A steel-concrete composite beam cable-stayed bridge girder erecting crane and construction method thereof

Abstract

The application provides a steel-concrete composite beam cable-stayed bridge girder erection crane and a construction method thereof. The crane adopts a non-rotating truss type main body structure combined with a main truss and a tail triangular truss, integrates a steel beam lifting system, a leveling spreader, a hoisting trolley, an auxiliary hanging cable block, multiple sets of supporting legs and a slide beam, forms a differentiated stress mode through supporting leg combination switching and hoisting trolley position control under different working conditions, and integrates three construction functions of steel beam installation, stay cable hanging and bridge deck panel hoisting. The scheme can reduce the self-weight of the cable-stayed bridge girder erection crane, effectively reduce the additional load on the installed steel beam and stay cable during the construction stage, simultaneously realize fast walking without a reversing device through dynamic regulation of the center of gravity, and effectively improve the walking efficiency. Through the collaborative design of the structural form, the stress system and the operation mode, the scheme improves the efficiency of the steel-concrete composite beam cable-stayed bridge cantilever construction, and has the advantages of reasonable structure stress, convenient construction and easy popularization and implementation.

Description

Technical Field

[0001] This application belongs to the field of bridge construction technology, specifically relating to a steel-concrete composite beam cable-stayed bridge main beam erection crane and its construction method. Background Technology

[0002] With the advancement of transportation infrastructure construction in my country, the number of long-span bridges spanning rivers and seas continues to grow. Steel-concrete composite girder cable-stayed bridges, with their advantages of rational structural stress distribution, strong spanning capacity, fast construction speed, and good overall economic efficiency, have become one of the mainstream bridge types for long-span bridges. A steel-concrete composite girder cable-stayed bridge mainly consists of three parts: the main tower, the stay cables, and the steel-concrete composite girder. It belongs to a highly statically indeterminate structural system. Its main girder typically adopts a steel beam lattice system composed of "steel longitudinal beams + steel transverse beams," with precast concrete bridge decks laid on top. The two are rigidly connected by shear studs welded to the top surface of the steel beams, forming a whole that shares the load. It combines the advantages of steel structures (light weight, high degree of prefabrication, fast construction speed) with concrete structures (high stiffness, good driving comfort, and low maintenance costs).

[0003] In the construction of the main girder of a steel-concrete composite cable-stayed bridge, the cantilever assembly method is a widely used construction technique. This involves starting from block 0 on both sides of the main tower, symmetrically cantilevering steel beams towards the mid-span, installing stay cables, laying bridge deck panels, and finally closing the span. Currently, the mainstream construction schemes fall into two categories, both of which have insurmountable technical shortcomings and economic drawbacks.

[0004] The first type of scheme is the integral steel-concrete composite beam segment hoisting scheme. This involves pre-assembling the steel beams and bridge deck in a factory or on-shore prefabrication yard to form integral steel-concrete composite beam segments, which are then hoisted into place using large floating cranes or bridge cranes. While this scheme reduces on-site high-altitude work, the self-weight of the assembled steel-concrete composite beam segments is substantial, typically reaching 200 tons per segment. This results in the stress on the main beam and stay cables during construction being far greater than the design internal forces during bridge operation, reducing structural safety redundancy. To meet the stress requirements during construction, it is necessary to increase the cross-sectional dimensions of the steel beams and improve the strength grade and safety factor of the stay cables, directly increasing the amount of engineering materials used and construction costs. Furthermore, hoisting large-tonnage segments places high demands on the lifting equipment's capacity, leading to higher equipment rental and transportation costs. Additionally, controlling the structural alignment and cable forces during construction is difficult, resulting in high construction risks. Therefore, except for small-span bridges or special conditions, this construction scheme is rarely used for large-span steel-concrete composite cable-stayed bridges.

[0005] The second approach involves the phased installation of steel beams and bridge decks. This involves first cantilevering the steel beams segment by segment and attaching the stay cables. Once the cantilever system is complete, precast bridge decks are laid one by one, ultimately forming a composite beam through wet joints and shear studs. This approach effectively reduces the weight of each lift and decreases the structural internal forces during construction, making it the mainstream construction method for similar bridges both domestically and internationally. However, in practical applications, this approach generally relies on full-rotation bridge deck cranes for the lifting operation, and these cranes have several inherent drawbacks: Firstly, the heavy weight of full-rotation cranes significantly impacts construction loads. To achieve 360° rotation and lifting capabilities, full-rotation cranes require heavy slewing bearings, platforms, and large counterweights, resulting in a total weight often far exceeding their rated lifting capacity. For example, a full-rotation bridge crane with a rated lifting capacity of 80t typically weighs 120t to 150t. This enormous weight applied to the cantilevered ends of steel beams significantly increases bending stress and cable tension, raising the structural stress calculation standards during construction and necessitating frequent adjustments to cable tension to control alignment, thus increasing construction control difficulty and project costs. In large cantilever conditions, construction stress may even exceed operational design values, hindering the bridge's spanning capacity and economic performance.

[0006] Secondly, the cranes have limited functionality, require significant investment, and suffer from poor workflow coordination. Conventional full-rotation bridge deck cranes typically only have the function of lifting steel beam segments. Cable-stayed bridge installation requires additional specialized cable-hanging trolleys and traction equipment, while precast bridge deck installation necessitates the deployment of a separate crawler crane or a second small crane. The simultaneous operation of multiple machines on the narrow bridge deck not only occupies limited construction space and increases the difficulty of safety management but also leads to poor workflow coordination. Equipment relocation and dismantling are time-consuming and labor-intensive, hindering overall construction efficiency. Furthermore, the combined costs of renting multiple machines and labor also increase the total construction cost of the project.

[0007] Thirdly, the crane's traveling procedure is cumbersome and inefficient. When a conventional bridge crane slides forward along the cantilever, due to its forward center of gravity and high risk of overturning, a reverse anchoring device must be installed at the outriggers. This device uses a reverse anchoring beam to hook the top flange of the steel beam to balance the overturning moment. Before each travel, the reverse anchoring structure needs to be disassembled and reassembled, and the reverse anchoring points need to be repeatedly changed during the travel process. Traveling a single segment usually takes half a day or even longer, slowing down the overall construction progress. At the same time, the long-term friction of the reverse anchoring device against the steel beam flange can also cause damage to the anti-corrosion coating of the steel beam, increasing the workload of subsequent anti-corrosion repair.

