A large double-layer steel truss beam installation method without support

Abstract

The present application provides a large double-layer steel truss beam without support installation method, through the installation of the main cross beam, temporary cross brace and node cross beam, the left truss piece and the right truss piece on both sides of the whole bridge form a stable load-bearing main body directly supported by the permanent support, avoiding the deformation of the truss piece during the subsequent installation of the bridge deck system; then, using the load-bearing main body as an aerial work platform and load-bearing foundation, the double-layer bridge deck system is installed from bottom to top by using a mobile hoisting device. The present application completely abandons the temporary support under the bridge, realizes the "zero interference, high efficiency and high safety" in the construction process, maximally reduces the expensive and complex temporary facilities, improves the economy, and is especially suitable for complex working conditions such as crossing sensitive facilities and deep valley rapids.

Description

Technical Field

[0001] This invention relates to the field of bridge construction technology, specifically to a method for installing large double-layer steel truss beams without supports. Background Technology

[0002] Double-deck steel truss structures are widely used in dual-purpose road-rail bridges, urban multi-level transportation hubs, and mega-bridges spanning wide canyons or rivers due to their ability to provide two independent bridge deck spaces, high load-bearing capacity, and strong structural rigidity. However, corresponding to their superior structural performance, their construction remains a significant challenge for the engineering community, especially in complex conditions such as crossing navigable rivers, busy traffic arteries, soft foundations, or being restricted by cultural heritage sites where temporary scaffolding is unsuitable or impossible. Therefore, it is necessary to study feasible and economical construction methods for double-deck steel truss beams under these special circumstances.

[0003] In existing technologies, the construction of double-layer steel truss beams mainly relies on the following traditional methods, each of which has significant limitations:

[0004] (1) Scaffolding method: This is the most traditional method, which involves erecting dense temporary scaffolding under the bridge site and assembling the entire bridge steel truss on the temporary scaffolding. Although this method is technically mature, the amount of temporary scaffolding work is large and the cost is high; the foundation treatment requirements for the scaffolding are high, and it is extremely difficult or even impossible to implement in soft foundations or deep water areas; the erection and dismantling cycle of the scaffolding is long and the construction efficiency is low; more importantly, this method occupies the space under the bridge for a long time, seriously hindering navigation or road traffic, and poses a huge safety risk under flash floods, flowing water or ship collisions.

[0005] (2) Floating towing and jacking method: A support frame is erected behind the abutment, segments are assembled, and the bridge is gradually jacked to the designed bridge position. However, this method requires the installation of a strong front guide beam and complex temporary jacking facilities. For large-tonnage double-layer steel truss beams, the synchronous control technology for jacking is extremely demanding. In particular, the floating towing vessel is greatly affected by the water flow, making stability difficult to control and posing a significant construction risk.

[0006] Therefore, it is necessary to study a construction method for double-layer steel truss beams to completely eliminate the dependence on temporary supports under the bridge and achieve "zero interference" to the environment; minimize expensive and complex temporary facilities and improve economic efficiency. Summary of the Invention

[0007] The present invention aims to solve at least one of the technical problems mentioned in the background art above, and provides a method for installing large double-layer steel truss beams without supports, completely eliminating the dependence on temporary supports under the bridge, minimizing expensive and complex temporary facilities, and improving economic efficiency.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for installing a large double-layer steel truss beam without supports, wherein the large double-layer steel truss beam includes two side spans and a middle span connecting the two side spans. Each side span and the middle span includes a left truss segment, a right truss segment, a lower bridge deck system, and an upper bridge deck system. The left and right truss segments are spaced apart relative to each other along the transverse direction of the bridge. The lower and upper bridge deck systems are laid on the corresponding left and right truss segments. The method for installing the large double-layer steel truss beam without supports includes the following steps:

[0010] S1, complete the construction of two sets of main piers and two sets of transition piers of the double-layer steel truss arch bridge, and install permanent supports on the top of the main piers and the transition piers. The two sets of transition piers are spaced apart along the longitudinal direction of the bridge, and the two sets of main piers are spaced apart along the longitudinal direction of the bridge and are both located between the two sets of transition piers.

