Single-side erection construction method of large-span steel truss bridge in alpine and canyon area

Abstract

The application discloses a high mountain and canyon area large-span steel truss bridge single-side erecting construction method and belongs to the technical field of bridge construction. The steps comprise the following steps: installing a cable crane device on a pushing bank and filling a construction platform; constructing abutments on both banks and temporary steel buttresses on the pushing bank; assembling and pushing a guide beam; connecting steel truss main bridge segments with the guide beam; pushing the steel truss main bridge in batches while removing the front end of the guide beam on the opposite bank in steps; and removing the remaining guide beam and the temporary steel buttresses after the steel truss main bridge is pushed into position. The application adopts a temporary steel buttress and guide beam combined support system to cooperate with cantilever pushing, realizes single-side rapid erection without a river pier through dragging in batches, real-time measurement and control correction, and front removal and rear connection optimization of the gravity center, is safe, economical and short in construction period, and fills the technical blank of the single-side erecting of the high mountain and canyon large-span steel bridge.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering construction technology, and in particular to a method for single-side erection of a long-span steel truss bridge in high mountain and canyon areas. Background Technology

[0002] In the construction of infrastructure such as water conservancy, hydropower, highways, and municipal works, especially in hydropower projects in high mountain and canyon areas, long-span steel truss bridges are key structures for solving the problem of transportation connections between the two sides of the canyon and meeting the needs of heavy-duty transport vehicles. However, high mountain and canyon areas are generally characterized by steep terrain, narrow valleys, rapid water flow, complex and changeable climate, and extremely difficult material transportation. Even more challenging is the fact that the working conditions on both sides of such areas are often highly asymmetrical. Often, only one bank (the pushing bank) has basic access conditions and a construction site, while the opposite bank is a steep cliff with no construction site or access route, making conventional construction work difficult. At the same time, due to multiple constraints such as flood control safety in the canyon channel, watershed ecological environment protection, project construction period, and investment costs, it is strictly prohibited or not advisable to set up permanent bridge piers in the river channel.

[0003] Under the aforementioned stringent constraints, conventional bridge construction methods face significant limitations in their applicability. Currently, conventional construction methods for long-span steel truss bridges mainly include cantilever assembly on both banks, cable-stayed installation, incremental launching, rotation construction, and large floating crane or helicopter lifting. However, these methods all have significant drawbacks when operating on one side of a high mountain canyon. Cantilever assembly method: requires large hoisting equipment to operate simultaneously or alternately on both sides of the river, and the high-altitude assembly operation is extremely risky, requiring sites on both sides of the river.

[0004] Cable hoisting method: The system is complex, has high requirements for the anchoring systems on both banks, and the assembly accuracy is difficult to control. It also depends on good conditions on both banks.

[0005] Traditional jacking method: Although it can achieve unilateral operation, it usually requires good relay conditions on both banks or the setting of multiple permanent or temporary piers in the water, which cannot meet the unilateral construction requirements without piers in the river.

[0006] Rotation construction method: The assembly before rotation requires a large construction site, and the bridge body and counterweight components have high space requirements during rotation, which is difficult to achieve in canyon areas.

[0007] Floating crane / helicopter hoisting: Construction requires large hoisting equipment, which is limited by canyon terrain, water flow speed, wind speed and high cost, and is not universally applicable.

[0008] In particular, existing cantilever launching technologies, when applied to large-span steel truss bridges with spans exceeding 70 meters without piers in high mountain and canyon areas, have revealed the following prominent problems: excessive cantilever length leads to a high risk of overturning; insufficient counterweight space; extreme difficulty in controlling the alignment and precision of the guide beam during long-distance launching; and complete inability to coordinate operations on the opposite bank. These technical deficiencies prevent existing methods from being directly, safely, and economically applied to such special scenarios.

[0009] In summary, most publicly available methods for erecting steel truss bridges rely on conditions requiring work on both sides, the installation of temporary or permanent piers within the riverbed, or the use of large specialized lifting equipment. For the specific high-altitude canyon scenario where "construction is possible on only one side, and the installation of permanent piers within the riverbed is strictly prohibited," a safe, rapid, economical, and technically mature specialized construction method is still lacking. Therefore, developing a construction process that can overcome these limitations and enable the rapid erection of large-span steel truss bridges on one side without piers in the river has become an urgent need to solve the challenges of canyon transportation construction. Summary of the Invention

[0010] This invention addresses the shortcomings of existing technologies in the construction of large-span steel truss bridges in high mountain and canyon areas, such as poor adaptability, high safety risks, and reliance on double-sided operations or piers in the riverbed. It provides a method for single-sided erection of large-span steel truss bridges in these areas. The technical problem this invention aims to solve is: to achieve safe, stable, precise, and rapid single-sided erection of large-span (single span over 70m) steel truss bridges in extreme environments with steep terrain, narrow valleys, construction conditions only on one side, and strict prohibition on setting permanent piers in the riverbed; effectively control structural deflection and overturning risks during cantilever pushing; and solve the problems of material transportation and pier construction when there is no construction on the opposite bank.