[0008] In response to the above problems, the industry has made many attempts to improve the system, such as using high-strength steel to reduce weight and optimizing the slewing bearing structure. However, none of these have broken away from the inherent configuration of the full-slewing crane. The reduction in self-weight is limited, and the problems of single function and low travel efficiency cannot be solved. Some projects have also tried to use truss cranes, but they can only realize the function of lifting a single steel beam. Other equipment is still required to complete the subsequent processes, and the travel still relies on the anti-locking device. No systematic solution has been formed.

[0009] Therefore, in order to systematically address the numerous shortcomings of existing construction schemes and hoisting equipment, reduce the impact of the crane's self-weight on the main beam and stay cables during the cantilever construction of steel-concrete composite girder cable-stayed bridges, and integrate multiple core functions such as steel beam installation, stay cable hanging, and bridge deck hoisting, while simplifying the crane's travel procedures, improving travel efficiency, and comprehensively improving the technical and economic indicators of steel-concrete composite girder cable-stayed bridge construction, it is currently urgent to make systematic improvements to the structural form, stress system, and supporting construction methods of bridge deck girder erection cranes to ensure the safety, economy, and efficiency of cantilever construction of large-span (≥200m) steel-concrete composite girder cable-stayed bridges. Summary of the Invention

[0010] This application addresses the aforementioned deficiencies in the prior art by providing a steel-concrete composite beam cable-stayed bridge main girder erection crane and its construction method. The aim is to solve the technical problems of existing full-rotation cranes, such as heavy self-weight, high additional load during construction, single crane function, high cost of multi-equipment coordination, and cumbersome and inefficient travel procedures. Through a collaborative design of a non-rotational truss structure, multi-leg working condition switching, multi-functional integration, and dynamic counterweight travel, the application achieves multiple technical goals of lightweight, multi-functionality, and high efficiency for the crane.

[0011] To achieve the above technical objectives, this application adopts the following technical solution: A steel-concrete composite girder cable-stayed bridge main girder erection crane includes a main truss, a tail triangular truss, a steel girder lifting system, a leveling hoist, a crane, tail auxiliary legs, a sliding beam, an auxiliary cable hoist, a middle leg, and a front leg. The main truss extends along the bridge direction and adopts a spatial structure of a double-piece planar truss with transverse bridge-direction connections. It serves as the core load-bearing structure at the front of the crane, used to fix and support the steel girder lifting system and the auxiliary cable hoist. It also reliably transfers the vertical loads and overturning moments generated during steel girder hoisting and cable installation to the installed steel girder segments through the leg structure.

[0012] The tail triangular truss is fixedly connected to the tail end of the main truss. It adopts a variable cross-section triangular truss structure. The root is rigidly connected to the lower chord and upper chord of the main truss to form an integral whole. The upper chord of the triangular truss is covered with a running track to support the crane and allow it to move back and forth. The tail triangular truss can transfer the vertical load transmitted by the crane during the installation of the bridge deck to the main truss and the tail auxiliary legs respectively, making full use of the advantages of the triangular structure in terms of reasonable stress distribution and high material utilization.

[0013] The steel beam lifting system is located in the front area of ​​the main truss. Its upper end is fixedly connected to the upper chord load-bearing node of the main truss, and its lower end is connected to the leveling lifting device through a flexible lifting device. It serves as the power execution unit for lifting the steel beam and provides the driving force for vertically lifting the steel beam to be installed.

[0014] The leveling lifting device is located below the steel beam lifting system and serves as an adaptable component for steel beam hoisting. It is used to reliably connect with the preset lifting points of the steel beam to be installed. The leveling lifting device has multi-point independent adjustment capability, which can independently adjust the vertical height of each lifting point during the lifting process, correct the spatial posture of the steel beam in real time, and ensure the levelness and alignment accuracy of the steel beam.

[0015] The overhead crane can be reciprocated along the bridge direction and is set on the upper chord track of the tail triangular truss. It has vertical lifting and longitudinal movement functions and serves as the core operation unit for bridge panel installation. It is used to complete the lifting, longitudinal movement and positioning of precast bridge panels. At the same time, the overhead crane can adjust the overall center of gravity of the crane by changing its own position, and also serves as a dynamic balance counterweight.

[0016] The tail auxiliary support leg is vertically connected to the lower node of the tail triangular truss and has telescopic adjustment and anchoring functions. It can be anchored to the pre-embedded parts on the top surface of the installed steel beam according to the working conditions. It can transmit vertical pressure and withstand upward pull force, and is a key component for realizing the switching of multiple working conditions.

[0017] The slide beam is laid along the entire length of the bridge on the top surface of the installed steel beam, and is fixed to the embedded parts by pressure plates. It serves as the load-bearing track for the crane to travel, supports the leg structure under the main truss, and provides a flat, low-friction sliding interface for the crane to slide forward as a whole.

[0018] The auxiliary cable hoist is connected to the front cantilever of the main truss and can move slightly along the front track. It has traction and lifting functions and serves as a special working unit for cable installation. It is used for cable traction, cable head alignment and initial tensioning, eliminating the need for additional cable hanging equipment.

[0019] The middle support leg and the front support leg are arranged sequentially below the main truss along the bridge direction, with the front support leg close to the front end of the main truss and the middle support leg located in the middle area of ​​the main truss. Both legs have dual functions of support and travel, and can be flexibly combined with the tail auxiliary support leg to form a support force mode that adapts to different construction procedures, so as to achieve the optimal force state under various working conditions.

[0020] In some feasible embodiments, during the installation of steel beams and stay cables, the girder erecting crane is supported on the installed steel beam by the tail auxiliary outrigger and the front outrigger, while the middle outrigger is detached from the installed steel beam. The overhead crane moves to the tail of the crane to balance the lifting moment at the front. At this time, the tail auxiliary outrigger is in tension and the front outrigger is in compression, forming a large-span lever force system, which can effectively reduce the peak value of concentrated load on the installed steel beam.