[0011] S2, Install the main crossbeam on the main pier, install the temporary cross brace on the transition pier, and sequentially hoist and erect the left and right trusses of the side span onto the permanent supports of the transition pier and the main pier. The two ends of the main crossbeam and the temporary cross brace are fixedly connected to the left and right trusses, so that the left truss, the right truss, the main crossbeam and the temporary cross brace form a load-bearing body directly supported by the permanent supports.

[0012] S3, using the load-bearing main body as a construction platform, to carry out the installation of the upper and lower bridge deck systems of the side span;

[0013] S4, install the left and right trusses of the middle span, so that the two ends of the left truss of the middle span are connected to the left trusses of the two side spans, and the two ends of the right truss of the middle span are connected to the right trusses of the two side spans, and install the node beam connecting the left and right trusses of the middle span.

[0014] S5. After the left and right trusses of the middle span are joined together, the installation of the upper and lower bridge deck systems of the middle span is carried out.

[0015] Furthermore, both the left and right trusses include truss segments connected in sequence. Before installation, several truss segments of the left and right trusses need to be pre-assembled. During pre-assembly, one truss segment is reserved as a pre-assembly mother segment. The pre-assembly mother segment is first pre-assembled with the truss segments of the side span, and after the pre-assembly is completed, it is pre-assembled with the truss segments of the middle span.

[0016] Furthermore, the main crossbeam includes a first main crossbeam and a second main crossbeam. The installation of the main crossbeam in step S2 includes the following steps: First, the first main crossbeam is installed on the main pier; second, a truss segment is installed on the permanent support of the main pier as a truss reference segment, and the truss reference segment is fixedly connected to the permanent support and the first main crossbeam; subsequently, the top of the truss reference segment of the left truss segment and the top of the truss reference segment of the right truss segment of the side span are fixedly connected by the second main crossbeam, so that the main crossbeam, the left truss segment and the right truss segment form a frame structure.

[0017] Furthermore, the temporary cross bracing includes a first temporary cross bracing and a second temporary cross bracing. The steps of installing the temporary cross bracing on the transition pier and sequentially hoisting and erecting the left and right truss segments of the side span onto the permanent supports of the transition pier and the main pier include:

[0018] Before hoisting the left and right trusses of the side span, the first temporary cross bracing is first installed on the transition pier.

[0019] After several truss segments of the left and right trusses of the side span are pre-assembled between the main pier and the transition pier, they are directly lifted and installed in place by crawler crane. The bottom of the left and right trusses is connected to the permanent support. The ends of the left and right trusses near the main pier are fixedly welded to the truss reference segment. The ends of the left and right trusses near the transition pier are welded to the first temporary cross brace, thereby fixing the left and right trusses.

[0020] After the left and right trusses are installed, the second temporary cross brace is installed on the ends of the left and right trusses near the transition pier. The two ends of the second temporary cross brace are fixedly connected to the tops of the left and right trusses, respectively, so that the left and right trusses, the main beam and the temporary cross brace of the side span form a stable frame structure.

[0021] Furthermore, the installation of the upper bridge deck system and the lower bridge deck system specifically includes the following steps: using a crawler crane on land, the lower bridge deck system and the upper bridge deck system are installed alternately from the main pier side to the transition pier side, with the lower bridge deck system installed first and the upper bridge deck system installed afterward, so that the lower bridge deck system is one bridge deck segment ahead of the upper bridge deck system; when the upper bridge deck system and the lower bridge deck system are installed to a preset length such that the length of the free end of the left truss and the right truss near the transition pier side is reduced to a preset range, the temporary cross bracing is removed in order to reserve space for the crawler crane to lift.

[0022] Furthermore, both the upper bridge deck system and the lower bridge deck system include bridge deck beams and bridge deck panels. When installing the upper bridge deck system and the lower bridge deck system, the bridge deck beams are installed first, so that the two ends of the bridge deck beams are fixedly connected to the left truss and the right truss respectively. Then the bridge deck panels are installed, so that the bridge deck panels are erected on the corresponding bridge deck beams.

