of 68t > 54t, which meets the lifting requirements. The crane outriggers are located at the position of the old bridge web, and the end crossbeam and one middle crossbeam are installed simultaneously. The piers have pre-embedded steel sections, which are welded to the tie rods to form a solid connection.

[0079] The S604 side span steel truss arch GK01 arch rib upper chord, segment weight 36.56t, was lifted using a single 260t crane with a rotation radius of 12m, boom length of 18m, and rated lifting capacity of 68t (greater than 36.56t), meeting the lifting requirements. The corresponding main bridge stress at this stage is a maximum of 7.7 N / mm². 2 The maximum pile reaction force is 37t;

[0080] The lower chord of the side span steel truss arch GK02, with a segment weight of 40.55t, was erected using a single 260t crane with a rotation radius of 10m, a boom length of 18m, and a rated lifting capacity of 81t > 40.55t, which met the hoisting requirements.

[0081] The S606 side span steel truss arch GK02 arch rib upper chord, segment weight 44.9t, was lifted using a single 260t crane with a rotation radius of 12m, boom length of 18m, and rated lifting capacity of 68t (greater than 44.9t), meeting the lifting requirements. The corresponding main bridge stress at this stage is a maximum of 7.7 N / mm². 2 , the maximum pile reaction force is 52.5t;

[0082] The S607 side span steel truss arch GK03 arch rib lower chord and segment weight is 49t. A 260t crane is used for single-machine lifting, with a rotation radius of 12m, a boom length of 18m, and a rated lifting capacity of 68t > 49t, which meets the lifting requirements.

[0083] The upper chord segment of the GK03 arch rib of the side span steel truss arch erected by S608 weighs 64t. A single 260t crane is used for lifting, with a rotation radius of 12m, a boom length of 22.5m, and a rated lifting capacity of 65t > 64t, which meets the lifting requirements.

[0084] S609 erects a lower support (support 3~4) on the side of the steel truss arch near the main span, then erects a side tie beam GK05 on the top of the lower support on the side of the old bridge deck, and then erects an upper support (support 3~4) on the top of the side tie beam GK05 and the lower support on the side of the lower support away from the old bridge deck.

[0085] The S610 main span steel truss arch GK04 arch rib lower chord and segment weight is 40.3t; a 260t crane is used for single-machine lifting; the rotation radius is 12m, the boom length is 22.5m, and the rated lifting capacity is 65t>40.3t, which meets the lifting requirements;

[0086] The S611 main span steel truss arch GK04 arch rib upper chord, segment weight 40.6t, was lifted using a single 260t crane with a rotation radius of 12m, boom length of 27m, and rated lifting capacity of 66.2t > 40.6t, meeting the lifting requirements; the corresponding main bridge stress was: maximum stress 92.5N / mm². 2 The maximum pile reaction force is 60.1t; the maximum displacement is 78.8mm; and the minimum stability coefficient is 18.

[0087] Example 3: Reference Figure 9 and Figure 10 This invention discloses a construction method for converting an existing bridge into a steel truss arch bridge. The difference between this method and Example 1 is that S7 includes...

[0088] S71 erects a bridge deck support (support 5) with cantilevered arms on the old bridge deck. The lower steel wire rope of the cantilevered arms is used as a hook to temporarily fix multiple segments of the central tie beam, so as to adjust the segment position and connect the whole during the temporary fixing of the central tie beam and the side tie beam.

[0089] The S72 intermediate girder GK05 weighs 90t and is installed in 3 segments, with a maximum lifting capacity of 30t. During installation, lifting points are provided using the bridge's support structure. A single 260t crane is used, with a rotation radius of 22m, a boom length of 40.4m, and a rated lifting capacity of 32.5m (greater than 30t), meeting the lifting requirements. The corresponding stress on the main bridge at this stage is a maximum stress of 11.5 N / mm². 2 The maximum pile reaction force is 55.3t.

[0090] After the tie beam is closed, S73 disconnects the connection between the cantilever and the central tie beam.

[0091] Example 4: Reference Figure 11 and Figure 12 This invention discloses a construction method for converting an existing bridge into a steel truss arch bridge. The difference between this method and Example 1 is that S8 includes...