[0021] In some feasible embodiments, during bridge deck installation, the girder erecting crane is supported on the installed steel beam by the tail auxiliary outrigger and the middle outrigger, the front outrigger is suspended in the air, the crane as a whole is in a simply supported state, the internal force of the structure is evenly distributed, the load-bearing efficiency is high, and the load transmitted to the bridge deck is evenly distributed.

[0022] In some feasible embodiments, when the crane is traveling, the overhead crane moves to the front end of the tail triangular truss and is located directly above the middle outrigger. The center of gravity of the whole machine falls between the front outrigger and the middle outrigger. Both the front outrigger and the middle outrigger are under pressure. The crane has no risk of overturning and does not need to be equipped with a reverse buckling device. It can slide forward smoothly along the slide beam.

[0023] In some feasible embodiments, the steel beam lifting system includes at least two sets of lifting jacks and matching high-strength, low-relaxation steel strands. The lifting jacks are fixed to the upper chord load-bearing nodes of the main truss by anchors. After the steel strands are vertically inserted downwards, their lower ends are connected to the top lifting lugs of the leveling device by special anchors, so as to achieve stable and stepless vertical lifting.

[0024] In some feasible embodiments, the leveling lifting device includes a main beam of the lifting device arranged in the transverse direction and at least 4 sets of independent adjustable lifting points. Each set of lifting points is equipped with a stroke adjustment cylinder and a load sensor, which can independently adjust the lifting height of a single lifting point. The attitude adjustment accuracy is controlled within ±3mm. At the same time, the load of each lifting point is monitored in real time to ensure that the force is balanced during the lifting process.

[0025] To address the technical problems raised in this application, this application also provides a construction method for the main beam erection crane of the aforementioned steel-concrete composite cable-stayed bridge, which includes a sequential cycle of steel beam and cable-stayed cable installation, bridge deck installation, and crane travel. The three processes correspond to three different leg combination methods and structural stress modes, and efficient construction throughout the entire process is achieved through working condition switching.

[0026] In some feasible embodiments, the installation process of the steel beam and stay cables includes the following steps: Step S11: Preparation for switching working conditions. Lower the auxiliary outriggers at the rear of the girder erecting crane and reliably connect them to the pre-embedded anchor plates on the top surface of the installed steel beam through precision-rolled threaded steel bars to ensure they can withstand upward pulling forces; lower the front outriggers to support the corresponding positions at the front end of the installed steel beam, and secure the bottom of the outriggers to the top surface of the steel beam; retract the middle outriggers upwards and release their fixed connection to the installed steel beam, leaving it in a suspended state; simultaneously move the crane along the track of the rear triangular truss to the final limit position, using the crane's own weight as a counterweight to counteract the overturning moment generated by the hoisting of the front steel beam.

[0027] Step S12: Steel beam lifting and alignment installation. The leveling lifting device is slowly lowered via the steel beam lifting system to the top of the steel beam to be installed, which is loaded onto the bridge beam transport vehicle. With manual assistance, the lifting device is connected and locked to the four pre-set lifting points on the steel beam. After confirming the connection is reliable, a trial lift is performed. The steel beam lifting system is then started, and the steel beam is slowly lifted to 100mm above the bridge beam transport vehicle surface and stopped. After standing still for 5 minutes, the stress on the lifting device, the working status of the jacks, and the posture of the steel beam are thoroughly checked. Once no abnormalities are confirmed, lifting continues at a constant speed. During lifting, the height of each lifting point is adjusted in real time using the stroke adjustment cylinders of the leveling lifting device to maintain the horizontal deviation of the steel beam in both the transverse and longitudinal directions of the bridge no greater than 1 / 1000. After the bottom of the steel beam is lifted to 50mm above the top surface elevation of the already installed steel beam, the position of the steel beam is finely adjusted in the transverse direction, and then slowly lowered for alignment. The bevel joint of the steel beam segments is completed, and temporary bolts are fastened. Welding then commences.

[0028] Step S13: Cable Installation and Initial Tensioning. After the steel beam butt welding is completed and the flaw detection is qualified, the auxiliary cable hoist at the front end of the main truss is used in conjunction with the cable release plate on the bridge deck to pull the cable head of the cable. First, the lower end of the cable is connected and anchored to the anchor seat on the steel beam. Then, the upper end of the cable is pulled to the corresponding cable guide position on the main tower to complete the cable installation at the tower end. After the cable is installed, the tensioning jack is installed to perform initial tensioning of the cable. The cable force is gradually adjusted to the control value given by the construction monitoring to complete the installation of the cable in the current segment.

[0029] In some feasible embodiments, the bridge deck installation process includes the following steps: Step S21: Force System Switching. After the steel beams and stay cables are installed, the middle outrigger is slowly lowered to support the corresponding position of the installed steel beam. The outrigger height is adjusted to ensure even force distribution and then locked in place. Subsequently, the front outrigger is retracted upwards to release the support constraints and place it in a suspended state. The rear auxiliary outrigger remains in a supported and anchored state. At this time, the girder erecting crane forms a double-support simply supported force system with the middle outrigger through the rear auxiliary outrigger, providing a stable load-bearing foundation for the bridge deck installation.

[0030] Step S22: Install precast bridge panels piece by piece. Transport the precast bridge panels to the working area at the rear of the crane using a bridge deck transport vehicle. Move the overhead crane directly above the bridge panel and lower the lifting device to connect with the pre-embedded lifting points on the bridge panel. After confirming a reliable connection, lift the bridge panel and raise it to a safe height. Then, move the overhead crane forward along the track to transport the bridge panel directly above the installation position. By fine-tuning the longitudinal position of the overhead crane and the height of the lifting device, accurately position the bridge panel to the designed position of the steel beam lattice. After adjusting the alignment, temporarily fix it. Repeat the above lifting, longitudinal movement, and positioning process to complete the laying and temporary fixing of all precast bridge panels in the current segment. The subsequent wet joint pouring operation will then be carried out.