[0023] Furthermore, the left and right trusses of the middle span are installed using floating cranes, and several truss segments of the left and right trusses are hoisted separately. The truss segment of the middle span used to connect with the reference segment of the truss is a cantilever segment, and the node beam is installed on the cantilever segment.

[0024] Further, in step S5, after the left and right trusses of the middle span are joined to form the main load-bearing frame, the upper and lower bridge deck systems of the middle span are installed using the main load-bearing frame as the load-bearing foundation. The crawler crane is disassembled and transferred to the upper bridge deck system of the side span that has been installed, and then assembled. The upper and lower bridge deck systems of the middle span are alternately lifted from both banks to the middle of the span by the crawler crane. The lower bridge deck system is lifted first, and then the upper bridge deck system is installed, so that the lower bridge deck system is ahead of the upper bridge deck system by one bridge deck segment, until the bridge deck is joined.

[0025] By adopting the above technical solution, the present invention has the following beneficial effects:

[0026] The aforementioned method for installing large double-layer steel truss beams without supports overturns the traditional "bottom-up" or "parallel" construction sequence. Its core lies in: through the main crossbeams and temporary cross braces installed in step S2, and the node crossbeams installed in step S4, the left and right truss sections on both sides of the bridge form a stable load-bearing structure directly supported by permanent bearings, preventing deformation of the truss sections during subsequent bridge deck installation. Subsequently, using this load-bearing structure as an aerial work platform and load-bearing foundation, the double-layer bridge deck system is installed from bottom to top using mobile hoisting equipment. This invention completely eliminates the need for temporary supports under the bridge, achieving "zero interference, high efficiency, and high safety" in the construction process, minimizing expensive and complex temporary facilities, improving economic efficiency, and is particularly suitable for complex conditions such as crossing sensitive facilities, deep valleys, and rapid currents. Attached Figure Description

[0027] Figure 1 This is a flowchart of a preferred embodiment of the present invention for the bracketless installation method of a large double-layer steel truss beam.

[0028] Figure 2 This is a schematic diagram of the pre-assembly of the left and right truss segments in the bracketless installation method for a large double-layer steel truss beam, which is a preferred embodiment of the present invention.

[0029] Figures 3-13This is a schematic diagram of the side span installation of the bracketless installation method for a large double-layer steel truss beam according to a preferred embodiment of the present invention.

[0030] Figures 14-17 This is a schematic diagram of the installation of the mid-span of the bracketless installation method for a large double-layer steel truss beam according to a preferred embodiment of the present invention.

[0031] Explanation of main component symbols

[0032] 11. Side span; 12. Mid-span; 120. Cantilever section; 131. Left truss; 132. Right truss; 133. Truss segment; 134. Truss base segment; 135. Top chord; 136. Bottom chord; 137. Web member; 151. Lower deck system; 152. Upper deck system; 20. Main pier; 30. Transition pier; 50. Main crossbeam; 51. First main crossbeam; 53. Second main crossbeam; 60. Temporary cross brace; 61. First temporary cross brace; 62. Second temporary cross brace; 70. Node crossbeam. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] It should be noted that when a component is described as "fixed to" another component, it can be directly on the other component or may have a component in between. When a component is considered "connected to" another component, it can be directly connected to the other component or may have a component in between. When a component is considered "set on" another component, it can be directly set on the other component or may have a component in between. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0036] Please also see Figure 1 and Figure 17A preferred embodiment of the present invention provides a method for installing a large double-layer steel truss beam without supports. The large double-layer steel truss beam is the bridge deck structure of a double-layer steel truss arch bridge, which includes two side spans 11 and a middle span 12 connecting the two side spans 11. Both the side spans 11 and the middle span 12 include a left truss 131, a right truss 132, a lower bridge deck system 151, and an upper bridge deck system 152. The left truss 131 and the right truss 132 are arranged at intervals along the transverse direction of the bridge. The lower bridge deck system 151 and the upper bridge deck system 152 are laid at intervals from bottom to top on the corresponding left truss 131 and right truss 132.

