A construction method for reverse installation of a double-deck steel truss arch bridge

Abstract

The invention discloses a construction method for reverse installation of a double-deck steel truss arch bridge, which includes processes such as middle part erection, lower chord assembly and extension, middle part panel installation, upper chord assembly and extension, panel assembly and extension, erection of main arch supports, segmented installation of the main arch, removal of gantry cranes, installation of suspension cables, and removal of under-arch supports. Based on the principle of reasonable segmentation and scientific calculation, and on the premise of limited space and without increasing the number of temporary supports for steel trusses, through the cooperation of gantry cranes and truck cranes, each component is analyzed and marked in segments, so that the hoisting, transportation, and installation sequence of each component during installation do not need to completely follow the traditional method of one by one section and layer by layer. Thus, multiple work sections can be constructed simultaneously, that is, the processes of installation, extension, and fixation of each component are carried out alternately, significantly shortening the construction period and improving the construction efficiency while ensuring the quality.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge engineering, and particularly relates to a construction method for reverse installation of a double-deck steel truss arch bridge. Background Art

[0002] With the substantial increase in traffic volume, especially the popularization of high-speed railway lines in China, bridges not only have to cope with the operation of highway vehicles but also meet the passage of trains. Ordinary traditional separated highway-railway bridges (such as the Nanjing Yangtze River Bridge and the Wuhan Yangtze River Bridge) cannot meet the operation requirements. In particular, traditional bridges take a long time to build and are suitable for river bridges with extremely long spans. Especially, railway and highway are often completely separated, which does not meet the requirements of railway construction and highway transportation in China.

[0003] Therefore, double-deck steel truss arch bridges came into being. Steel truss arch bridges are usually installed by pre-assembly and hoisting, and are connected by welding, bolts, etc. The steel truss adopts integral joint members, which requires high hole-making precision for connection hole groups in all directions. The pre-hole method can make holes in batches during the production of unit components, with high efficiency, and is suitable for components with small welding deformation, strong deformation regularity or a section of hole group connection. The post-hole method makes holes after welding is completed and can be used for components with high precision requirements. The connection between members of large-span steel truss girders is in bolted form, and it is difficult to control the construction line shape. The steel box arch has high requirements for line shape control accuracy. When assembling on site, it is necessary to ensure that the as-built line shape meets the design line shape requirements at the same time, which improves the construction precision requirements and construction difficulty.

[0004] However, most of the existing steel truss arch bridges are constructed step by step, using a construction method from the lower layer to the upper layer section by section. However, the component sizes and weights of each section of the steel truss are different, the forces affect each other, and the installation equipment required is also different. This results in the need for various equipment to constantly go up and down the bridge during installation, which is actually very inconvenient.

[0005] Based on the above analysis, the present invention attempts to propose a construction method in which the component segments can be installed out of sequence through the segmented analysis of steel truss components, so as to strive for the distribution and simultaneous construction of each segment, and while ensuring quality, greatly reduce the construction period and improve construction efficiency. Summary of the Invention

[0006] The purpose of the present invention is to solve the deficiencies existing in the prior art, and to propose a construction method for reverse installation of a double-deck steel truss arch bridge.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A construction method for reverse installation of a double-deck steel truss arch bridge includes the following overall steps:

[0009] The first step: Install the gantry crane and the hoisting support structure

[0010] Two gantry cranes are arranged in a single layout, and a total of 4 gantry cranes are put into use for the whole bridge; the span of the gantry crane on the left side is 36.5 m, and the lifting height is 21 m; the span of the gantry crane on the right side is 26 m, and the lifting height is 23 m; the track foundation of the gantry crane adopts a concrete spread foundation, and the part where the foundation bearing capacity does not meet the requirements is excavated and backfilled for treatment;

[0011] Step 2: Install the steel trusses of the gantry crane on the left and right sides

[0012] The main components of the steel truss include upper chord members, lower chord members and web members. Before the installation of the steel truss, the following two processes need to be carried out first:

[0013] 1) Build the temporary pier system structure of the steel truss:

[0014] Viewed from the bridge width direction, there are a total of four columns of the temporary pier system of the steel truss. Each column has equally spaced temporary piers. A single pier is mainly a three-dimensional steel pier connected by φ630*10mm steel pipes and [14a channel steels. The pier height is 2 - 3 m; 400*800mm steel plates with different plate thicknesses are set at the top of the pier as adjusting steel pipes; at the same time, steel corbels are set on the side of each set of temporary pier steel pipes, and 25t hydraulic jacks can be placed above the corbels to adjust the height of the steel truss girder; for the support at the mid-span position, an additional steel pipe is added and set as a fixed support, and welding and locking are carried out after hoisting;

[0015] 2) Area division:

[0016] Viewed from the bridge width direction, there are a total of four columns of truss structures. The outer sides are two groups of side trusses. Each single side truss surface is divided into 17 upper chord segments, 16 lower chord segments, and 33 web members; the side arch ribs are divided into 10 segments; the outer sides are two groups of middle trusses. Each single middle truss surface is divided into 17 upper chord segments, 16 lower chord segments, and 33 web members; the middle arch ribs are divided into 10 segments;

[0017] Step 3: Use a truck crane to install the upper and lower deck systems and the cantilever system structures between the left and right sides

[0018] The connection structure between the deck system and the chord members is mainly composed of bridge deck plates, cross beams, U ribs, plate ribs, etc. The deck system structure is divided into a municipal deck system, a track deck system, and a pipeline deck system;

[0019] The cantilever system structure includes two forms: the lower sidewalk cantilever and the upper maintenance passage cantilever;

[0020] Step 4: Use a truck crane to go onto the bridge to install the arch ribs and wind braces

[0021] The arch rib adopts a box section, with an outer height of 1800 mm, an outer width of 1100 mm, and a plate thickness of 36 - 50 mm. The arch ribs are connected by full welding, and the inner stiffeners are connected by high-strength bolts.

[0022] Step 5: Tension the suspender and remove the support

[0023] The suspenders are flexible suspenders with a standard spacing of 9m; the upper end is anchored at the bottom of the arch rib and is the tensioning end; the lower end is anchored at the upper chord node and is the anchoring end.

[0024] The core idea of the installation of the present invention lies in that in the above construction method for reverse installation of a double-layer steel truss arch bridge, the components in the second to fifth steps have a staggered installation process of cross-installation during the construction process, including the following specific processes:

[0025] ① Middle part construction: Use two sets of gantry cranes arranged horizontally. On two sets of adjacent steel truss temporary piers along the length direction in the middle of the bridge, construct the lower chord, including two side truss beam lower chords and two middle truss beam lower chords; Move four sets of gantry cranes and extend and construct another set of lower chords at both ends of the already constructed lower chords. At this point, each row of truss structures already has 6 lower chords; Use two sets of gantry cranes arranged longitudinally. On one row of side truss and one row of middle truss that have been constructed, install the lower-layer municipal bridge deck, and then install the sidewalk slabs on the left side. This step can be carried out alternately according to the installation progress of the lower chords and web members; On the upper surface of the already constructed lower chords, install the main truss web members, and install the upper chords on the main truss web members, including two rows of side truss beam upper chords and two rows of middle truss beam upper chords; Install the upper-layer municipal bridge deck on the already constructed upper chords. This step can be carried out alternately according to the installation progress of the upper chords.

[0026] ② Lower chord assembly and extension: At both ends of the already constructed lower chords, carry out assembly and extension construction simultaneously, install ordinary lower chords, install bearing lower chords at both ends of the ordinary lower chords, install the bridge deck of the lower-layer end cross beam on the bearing lower chords and their adjacent ordinary lower chords, and continue the assembly and extension construction with the lower-layer municipal bridge deck constructed in step ①, and install all the lower-layer municipal bridge decks and the sidewalk slabs on the left side. This step can be carried out alternately according to the installation progress of the lower chords and web members.