[0031] In some feasible embodiments, the crane traveling process includes the following steps: Step S31: Adjusting the overall center of gravity of the crane. After the installation of the steel beams, tensioning of the stay cables, and laying of the bridge deck of the current segment are completed, prepare to move the crane to the next segment. First, slowly move the overhead crane forward along the track of the tail triangular truss until it stops directly above the middle outrigger. By moving the crane forward, the overall center of gravity of the crane is shifted forward, and finally it is accurately placed in the area between the two support points of the front outrigger and the middle outrigger, ensuring that both outriggers bear the vertical pressure.

[0032] Step S32: Preparatory work before travel. Disconnect the anchoring connection of the fine-rolled threaded steel bars between the tail auxiliary outriggers and the installed steel beam, and retract the outriggers upwards to a safe height, keeping them suspended; clean the debris and dust from the top surface of the slide beam, and evenly apply silicone grease to the surface of the slide beam to reduce sliding friction resistance; check the traveling shoes at the bottom of the front and middle outriggers to ensure that the shoes are fully in contact with the top surface of the slide beam, the guide device clearance meets the requirements, and the hydraulic synchronous traction system is reliably connected.

[0033] Step S33: Synchronous Sliding and Anchoring. Activate the hydraulic synchronous traction system to drive the front and middle outriggers to slide forward synchronously along the slide beam, controlling the sliding speed within the range of 3m / min to 5m / min. During the sliding process, the displacement sensors monitor the movement of the two outriggers in real time, ensuring the synchronous deviation does not exceed 10mm. If a deviation occurs, correct it promptly using the speed control valve. Once the crane has slid to the preset construction position for the next segment, immediately stop traction, install limit blocks to fix the outrigger positions, and then lower the corresponding outriggers according to the procedure requirements to complete the anchoring. This completes one standard segment's travel cycle, allowing the next round of construction work to begin.

[0034] Compared with the prior art, this application has the following beneficial effects: The steel-concrete composite girder cable-stayed bridge main girder erection crane and its construction method provided in this application abandon the conventional slewing base configuration of full-rotation cranes and adopt a pure truss main structure composed of a main truss and a tail triangular truss. The overall weight of the machine is reduced by more than 30% compared with a full-rotation crane of the same tonnage, effectively reducing the additional load on the installed steel beams and cable stays during the construction stage, without the need for additional structural design standards. Through the differentiated combination of three sets of outriggers and the position adjustment of the crane, a system adaptable to steel beam hoisting, bridge deck installation, and overall machine travel is formed. The system employs three dedicated stress modes for different working conditions, achieving optimal structural stress and minimized bridge deck load in each case. Simultaneously, a single crane integrates three core functions: steel beam installation, cable-stayed bridge installation, and bridge deck hoisting, eliminating the need for additional cable-stayed and bridge deck hoisting equipment, thus reducing equipment investment and interference with bridge deck operations. Crucially, the mobile overhead crane also functions as a dynamic counterweight, enabling rapid movement without anti-locking devices through center-of-gravity adjustment, eliminating the need for disassembly and assembly of anti-locking structures, and improving movement efficiency by over 50% compared to conventional cranes. Through synergistic innovation in structural form, stress system, and operational mode, the overall solution systematically addresses several technical deficiencies of existing technologies, improving the efficiency and technical economy of cantilever construction of steel-concrete composite girder cable-stayed bridges. It boasts advantages such as rational structural stress, convenient and efficient construction, strong engineering adaptability, and ease of promotion and implementation. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall structure of a steel-concrete composite beam cable-stayed bridge main beam erection crane according to this application.

[0036] Figure 2 This application Figure 1 A magnified view of a portion of point A in the middle.

[0037] Figure 3 This application Figure 1 A magnified view of a section at point B.

[0038] Figure 4 This is a schematic diagram of the stress state of the girder erecting crane in the installation of steel beams and cable stays.

[0039] Figure 5 This is a schematic diagram of the stress state of the girder erecting crane in the bridge deck installation process of this application.

[0040] Figure 6 This is a schematic diagram of the beam erecting crane in the traveling state of this application. Detailed Implementation

[0041] The technical solution of this application will be further described in detail below with reference to the accompanying drawings and specific embodiments. The specific embodiments described are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0042] See Figures 1-6 This embodiment provides a steel-concrete composite girder cable-stayed bridge main girder erection crane, which is mainly composed of ten parts: main truss 1, tail triangular truss 2, steel beam lifting system 3, leveling hoist 4, crane 5, tail auxiliary support leg 6, slide beam 7, auxiliary cable hoist 8, middle support leg 11, and front support leg 12. The whole is arranged along the longitudinal direction of the bridge and supported on the top surface of the installed steel beam 9. It is used to complete the cantilever construction of the steel beam 10, cable stays, and bridge deck 13 to be installed.

[0043] Specifically, the main truss 1 adopts a double-section parallel chord truss structure, with a single truss height of 4.5m, a section length of 3m, and a total length of approximately 24m. The upper and lower chords and web members of the truss are all made of Q355B welded H-beams, connected at the joints with high-strength bolts. A transverse bridge connection system and cross bracing are installed between the two trusses to form a stable spatial load-bearing system. The front 8m section of the main truss 1 is the steel beam hoisting area, the middle section has a connecting node for the central support leg 11, and the rear section is rigidly connected to the rear triangular truss 2 as a whole. As the core load-bearing structure, the main truss 1 bears all the loads of steel beam lifting and cable-stayed installation, and transfers the load to the installed steel beam 9 through the support legs.

[0044] The tail triangular truss 2 adopts a variable cross-section triangular configuration, with its root height matching that of the main truss 1 and its end height of 2.5m, for a total length of approximately 18m. The upper chord of the triangular truss utilizes a continuous track beam, on which QU80 crane rails are laid for the reciprocating movement of the overhead crane 5. The root of the lower chord of the tail triangular truss 2 is rigidly connected to the lower chord of the main truss 1, while the upper chord is connected to the upper chord of the main truss 1 via diagonal web members, forming a stable triangular force-bearing system that efficiently transmits the vertical load of the overhead crane 5. Compared to parallel trusses, the triangular structure exhibits superior load-bearing performance when subjected to moving concentrated loads, allowing for a reduction in member cross-sectional dimensions and further reducing the structure's self-weight.