[0037] Specifically, please refer to the following: Figure 2 The left truss 131 and right truss 132 both adopt a triangular truss structure, including an upper chord 135 and a lower chord 136 arranged at intervals, and a web member 137 connecting the upper chord 135 and the lower chord. For ease of hoisting, both the left truss 131 and right truss 132 are divided into several truss segments 133 connected sequentially along the longitudinal direction of the bridge. The upper bridge deck system 152 and the lower bridge deck system 151 both include several bridge deck segments (not shown in the figure) connected sequentially. The bridge deck segments include bridge deck beams (not shown in the figure) and bridge deck panels (not shown in the figure). The bridge deck beams are fixedly connected to the left and right trusses, and the bridge deck panels are laid on the bridge deck beams. The structure of the large double-layer steel truss beam is existing technology and will not be described in detail here for brevity.

[0038] The method for installing large double-layer steel truss beams without supports includes the following steps:

[0039] S1, please refer to it as well. Figure 3 and Figure 13 The construction of the two main piers 20 and two transition piers 30 of the double-layer steel truss arch bridge was completed, and permanent supports (not shown in the figure) were installed on the top of the main piers 20 and transition piers 30. The two transition piers 30 were set at intervals along the longitudinal direction of the bridge, and the two main piers 20 were set at intervals along the longitudinal direction of the bridge and were located between the two transition piers 30.

[0040] In this embodiment, the two sets of main piers 20 are piers 4 and 5, and the two sets of transition piers 30 are piers 3 and 6. Piers 3, 4, 5, and 6 are arranged alternately along the longitudinal direction of the bridge. The space between piers 3 and 4, and between piers 5 and 6, is used to install the two side spans 11, respectively, while the space between piers 4 and 5 is used to install the middle span 12. The construction of the main piers 20 and the structure and installation method of the permanent supports are existing technologies and will not be described in detail here for brevity.

[0041] S2, install the main crossbeam 50 on the main pier 20, install the temporary cross brace 60 on the transition pier 30, and hoist the left truss 131 and right truss 132 of the side span 11 in sequence and erect them on the permanent supports of the transition pier 30 and the main pier 20, so that the two ends of the main crossbeam 50 and the temporary cross brace 60 are fixedly connected to the left truss 131 and the right truss 132, so that the left truss 131, the right truss 132, the main crossbeam 50 and the temporary cross brace 60 form a load-bearing main body directly supported by the permanent supports in the longitudinal direction of the bridge.

[0042] In this embodiment, the main crossbeam 50 includes a first main crossbeam 51 and a second main crossbeam 53. Installing the main crossbeam 50 on the main pier 20 specifically includes the following steps:

[0043] First, the first main crossbeam 51 is installed on the main pier 20. In this embodiment, the first main crossbeam 51 is installed on both piers 4 and 5. Specifically, the planar position of the first main crossbeam 51 is accurately laid out, and the edge line of the position of the first main crossbeam 51 is marked on the main pier 20. The elevation and axis of the main crossbeam 50 are adjusted to the design position by using a crawler crane for hoisting operation.

[0044] Secondly, a truss segment 133 is installed on the permanent support of the main pier 20 as the truss reference segment 134, and the truss reference segment 134 is fixed to the permanent support and the first main crossbeam 51. Specifically, one side of the truss (left or right truss) is installed first, and precise alignment is performed during hoisting to ensure that the support bolts on the permanent support can accurately pass through the pre-drilled holes at the bottom of the truss. After the elevation axis and verticality of the truss reference segment 134 are adjusted to meet the design requirements, the truss is fixed by tightening the support nuts. At the same time, the truss reference segment 134 is promptly welded to one end of the first main crossbeam 51 to prevent overturning. After construction is completed, the other side of the truss is installed and fixed to the other end of the permanent support and the first main crossbeam 51.