[0027] ③ Middle part panel installation: Install web members. Use a truck crane to install the pipe bridge deck of the lower-layer pipe bridge deck system on 6 lower chords in the middle along the length direction of the two rows of middle trusses, and immediately install the track bridge deck of the upper-layer track bridge deck system directly above it.

[0028] ④ Upper chord assembly and extension: Through the gantry crane, carry out assembly and extension construction simultaneously at both ends of the already constructed upper chords, install the suspender upper chords, use a truck crane to construct the bearing upper chords on the web members at both ends, and install the arch beam connection section between the suspender upper chords and the bearing upper chords. The upper chords include the bearing upper chords, the arch beam connection section, and the suspender upper chords. At this point, the main truss construction is completed.

[0029] ⑤ Panel assembly and extension: Use a car crane to install the bridge deck of the upper end crossbeam on the upper chord of the support, and continue the assembly and extension construction between the upper municipal bridge deck built in step ①, and install all the upper municipal bridge decks and the upper maintenance channel panels. This step can be staggered according to the installation progress of the lower chord and web bars; at both ends of the bridge length direction, use a gantry crane to install the crossbeam of the lower pipeline bridge system, and install the lower pipeline bridge deck and the upper track bridge deck at the end thereon, and continue the assembly and extension construction between the pipeline bridge deck and the track bridge deck built in step ③, and install all the lower pipeline bridge decks and most of the upper track bridge decks. Leave gaps at both ends of the upper track bridge deck to install the thrust device of the car crane after getting on the bridge;

[0030] ⑥Build the main arch support: Use a 125t gantry crane on each side to lift two 50t truck cranes to the upper deck, and install the main arch support using the truck crane;

[0031] The temporary pier system structure of the main arch support is as follows: a single arch rib support is mainly composed of φ377*8mm steel pipe channel steel [14 connected to form a three-dimensional steel pier, with a pier height of 4-27m; a 400*300 H-shaped steel adjustment pad is set on the top of the pier, and a steel plate is placed under the support steel pipe to increase the contact area with the bridge deck top plate to avoid deformation;

[0032] ⑦ Main arch segment installation: Install the main arch at the end of the arch-beam joint section, and install wind braces between adjacent main arches in the left and right sections. Use a truck crane to install each section of the main arch from bottom to top. After each section of the main arch is installed, the wind brace of that section is installed;

[0033] ⑧ Gantry crane removal: Use the gantry crane to hoist the remaining components to the designated position of the upper deck of the main bridge, and use the truck crane to remove the gantry crane; remove the redundant parts of the deck, install the lower sidewalk slab of the right span, and install all the lower pipeline decks and upper track decks. At this point, the steel truss structure is completed;

[0034] ⑨ Installation of slings, that is, installing slings between the upper chord of the suspender and the lugs carried by the main arch, making each sling vertical, removing the main arch support, and paving the bridge deck;

[0035] ⑩ The support under the arch was removed, the entire bridge was painted, the cables were tensioned for the second time, and the entire bridge was completed.

[0036] Preferably, the municipal bridge deck is composed of a crossbeam + a bridge deck, which is divided horizontally, has a length of 4.5m, a crossbeam spacing of 3m, an inverted I-section, the web of the crossbeam is bolted to the chord, and the top plate and wing plate are welded; the bridge deck adopts U-ribs, and the U-ribs are butt-jointed by welding, and are welded to the bridge deck with 80% single-sided welding.

[0037] Preferably, the rail deck slab in the track bridge deck system adopts a (14 + 3) mm composite steel plate, which is transversely divided with a length of 4.5 m and a crossbeam spacing of 3 m. It adopts an inverted T-shaped cross-section, with the crossbeam web bolted to the chord and the top slab and wing plate welded. The track bridge deck uses 4 small longitudinal beams with an inverted T-shaped cross-section, and the crossbeams are perforated for the longitudinal beams to pass through. The track bridge deck uses U ribs, and the butt joints of the U ribs are welded, and double-sided welding with 80% penetration depth is used for the connection with the bridge deck.

[0038] Preferably, the pipe bridge deck system consists of crossbeams + bridge deck + longitudinal beams, which is longitudinally divided with a crossbeam spacing of 9 m. It adopts an inverted I-shaped cross-section, with the crossbeam web bolted to the chord and the top slab and wing plate welded. The top slab uses flat steel and is bolted to the I-shaped crossbeam. The longitudinal beams adopt an inverted T-shaped cross-section and are bolted to the I-shaped crossbeam.

[0039] Preferably, the web of the sidewalk cantilever is bolted to the lower chord of the side truss, the top slab and the cantilever wing plate are welded, and the inspection path cantilever is welded to the upper chord of the side truss.

[0040] Preferably, the web of the sidewalk cantilever is bolted to the lower chord of the side truss, the top slab and the cantilever wing plate are welded, and the inspection path cantilever is welded to the upper chord of the side truss.

[0041] Preferably, the upper chord adopts a box-shaped cross-section with an upper flange plate with extended limbs. The inner height of the side truss is 1400 mm, the inner width is 1000 mm, and the plate thickness is 24 - 44 mm; the inner height of the middle truss is 1650 mm, the inner width is 1000 mm, and the plate thickness is 24 - 44 mm; the upper flange of the upper chord is welded with full penetration, and the connection method of equal-strength butt joint with high-strength bolts (M30 high-strength bolts) is used for the other three sides.

[0042] Preferably, the lower chord adopts a box-shaped cross-section with an upper flange plate with extended limbs. The inner height of the side truss is 1400 mm, the inner width is 1000 mm, and the plate thickness is 32 - 44 mm; the inner height of the middle truss is 1650 mm, the inner width is 1000 mm, and the plate thickness is 32 - 44 mm; the upper flange of the upper chord is welded with full penetration, and the connection method of equal-strength butt joint with high-strength bolts (M30 high-strength bolts) is used for the other three sides.

[0043] Preferably, the web members have two forms: box-shaped web members and H-shaped web members. The cross-section of the box-shaped straight web member has an inner height of 1000 mm, an inner width of 1000 mm, and a plate thickness of 32 mm, and all four sides are bolted; the cross-section of the box-shaped diagonal web member has an inner height of 1800 mm, an inner width of 1000 mm, and a plate thickness of 50 mm; the cross-section of the H-shaped web has an inner height of 1000 mm, an inner width of 700 mm, and a plate thickness of 28 - 32 mm; the diagonal web member is connected to the main truss node by internal inserted high-strength bolts (M30 high-strength bolts).

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] 1. The present invention breaks away from the traditional step-by-step construction method for bridges. By dividing each component of the steel truss (mainly including the division of side trusses, middle trusses, and deck systems), and numbering and evaluating the lifting weights of each component after division, the number of components that can be constructed simultaneously is determined.

[0046] Furthermore, the present invention adopts a combined installation line of gantry cranes and truck cranes. The gantry crane can bear part of the weight of the components. After the upper deck slab is built on-site, the truck crane can directly drive onto the bridge for the auxiliary installation of the main arch support, arch ribs, wind braces, and suspension rods.

[0047] Furthermore, during the construction process of the present invention, in order to facilitate the access of construction workers and related equipment to and from the bridge, and at the same time to reduce the influence of the construction space and the total weight of the construction steel truss, only the lower-layer municipal deck slab and the left-side sidewalk slab are installed before the installation of the arch ribs in this construction method. After removing the gantry crane and the redundant components of the deck slab, the lower-layer right-side sidewalk slab is installed, and all the lower-layer pipe deck slabs and upper-layer track deck slabs are additionally installed. Only then is the construction of the steel truss structure officially completed, effectively reducing the stress on the temporary support of the steel truss during installation, thereby further increasing the possibility of constructing multiple components.