[0011] To achieve the above objectives, this invention proposes a method for single-side erection of a long-span steel truss bridge in high mountain and canyon areas, comprising the following steps: Step 1: Complete the installation of cable-stayed crane equipment on the push bank and fill in the construction platform to form a single-sided construction site that meets the needs of hoisting, assembly, material stacking and equipment operation; Step 2: First, carry out the concrete pouring and ancillary facility construction of the push bank bridge abutment. Then, use the cable hoisting equipment to transport personnel, materials and machinery to the opposite bank for concrete pouring and ancillary facility construction of the opposite bank bridge abutment. At the same time, construct temporary steel supports on the construction platform of the push bank according to the design requirements. Step 3: Complete the assembly of the guide beam on the pushing bank construction platform, and use the pushing device to push the guide beam smoothly towards the opposite bank to form a cantilever pushing pilot structure, and control the pushing line and attitude. Step 4: After the guide beam is pushed into place, the steel truss main bridge segment is connected to the guide beam on the pushing bank to form a continuous pushing structure; Step 5: Continue to push the completed steel truss main bridge to the opposite bank. Based on the cantilever length and construction requirements, continue to extend the steel truss main bridge in stages on the pushing bank, and remove the excess section at the front end of the guide beam in stages on the opposite bank to optimize the structural center of gravity and stability. Step Six: Push the entire steel truss main bridge to the design position to complete the preliminary positioning of the bridge alignment and elevation. After the steel truss main bridge is lowered, dismantle all remaining guide beam structures. Step 7: Remove the temporary steel supports in stages and steps.

[0012] Preferably, in step two, the cable-stayed crane is used to transfer all personnel, materials and equipment required for the construction of the bridge abutment on the opposite bank, so that the bank that does not meet the construction conditions can complete the early formation of the bridge pier through a single-sided operation system.

[0013] Preferably, in step five, the steel truss main bridge is pushed in stages, with the length of each stage controlled according to the structural center of gravity balance requirements, and reinforcing bars are used for braking during the pushing process to prevent slippage.

[0014] Preferably, the number of drags is 7, and the drag lengths for each drag are as follows: 9.144m for the first drag, 9.144m for the second drag, 9.144m for the third drag, 3.98m for the fourth drag, 13.847m for the fifth drag, 12.192m for the sixth drag, and 12.192m for the seventh drag.

[0015] Preferably, in step five, the pushing speed of the steel truss main bridge is controlled within 0.5 m / min during the pushing process.

[0016] Preferably, the process of assembling and pushing the guide beam and pushing the steel truss main bridge also includes a step of real-time monitoring of the alignment and attitude, and synchronous measurement and control correction based on the monitoring results.

[0017] Preferably, the superstructure of the steel truss main bridge adopts a double-row steel truss, the truss unit adopts H-beams, the bridge deck beam adopts I-beams, and the bridge deck panel adopts patterned steel plates and U-beams.

[0018] Preferably, the temporary steel piers and guide beams form a combined support system to reduce the pushing cantilever length, reduce the counterweight requirements, and avoid setting permanent piers that encroach on the flood passage section in the riverbed after the main steel truss bridge is formed.

[0019] Preferably, after step seven, the method further includes: Step 8: Conduct load tests on the formed steel truss main bridge to verify the structural stress and deformation performance. After the test is passed, clean up the push-ashore construction platform and restore the riverbed to the original design cross-section. Step Nine: Carry out construction of bridge deck paving, railings, and expansion joints; Step 10: Complete the construction of the wing walls on both sides of the bridge, and open the bridge to traffic after the entire bridge passes inspection.

[0020] Preferably, if existing or newly built tunnels can be used as assembly space on the pushing bank, then the temporary steel supports in the river channel can be eliminated, and the steel truss bridge can be assembled and pushed as a whole in one go.