[0045] The steel beam lifting system 3 is located at the upper chord node at the front of the main truss 1. In this embodiment, two lifting jacks with a rated lifting force of 100t are configured, equipped with φ15.24mm high-strength, low-relaxation steel strands. Each jack is equipped with 19 steel strands. The jacks are fixed to the upper chord of the main truss 1 via anchors and reaction frames. The steel strands pass vertically downward through the truss nodes, and the lower ends are connected to the top lifting lugs of the leveling lifting device 4 via special lifting anchor heads. The lifting jacks have the functions of stepless speed regulation, load balancing, and synchronous lifting. The lifting speed range is 0-8m / h, which can meet the requirements of stable lifting and fine-tuning of the steel beam.

[0046] The leveling lifting device 4 adopts a box-section main beam structure, with the main beam length matching the width of the steel beam. Four sets of independently adjustable lifting points are arranged in a rectangular pattern below the main beam. Each lifting point is equipped with a 200mm stroke hydraulic adjusting cylinder and a pressure sensor. The lower end of the cylinder is connected to a lifting lug and a shackle for connecting to the lifting point of the steel beam 10 to be installed. Through the independent extension and retraction of the four sets of cylinders, the height of the four lifting points can be adjusted separately, achieving adjustment of the steel beam's cross slope and longitudinal slope, with a leveling accuracy of ±3mm. The pressure sensor can monitor the load of each lifting point in real time, avoiding single-point overload and ensuring lifting safety.

[0047] The overhead crane 5 is a gantry crane with a rated lifting capacity of 20t. It is equipped with an electric winch lifting mechanism and a traveling mechanism. The traveling wheels roll along the track on the rear triangular truss 2 at a speed of 0-10m / min. The overhead crane 5 is mainly responsible for lifting and longitudinally moving the precast bridge deck 13. At the same time, its own weight of about 15t can be used as a dynamic counterweight. By moving back and forth along the track, the overall center of gravity of the crane can be adjusted to achieve force balance under different working conditions. There is no need to set up additional fixed counterweights, which effectively reduces the total weight of the crane.

[0048] The rear auxiliary outrigger 6 is located at the lower end node of the rear triangular truss 2. It adopts a telescopic box-type column structure with a telescopic stroke of 500mm. An anchoring flange is installed at the bottom, which can be connected to the pre-embedded anchor plate on the top surface of the installed steel beam 9 through four φ32mm precision-rolled threaded steel bars. It can transmit vertical pressure and withstand upward pull force, with a tensile and compressive bearing capacity of not less than 200t. The outrigger telescopic is hydraulically driven, which can quickly adjust the outrigger height to adapt to the support requirements of different working conditions.

[0049] The sliding beam 7 is constructed from double-section I45b I-beams, each 12m in length. It is symmetrically laid along the bridge direction on the top surfaces of the longitudinal beams on both sides of the already installed steel beam 9. It is fixed to the top surface of the steel beams by pressure plates and embedded parts, ensuring the straightness and stability of the track. The top surface of the sliding beam 7 serves as the sliding working surface; it is ground and rust-removed, and lubricated with silicone grease during sliding, keeping the coefficient of friction below 0.1. The sliding beam can be progressively extended and reconnected as the crane moves, meeting the requirements of continuous cantilever construction.

[0050] Two auxiliary cable-hanging hoists (8) are installed on the cantilever rail at the front end of the main truss (1). Each hoist has a rated traction force of 10t and can move slightly along the front transverse bridge rail. They are equipped with wire ropes and cable clamps. These auxiliary cable-hanging hoists are mainly used for traction, cable head alignment, and initial tensioning of the stay cables. They meet the installation requirements of standard stay cables, eliminating the need for additional large cable-hanging equipment on the bridge deck, thus saving on equipment investment and operating space.

[0051] The middle support leg 11 and the front support leg 12 are sequentially located at corresponding nodes below the main truss 1. The two support legs have basically the same structural form, both adopting a box-shaped column structure with a bottom sliding shoe. The sliding shoe is made of cast steel, with a polytetrafluoroethylene sliding plate inlaid on the bottom surface, which cooperates with the top surface of the sliding beam 7 to achieve low-friction sliding. The support leg is equipped with a hydraulic lifting cylinder, which can realize the extension and retraction adjustment of the support leg height. The front support leg 12 is located at about 4m at the front end of the main truss 1, and the middle support leg 11 is located in the middle of the main truss 1, with a center-to-center distance of about 12m between the two support legs.

[0052] The following describes in detail the specific working process and force principle of this crane under three working conditions: Working Condition 1: Installation of Steel Beams and Cable Stays See Figure 4 This work condition is the core process of cantilever construction, which mainly involves hoisting and connecting the steel beam 10 to be installed and hanging and tensioning the corresponding segment stay cables.

[0053] Before operation, the working conditions are switched: the tail auxiliary outrigger 6 is lowered, the bottom flange is aligned with the pre-embedded anchor plate of the installed steel beam 9, the fine-rolled threaded steel bar is inserted and pre-tightened to ensure that it can withstand the upward pull force; the front outrigger 12 is lowered, the bottom slip shoe is placed on the front top surface of the installed steel beam 9, and pre-pressure is applied to make the outrigger evenly stressed; the middle outrigger 11 is retracted upward, the bottom slip shoe is removed from the top surface of the slide beam 7 and kept in a suspended state; at the same time, the crane 5 is operated to move backward along the track to the rearmost limit position of the tail triangular truss 2, and the crane's own weight is used to form a tail counterweight to balance the overturning moment of the front hoisting.