[0048] 2. Supported by the above operations, a construction method process of reverse installation of each component is finally formed: ① First, install the lower chord, lower-layer deck slab (including the left-side sidewalk slab), web members, upper chord, and upper-layer deck slab (including the inspection passage slab) in the middle of the bridge; ② At both ends of the middle lower chord, carry out assembly and elongation construction simultaneously, including the construction of the crossbeam between the two rows of lower chords and the upper deck slab thereon; ③ Install the web members, and install the pipe deck slab and track deck slab in the middle of the bridge; ④ At both ends of the upper chord in the middle, carry out assembly and elongation construction simultaneously to build the main deck truss; ⑤ Panel assembly and elongation: Construct from the middle to both ends to install the upper-layer municipal deck slab and upper-layer inspection passage slab; construct from both ends to the middle simultaneously to install the pipe deck slab and track deck slab; and most of the components in the above ① - ⑤ can be carried out alternately according to the installation progress of the lower chord and web members; ⑥ Build the main arch support; ⑦ Segmented installation of the main arch: The main arch and wind braces are constructed in segments from bottom to top; ⑧ Remove the gantry crane, and remove the redundant components of the deck slab, install the lower-layer right-side sidewalk slab, and additionally install all the lower-layer pipe deck slabs and upper-layer track deck slabs. Only then is the construction of the steel truss structure completed; ⑨ Install the suspension cables, remove the main arch support, and carry out bridge deck paving construction; ⑩ Remove the under-arch support, carry out full-bridge painting construction, secondary tensioning of the suspension cables, and the whole bridge is completed.

[0049] 3. In summary, based on the principles of reasonable segmentation and scientific calculation, the present invention, under the premise of limited space and without increasing the number of temporary steel truss supports, through the cooperation of gantry cranes and truck cranes, analyzes and marks each component in segments, so that the hoisting, transportation and installation sequence of each component during installation do not need to fully follow the traditional method of constructing section by section and layer by layer. Therefore, multi-section construction can be carried out. At most, 6 segments of components are under construction simultaneously on site (respectively, the laying of cross beams at both ends of the bridge, the assembly and extension of the upper municipal bridge deck, and the hoisting and transportation of the two ends of the pipe bridge deck in the middle of the bridge to the construction site), that is, the installation, extension and fixation processes of each component are carried out alternately, significantly shortening the construction period and improving the construction efficiency while ensuring the quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is the bridge structure diagram during the installation of the arch rib in the construction method of the present invention; Figure 2 It is the cross-sectional view of the overall bridge after the installation of the construction method of the present invention is completed; Figure 3 It is the longitudinal view of the overall bridge after the installation of the construction method of the present invention is completed; Figure 4 It is the installation structure diagram of the gantry crane during the construction process of the present invention; Figure 5 It is the installation structure diagram of the steel truss during the construction process of the present invention; Figure 6 It is the installation structure diagram of the bridge deck system during the construction process of the present invention; Figure 7 It is the installation structure diagram of the arch rib and wind bracing during the construction process of the present invention; Figure 8 It is the structure diagram of the whole bridge after the removal of the support during the construction process of the present invention.

[0051] In the figures: 1. Gantry crane, 2. Truck crane, 3. Temporary steel truss pier, 4. Main arch support, 5. Arch rib, 6. Wind bracing, 7. Suspender, 8. Lower chord of side truss beam, 9. Lower chord of middle truss beam, 10. Lower layer municipal bridge deck, 11. Lower layer pipe bridge deck, 12. Lower layer sidewalk slab, 13. Web member, 14. Upper chord of side truss beam, 15. Upper chord of middle truss beam, 16. Upper layer municipal bridge deck, 17. Upper layer track bridge deck, 18. Upper layer inspection passage slab, 101. Ordinary lower chord rod, 102. Support lower chord rod, 201. Suspender upper chord rod, 202. Support upper chord rod, 203. Arch beam joint section. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0053] Introduction to the main bridge structure of the present invention: Refer to Figure 1-2, this project is the combined construction of a municipal bridge and a railway bridge across the canal, adopting a 153m-span double-deck steel truss arch bridge scheme: the upper bridge is 47.5m wide, with 6 lanes for urban two-way traffic + subway; the lower bridge is 56m wide, with 4 lanes for two-way traffic + slow traffic system.

[0054] Its steel truss structure is as Figure 3 shown, including the following components:

[0055] (I) Upper chord

[0056] The upper chord adopts a box section with an extended limb on the upper flange. The inner height of the side truss is 1400mm, the inner width is 1000mm, and the plate thickness is 24 - 44mm. The inner height of the middle truss is 1650mm, the inner width is 1000mm, and the plate thickness is 24 - 44mm; the upper flange of the upper chord is welded by full penetration, and the other three sides are connected by high-strength bolts (M30 high-strength bolts) with equal strength for butt joint.

[0057] (II) Lower chord

[0058] The lower chord adopts a box section with an extended limb on the upper flange. The inner height of the side truss is 1400mm, the inner width is 1000mm, and the plate thickness is 32 - 44mm. The inner height of the middle truss is 1650mm, the inner width is 1000mm, and the plate thickness is 32 - 44mm; the upper flange of the upper chord is welded by full penetration, and the other three sides are connected by high-strength bolts (M30 high-strength bolts) with equal strength for butt joint.

[0059] (III) Web members

[0060] The web members have two forms: box web members and H-shaped web members. The cross-section of the box-shaped straight web member has an inner height of 1000mm, an inner width of 1000mm, and a plate thickness of 32mm, and all four sides are bolted; the cross-section of the box-shaped inclined web member has an inner height of 1800mm, an inner width of 1000mm, and a plate thickness of 50mm; the cross-section of the H-shaped web has an inner height of 1000mm, an inner width of 700mm, and a plate thickness of 28 - 32mm; the inclined web member is connected to the main truss node by internal inserted high-strength bolts (M30 high-strength bolts).

[0061] (IV) Arch rib structure

[0062] The arch rib adopts a box section, with an outer height of 1800mm, an outer width of 1100mm, and a plate thickness of 36 - 50mm. The arch rib is connected by full welding, and the inner stiffening is connected by high-strength bolts;

[0063] (V) Suspender

[0064] The suspender adopts a flexible suspender, with a standard spacing of 9m. The upper end is anchored at the bottom of the arch rib, which is the tension end, and the lower end is anchored at the upper chord node, which is the anchorage end.

[0065] Its bridge deck system structure: The steel bridge deck system is connected to the chord members and consists of bridge deck panels, cross beams, U-ribs, plate ribs, etc. The steel bridge deck system is divided into municipal bridge deck systems, railway bridge deck systems, and pipeline bridge deck systems.

[0066] (1) Municipal bridge deck system

[0067] The municipal bridge deck system consists of cross beams + bridge deck panels. It is divided transversely with a length of 4.5 m. The cross beam spacing is 3 m, and the inverted I-shaped section is adopted. The web of the cross beam is bolted to the chord member, and the top plate and flange are welded. The bridge deck panel uses U-ribs, and the butt joints of the U-ribs are welded, and the single-sided welding with 80% penetration depth is used for connection with the bridge deck panel.