[0021] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows: This invention creatively proposes a construction method that relies solely on unilateral operation and eliminates the need for any permanent intermediate piers in the riverbed. By utilizing cable-stayed cranes, the methods solve the problems of material transfer and abutment construction on the opposite bank, allowing pier construction to be completed without any construction site or access road on the opposite bank. This method is perfectly suited to extreme scenarios in high mountain and canyon regions where only one bank is suitable for construction, completely solving the problem that existing technologies cannot safely construct under such special geographical conditions. Compared to existing technologies, the adaptability advantages of this invention are reflected in: no symmetrical requirements for operation conditions on both banks; no need for piers in the river, meeting flood control and environmental protection requirements; and no need for construction sites and roads on the opposite bank, significantly reducing the total project investment. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings in the embodiments will be briefly described below.

[0023] Figure 1 This is a schematic diagram of the overall process of the method of the present invention.

[0024] Figure 2 This is a construction process view of an engineering example of the present invention (temporary steel support pier stage).

[0025] Figure 3 This is a construction process view of an engineering example of the present invention (steel truss main bridge pushing stage).

[0026] Figure 4 This is a completed view of an engineering example of the present invention.

[0027] Figure 5 This is a structural diagram of the temporary steel support pier of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings. These specific embodiments are only for explaining the invention and do not constitute a limitation on the scope of protection of this invention.

[0029] Combination Figures 1 to 5 The image shows a specific embodiment of a method for constructing a large-span steel truss bridge on one side in a high mountain canyon area, as provided by the present invention.

[0030] This embodiment takes a large-span steel truss bridge project located in a high mountain canyon area in the Tibet Autonomous Region, spanning the Lancang River, as an example to illustrate the specific implementation process and technical effects of the present invention.

[0031] 1. Project Overview The bridge is located in the reservoir area of ​​a hydropower station in the Tibet Autonomous Region, spanning the Lancang River. The main technical parameters of the bridge are as follows: A. Total length of the bridge: 93.6 meters; B. Main span: 72.7 meters; C. Bridge deck width: 4.2 meters (designed for a single lane); D. Elevation of bridge deck and abutments on both banks: 2917.40 meters; E. Design load: 60 tons for a single vehicle (single vehicle passage conditions). F. Design service life: 5 years (temporary bridge); G. Design flood recurrence period: once in 50 years (corresponding flood level 2915.500 meters).

[0032] The superstructure of the main steel truss bridge adopts a double-row steel truss form, and its specific construction is as follows: (1) The cross-section of the 7th section of the upper chord in the middle of the span is reinforced with a piece of H300×250×14×14 H-beam on each side.

[0033] (2) The wind-resistant tie rod is made of No. 8 channel steel.

[0034] (3) The standard truss unit adopts H300×250×14×14 H-beams.

[0035] (4) The bridge deck crossbeams are made of H400×200×8×13mm I-beams.

[0036] (5) The bridge deck is made of 10mm thick Q235B patterned steel plate and 6mm thick Q355D U-shaped steel.

[0037] The terrain conditions at the project site are extremely challenging: the canyon walls are steep, with an average slope exceeding 60°; only the right bank has the necessary construction site and access transportation, with a simple road leading to the bridge site; the left bank is a near-vertical rock face, completely lacking any transportation or construction conditions, with no access road and no construction site. The riverbed is approximately 80 meters wide, extremely narrow, and the current is rapid. Based on comprehensive considerations of flood control safety, ecological protection, and project investment, the construction of any form of permanent bridge pier in the riverbed is strictly prohibited.

[0038] To address the aforementioned extreme conditions, the construction method provided by this invention is used for bridge erection.

[0039] 2. Construction preparation and resource allocation The following preparatory work should be completed before construction: 2.1 Selection and Installation of Cable Lifting Equipment Based on the terrain conditions of a 93.6m bridge span and an elevation difference of approximately 15m between the two banks, a 110m span cable-stayed crane was selected. The main cable of the cable-stayed crane uses a 28mm diameter steel wire rope, with a designed lifting capacity of 5 tons, to meet the lifting requirements for concrete (approximately 3 tons / lift), reinforcing steel (approximately 1 ton / lift), and small machinery (approximately 0.5 tons / lift) required for the construction of the bridge abutment on the opposite bank. The towers of the cable-stayed crane are respectively set behind the construction platform on the right bank and above the bridge abutment on the left bank, and the anchoring system utilizes the stable rock mass on both banks for anchoring.