[0045] Subsequently, the top of the truss reference section 134 of the left truss 131 and the top of the truss reference section 134 of the right truss 132 are fixedly connected by the second main beam 53, so that the main beam 50, the left truss 131 and the right truss 132 form a frame structure, enhancing the overall stability of the structure. Specifically, the two ends of the first main beam 51 are fixedly connected to the lower chord members 136 of the left and right trusses, respectively; the second main beam 53 is located above the first main beam 51, and the two ends of the second main beam 53 are fixedly connected to the upper chord members 135 of the left truss 131 and the right truss 132, respectively.

[0046] Several truss segments 133 of the left truss 131 and right truss 132 need to be pre-assembled before installation. During pre-assembly, one truss segment 133 is reserved as a pre-assembly master segment. The pre-assembly master segment is first pre-assembled with the truss segment 133 of the side span 11, and then pre-assembled with the truss segment 133 of the middle span 12 to ensure the overall alignment of the main truss of the entire bridge. Specifically, the left truss 131 and right truss 132 of the middle span 12 are pre-assembled in the assembly plant, while the left truss 131 and right truss 132 of the side span 11 are pre-assembled directly in the assembly area arranged between the main pier 20 and the transition pier 30. During pre-assembly, the upper and lower chords 135 and 136 of truss segment 133 are placed on the assembly jig to conform to the camber line. After adjusting to ensure that the dimensions in all directions are qualified, temporary mounting plates are used to position the upper and lower chords 135 and 136. The web members 137 are assembled in sequence. By adjusting the relative positional relationship of each member, the optimal line requirement is achieved, and then the welds between truss segments 133 are welded.

[0047] In this embodiment, the temporary cross brace 60 includes a first temporary cross brace 61 and a second temporary cross brace 62. The steps of installing the temporary cross brace 60 on the transition pier 30 and sequentially hoisting and erecting the left truss segment 131 and the right truss segment 132 of the side span 11 onto the permanent supports of the transition pier 30 and the main pier 20 include:

[0048] Before hoisting the left truss 131 and right truss 132 of the side span 11, the first temporary cross brace 61 is first installed on the transition pier 30, and temporary corbels (not shown in the figure) are welded on the already installed truss reference section 134; specifically, temporary corbels are welded to both ends of the lower chord 136 of the truss reference section 134 to facilitate the docking and positioning of the truss segment 133.

[0049] After several truss segments 133 of the left truss 131 and right truss 132 of the side span 11 are pre-assembled between the main pier 20 and the transition pier 30, they are directly lifted and installed in place by crawler crane. The bottom of the left truss 131 and right truss 132 is connected to the permanent support. The ends of the left truss 131 and right truss 132 near the main pier 20 are fixed and welded to the truss reference segment 134. The ends of the left truss 131 and right truss 132 near the transition pier 30 are welded to the first temporary cross brace 61, thereby fixing the left truss 131 and right truss 132. In this embodiment, the left truss segment 131 is first installed. It is then slowly adjusted using the crawler crane boom and traction rope to bring it close to the design position. Priority is given to adjusting the end of the left truss segment 131 closest to the transition pier 30, ensuring the support bolts on the permanent support of the transition pier 30 are precisely inserted into the pre-drilled holes at the bottom of the left truss segment 131. Next, the other end of the left truss segment 131 is placed against the temporary limiting plate on the truss segment reference section 134. Fine-tuning is then performed to ensure the planar position and elevation of the left truss segment 131 meet the design requirements. Finally, the support nuts are tightened. The left truss 131 is then secured by welding the end of the main pier 20 side truss to the truss reference section 134. Specifically, the upper chord 135 of the left truss 131 is welded to the upper chord 135 of the truss reference section 134, and the lower chord 136 of the left truss 131 is welded to the lower chord 136 of the truss reference section 134. The end of the left truss 131 on the transition pier 30 side is then welded to the first temporary cross brace 61. Specifically, the lower chord 136 near the end of the transition pier 30 side is welded to the first temporary cross brace 61, thereby fixing the left truss 131. Then, the right truss 132 is installed using the same method.