[0068] (2) Railway bridge deck system

[0069] The top plate of the railway bridge deck uses a (14 + 3) mm composite steel plate. It is divided transversely with a length of 4.5 m. The cross beam spacing is 3 m, and the inverted T-shaped section is adopted. The web of the cross beam is bolted to the chord member, and the top plate and flange are welded. The railway bridge deck panel uses 4 small longitudinal beams with an inverted T-shaped section, and the longitudinal beams pass through the cross beams with holes in the cross beams. The railway bridge deck panel uses U-ribs, and the butt joints of the U-ribs are welded, and the double-sided welding with 80% penetration depth is used for connection with the bridge deck panel.

[0070] (3) Pipeline bridge deck system

[0071] The pipeline bridge deck system consists of cross beams + bridge deck panels + longitudinal beams. It is divided longitudinally. The cross beam spacing is 9 m, and the inverted I-shaped section is adopted. The web of the cross beam is bolted to the chord member, and the top plate and flange are welded. The top plate uses flat steel and is bolted to the I-shaped cross beam. The longitudinal beam uses an inverted T-shaped section and is bolted to the I-shaped cross beam.

[0072] Its cantilever system structure:

[0073] There are two forms of the cantilever structure: the lower sidewalk cantilever and the upper inspection passage cantilever. The web of the sidewalk cantilever is bolted to the lower chord of the side truss, and the top plate and the flange of the cantilever beam are welded. The inspection passage cantilever is welded to the upper chord of the side truss.

[0074] Engineering quantity statistical table

[0075] The main structure material of the whole bridge all adopts Q345qD. For the inner node plates of the side trusses, the middle truss node plates, the upper and lower anchorage points of the suspenders and the corresponding top and bottom plates of the arch ribs, truss members, and the joints of the wind bracings and the arch ribs, the performance requirements of the web steel plates inside the arch ribs should be Z35 steel with anti-laminar tearing Z-direction performance.

[0076] The bridge deck panels in the railway bridge deck system area adopt (14 + 3 mm) stainless steel composite plates. The base layer of the composite plate adopts Q345qD, and the cladding layer adopts stainless steel with the material of O22Cr17Ni12Mo2 (316L).

[0077] Segmentation:

[0078] (1) Segmentation of side trusses

[0079] A single side truss plane is divided into 17 upper chord segments, 16 lower chord segments, and 33 web members; the side arch rib is divided into 10 segments.

[0080] (2) Segmentation of middle trusses

[0081] A single middle truss plane is divided into 17 upper chord segments, 16 lower chord segments, and 33 web members; the middle arch rib is divided into 10 segments.

[0082] (3) Segmentation of bridge deck systems

[0083] The municipal bridge deck system is transversely divided, with a length of about 4.5 m and a width of 12 m.

[0084] The track bridge deck system is transversely divided, with a length of about 4.5 m and a width of 12 m.

[0085] The pipeline bridge deck system is longitudinally divided, with a length of about 9 m, a width of about 4 m, and the transverse width is divided into 3 segments.

[0086] The numbers and lifting weights of each component after the segmentation of the present invention are as follows in the table:

[0087]

[0088]

[0089]

[0090]

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097] The overall installation idea of the present invention: The steel truss and the bridge deck system are installed with the cooperation of 4 125-ton gantry cranes and truck cranes. After the installation of a single-span truss is completed, the truck crane is used to install the bridge deck system between the left and right spans and connect them into an integral whole. Finally, the truck crane is used to install the arch rib on the bridge.

[0098] The present invention includes the following main steps:

[0099] Step 1: Install the gantry crane and the lifting support structure, such as Figure 4 Shown

[0100] Two gantry cranes are arranged on each span, and a total of four gantry cranes are deployed on the entire bridge; the span of the left gantry crane is 36.5m, and the lifting height is 21m; the span of the right gantry crane is 26m, and the lifting height is 23m; the gantry crane track foundation adopts a concrete expansion foundation, and the part that does not meet the bearing capacity requirements is excavated and replaced;

[0101] Step 2: Install the left and right steel trusses on the gantry crane. Figure 5 As shown;

[0102] Step 3: Install the upper and lower bridge deck systems and cantilever arm systems between the left and right sides of the truck crane, such as Figure 6 As shown;

[0103] Step 4: Install the arch ribs and wind bracing by crane. Figure 7 As shown;

[0104] Step 5: Tension the suspender and remove the bracket, such as Figure 8 shown.

[0105] Analysis of the key and difficult points of this project:

[0106] (1) The steel truss members are bolted together, making it difficult to control the construction line shape.

[0107] Construction countermeasures: After the rods are manufactured in the factory, a trial assembly process is adopted, and the bolt holes between the rods are matched and drilled to ensure that the on-site construction line meets the design requirements and the bolt joints meet the specifications.

[0108] (2) The linear control accuracy of steel trusses is high. During on-site assembly, it is necessary to ensure that the linear shape of the completed bridge meets the design linear shape requirements. The accuracy requirements are high and the control difficulty is high.

[0109] ① The arch rib line shape is combined with the pre-camber precision setting provided by the design institute and the monitoring unit;

[0110] ② The arch ribs are manufactured using the “long line method” for horizontal assembly to ensure accurate manufacturing line shape of the arch rib segments;

[0111] ③ By adjusting the bracket and equipping professional surveying personnel with total station for measurement, it is possible to ensure the accuracy of the control network measurement and the accuracy of the arch rib installation line.

[0112] (3) Safety assurance during the construction process.

[0113] Construction countermeasures: ① Based on the "Guidelines for the Assessment of Construction Safety Risks in Highway Bridges and Tunnels Projects", clarify the distribution of construction hazard sources in combination with the specific links of the actual steel beam construction plan to ensure the pertinence of this special safety plan;

[0114] ② Establish a safety and quality management leading group at the site with the project manager as the team leader, the project deputy manager and the project chief engineer as the deputy team leaders, and participated by the person in charge of each functional department of the project department and the person in charge of each construction team, and actively organize and carry out comprehensive safety management.

[0115] Principles of construction layout

[0116] (1) Reasonably arrange the construction area according to the actual overall construction layout on site and the construction progress arrangement;

[0117] (2) Ensure the convenience of component transportation, stacking and transfer. The construction access road must be safe and unobstructed, and there should be no obstacles in the crane operation area.

[0118] Finally, the installation process flow of reverse installation of each component is as follows:

[0119] (1) Fabrication and installation of temporary supports, installation of gantry crane.

[0120] (2) Installation of the lower chords SE10SE9 of the side truss beam and the lower chords ME10ME9 of the middle truss beam:

[0121] Use one 125t gantry crane to install the lower chords SE10SE9 of the side truss beam. The maximum weight of SE10SE9 is 30t, and the load rate is 24.1%, meeting the construction requirements;

[0122] Use one 125t gantry crane to install the lower chords ME10ME9 of the middle truss beam. The maximum weight of ME10ME9 is 29.6t, and the load rate is 23.7%, meeting the construction requirements;

[0123] If the gantry crane is not installed, this step can be hoisted by a truck crane. Use one 130t truck crane, with an operating radius of 10m, a boom length of 21.28m, and a rated lifting weight of 45.3t, and the load rate is 66%, meeting the construction requirements.

[0124] (3) Installation of the lower chords SE6SE7 / SE12SE11 of the side truss beam and the lower chords ME6ME7 / ME12ME11 of the middle truss beam:

[0125] Use one 125t gantry crane to install the lower chords SE6SE7 / SE12SE11 of the side truss beam. The maximum weight of SE6SE7 / SE12SE11 is 24.1t, and the load rate is 19.3%, meeting the construction requirements;

[0126] Use one 125t gantry crane to install the lower chord ME6ME7 / ME12ME11 of the middle truss beam. The maximum weight of ME6ME7 / ME12ME11 is 23.6t, and the load rate is 18.9%, meeting the construction requirements.