[0040] 2.2 Construction Platform Filling The right bank construction platform utilizes the relatively gentle slope behind the bridge abutment for widening and filling, with a filling area of ​​approximately 800 square meters and a filling height of 3-5 meters. It employs layered compaction of crushed stone and soil, followed by a 20cm thick layer of C20 concrete for hardening. The platform is designed to withstand a load of 10 tons per square meter, accommodating the passage of 60-ton transport vehicles and the storage of steel truss components.

[0041] 2.3 Design and fabrication of temporary steel supports Based on structural calculations, three temporary steel supports were installed along the pushing path. The temporary steel supports adopted... Made of 426×10mm steel pipe, with a height of 8~12 meters (adjusted according to terrain), and equipped with a slide rail and PTFE sliding plate at the top to reduce pushing friction.

[0042] 3. Detailed description of construction steps Step 1: Cable crane installation and construction platform filling.

[0043] On the push bank where transportation and construction conditions are suitable, the installation of the cable-stayed crane equipment will be completed first. The cable-stayed crane equipment is crucial for transferring construction materials to the opposite bank; its span must cover the distance between the bridge abutments on both banks, and its lifting capacity must meet the requirements for transporting concrete, reinforcing steel, formwork, and small machinery needed for the construction of the bridge abutments on the opposite bank. After the cable-stayed crane equipment is installed, the selected construction site on the push bank will be leveled, filled, and hardened as necessary, forming a single-sided construction site suitable for subsequent steel truss main bridge segment hoisting, guide beam assembly, material stacking, and construction equipment operation. The area and load-bearing capacity of the construction platform should be determined according to the scale of the steel truss main bridge, generally needing to meet the requirements for truss segment assembly, welding, temporary stacking, and the arrangement of the push equipment. This construction platform is the core working surface for all subsequent construction, and its stability and load-bearing capacity are directly related to construction safety.

[0044] Specific processes combined Figure 2 As shown: On the right bank (pushing bank), complete the tower installation, main cable erection, and anchoring system construction of the cable crane equipment. After the trolley and hook of the cable crane equipment are installed and debugged, conduct a trial lift to confirm that the equipment is working properly.

[0045] The construction platform on the right bank was then constructed. First, the surface vegetation and loose cover were removed. Then, crushed stone and soil were filled in layers, each layer not exceeding 30cm in thickness. The layers were compacted using a vibratory roller to meet the design load requirements. The construction platform did not need to be hardened, and its dimensions only needed to meet the space requirements, thus accommodating the assembly and temporary storage of the steel truss main bridge segments (each segment approximately 9m in length).

[0046] Step 2: Construction of bridge abutments on both sides, construction of ancillary facilities and temporary steel supports.

[0047] After the construction platform on the right bank is formed, the first step is to pour concrete for the bridge abutments and construct related ancillary facilities. The construction of the bridge abutments on the right bank utilizes the lifting equipment on the construction platform for material hoisting and formwork operations. Specifically, the right bank abutments are surveyed and laid out on the right bank construction platform, followed by rebar tying, formwork installation, and C30 concrete pouring. The abutments are poured in two stages, each no more than 2 meters high, and compacted thoroughly with vibration. The formwork is removed after the abutment concrete has cured for 7 days.

[0048] Simultaneously or after the construction of the bridge abutments on the opposite bank, the cable-stayed cranes installed in the first step are used to transport the necessary construction personnel, building materials (concrete, steel bars, etc.), and small construction machinery in batches to the opposite bank, where there are no transportation or construction conditions. The use of cable-stayed cranes eliminates reliance on ground transportation and site conditions for construction on the opposite bank, requiring only a very small working area at the bridge abutment location. The concrete pouring for the bridge abutments and the construction of related ancillary facilities are completed on the opposite bank, thus achieving the initial formation of the bridge abutments on both banks. Specifically, the left bank bridge abutment is located on a steep rock face with a narrow working area. The foundation is roughened using manual labor and small pneumatic picks, followed by steel bar binding, installation of small formwork, and pouring of C30 concrete. The concrete is transported using a 0.5 cubic meter bucket lifted by the cable-stayed cranes. After the concrete pouring for the left bank bridge abutment is completed, it is cured by covering it with plastic film.