[0050] After the left truss 131 and right truss 132 are installed, a second temporary cross brace 62 is installed on the end of the left truss 131 and right truss 132 near the transition pier 30. The second temporary cross brace 62 is fixedly connected to the top of the left truss 131 and right truss 132, thereby forming a stable frame structure of the left truss 131, right truss 132, first temporary cross brace 61, second temporary cross brace 62 and main beam 50 of the side span 11. Specifically, one end of the second temporary cross brace 62 is fixed to the connection node between the upper chord 135 and the web member 137 of the left truss 131, and the other end is fixed to the connection node between the upper chord 135 and the web member 137 of the right truss 132.

[0051] S3 uses the load-bearing main body as a construction platform to carry out the installation of the upper bridge deck system 152 and the lower bridge deck system 151 of the side span 11.

[0052] In this embodiment, the installation of the upper bridge deck system 152 and the lower bridge deck system 151 specifically includes the following steps: using a crawler crane on land, the lower bridge deck system 151 and the upper bridge deck system 152 are installed alternately from the main pier 20 side to the transition pier 30 side, with the lower bridge deck system 151 installed first and the upper bridge deck system 152 installed afterward, so that the lower bridge deck system 151 is one bridge deck segment ahead of the upper bridge deck system 152; when the installation of the upper bridge deck system 152 and the lower bridge deck system 151 reaches a preset length, causing the length of the free end of the left truss 131 and the right truss 132 near the transition pier 30 to decrease to a preset range, the temporary cross brace 60 is removed in order to reserve space for the crawler crane to lift. When installing the upper bridge deck system 152 and the lower bridge deck system 151, the bridge deck crossbeams are installed first, so that the two ends of the bridge deck crossbeams are fixedly connected to the left truss 131 and the right truss 132 respectively. Specifically, the two ends of the bridge deck crossbeams of the lower bridge deck system 151 are fixedly connected to the lower chord 136 of the left truss 131 and the right truss 132 respectively, and the two ends of the bridge deck crossbeams of the upper bridge deck system 152 are fixedly connected to the upper chord 135 of the left truss 131 and the right truss 132 respectively. Then the bridge deck panels are installed, so that the bridge deck panels are erected on the corresponding bridge deck crossbeams.

[0053] S4, please refer to the above as well. Figure 14 and Figure 16 Install the left truss 131 and the right truss 132 of the middle span 12, so that the two ends of the left truss 131 of the middle span 12 are connected to the left truss 131 of the two side spans 11, and the two ends of the right truss 132 of the middle span 12 are connected to the right truss 132 of the two side spans 11. Install the node beam 70 connecting the left truss 131 and the right truss 132 of the middle span 12.

[0054] In this embodiment, the left truss 131 and right truss 132 of the middle span 12 are installed using a floating crane. To reduce the lifting weight at mid-span, several truss segments 133 of the left truss 131 and right truss 132 are lifted separately. Among them, the truss segment 133 of the middle span 12 used to connect with the truss reference segment 134 is a cantilever segment 120. The node beam 70 is installed on the cantilever segment 120 and is located at the end of the cantilever segment 120 away from the truss reference segment 134.

[0055] During the installation of the left truss 131 and right truss 132 of the middle span 12, the cantilever section 120 is installed first. The floating crane, through micro-movements, aligns the interface end of the cantilever section 120 with the interface of the already installed truss reference section 134, and places it on the temporary bracket of the truss reference section 134. The elevation and axis of the cantilever section 120 are adjusted. Once the elevation and axis of the cantilever section 120 meet the design requirements, temporary fixing is immediately performed. After the temporary connection forms a stable load-bearing system, the floating crane hook can be slowly unloaded until it is completely detached from the lifting lug of the cantilever section 120. Finally, the node beam 70 is installed to ensure structural stability. The two ends of the node beam 70 are fixedly connected to the cantilever sections 120 of the left truss 131 and right truss 132 of the middle span 12, respectively, and are fixedly connected to the connection nodes of the web member 137 and the lower chord member 136 or the connection nodes of the web member 137 and the upper chord member 135.

[0056] S5, after the left truss 131 and right truss 132 of the middle span 12 are joined, the installation of the upper deck system 152 and the lower deck system 151 of the middle span 12 is carried out, such as Figure 17 As shown.