[0092] The main span steel truss arch GK06 of S81 was erected. The lower chord segment of the arch rib weighs 39.5 tons. A single 260-ton crane was used for lifting, with a rotation radius of 12 meters, a boom length of 31.4 meters, and a rated lifting capacity of 66 tons, which is greater than 39.5 tons, meeting the lifting requirements. The corresponding stress on the main bridge at this stage is a maximum stress of 16.1 N / mm². 2 The maximum pile reaction force is 55.0t;

[0093] The lower chord of the S82 arch rib is formed and begins to bear load: The main span steel truss arch GK07 is erected, with a segment weight of 49.37 kg / m². A 260t double-crane platform crane is used, with each crane capable of bearing 24.68t; the rotation radius is 12m, and the boom length is 35.9m. The rated lifting capacity is 50.6t * 0.8 = 40.48t > 24.68t; the corresponding stress on the main bridge at this stage is a maximum stress of 16.3 N / mm². 2 The maximum pile reaction force is 55.3t; the self-weight of a single bridge support + tie beam + superstructure pressure = 65t;

[0094] The main span steel truss arch GK08 ​​was erected on S83. The upper chord segment of the arch rib weighs 39.4t. A single 260t crane was used for lifting, with a rotation radius of 12m, a boom length of 35.5m, and a rated lifting capacity of 65t, which is greater than 39.4t, meeting the lifting requirements. The corresponding stress on the main bridge at this stage is a maximum stress of 18.0 N / mm². 2 The maximum pile reaction force is 55.2t;

[0095] The S84 main span steel truss arch GK09 was erected. The upper chord segment of the arch rib weighs 39.4t. A dual-crane 260t crane was used, with each crane capable of bearing 19.7t. The rotation radius is 16m, the boom length is 40.4m, and the rated lifting capacity is 47.8t, which is greater than 19.7t, meeting the lifting requirements. The corresponding stress on the main bridge at this stage is a maximum stress of 19.4 N / mm². 2 The maximum pile reaction force is 55.3t.

[0096] Example 5: Refer to Figure 13 and Figure 14 This invention discloses a construction method for converting an existing bridge into a steel truss arch bridge. The difference between this method and Example 1 is that S9 includes...

[0097] The S91 jacks on the bridge deck support were removed, and the weight of the steel truss arch ribs was borne entirely by the arch ribs themselves. Temporary wind bracing was installed symmetrically from the mid-span to both sides. The maximum weight of the temporary wind bracing was 15t, and a 260t crane with two cranes was used. The rotation radius was 24m, the boom length was 44.9m, and the rated lifting capacity was 25.9t > 15t.

[0098] S92 installation of slings, removal of upper supports and bridge deck supports, tensioning of slings three times, and removal of lower supports.

[0099] Example 6: Refer to Figure 15 , Figure 16 and Figure 17 This invention discloses a construction method for converting an existing bridge into a steel truss arch bridge. The difference between this method and Example 1 is that S10 includes...

[0100] S101 pre-lays rails on the tie beam and installs a sliding trolley on the rails for transporting the crossbeam;

[0101] S102 first uses steel connecting rods to connect the bridge deck beams and tie beams of the old bridge. Then, following the order from the middle of the span to the side spans, the bridge deck of the old bridge is cut off in sections of 3m each, symmetrically in sequence. After each section of the old bridge deck is cut, a crossbeam is transported and installed using a sliding trolley. The maximum weight of the crossbeam is 25t. A 100t crane with a rotation radius of 9m, a boom length of 12m, and a rated lifting capacity of 27t is used to meet the lifting requirements.