[0049] While constructing the bridge abutments on both banks, temporary steel supports were built strictly according to the pre-designed locations and elevations. These temporary steel supports are crucial temporary structures supporting the main steel truss bridge and guide beams during the pushing process. Their number and location should be calculated and determined based on the span, weight, and stress state of the main steel truss bridge during pushing. Temporary steel supports are typically made of steel pipes, with sliding rails or sliding devices installed at the top to facilitate the pushing of the main steel truss bridge. The use of temporary steel supports allows the large-span pushing process to be broken down into several smaller spans, significantly reducing the cantilever length during pushing, lowering the risk of overturning, and reducing structural deflection.

[0050] Step 3: Assemble and push the guide beam.

[0051] The guide beam is a temporary structure installed at the front end of the steel truss main bridge during the pushing process. Its function is to guide the steel truss main bridge forward and reduce the cantilever length and deflection during pushing. On the construction platform on the pushing bank, the guide beam is assembled in sections according to design requirements and reliably connected to form a whole. The length of the guide beam should be calculated and determined based on the span of the steel truss main bridge, the spacing of temporary steel supports, and the position of the center of gravity during the pushing process.

[0052] After the guide beam is assembled, it is smoothly pushed towards the opposite bank using a pushing device. This device can be a hydraulic jack, a winch traction system, or a cable-stayed crane. During the pushing process, the speed and direction must be strictly controlled to avoid impact and deviation. Once in place, the guide beam forms a cantilevered pilot structure, its front end potentially crossing one or more temporary steel supports. During the pushing process, surveyors should use equipment such as a total station to monitor the guide beam's axial position and front-end deflection in real time, making timely adjustments to ensure accurate guidance.

[0053] In this embodiment, the guide beam is made of H400×200×8×13mm I-beams, with a total length of 65m, divided into 7 sections, each approximately 9.3m long. The sections are connected by high-strength bolts. Guide wheels and anti-jamming devices are installed at the front end of the guide beam. After the guide beam is assembled, it is pushed towards the opposite bank using cable-stayed crane traction power on a slide rail atop a temporary steel pier. The pushing speed is controlled within 0.3m / min, with a pause every 5m to measure the axial deviation and front-end deflection of the guide beam. This pushing process is completed in 7 stages, with the front end of the guide beam finally reaching the vicinity of the left bank abutment.

[0054] Step 4: Connecting the guide beam to the main steel truss bridge.

[0055] After the guide beam is pushed to the designated position, the pre-assembled steel truss main bridge segments are reliably connected to the positioned guide beam on the construction platform on the pushing bank. The connection method can be high-strength bolts or welding, depending on the design requirements. After connection, the guide beam and the steel truss main bridge form an integrated, continuously pushable monolithic structure. At this point, the guide beam, as an extension of the steel truss main bridge, effectively guides the steel truss main bridge across the span between temporary steel piers, reducing the cantilever length of the steel truss main bridge body.

[0056] Step 5: Pushing the main steel truss bridge and dismantling the guide beam section.

[0057] The completed steel truss main bridge, along with the guide beams, will be continuously and gradually pushed towards the opposite bank. On the pushing bank, subsequent steel truss main bridge segments will be connected in stages, based on changes in cantilever length and structural center of gravity. The length of each push should be strictly controlled according to the structural center of gravity balance requirements to ensure that the structure remains stable throughout the pushing process and that the overturning safety factor meets the specifications. The pushing speed should be kept uniform to avoid impact.

[0058] Meanwhile, on the opposite bank, as the pushing progresses, excess segments at the front end of the guide beam, which have already fulfilled their guiding function, are dismantled in stages. The timing and length of guide beam dismantling should be dynamically determined based on the structure's center of gravity and cantilever length. Through this coordinated "front-dismantling and rear-connecting" operation, the center of gravity of the entire pushing structure can be dynamically optimized, ensuring the structure remains stable and preventing overturning due to excessive cantilever length.

[0059] During the pushing process, anti-slip measures such as inserting reinforcing bars should be adopted to prevent uncontrolled slippage of the structure in the event of an unexpected failure of the pushing system. Inserting reinforcing bars are typically installed on the slide rail or pushing path with quick-insertion steel reinforcing bars. When braking is required, the reinforcing bars are inserted into predetermined holes to stop the pushing structure from moving forward.