[0054] After the working condition switch is completed, the steel beam hoisting begins: the beam transport vehicle delivers the steel beam 10 to be installed to the area directly below the crane. The operator controls the steel beam lifting system 3 to slowly lower the leveling lifting device 4. Ground workers assist in connecting the four sets of lifting points to the steel beam lifting lugs, threading the shackles, and locking them securely. After confirming that the connection is correct, the lifting system is started for a trial lift. The steel beam slowly rises to 100mm above the beam transport vehicle's surface and stops. After standing still for 5 minutes, a comprehensive check is performed on the stress at each lifting point, the hydraulic pressure of the jacks, and the posture of the steel beam. Once it is confirmed that there are no abnormalities, the formal lifting begins. During the lifting process, the lifting speed is maintained at approximately 5m / h. The leveling lifting device 4's hydraulic cylinders are used to adjust the steel beam's level in real time, ensuring that the deviations in the transverse and longitudinal directions are within the allowable range.

[0055] Once the bottom surface of the steel beam exceeds the top surface of the installed steel beam 9 by 50mm, the lifting is stopped. The transverse bridge position of the steel beam is adjusted using a transverse bridge fine-tuning device (hydraulic rod, which is integrated into the leveling hoist or the front end of the main truss). Then, it is slowly lowered for alignment. After alignment, temporary punches and high-strength bolts are installed to temporarily fix the steel beam. Then, circumferential welding is performed. After welding, the weld is subjected to non-destructive testing. Only after the test is qualified can subsequent processes be carried out.

[0056] After the steel beams are installed, the stay cables are installed: the cable trays on the bridge deck are deployed, and the cable heads are pulled using the auxiliary cable hoist 8. First, the lower end anchor head of the stay cable is inserted into the steel beam anchor seat and the nut is tightened. Then, the upper end cable head is pulled upward to the main tower cable guide pipe to complete the cable threading and anchoring at the tower end. After the cable is hung, tension jacks are installed at the tower end, and initial tensioning is carried out in stages according to the construction monitoring instructions until the cable force reaches the design control value, thus completing the installation of the stay cables for the current segment.

[0057] Under this condition, the load of the steel beam at the front of the crane and the traction force of the stay cables are transferred to the front outrigger 12 through the main truss 1, where the front outrigger 12 bears the vertical pressure. The moment generated by the self-weight of the crane 5 and the structure at the rear is transferred to the rear auxiliary outrigger 6 through the rear triangular truss 2, causing the rear auxiliary outrigger 6 to bear the upward pull. The large distance between the two support points forms a large-span lever force system, which can effectively distribute and transfer concentrated loads, significantly reduce the local compressive stress on the installed steel beam 9, and at the same time reduce the bending moment at the cantilever end and reduce the increase in cable force of the stay cables.

[0058] Working Condition 2: Bridge Deck Installation See Figure 5 This work condition is carried out after the steel beam and cable stays are completed, and the main task is to lay and install the precast bridge deck 13 of the current segment.

[0059] Before operation, the load-bearing system is converted: the middle support leg 11 is slowly lowered, and the bottom slipper rests on the top surface of the slide beam 7. Pre-pressure is applied by lifting it with the built-in hydraulic cylinder, so that the middle support leg 11 bears the load evenly and is locked. Then, the front support leg 12 is retracted upwards, detached from the bridge deck and suspended in the air. The rear auxiliary support leg 6 remains in a supported and anchored state, bearing the vertical pressure. At this time, the entire crane forms two vertical support points through the rear auxiliary support leg 6 and the middle support leg 11, and is in a simply supported beam load-bearing state.

[0060] During bridge deck installation, a flatbed transport vehicle moves the precast bridge deck 13 to the rear of the crane. The overhead crane 5 moves to directly above the bridge deck and lowers the lifting device to connect with the pre-embedded lifting rings on the bridge deck. After lifting to a safe height, the overhead crane 5 moves forward along the track, transporting the bridge deck to above the installation position. Operators use the crane's fine-tuning mechanism and lifting mechanism to precisely position the bridge deck in the designed position of the steel beam lattice. After adjusting the elevation and alignment, temporary supports are used for fixation. The above process is repeated, laying all bridge decks of the current segment sequentially from the middle to both sides. After completion, shear studs and wet joint pouring are performed.

[0061] Under this condition, the crane is a simply supported system. The moving load of the overhead crane 5 and the weight of the bridge deck are evenly borne by the two supports. The internal force distribution of the truss members is reasonable and the material utilization rate is high. At the same time, the load is evenly transferred to the installed steel beam 9 through the two supports, avoiding the local impact of concentrated load on the steel beam. The structure has good stability and high safety during construction.

[0062] Operating Condition 3: Crane forward movement operation See Figure 6 Once all construction work for the current segment is completed, the crane needs to slide forward one segment to begin the next cycle of construction.

[0063] Before traveling, the center of gravity is adjusted: the crane 5 is slowly moved forward from the rear until it stops directly above the middle outrigger 11; through center of gravity calculation and actual verification, at this time the overall center of gravity of the crane falls exactly between the two support points of the front outrigger 12 and the middle outrigger 11, and the distance from the two support points is equal, ensuring that both outriggers bear vertical pressure and no overturning moment is generated.

[0064] After the center of gravity is adjusted, release the fine-rolled threaded steel bar anchorage of the tail auxiliary outrigger 6, and retract the outrigger upward to a safe height to avoid scraping against the bridge deck components during travel; clean the debris on the top surface of the slide beam 7 and apply silicone grease; check the guide device of the front outrigger 12 and the middle outrigger 11, and connect the traction cable of the hydraulic synchronous traction system.

[0065] After the preparation work is completed, the synchronous hydraulic traction system is started to pull the front outrigger 12 and the middle outrigger 11 to slide forward synchronously along the slide beam 7. The sliding speed is controlled at about 4m / min. During the sliding process, the displacement of the two outriggers is collected in real time by the displacement sensor. The synchronous control system keeps the displacement deviation of the two outriggers no more than 10mm to prevent the crane from tilting and getting stuck on the rail.

[0066] When the crane travels to the preset position of the next segment, traction is stopped, and front and rear limit blocks are installed to fix the outriggers; then, according to the requirements of the next process, the corresponding outriggers are lowered and anchored to complete the entire travel process.