[0127] If the gantry crane is not installed, a truck crane can be used for hoisting in this step. Use one 130t truck crane with an operating radius of 10m, boom length of 21.28m, and rated lifting weight of 45.3t. The load rate is 66%, meeting the construction requirements.

[0128] (4)Installation of bridge deck, installation of left - hand side RX3 sidewalk slab:

[0129] Use one 125t gantry crane to install the lower - layer bridge deck. The maximum weight of the bridge deck is 20.0t, and the load rate is 16.1%, meeting the construction requirements.

[0130] Use one 125t gantry crane to install the left - hand side lower - layer RX3 sidewalk slab. The maximum weight of the sidewalk slab is 13t, and the load rate is 10.4%, meeting the construction requirements.

[0131] If the gantry crane is not installed, a truck crane can be used for hoisting in this step. Use one 130t truck crane with an operating radius of 10m, boom length of 21.28m, and rated lifting weight of 45.3t. The load rate is 45%, meeting the construction requirements.

[0132] This step can be carried out alternately according to the installation progress of the lower chord and web members.

[0133] (5)Installation of main truss web members:

[0134] Use one 125t gantry crane to install the main truss web members. The maximum weight of the web members is 26.2t, and the load rate is 21.0%, meeting the construction requirements.

[0135] If the gantry crane is not installed, a truck crane can be used for hoisting in this step. Use one 130t truck crane with an operating radius of 10m, boom length of 21.28m, and rated lifting weight of 45.3t. The load rate is 58%, meeting the construction requirements.

[0136] (6)Installation of upper chord SA8 / SA8SA9 / SA10SA9 of side truss beam and upper chord MA8 / MA8MA9 / MA10MA9 of middle truss beam:

[0137] Use one 125t gantry crane to install the upper chord SA8 / SA8SA9 / SA10SA9 of side truss beam. The maximum weight of SA8 / SA8SA9 / SA10SA9 is 30.3t, and the load rate is 24.2%, meeting the construction requirements.

[0138] Use one 125t gantry crane to install the upper chords MA8 / MA8MA9 / MA10MA9 of the middle truss girder. The maximum weight of MA8 / MA8MA9 / MA10MA9 is 33.4t, and the load rate is 26.7%, meeting the construction requirements.

[0139] If the gantry crane is not installed, a truck crane can be used for hoisting in this step. Use a 130t truck crane with an operating radius of 10m, a boom length of 21.28m, and a rated lifting weight of 45.3t. The load rate is 74%, meeting the construction requirements.

[0140] (7) Installation of the upper chords SA7SA8 / SA11SA10 of the side truss girder and installation of the upper chords MA7MA8 / MA11MA10 of the middle truss girder:

[0141] Use one 125t gantry crane to install the upper chords SA7SA8 / SA11SA10 of the side truss girder. The maximum weight of SA7SA8 / SA11SA10 is 19.5t, and the load rate is 15.6%, meeting the construction requirements.

[0142] Use one 125t gantry crane to install the upper chords MA7MA8 / MA11MA10 of the middle truss girder. The maximum weight of MA7MA8 / MA11MA10 is 22.5t, and the load rate is 18%, meeting the construction requirements.

[0143] If the gantry crane is not installed, a truck crane can be used for hoisting in this step. Use a 130t truck crane with an operating radius of 10m, a boom length of 21.28m, and a rated lifting weight of 45.3t. The load rate is 74%, meeting the construction requirements.

[0144] (8) Installation of the upper layer of the municipal bridge deck:

[0145] Use one 125t gantry crane to install the upper layer of the municipal bridge deck. The maximum weight of the bridge deck is 20.0t, and the load rate is 16.0%, meeting the construction requirements.

[0146] This step can be carried out alternately according to the installation progress of the upper chord.

[0147] (9) Installation of the lower chords SE3SE4 - SE5SE6, SE13SE12 - SE15SE14 of the side truss girder and installation of the lower chords ME3ME4 - ME5ME6, ME13ME12 - ME15ME14 of the middle truss girder: Extension and assembly of the lower chords SE1SE2 - SE2SE3, SE16SE15 - SE17SE16 of the side truss girder and extension and assembly of the lower chords ME1ME2 - ME2ME3, ME16ME15 - ME17ME16 of the middle truss girder:

[0148] Use one 125t gantry crane to hoist the lower chord segments SE3SE4-SE5SE6 and SE13SE12-SE15SE14 of the side truss beam. The maximum weight of the segment is 24.2t, and the load rate is 19.4%, meeting the construction requirements;

[0149] Use one 125t gantry crane to hoist the lower chord segments ME3ME4-ME5ME6 and ME13ME12-ME15ME14 of the side truss beam. The maximum weight of the segment is 24.2t, and the load rate is 19.4%, meeting the construction requirements;

[0150] Use one 125t gantry crane to assemble and extend SE1SE2-SE2SE3 at the temporary support area of the lower chord of the side truss beam. The maximum weight of the segment is 62.8t, and the load rate is 50.2%, meeting the construction requirements;

[0151] Use one 125t gantry crane to assemble and extend SE16SE15-SE17SE16 at the temporary support area of the lower chord of the side truss beam. The maximum weight of the segment is 62.8t, and the load rate is 50.2%, meeting the construction requirements;

[0152] Use one 125t gantry crane to assemble and extend ME1ME2-ME2ME3 at the temporary support area of the lower chord of the middle truss beam. The maximum weight of the segment is 62.8t, and the load rate is 50.2%, meeting the construction requirements;

[0153] Use one 125t gantry crane to assemble and extend ME16ME15-ME17ME16 at the temporary support area of the lower chord of the middle truss beam. The maximum weight of the segment is 62.8t, and the load rate is 50.2%, meeting the construction requirements;

[0154] (10)Installation of the lower chord SE1SE2-SE2SE3 and SE16SE15-SE17SE16 of the side truss beam, and installation of the lower chord ME1ME2-ME2ME3 and ME16ME15-ME17ME16 of the middle truss beam:

[0155] Use one 125t gantry crane to hoist the segments SE1SE2-SE2SE3 and SE16SE15-SE17SE16 of the lower chord of the side truss beam. The maximum weight of the segment is 91.6t, and the load rate is 73.3%, meeting the construction requirements;

[0156] Use one 125t gantry crane to hoist the segments ME1ME2-ME2ME3 and ME16ME15-ME17ME16 of the lower chord of the middle truss beam. The maximum weight of the segment is 92.2t, and the load rate is 73.8%, meeting the construction requirements;

[0157] (11)Installation of the lower deck end girder SZ1M bridge deck:

[0158] Use a 130t truck crane to install the lower-layer end crossbeam SZ1M bridge deck. The maximum weight of the bridge deck is 24.3t, the maximum working radius is 10.0m, the maximum boom length is 21.4m, the boom angle is 65°, the lifting height is 22.6m, the rated lifting capacity is 35t, and the load rate is 69.4%, meeting the construction requirements;

[0159] (12)Installation of bridge deck, installation of RX3 sidewalk slab:

[0160] Use a 125t gantry crane to install the lower-layer bridge deck in sequence. The maximum weight of the bridge deck is 20.0t, and the load rate is 16.1%, meeting the construction requirements;

[0161] Use a 125t gantry crane to install the lower-layer left-side RX3 sidewalk slab in sequence. The maximum weight of the sidewalk slab is 13t, and the load rate is 10.4%, meeting the construction requirements;

[0162] This step can be carried out alternately according to the installation progress of the lower chord and web members;

[0163] (13)Installation of the lower-layer pipe bridge deck system GDX2 bridge deck:

[0164] Use a 125t gantry crane to hoist the lower-layer pipe bridge deck system GDX2 bridge deck to the designated position on the upper-layer main truss bridge deck;

[0165] Use an 80t truck crane to install the lower-layer pipe bridge deck system GDX2 bridge deck. The maximum weight of the bridge deck is 6.8t, the maximum working radius is 12.0m, the maximum boom length is 24.0m, the boom angle is 63°, the lifting height is 23.8m, the rated lifting capacity is 14.2t, and the load rate is 47.9%, meeting the construction requirements;

[0166] (14)Installation of the upper-layer track bridge deck system GDX1 bridge deck:

[0167] Use a 125t gantry crane to hoist the upper-layer track bridge deck system GDX1 bridge deck to the designated position on the upper-layer main truss bridge deck;

[0168] Use a 180t truck crane to install the upper-layer track bridge deck system GDX1 bridge deck. The maximum weight of the bridge deck is 16.6t, the maximum working radius is 18.0m, the maximum boom length is 26.77m, the boom angle is 56°, the lifting height is 23.5m, the rated lifting capacity is 32t, and the load rate is 51.9%, meeting the construction requirements;

[0169] This step can be carried out alternately according to the installation progress of the upper and lower chord members;

[0170] Installation of the upper chords SA4SA5 - SA6SA7 / SA12SA11 - SA14SA13 of the side truss girder and MA4MA5 - MA6MA7 / MA12MA11 - MA14MA13 of the middle truss girder:

[0171] Use one 125t gantry crane to install the upper chords SA4SA5 - SA6SA7 / SA12SA11 - SA14SA13 of the side truss girder (installed with a cantilever). The maximum weight of SA4SA5 - SA6SA7 / SA12SA11 - SA14SA13 is 21.1t, and the load rate is 16.9%, meeting the construction requirements;

[0172] Use one 125t gantry crane to install the upper chords MA4MA5 - MA6MA7 / MA12MA11 - MA14MA13 of the middle truss girder. The maximum weight of MA4MA5 - MA6MA7 / MA12MA11 - MA14MA13 is 22.6t, and the load rate is 18.1%, meeting the construction requirements;

[0173] This step can be carried out alternately according to the installation progress of the upper and lower chord members;

[0174] Installation of the upper chords SA1SA2 / SA17SA16 of the side truss girder and MA1MA2 / MA17MA16 of the middle truss girder:

[0175] Use one 150t truck crane to install the upper chords SA1SA2 / SA17SA16 of the side truss girder (installed with a cantilever). The maximum weight of SA1SA2 / SA17SA16 is 24.2t, the maximum working radius is 12.0m, the maximum boom length is 29.8m, the boom angle is 68°, the lifting height is 31m, the rated lifting capacity is 36.0t, and the load rate is 67.2%, meeting the construction requirements;

[0176] Use one 150t truck crane to install the upper chords MA1MA2 / MA17MA16 of the middle truss girder. The maximum weight of MA1MA2 / MA17MA16 is 28.0t, the maximum working radius is 12.0m, the maximum boom length is 29.8m, the boom angle is 68°, the lifting height is 31m, the rated lifting capacity is 36.0t, and the load rate is 77.8%, meeting the construction requirements;

[0177] Use one 180t truck crane to install the upper layer track bridge deck GD1 bridge deck. The maximum weight of the bridge deck is 16.6t, the maximum working radius is 18.0m, the maximum boom length is 26.77m, the boom angle is 56°, the lifting height is 23.5m, the rated lifting capacity is 32t, and the load rate is 51.9%, meeting the construction requirements;

[0178] Installation of the upper layer end crossbeam SZ1M bridge deck:

[0179] Use one 150t truck crane to install the upper end cross beam SZ1M bridge deck. The maximum weight of the bridge deck is 24.3t, the maximum working radius is 12.0m, the maximum boom length is 29.8m, the boom angle is 68°, the lifting height is 31.0m, the rated lifting capacity is 36t, and the load rate is 67.5%, meeting the construction requirements;

[0180] (18) Installation of the upper SZ2M bridge deck:

[0181] Use one 150t truck crane to install the upper SZ2M bridge deck. The maximum weight of the bridge deck is 19.45t, the maximum working radius is 16.0m, the maximum boom length is 29.8m, the boom angle is 62°, the lifting height is 28.9m, the rated lifting capacity is 27.0t, and the load rate is 72.0%, meeting the construction requirements;

[0182] (19) Installation of the lower pipeline bridge deck system GDHL cross beam and GDX2 bridge deck:

[0183] Use one 125t gantry crane to lift the lower pipeline bridge deck system GDHL cross beam and GDX2 bridge deck to the designated position of the upper main truss bridge deck;

[0184] Use one 80t truck crane to install the lower pipeline bridge deck system GDHL cross beam. The weight of the cross beam is 5.5t, the maximum working radius is 12.0m, the maximum boom length is 24.0m, the boom angle is 64°, the lifting height is 24.5m, the rated lifting capacity is 14.2t, and the load rate is 38.7%, meeting the construction requirements;

[0185] Use one 80t truck crane to install the lower pipeline bridge deck system GDX2 bridge deck. The maximum weight of the bridge deck is 6.8t, the maximum working radius is 12.0m, the maximum boom length is 24.0m, the boom angle is 63°, the lifting height is 23.8m, the rated lifting capacity is 14.2t, and the load rate is 47.9%, meeting the construction requirements;

[0186] (20) Installation of the main arch support:

[0187] For both the left and right sides, use one 125t gantry crane to lift two 50t truck cranes onto the upper bridge deck system, and install the main arch support through the truck crane;

[0188] (21) Segmented installation of the main arch SG2SG3SG4 and SG14SG15SG16:

[0189] Use one 125t gantry crane to lift one 200t truck crane onto the upper bridge deck system, and install the segments of the main arch SG2SG3SG4 and SG14SG15SG16 through the truck crane;

[0190] Use one 125t gantry crane to hoist the segments SG2SG3SG4 and SG14SG15SG16 onto the upper deck system. The maximum weight of a segment is 44.2t, and the load rate is 35.4%, meeting the construction requirements;

[0191] For the main arch segments SG2SG3SG4 and SG14SG15SG16, the maximum weight is 44.2t, the maximum working radius is 8.0m, the maximum boom length is 18.12m, the boom angle is 66°, the lifting height is 20.5m, the rated lifting capacity is 73.0t, and the load rate is 60.6%, meeting the construction requirements;

[0192] (22) Installation of the main arch segments SG3SG4SG5 and SG13SG14SG15, and installation of the main arch wind bracing segment FC3-1:

[0193] Use one 125t gantry crane to hoist the segments SG3SG4SG5 and SG13SG14SG15 onto the upper deck system. The maximum weight of a segment is 29.5t, and the load rate is 23.6%, meeting the construction requirements;

[0194] For the main arch segments SG3SG4SG5 and SG13SG14SG15, the maximum weight is 29.5t, the maximum working radius is 8.0m, the maximum boom length is 22.4m, the boom angle is 66°, the lifting height is 20.5m, the rated lifting capacity is 59.0t, and the load rate is 50.0%, meeting the construction requirements;

[0195] Use one 125t gantry crane to hoist the main arch wind bracing segment FC3-1 onto the upper deck system. The maximum weight of a segment is 10.2t, and the load rate is 8.2%, meeting the construction requirements;

[0196] For the main arch wind bracing segment FC3-1, the maximum weight is 10.2t, the maximum working radius is 10.0m, the maximum boom length is 22.4m, the boom angle is 66°, the lifting height is 23.6m, the rated lifting capacity is 59.0t, and the load rate is 17.3%, meeting the construction requirements;

[0197] (23) Installation of the main arch segments SG5SG6 and SG12SG13:

[0198] Use one 125t gantry crane to hoist the segments SG5SG6 and SG12SG13 onto the upper deck system. The maximum weight of a segment is 48.7t, and the load rate is 39.0%, meeting the construction requirements;

[0199] For the main arch segments SG5SG6 and SG12SG13, the maximum weight is 48.7t, the maximum working radius is 8.0m, the maximum boom length is 26.77m, the boom angle is 73°, the lifting height is 30.1m, the rated lifting capacity is 72.0t, and the load rate is 67.6%, meeting the construction requirements;

[0200] (24) Segment installation of main arch SG9 - SG10:

[0201] Use one 125t gantry crane to hoist the segments of SG9 - SG10 onto the upper deck system. The maximum weight of a segment is 33.3t, and the load rate is 26.6%, meeting the construction requirements.