[0060] Specifically, in this embodiment, a seven-stage towing process is adopted, with the following parameters for each stage: Stage 1: 9.144m; Stage 2: 9.144m; Stage 3: 9.144m; Stage 4: 3.98m (guide beam reaches temporary steel support pier #1, forming the maximum cantilever); Stage 5: 13.847m; Stage 6: 12.192m; Stage 7: 12.192m (steel truss main bridge in place). The towing speed is controlled within 0.5m / min. After each towing is completed, the process is paused to measure the axis deviation and deflection, and corrective measures are taken if necessary. During each pause, a guide rail is inserted... 25mm steel reinforcing bars are used for mechanical braking to prevent slippage. During the pushing process, as the front end of the guide beam extends beyond the left bank abutment, excess segments at the front end of the guide beam are dismantled in stages on the left bank side using gas cutting equipment, with each dismantling length being approximately 9m. The dismantled guide beam segments are then hoisted to the ground by cable-stayed crane equipment.

[0061] Step 6: Push the steel truss main bridge into place and remove all guide beams.

[0062] Continue pushing the bridge in stages until the entire steel truss main bridge structure is pushed to the final position specified in the design. After the seventh pull, the front end of the steel truss main bridge should accurately reach the left bank abutment support. At this point, the front end of the steel truss main bridge should accurately reach the opposite bank abutment, and the rear end should be located at the pushing bank abutment. Then, a precise lowering operation is performed, using jacks or other lifting equipment to smoothly lower the steel truss main bridge onto the permanent supports on both banks, completing the initial positioning of the bridge's alignment and elevation.

[0063] After the main steel truss bridge is lowered and initially stabilized, all remaining guide beam structures will be dismantled. The dismantling of the guide beams will be carried out using cable-stayed cranes, transporting the guide beam segments from the opposite bank to the ground. Once all guide beams are dismantled, the main steel truss bridge will be completely independent of the load-bearing structure.

[0064] Step 7: Remove the temporary steel supports.

[0065] According to the predetermined construction plan, all temporary steel piers and other temporary support structures were dismantled in stages, steps, and symmetrically. During dismantling, care was taken to unload gradually to avoid sudden impact on the main steel truss bridge structure. Specifically, before dismantling each temporary steel pier, temporary supports were installed in adjacent locations to prevent sudden changes in structural stress. After the temporary steel piers were dismantled, the bridge structural load was entirely borne by the permanent supports on both banks, completing a smooth transition from a temporary support system to a permanent structural system.

[0066] Step 8: Load testing and construction platform cleanup.

[0067] Comprehensive load tests, including static and dynamic load tests, were conducted on the completed steel truss main bridge. Static load tests verified whether the structure's stress performance and deformation characteristics under static loads met design requirements; dynamic load tests verified whether the structure's dynamic response under vehicle traffic conditions met comfort and safety requirements. After passing the tests, the construction platform on the push-out bank was thoroughly cleared, temporary facilities such as cable-stayed cranes were dismantled, and the foundations of temporary steel supports in the riverbed were cleaned, restoring the river channel to its original design cross-section to meet flood control requirements.

[0068] In this embodiment, the static load test was conducted using eight 60-ton heavy-duty trucks, with the load applied in stages to the design load. The deflection and strain at each control section were measured. Test results: The maximum deflection of the steel truss main bridge was 79.95 mm, equivalent to 1 / 915 of the calculated span, which is far less than the specification limit L / 400 = 181.75 mm; the maximum deflection of the bridge deck was 2.14 mm; the residual deflection was less than 20% of the theoretical value, and the structural stress performance met the requirements.

[0069] Step 9: Construction of the bridge deck and ancillary facilities.

[0070] Construction of ancillary facilities such as bridge deck pavement, safety railings on both sides, and temperature expansion joints will be carried out to improve the final functionality of the bridge. The bridge deck pavement can be constructed using welded and fixed patterned steel plates, the railings can be made of structural steel, and the expansion joints should be selected according to the bridge length and temperature variation range. In this embodiment, a 10mm thick patterned steel plate bridge deck pavement layer will be laid and welded in place, and safety railings (1.2m high) will be installed on both sides.

[0071] Step 10: Wing wall pouring and completion for traffic opening.

[0072] Finally, the finishing construction of the wing walls on both sides of the bridge is completed. The wing walls connect the abutments to the roadbed, serving as retaining walls and providing a transition. After the wing wall construction is completed, a final quality inspection of the entire bridge is conducted. In this embodiment, the wing walls are 4-6 meters high and made of C25 concrete. After passing the inspection, the bridge is officially opened to traffic.

[0073] 4. Summary of Implementation Results In this embodiment, the entire main structure of the bridge was constructed on the right bank (pushing bank), while the left bank only underwent concrete pouring for the abutments using cable-stayed cranes, requiring no large equipment or site construction. No permanent piers were installed in the river during the entire construction process, fully meeting the requirements for flood control and investment control.