[0102] S103 bridge deck system installation.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A construction method for converting an existing bridge into a steel truss arch bridge, characterized in that: Includes the following steps, S1 collects the bridge as-built drawings and bridge inspection reports of the old bridge, and assesses the load-bearing capacity reduction parameters of the old bridge due to the increase in service life; S2 uses finite element analysis software to establish a joint model of the old bridge and the steel truss arch bridge, simulates the construction steps S6~S9 below, the loading sequence of the steel truss arch bridge components, the changes in boundary conditions, and analyzes the deformation of the old bridge during the support installation, steel truss arch closure, and tie beam closure in S6~S9 below. Based on the analysis results of S2, S3 presets the positions of the lower support, upper support, and bridge deck support so that the old bridge can meet the preset stress requirements in the following steps S6 to S9. For the complex structural nodes of the old bridge, S4 uses finite element analysis software to perform solid element analysis, and proposes control measures for the deformation of key structural parts based on the analysis results of S2, so as to ensure that the local stress of the old bridge meets the preset stress requirements. S5 uses finite element analysis software to simulate the stress changes during the construction steps of S10 and the removal of the old bridge sections, so that the old bridge after the segment removal meets the preset stress requirements when installing the crossbeams. After the S6 side span steel truss arch is closed, the lower support, side tie beam, upper support, and end segment of the main span steel truss arch are erected sequentially from bottom to top on the side of the side span steel truss arch near the main span. After S7 erected a bridge deck support with cantilevered arms on the old bridge deck, the segments of the tie beam were erected to the closure joint through the cantilevered arms, and the segments were adjusted to complete the closure of the tie beam. S8 erects the middle segment of the main span steel truss arch on the upper support and the bridge deck support to complete the closure of the main span steel truss arch; Install temporary wind braces on S9, install slings, remove the upper support and bridge deck support, tension the slings, and remove the lower support; S10 follows the sequence from the middle span to the side spans, segmentally cutting off the old bridge deck and installing crossbeams, and installing the bridge deck system.

2. The construction method for reconstructing a steel truss arch bridge using an existing bridge according to claim 1, characterized in that: In S6, approach bridges are pre-installed at both ends of the old bridge deck, then piles are driven and temporary supports are erected. Then, in the order from the lower chord of the arch rib to the upper chord of the arch rib, multiple segments of the side span steel truss arch are erected on the temporary supports to complete the closure of the side span steel truss arch.

3. The construction method for reconstructing a steel truss arch bridge using an existing bridge according to claim 1, characterized in that: In S6, the side tie beam is erected on the top of the lower support on the side closer to the old bridge deck, and the lower support is erected on the top of the side tie beam and the lower support on the side away from the old bridge deck.

4. The construction method for reconstructing a steel truss arch bridge using an existing bridge according to claim 1, characterized in that: In S7, multiple segments of the central tie beam are temporarily fixed by the lower steel wire rope of the cantilever as a hook, so as to adjust the segment position and connect the whole during the temporary fixing process of the central tie beam and the side tie beam. After the tie beam is closed, the connection between the cantilever and the central tie beam is released.

5. A construction method for reconstructing a steel truss arch bridge using an existing bridge according to claim 1, characterized in that: In S8, following the order from the side span to the middle span, the lower chords of the arch ribs of multiple middle segments of the main span steel truss arch are first erected symmetrically on the upper support and the bridge deck support, and then the upper chords of the arch ribs of multiple middle segments of the main span steel truss arch are erected symmetrically on the lower chords of the arch ribs, thus completing the closure of the main span steel truss arch.

6. The construction method for reconstructing a steel truss arch bridge using an existing bridge according to claim 1, characterized in that: In S6~S8, a stiffening rib is pre-installed on the web of the segments of the side span steel truss arch and the main span steel truss arch, and a stiffening rib is installed on the top and bottom plates. Two stiffening ribs are installed on the web of the segments of the side tie beam and the middle tie beam, and a stiffening rib is installed on the top and bottom plates.

7. A construction method for reconstructing a steel truss arch bridge using an existing bridge according to claim 1, characterized in that: In S9, multiple temporary wind braces are symmetrically installed between the main span steel truss arches on both sides of the arch bridge in sequence from the middle span to the side spans.

8. A construction method for reconstructing a steel truss arch bridge using an existing bridge according to claim 1, characterized in that: In S10, steel rails are laid on the tie beam in advance, and a sliding trolley for transporting the crossbeam is installed on the steel rails.

9. A construction method for reconstructing a steel truss arch bridge using an existing bridge according to claim 1, characterized in that: In S10, the bridge deck beams and tie beams of the old bridge are pre-connected with steel connecting rods, and then the bridge deck of the old bridge is cut off segment by segment.

10. A construction method for reconstructing a steel truss arch bridge using an existing bridge according to claim 1, characterized in that: In S10, the old bridge deck is cut off in segments of 2-4m each, symmetrically, from the middle of the span to the side spans. After each segment of the old bridge deck is cut off, a crossbeam is installed.

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