[0202] The maximum weight of the segments of main arch SG9 - SG10 is 33.3t, the maximum working radius is 8.0m, the maximum boom length is 31.09m, the boom angle is 76°, the lifting height is 34.7m, the rated lifting capacity is 64.0t, and the load rate is 52.0%, meeting the construction requirements.

[0203] (25)Segment installation of main arch SGK1:

[0204] Use one 125t gantry crane to hoist the segments of SGK1 onto the upper deck system. The maximum weight of a segment is 31.2t, and the load rate is 25%, meeting the construction requirements.

[0205] The maximum weight of the segments of main arch SGK1 is 31.2t, the maximum working radius is 8.0m, the maximum boom length is 31.09m, the boom angle is 76°, the lifting height is 34.7m, the rated lifting capacity is 64.0t, and the load rate is 48.8%, meeting the construction requirements.

[0206] (26)Segment installation of main arch wind bracing FC1 - 3:

[0207] Use one 125t gantry crane to hoist the segments of main arch wind bracing FC1 - 3 onto the upper deck system. The maximum weight of a segment is 2.1t, and the load rate is 1.7%, meeting the construction requirements.

[0208] The maximum weight of the segments of main arch wind bracing FC1 - 3 is 2.1t, the maximum working radius is 8.0m, the maximum boom length is 31.09m, the boom angle is 72°, the lifting height is 33.2m, the rated lifting capacity is 64.0t, and the load rate is 3.3%, meeting the construction requirements.

[0209] (27)Demolition of the gantry crane, installation of the sidewalk slabs RX1 / RX2 on the lower right - hand side, and installation of the deck slabs GD1 and GD2 of the upper - layer track deck system:

[0210] Use a 125t gantry crane to hoist the remaining components to the designated positions on the upper - layer deck of the main bridge, and use two 80t truck cranes to demolish the four gantry cranes.

[0211] Use a 200t truck crane to install the upper track bridge deck system GD1 and GD2 bridge slabs. The maximum weight of the bridge slab is 20.8t, the maximum working radius is 18.0m, the maximum boom length is 26.77m, the boom angle is 56°, the lifting height is 23.5m, the rated lifting capacity is 32t, and the load factor is 65%, meeting the construction requirements;

[0212] Use a 100t truck crane to install the right - hand lower - layer RX1 / RX2 sidewalk slabs. The maximum weight of the RX1 / RX2 sidewalk slabs is 11.8t, the maximum working radius is 12.0m, the maximum boom length is 17.2m, the boom angle is 55°, the lifting height is 18.9m, the rated lifting capacity is 23t, and the load factor is 51.3%, meeting the construction requirements;

[0213] (28) Installation of the upper - track bridge deck system GD1 and GD2 bridge slabs:

[0214] Use a 200t truck crane to install the upper track bridge deck system GD1 and GD2 bridge slabs. The maximum weight of the bridge slab is 20.8t, the maximum working radius is 18.0m, the maximum boom length is 26.77m, the boom angle is 56°, the lifting height is 23.5m, the rated lifting capacity is 32t, and the load factor is 65%, meeting the construction requirements;

[0215] (29) Installation of sling, removal of main - arch supports, and construction of bridge - deck paving.

[0216] (30) Removal of under - arch supports, construction of full - bridge painting, secondary tensioning of slings, and completion of the whole bridge.