[0074] This embodiment fully verifies the feasibility, safety, economy, and practicality of the method of the present invention under extreme conditions of high mountains and canyons, and provides a replicable and scalable technical solution for similar projects.

[0075] This invention achieves stable and controllable operation throughout the entire process of pushing the steel truss bridge through multi-level stability control measures: The first layer of control involves setting up temporary steel supports to break down the large-span push into several smaller span pushes, significantly reducing the cantilever length of the push and fundamentally reducing the risk of overturning and structural deflection.

[0076] The second layer of control employs a dynamic center of gravity control strategy of "front dismantling and rear connection". This involves adding weight to the rear end of the main bridge segment by connecting the steel truss on the pushing bank, and reducing the front end weight by removing the front end segment of the guide beam on the opposite bank. This bidirectional dynamic adjustment ensures the structure's center of gravity remains within a stable region.

[0077] The third layer of control employs a segmented dragging method, with the length of each drag strictly controlled according to the center of gravity balance requirements. In a specific embodiment, dragging is performed in 7 segments, with the maximum single drag length controlled at 13.847m, effectively avoiding sudden changes in the center of gravity caused by excessively long single pushes.

[0078] Fourth-level control: Real-time monitoring of alignment and attitude, timely correction of deviations, and prevention of instability caused by accumulated deviations.

[0079] Fifth layer of control: Anti-slip measures such as inserting reinforcing bars are adopted to prevent structural loss of control in the event of unexpected failure of the pushing system.

[0080] Through the aforementioned multi-level stability control measures, this invention effectively controls the deflection and stability of the cantilever structure, reduces the risk of instability and overturning, eliminates various construction safety hazards, and ensures a safe and reliable construction process. Load test results from a specific embodiment verify the safety of this invention: the maximum deflection of the steel truss main bridge is 79.95 mm (1 / 915), far less than the standard limit L / 400 = 181.75 mm.

[0081] This construction method has a clear process flow, with all core procedures completed on a single-sided construction platform, offering the following economic advantages: First, the construction of the bridge abutments on the opposite bank can be completed using only cable-stayed cranes, eliminating the need for substantial investments in infrastructure such as site leveling, road construction, and large equipment installation on the other side. In high mountain and canyon areas, the cost of constructing access roads from the opposite bank is often extremely high; this method directly eliminates this cost item.

[0082] Secondly, there is no need to set up permanent bridge piers in the river, which avoids the high costs of underwater operations and deep foundation construction. At the same time, it eliminates the encroachment of bridge piers on the flood discharge section of the river channel and meets the regulatory requirements of the water conservancy department.

[0083] Secondly, no large lifting equipment is required; the cable hoisting equipment and pushing devices used are all conventional equipment, resulting in low equipment purchase or rental costs.

[0084] This invention ensures that construction accuracy meets design requirements through a real-time monitoring and synchronous measurement and control correction mechanism. During the assembly and pushing of the guide beam and the pushing of the steel truss main bridge, precision measuring equipment such as a total station is used to monitor the axial position and elevation of the structure in real time, and any deviations are promptly adjusted through the correction device.

[0085] This invention also offers high flexibility. If existing or specially constructed tunnels can be used as pre-assembly space for the steel truss main bridge near the pushing bank, the temporary steel supports in the river channel can be further eliminated, enabling the steel truss main bridge to be assembled and pushed as a whole in one go. This variant can further reduce the amount of temporary engineering work, lower construction risks and costs, and is particularly suitable for engineering scenarios where there are usable tunnels behind the pushing bank.

[0086] This invention proposes a method for single-sided erection of long-span steel truss bridges in high mountain and canyon areas, enabling safe, rapid, and economical bridge construction under extreme terrain conditions. The method is technologically mature, utilizing conventional construction equipment such as cable-stayed cranes, pushing devices, and temporary steel supports. It does not rely on the conditions of the opposite bank and avoids the need for piers in the river, demonstrating high industrial applicability. It can be widely applied to similar bridge construction projects in water conservancy, hydropower, highways, and municipal transportation, providing strong technical support, especially for infrastructure construction in the challenging mountainous regions of western China, filling the technological gap in the rapid single-sided erection of long-span steel truss bridges in narrow mountain valleys without piers in the river.