[0067] Under this condition, since the center of gravity is controlled between the two support points and both legs are under pressure, the crane itself is in a stable state. It does not require the anti-locking device and anti-locking beam structure configured in conventional cranes, eliminating the cumbersome procedures of installing anti-locking devices before travel and switching anti-locking devices during travel. The travel time of a single section can be shortened to 1 to 2 hours, which is more than 50% more efficient than conventional cranes. At the same time, it avoids the wear and damage to the anti-corrosion coating of the steel beam flange caused by the anti-locking device, reducing the amount of subsequent repair work.

[0068] Based on the detailed description of the above specific embodiments, this application achieves several technical advantages over the prior art, as follows: First, the structural lightweighting effect is significant, reducing additional construction loads. This design abandons the bulky slewing bearing, slewing platform, and fixed counterweight system of a full-rotation crane, adopting a truss-type main structure with higher stress efficiency. Simultaneously, the overhead crane is used as a dynamic counterweight, achieving functional reuse of the overhead crane. Calculations show that, under the same lifting capacity, the overall weight of this crane is reduced by 30%–35% compared to a conventional full-rotation crane, directly reducing the vertical load and bending moment at the cantilever end. This significantly reduces the stress increase in steel beams and cable tension during construction, eliminating the need for additional structural design standards, effectively reducing construction costs, and improving the overall technical and economic indicators of the bridge. This effect is not simply lightweighting through material replacement, but a significant weight reduction achieved through configuration optimization and functional reuse.

[0069] Secondly, precise adaptation to stress under multiple working conditions and dual optimization of structure and bridge deck. Through the flexible combination of three sets of outriggers, customized stress modes are implemented for three different construction processes: a large-span tension-compression lever system is used to distribute the load during steel beam installation; a simply supported system is used to optimize internal force distribution during bridge deck installation; and a double-compression support point is used to ensure stability during travel. Under each working condition, the stress on the crane's own structure and the load transmitted to the bridge deck are both optimized, which not only improves the load-bearing efficiency and safety reserve of the crane structure but also minimizes the local stress impact on the existing steel beams.

[0070] Third, the multi-functional integration reduces equipment investment and process interference. A single crane simultaneously performs three core functions: steel beam hoisting, cable-stayed cable installation, and bridge deck installation, covering all major processes in the cantilever construction of steel-concrete composite beams. This replaces the conventional combination of a bridge deck crane, cable-stayed cable installation equipment, and bridge deck crane, significantly reducing equipment rental costs and operator staffing. It also avoids spatial conflicts and safety risks associated with multiple machines operating simultaneously on narrow bridge decks, resulting in smoother process transitions and a faster overall construction pace. This multi-functional integration is not simply a matter of adding functions together; rather, it utilizes the same main truss, outriggers, and traveling system, achieving functional reuse and structural simplification. The overall weight is actually lighter than a single full-rotation crane, achieving the dual benefits of functional integration and structural lightweighting.

[0071] Fourth, the rapid, non-reverse-locking travel significantly improves construction efficiency. Utilizing a mobile overhead crane as a dynamic counterweight, the crane's center of gravity is adjusted to ensure it always lies between the two outriggers during travel, reducing the risk of tipping over mechanically and eliminating the need for the reverse-locking device and beam structure found in conventional cranes. This improvement not only simplifies the crane's structure but, more importantly, eliminates the cumbersome procedures of installing, replacing, and removing the reverse-locking device during travel. The travel time for a single section is reduced from over half a day to less than two hours, increasing travel efficiency by over 50% and effectively accelerating the overall progress of cantilever construction.

[0072] In summary, the steel-concrete composite beam cable-stayed bridge main beam erection crane and its construction method provided in this application have made systematic innovations in four dimensions: structural configuration, stress system, functional integration, and travel mode. The various technical features support and synergize with each other, jointly achieving multiple technical goals of weight reduction, efficiency improvement, and cost reduction. It effectively solves many long-standing defects in existing technologies and has engineering application value for improving the construction technology level and economic performance of large-span steel-concrete composite beam cable-stayed bridges.

[0073] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application. Contents not described in detail in this specification are all prior art known to those skilled in the art.

Claims

1. A main beam erection crane for a steel-concrete composite cable-stayed bridge, characterized in that, It includes the main truss (1), the tail triangular truss (2), the steel beam lifting system (3), the leveling hoist (4), the crane (5), the tail auxiliary outrigger (6), the slide beam (7), the auxiliary cable hoist (8), the middle outrigger (11), and the front outrigger (12). The main truss (1) extends along the bridge direction to support the steel beam lifting system (3) and the auxiliary cable hoist (8), and to transfer the vertical load and overturning moment of the steel beam and cable installation process to the installed steel beam (9). The tail triangular truss (2) is fixedly connected to the tail end of the main truss (1) to support the crane (5) and transfer the load during the bridge deck installation process to the main truss (1) and the tail auxiliary leg (6). The steel beam lifting system (3) is located in the front area of ​​the main truss (1) and is connected to the main truss (1) and the leveling hoist (4) respectively, for vertically lifting the steel beam (10) to be installed. The leveling lifting device (4) is used to connect with the lifting points of the steel beam (10) to be installed, and independently adjusts the height of each lifting point during the lifting process to correct the spatial posture of the steel beam; The overhead crane (5) can be reciprocated along the bridge direction and set on the upper chord track of the tail triangular truss (2) for lifting and positioning the bridge deck (13). The tail auxiliary support leg (6) is vertically connected to the lower end of the tail triangular truss (2) and can be anchored to the installed steel beam (9) to transmit vertical support force or upward force. The slide beam (7) is laid along the bridge direction on the top surface of the installed steel beam (9) to support the main truss (1) and allow the main truss (1) to slide along the bridge direction; The auxiliary cable hoist (8) is connected to the front cantilever of the main truss (1) and is used for the traction, installation and initial tensioning of the stay cables. The middle support leg (11) and the front support leg (12) are arranged sequentially below the main truss (1) along the bridge direction, and are used to cooperate with the tail auxiliary support leg (6) to switch the support force mode for different construction conditions.