[0057] In this embodiment, in step S5, after the left truss 131 and right truss 132 of the middle span 12 are joined together to form the main load-bearing frame, the upper and lower bridge deck systems of the middle span 12 are installed using the load-bearing frame as the load-bearing foundation. The crawler crane is disassembled and transferred to the upper bridge deck system 152 of the side span 11 that has been installed, and then assembled. The upper and lower bridge deck systems 152 and 151 of the middle span 12 are alternately lifted from both banks to the middle of the span by the crawler crane. The lower bridge deck system 151 is lifted first, and then the upper bridge deck system 152 is installed, so that the lower bridge deck system 151 is ahead of the upper bridge deck system 152 by one bridge deck segment, until the bridge deck is joined together.

[0058] During the installation of the upper bridge deck system 152 and the lower bridge deck system 151, the bridge deck crossbeams are installed first, so that the two ends of the bridge deck crossbeams are fixedly connected to the left truss 131 and the right truss 132 of the middle span 12, respectively. Specifically, the two ends of the bridge deck crossbeams of the lower bridge deck system 151 are fixedly connected to the lower chord 136 of the left truss 131 and the right truss 132, respectively, and the two ends of the bridge deck crossbeams of the upper bridge deck system 152 are fixedly connected to the upper chord 135 of the left truss 131 and the right truss 132, respectively. Then the bridge deck panels are installed, so that the bridge deck panels are erected on the corresponding bridge deck crossbeams.

[0059] The aforementioned method for installing large double-layer steel truss beams without supports overturns the traditional "bottom-up" or "parallel" construction sequence. Its core lies in: through the main crossbeam 50 installed in step S2, the temporary cross brace 60, and the node crossbeam 70 installed in step S4, the left truss 131 and right truss 132 on both sides of the bridge form a stable load-bearing body directly supported by permanent supports, preventing deformation of the truss girders during subsequent bridge deck installation. Subsequently, using this load-bearing body as an aerial work platform and load-bearing foundation, the double-layer bridge deck system is installed from bottom to top using mobile hoisting equipment. This invention completely eliminates the need for temporary supports under the bridge, achieving "zero interference, high efficiency, and high safety" in the construction process, minimizing expensive and complex temporary facilities, improving economic efficiency, and is particularly suitable for complex conditions such as crossing sensitive facilities and deep valleys with rapid currents.