[0217] The above - mentioned is only the preferred specific implementation mode of the present invention. However, the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A construction method for reverse installation of a double - layer steel truss arch bridge, characterized in that, The overall steps include: Step 1: Install the gantry crane and the lifting bracket structure Two gantry cranes are arranged on each span, and a total of four gantry cranes are deployed on the entire bridge; the left span gantry crane has a span of 36.5m and a lifting height of 21m; The right gantry crane has a span of 26m and a lifting height of 23m. The gantry crane track foundation adopts a concrete expansion foundation, and the part where the foundation bearing capacity does not meet the requirements is excavated and replaced with fill. Step 2: Install the left and right steel trusses on the gantry crane The main components of the steel truss include an upper chord, a lower chord and a web. The steel truss needs to go through the following two processes before installation: 1) Build a temporary steel truss pier system: From the width of the bridge, there are four rows of temporary steel truss pier systems, each row has equally spaced temporary piers. A single pier is mainly a three-dimensional steel pier connected by φ630*10mm steel pipes and [14a channel steels, with a pier height of 2-3m. 400*800mm steel plates of different thicknesses are set on the top of the pier as adjustment steel pipes. At the same time, steel brackets are set on the side of each set of temporary pier steel pipes, and 25t hydraulic jacks are placed above the brackets to adjust the height of the steel trusses. A steel pipe is added to the mid-span bracket to set it as a fixed bracket, which is welded and locked after hoisting. 2) Regional division: From the width direction of the bridge, there are four rows of truss structures, with two groups of side trusses on the outside, and a single side truss surface is divided into 17 upper chord segments, 16 lower chord segments, and 33 web members; the side arch ribs are divided into 10 segments; the outside is two groups of middle trusses, and a single middle truss surface is divided into 17 upper chord segments, 16 lower chord segments, and 33 web members; the middle arch ribs are divided into 10 segments; Step 3: Install the upper and lower bridge deck systems and cantilever arm system between the left and right sides of the truck crane The connection structure between the bridge deck system and the chord rod is mainly composed of a bridge deck, a crossbeam, a U-rib, and a plate rib part. The bridge deck system structure is divided into a municipal bridge deck system, a rail bridge deck system, and a pipeline bridge deck system; The cantilever system structure includes two forms: a cantilever for the lower pedestrian walkway and a cantilever for the upper maintenance passage; Step 4: Install arch ribs and wind bracing on the bridge using a car crane The arch rib adopts a box-shaped section, with an outer height of 1800mm, an outer width of 1100mm, and a plate thickness of 36-50mm. The arch rib is connected by full welding, and the inner side reinforcement is connected by high-strength bolts; Step 5: Tension the boom and remove the bracket The suspenders are flexible suspenders with a standard spacing of 9m; the upper end is anchored at the bottom of the arch rib as the tension end; the lower end is anchored at the upper chord node as the anchor end; The components in steps 2 to 5 are installed in a cross-sequence during the construction process, including the following specific steps: ①Central construction: Two sets of gantry cranes arranged horizontally are used. On two adjacent temporary steel truss piers along the length direction in the middle of the bridge, the lower chords are constructed, including two lower chords of the side truss girders and two lower chords of the middle truss girders. Move the four sets of gantry cranes and extend and construct another set of lower chords at both ends of the already constructed lower chords. At this point, each column of the truss structure already has 6 lower chords. Two sets of gantry cranes arranged longitudinally are used to install the lower-layer municipal bridge deck on one column of side trusses and one column of middle trusses that have been constructed, and then install the sidewalk slabs on the left side. This step is carried out alternately according to the installation progress of the lower chords and web members. On the upper surface of the already constructed lower chords, install the main truss web members, and install the upper chords on the main truss web members, including two upper chords of the side truss girders and two upper chords of the middle truss girders. Install the upper-layer municipal bridge deck on the already constructed upper chords. This step is carried out alternately according to the installation progress of the upper chords. ②Lower chord assembly and extension: At both ends of the already constructed lower chords, carry out assembly and extension construction simultaneously. Install the ordinary lower chords. At both ends of the ordinary lower chords, install the lower chords of the supports. Install the bridge deck of the lower-layer end crossbeam on the lower chords of the supports and their adjacent ordinary lower chords, and continue the assembly and extension construction between it and the lower-layer municipal bridge deck constructed in step ① to install all the lower-layer municipal bridge decks and the sidewalk slabs on the left side. This step is carried out alternately according to the installation progress of the lower chords and web members. ③Central panel installation: Install the web members. Use a truck crane to install the pipe bridge deck of the lower-layer pipe bridge deck system on 6 lower chords in the middle along the length direction of the two columns of middle trusses, and immediately install the track bridge deck of the upper-layer track bridge deck system directly above it. ④Upper chord assembly and extension: Use gantry cranes to carry out assembly and extension construction simultaneously at both ends of the already constructed upper chords. Install the upper chords of the suspenders. Use a truck crane to construct the upper chords of the supports on the web members at both ends, and install the arch beam connection section between the upper chords of the suspenders and the upper chords of the supports. The upper chords include the upper chords of the supports, the arch beam connection section, and the upper chords of the suspenders. At this point, the main truss construction is completed. ⑤Panel assembly and extension: Use a truck crane to install the bridge deck of the upper-layer end crossbeam on the upper chords of the supports, and continue the assembly and extension construction between it and the upper-layer municipal bridge deck constructed in step ① to install all the upper-layer municipal bridge decks and the upper-layer inspection passage slabs. This step is carried out alternately according to the installation progress of the lower chords and web members. At both ends in the bridge length direction, use gantry cranes to install the crossbeams of the lower-layer pipe bridge deck system, and install the end lower-layer pipe bridge decks and upper-layer track bridge decks on them, and continue the assembly and extension construction between them and the pipe bridge decks and track bridge decks constructed in step ③ to install all the lower-layer pipe bridge decks and most of the upper-layer track bridge decks, leaving gaps at both ends of the upper-layer track bridge decks to install the thrust devices of the truck crane after getting on the bridge. ⑥Construct the main arch support: On each of the left and right sides, use 1 set of 125t gantry crane to hoist 2 sets of 50t truck cranes onto the upper bridge deck system, and install the main arch support through the truck crane. The temporary pier system structure of the main arch support is as follows: a single arch rib support is mainly composed of a three-dimensional steel pier connected by φ377*8mm steel pipe channel steel [14, with a pier height of 4-27m; a 400*300 H-shaped steel adjustment pad is set on the top of the pier, and a steel plate is placed under the support steel pipe to increase the contact area with the bridge deck top plate to avoid deformation; ⑦ Main arch segment installation: Install the main arch at the end of the arch-beam joint section, and install wind braces between adjacent main arches in the left and right sections. Use a truck crane to install each section of the main arch from bottom to top. After each section of the main arch is installed, the wind brace of that section is installed; ⑧ Gantry crane removal: Use the gantry crane to hoist the remaining components to the designated position of the upper deck of the main bridge, and use the truck crane to remove the gantry crane; remove the redundant parts of the deck, install the lower sidewalk slab of the right span, and install all the lower pipeline decks and upper track decks. At this point, the steel truss structure is completed; ⑨ Installation of slings, that is, installing slings between the upper chord of the suspender and the lugs carried by the main arch, making each sling vertical, removing the main arch support, and paving the bridge deck; ⑩ The support under the arch was removed, the entire bridge was painted, the cables were tensioned for the second time, and the entire bridge was completed.

2. The construction method for reverse installation of a double - layer steel truss arch bridge according to claim 1, characterized in that, The municipal bridge deck is composed of a crossbeam + a bridge deck, which is divided horizontally, with a length of 4.5m, a crossbeam spacing of 3m, an inverted I-section, a crossbeam web bolted to the chord, and a top plate welded to the wing plate; the bridge deck adopts U-ribs, and the U-ribs are welded together, with 80% penetration single-sided welding to the bridge deck.

3. The construction method for reverse installation of a double - layer steel truss arch bridge according to claim 1, characterized in that, The rail transit top plate in the rail bridge deck system adopts 14mm+3mm composite steel plate, which is divided horizontally, 4.5m in length, 3m in beam spacing, and an inverted T-shaped section. The web of the beam is bolted to the chord, and the top plate is welded to the wing plate; the rail transit bridge deck adopts 4 small longitudinal beams with an inverted T-shaped section, and the longitudinal beams pass through the beams with openings; the rail transit bridge deck adopts U-ribs, and the U-ribs are connected by welding, and 80% penetration depth double-sided welding is adopted with the bridge deck.

4. The construction method for reverse installation of a double - layer steel truss arch bridge according to claim 1, characterized in that, The pipeline bridge deck is composed of a crossbeam + a bridge deck + a longitudinal beam, and is divided longitudinally. The crossbeam spacing is 9m, an inverted I-shaped section is adopted, the web of the crossbeam is bolted to the chord, the top plate is welded to the wing plate, the top plate is made of flat steel and bolted to the I-shaped crossbeam, and the longitudinal beam is made of an inverted T-shaped section and bolted to the I-shaped crossbeam.

5. The construction method for reverse installation of a double - layer steel truss arch bridge according to claim 1, characterized in that, The web of the sidewalk cantilever arm and the lower chord of the side truss are bolted, the top plate and the wing plate are welded, and the cantilever arm of the inspection road and the upper chord of the side truss are welded.

6. The construction method for reverse installation of a double - layer steel truss arch bridge according to claim 1, characterized in that, The upper chord adopts a box-type section with an upper flange plate with an extended limb. The inner height of the side girder is 1400mm, the inner height is 1000mm, and the plate thickness is 24-44mm; the inner height of the middle girder is 1650mm, the inner width is 1000mm, and the plate thickness is 24-44mm; the upper flange of the upper chord is fully welded, and the other three sides are connected by high-strength bolts and other strong splicing methods.

7. The construction method for reverse installation of a double - layer steel truss arch bridge according to claim 1, characterized in that, The lower chord adopts a box-shaped section with an upper flange plate with an extended limb. The side girders have an inner height of 1400mm, an inner height of 1000mm, and a plate thickness of 32-44mm; the middle girders have an inner height of 1650mm, an inner width of 1000mm, and a plate thickness of 32-44mm; the upper flange of the upper chord is fully penetrated and welded, and the other three sides are connected by high-strength bolts and other strong butt-jointed connection methods.

8. The construction method for reverse installation of a double - layer steel truss arch bridge according to claim 1, characterized in that, The web members have two forms: box-shaped web members and H-shaped web members. The box-shaped straight web member has a cross-sectional inner height of 1000 mm, an inner width of 1000 mm, a plate thickness of 32 mm, and is bolted on all four sides; the box-shaped inclined web member has a cross-sectional inner height of 1800 mm, an inner width of 1000 mm, and a plate thickness of 50 mm; the H-shaped web has a cross-sectional inner height of 1000 mm, an inner width of 700 mm, and a plate thickness of 28 - 32 mm; the inclined web member is connected to the main truss node by an inserted high-strength bolt.

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