2. The main girder erection crane for a steel-concrete composite cable-stayed bridge according to claim 1, characterized in that, During the installation of steel beams and cable stays, the girder erecting crane is supported on the installed steel beam (9) by the tail auxiliary outrigger (6) and the front outrigger (12). The middle outrigger (11) is disengaged from the installed steel beam (9), and the overhead crane (5) can move to the tail of the crane to balance the front lifting torque.

3. The main girder erection crane for a steel-concrete composite cable-stayed bridge according to claim 1, characterized in that, During bridge deck installation, the girder erecting crane is supported on the installed steel beam (9) by the tail auxiliary leg (6) and the middle leg (11), and the front leg (12) is suspended in the air.

4. The main girder erection crane for a steel-concrete composite cable-stayed bridge according to claim 1, characterized in that, When the crane is traveling, the overhead crane (5) moves to the front end of the tail triangular truss (2) and is located directly above the middle support leg (11). The center of gravity of the overhead crane (5) falls between the front support leg (12) and the middle support leg (11). Both the front support leg (12) and the middle support leg (11) are under pressure. The girder crane can slide forward along the slide beam (7) through the front support leg (12) and the middle support leg (11).

5. The main girder erection crane for a steel-concrete composite cable-stayed bridge according to claim 1, characterized in that, The steel beam lifting system (3) includes at least two sets of lifting jacks and matching steel strands. The lifting jacks are fixed at the upper chord node of the main truss (1). After the steel strands are laid downwards, their lower ends are connected to the top lugs of the leveling hoist (4).

6. The main girder erection crane for a steel-concrete composite cable-stayed bridge according to claim 1, characterized in that, The leveling lifting device (4) includes a main beam and at least 4 sets of independent adjustable lifting points. Each set of lifting points is equipped with a stroke adjustment cylinder. The stroke adjustment cylinder is used to independently adjust the lifting height of a single lifting point. The adjustment accuracy of the stroke adjustment cylinder is ±3mm.

7. The construction method of the main girder erection crane for a steel-concrete composite cable-stayed bridge according to any one of claims 1 to 6, characterized in that, This includes the sequential installation of steel beams and stay cables, bridge deck installation, and crane travel.

8. The construction method of the main girder erection crane for a steel-concrete composite cable-stayed bridge according to claim 7, characterized in that, The installation process for the steel beams and stay cables includes the following steps: Step S11: Preparation for switching working conditions. Anchor the tail auxiliary support leg (6) of the girder erecting crane to the pre-embedded part on the top surface of the installed steel beam (9) through the fine-rolled threaded steel bar. Support and fix the front support leg (12) to the corresponding position at the front end of the installed steel beam (9). Release the fixed connection between the middle support leg (11) and the installed steel beam (9). Move the crane (5) along the track to the rear end of the tail triangular truss (2) as a counterweight. Step S12: Lifting and positioning of steel beams. The leveling lifting device (4) is lowered above the steel beam (10) to be installed on the bridge beam transport vehicle and connected and locked with the preset lifting points of the steel beam (10). The steel beam lifting system (3) is started for trial lifting. After the steel beam is 100mm off the ground, it is left to stand still for 5 minutes to check the stress state. After confirming that there are no errors, it is lifted at a uniform speed. During the lifting process, the height of each lifting point is adjusted in real time by the leveling lifting device (4) to keep the horizontal deviation of the steel beam no more than 1 / 1000. After the steel beam is lifted to the design elevation, the transverse and longitudinal bridge directions are finely aligned to complete the bevel joint and temporary consolidation of the steel beam segments. Step S13: Cable installation. After the steel beams are connected, the cable ends are pulled by the auxiliary cable hoist (8) at the front end of the main truss (1) to complete the beam end anchorage and tower end hanging in sequence. Then the cable is initially tensioned to adjust the cable force to the designed construction control value.

9. The construction method of the main girder erection crane for a steel-concrete composite cable-stayed bridge according to claim 7, characterized in that, The bridge deck installation process includes the following steps: Step S21: Switch working conditions, lower the middle support leg (11) to the corresponding position of the installed steel beam (9) and lock it in place, release the support constraint of the front support leg (12) so that it is suspended, retain the support anchoring state of the tail auxiliary support leg (6), so that the girder erecting crane forms a double-support simple force system with the middle support leg (11) through the tail auxiliary support leg (6); Step S22: Install the bridge deck panels one by one. Transport the precast bridge deck panels (13) to the crane's operating range using a bridge deck transport vehicle. Move the overhead crane (5) directly above the bridge deck panels and lower the lifting device to connect with the bridge deck panel lifting points. After lifting to the predetermined height, move the overhead crane (5) forward along the track to the position to be installed. By fine-tuning the crane position and the height of the lifting device, accurately place the bridge deck panels onto the grid structure of the installed steel beams. Repeat the above process to complete the laying and temporary fixing of all precast bridge deck panels in the current segment.

10. The construction method of the main girder erection crane for a steel-concrete composite cable-stayed bridge according to claim 7, characterized in that, The crane traveling process includes the following steps: Step S31: Center of gravity adjustment. After the current segment of steel beam, cable stays and bridge deck are all completed, move the crane (5) forward along the track of the tail triangular truss (2) to the position directly above the middle support leg (11), so that the overall center of gravity of the crane shifts forward and finally falls in the middle area between the two support points of the front support leg (12) and the middle support leg (11). Step S32: Travel preparation, disconnect the anchoring connection between the tail auxiliary leg (6) and the installed steel beam (9), and retract the tail auxiliary leg (6) to a suspended state; check the flatness and cleanliness of the top surface of the slide beam (7), and apply silicone grease to the surface of the slide beam (7) for lubrication; confirm that the travel shoes of the front leg (12) and the middle leg (11) are in good contact with the top surface of the slide beam (7); Step S33: Synchronous sliding into position, start the hydraulic synchronous traction system, drive the front outrigger (12) and the middle outrigger (11) to slide forward synchronously along the slide beam (7), control the sliding speed at 3m / min to 5m / min, monitor the synchronous deviation of the two outriggers in real time during the sliding process, and ensure that the deviation is not greater than 10mm; after the crane slides to the preset construction position of the next segment, lock the anchoring devices of the front outrigger and the middle outrigger to complete one cycle of travel operation.

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