[0060] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for bracketless installation of a large double-layer steel truss beam, wherein the large double-layer steel truss beam includes two side spans and a middle span connecting the two side spans, each side span and the middle span includes a left truss segment, a right truss segment, a lower deck system, and an upper deck system, the left truss segment and the right truss segment are arranged at relative intervals along the transverse direction of the bridge, each left truss segment and the right truss segment includes truss segments connected in sequence, and before installation, several truss segments of the left truss segment and the right truss segment need to be pre-assembled, during which one truss segment is reserved as a pre-assembly master segment, the pre-assembly master segment is first pre-assembled with the truss segments of the side span, and after the pre-assembly is completed, it is pre-assembled with the truss segments of the middle span, the lower deck system and the upper deck system are laid on the corresponding left truss segment and the right truss segment, characterized in that... The method for installing large double-layer steel truss beams without supports includes the following steps: S1, complete the construction of two sets of main piers and two sets of transition piers of the double-layer steel truss arch bridge, and install permanent supports on the top of the main piers and the transition piers. The two sets of transition piers are spaced apart along the longitudinal direction of the bridge, and the two sets of main piers are spaced apart along the longitudinal direction of the bridge and are both located between the two sets of transition piers. S2, Install a main crossbeam on the main pier. The main crossbeam includes a first main crossbeam and a second main crossbeam. The installation of the main crossbeam includes the following steps: First, install the first main crossbeam on the main pier; second, install a truss segment as a truss reference segment on the permanent support of the main pier, and fix the truss reference segment to the permanent support and the first main crossbeam; then, fix the top of the truss reference segment of the left truss segment of the side span to the top of the truss reference segment of the right truss segment through the second main crossbeam, so that the main crossbeam, the left truss segment, and the right truss segment form a frame structure. Temporary cross bracing is installed on the transition pier, the temporary cross bracing including a first temporary cross brace and a second temporary cross brace. The left and right trusses of the side span are sequentially hoisted and erected on the permanent supports of the transition pier and the main pier. Both ends of the main beam and the temporary cross brace are fixedly connected to the left and right trusses, so that the left truss, right truss, main beam and temporary cross brace form a load-bearing body directly supported by the permanent supports. The process includes the following steps: Before hoisting the left and right trusses of the side span, the first temporary cross bracing is first installed on the transition pier. After several truss segments of the left and right trusses of the side span are pre-assembled between the main pier and the transition pier, they are directly lifted and installed in place by crawler crane. The bottom of the left and right trusses is connected to the permanent support. The ends of the left and right trusses near the main pier are fixedly welded to the truss reference segment. The ends of the left and right trusses near the transition pier are welded to the first temporary cross brace, thereby fixing the left and right trusses. After the left and right trusses are installed, the second temporary cross brace is installed on the ends of the left and right trusses near the transition pier. The two ends of the second temporary cross brace are fixedly connected to the tops of the left and right trusses, respectively, so that the left and right trusses, the main beam and the temporary cross brace of the side span form a stable frame structure. S3, using the load-bearing main body as a construction platform, to carry out the installation of the upper and lower bridge deck systems of the side span; S4, install the left and right trusses of the middle span, so that the two ends of the left truss of the middle span are connected to the left trusses of the two side spans, and the two ends of the right truss of the middle span are connected to the right trusses of the two side spans, and install the node beam connecting the left and right trusses of the middle span. S5. After the left and right trusses of the middle span are joined together, the installation of the upper and lower bridge deck systems of the middle span is carried out.

2. The method for installing large double-layer steel truss beams without supports as described in claim 1, characterized in that, The installation of the upper bridge deck system and the lower bridge deck system specifically includes the following steps: using a crawler crane on land, the lower bridge deck system and the upper bridge deck system are installed alternately from the main pier side to the transition pier side, with the lower bridge deck system installed first and the upper bridge deck system installed afterward, so that the lower bridge deck system is one bridge deck segment ahead of the upper bridge deck system; when the upper bridge deck system and the lower bridge deck system are installed to a preset length so that the length of the free end of the left truss and the right truss near the transition pier side is reduced to a preset range, the temporary cross bracing is removed in order to reserve space for the crawler crane to lift.

3. The method for installing large double-layer steel truss beams without supports as described in claim 1, characterized in that, Both the upper bridge deck system and the lower bridge deck system include bridge deck beams and bridge deck panels. When installing the upper bridge deck system and the lower bridge deck system, the bridge deck beams are installed first, so that the two ends of the bridge deck beams are fixedly connected to the left truss and the right truss respectively. Then the bridge deck panels are installed, so that the bridge deck panels are erected on the corresponding bridge deck beams.

4. The method for installing large double-layer steel truss beams without supports as described in claim 1, characterized in that, The left and right trusses of the middle span are installed using floating cranes. Several truss segments of the left and right trusses are hoisted separately. The truss segment of the middle span that is used to connect with the reference segment of the truss is a cantilever segment, and the node beam is installed on the cantilever segment.

5. The method for installing large double-layer steel truss beams without supports as described in claim 1, characterized in that, In step S5, after the left and right trusses of the middle span are joined together to form the main load-bearing frame, the upper and lower bridge deck systems of the middle span are installed using the main load-bearing frame as the load-bearing foundation. The crawler crane is disassembled and transferred to the upper bridge deck system of the side span that has been installed, and then assembled. The upper and lower bridge deck systems of the middle span are alternately lifted from both banks to the middle of the span by the crawler crane. The lower bridge deck system is lifted first, and then the upper bridge deck system is installed, so that the lower bridge deck system is ahead of the upper bridge deck system by one bridge deck segment, until the bridge deck is joined together.

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