[0087] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for single-sided erection of a long-span steel truss bridge in a high mountain canyon area, characterized in that, Includes the following steps: Step 1: Complete the installation of cable-stayed crane equipment on the push bank and fill in the construction platform to form a single-sided construction site that meets the needs of hoisting, assembly, material stacking and equipment operation; Step 2: First, carry out the concrete pouring and ancillary facility construction of the push bank bridge abutment. Then, use the cable hoisting equipment to transport personnel, materials and machinery to the opposite bank for concrete pouring and ancillary facility construction of the opposite bank bridge abutment. At the same time, construct temporary steel supports on the construction platform of the push bank according to the design requirements. Step 3: Complete the assembly of the guide beam on the pushing bank construction platform, and use the pushing device to push the guide beam smoothly towards the opposite bank to form a cantilever pushing pilot structure, and control the pushing line and attitude; Step 4: After the guide beam is pushed into place, the steel truss main bridge segment is connected to the guide beam on the pushing bank to form a continuous pushing structure; Step 5: Continue to push the completed steel truss main bridge to the opposite bank. Based on the cantilever length and construction requirements, continue to extend the steel truss main bridge in stages on the pushing bank, and remove the excess section at the front end of the guide beam in stages on the opposite bank to optimize the structural center of gravity and stability. Step Six: Push the entire steel truss main bridge to the design position to complete the preliminary positioning of the bridge alignment and elevation. After the steel truss main bridge is lowered, dismantle all remaining guide beam structures. Step 7: Dismantle the temporary steel supports in stages and steps.

2. The method for single-sided erection of a long-span steel truss bridge in a high mountain canyon area according to claim 1, characterized in that: In step two, the cable-stayed crane is used to transfer all personnel, materials and equipment required for the construction of the bridge abutment on the opposite bank, so that the side that does not have the conditions for construction can complete the early formation of the bridge pier through a single-sided operation system.

3. The method for single-sided erection of a long-span steel truss bridge in a high mountain canyon area according to claim 1, characterized in that: In step five, the steel truss main bridge is pushed in stages, with the length of each pull controlled according to the structural center of gravity balance requirements. During the pushing process, reinforcing bars are used for braking to prevent slippage.

4. The method for single-sided erection of a long-span steel truss bridge in a high mountain canyon area according to claim 3, characterized in that: The number of drags is 7, and the drag lengths for each drag are as follows: 9.144m for the first drag, 9.144m for the second drag, 9.144m for the third drag, 3.98m for the fourth drag, 13.847m for the fifth drag, 12.192m for the sixth drag, and 12.192m for the seventh drag.

5. The method for single-sided erection of a long-span steel truss bridge in a high mountain canyon area according to claim 1, characterized in that: In step five, the pushing speed of the steel truss main bridge is controlled within 0.5 m / min during the pushing process.

6. The method for single-sided erection of a long-span steel truss bridge in a high mountain canyon area according to claim 1, characterized in that: The process of assembling and pushing the guide beam and pushing the steel truss main bridge also includes steps for real-time monitoring of the alignment and attitude, and synchronous measurement and control correction based on the monitoring results.

7. The method for single-sided erection of a long-span steel truss bridge in a high mountain canyon area according to claim 1, characterized in that: The superstructure of the main steel truss bridge adopts a double-row steel truss, the truss unit adopts H-beams, the bridge deck beam adopts I-beams, and the bridge deck panel adopts patterned steel plates and U-beams.

8. The method for single-sided erection of a long-span steel truss bridge in a high mountain canyon area according to claim 1, characterized in that: The temporary steel piers and guide beams form a combined support system to reduce the pushing cantilever length, reduce the counterweight requirements, and avoid setting up permanent piers that encroach on the flood passage section in the riverbed after the main steel truss bridge is formed.

9. The method for single-sided erection of a long-span steel truss bridge in a high mountain canyon area according to claim 1, characterized in that, Step seven is followed by: Step 8: Conduct load tests on the formed steel truss main bridge to verify the structural stress and deformation performance. After the test is passed, clean up the push-back bank construction platform and restore the riverbed to the original design cross-section. Step Nine: Carry out construction of bridge deck paving, railings, and expansion joints; Step 10: Complete the construction of the wing walls on both sides of the bridge, and open the bridge to traffic after the entire bridge passes inspection.

10. The method for single-sided erection of a long-span steel truss bridge in a high mountain canyon area according to claim 1, characterized in that: If existing or newly built tunnels can be used as assembly space on the pushing bank, then the temporary steel supports in the river channel can be eliminated, enabling the steel truss bridge to be assembled and pushed as a whole in one go.

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