A widened bridge seismic toughness system realizing cooperation of new and old frames and a design and construction method thereof

Abstract

This invention discloses a seismic toughness system for widened bridges that achieves coordinated seismic resistance between the old and new bridge sections, along with its design and construction method. The widened bridge consists of an old bridge, a new bridge, and a wet joint connecting the two. The old bridge includes the old bridge main girder, the old bridge bearing system, the old bridge cap beam, and the old bridge piers. The old bridge bearing system includes upper anchor bolts, an upper steel plate, a stainless steel plate, a limiting steel plate, a wear-resistant plate, a bearing body, a connecting steel plate, a lower steel plate, and lower anchor bolts. A sliding interface is formed between the wear-resistant plate and the stainless steel plate to reduce the horizontal stiffness of the old bridge bearing system. The new bridge includes the new bridge main girder, new bridge bearings, a new bridge cap beam, and new bridge piers. By tuning the horizontal stiffness of the old bridge bearing system and the new bridge bearings, the new bridge bears the main seismic load under earthquake action, while the old bridge operates in a low-damage state, achieving coordinated seismic resistance between the old and new bridge sections. This invention balances the protection of the old bridge with the performance of the new bridge, eliminating the need for large-scale reinforcement of the old bridge piers, and can be widely applied to the widening and reconstruction of existing bridges in high-seismic-intensity areas.

Description

Technical Field

[0001] This invention relates to the field of bridge seismic resistance and reinforcement technology, and more specifically, to a seismic toughness system for widened bridges that achieves cooperation between old and new spans, as well as its design and construction method. Background Technology

[0002] With the continuous advancement of transportation infrastructure construction in my country, highways and urban road networks have shifted from a phase of large-scale new construction to a development period that emphasizes both new construction and quality improvement. To meet the ever-increasing traffic demand and enhance the capacity of the road network, widening and upgrading existing bridges has become a core technical approach. However, many early-built simply supported beam bridges and continuous beam bridges, limited by the design standards, material properties, and construction techniques of their time, generally suffer from bottlenecks in seismic performance, such as low pier reinforcement ratios, insufficient shear capacity, and limited ductility reserves. With the implementation of the new seismic design code, both seismic fortification intensity and performance targets have been raised. If the original structural system is used after widening, the old bridge section will face the risk of pier damage or even beam collapse, making it difficult to quickly restore traffic after an earthquake. This contradicts the current high requirements for the seismic toughness of bridges.

[0003] In bridge widening projects, a construction model of "utilizing the old bridge + splicing with a new bridge" is often adopted. Under this model, the old and new structures differ significantly in dead load, stiffness, and dynamic characteristics. Traditional widening schemes focus on ensuring the coordinated stress and synchronous deformation of the old and new structures to guarantee smooth driving and overall stability. However, under seismic loads, this strong coordinated mechanism can transfer greater seismic forces to the relatively weaker seismic-resistant piers of the old bridge, making them the failure control point of the entire system. Once the old bridge piers experience plastic hinge concentration or shear failure, it can not only lead to local collapse but also trigger a chain reaction of damage to the new bridge, severely reducing the overall seismic safety and recoverability of the bridge. Therefore, how to effectively protect the old bridge, optimize structural stress, and improve overall seismic toughness during widening and reconstruction has become a key technical challenge that urgently needs to be solved in the engineering field.

[0004] Existing bridge seismic strengthening technologies, such as increasing cross-section, external steel plate cladding, and bonding FRP composite materials, can improve the load-bearing capacity of components to some extent. However, these methods generally have limitations, including long construction periods, significant traffic disruption, and a substantial increase in structural weight and stiffness. In some cases, increased stiffness may even exacerbate seismic response. While seismic isolation and damping technologies can effectively reduce the seismic demand on the substructure, their direct application to the renovation of old bridges often faces challenges such as complex bearing replacement and incompatibility between the dynamic characteristics of the old and new structures. These technologies are difficult to adapt to the unique system characteristics of expanded bridges, which involve "coexistence of old and new structures and collaborative operation across multiple spans." From a structural dynamics perspective, the distribution of seismic forces in a multi-span bridge system is primarily dominated by the horizontal stiffness of each substructure; the greater the stiffness, the greater the seismic shear force and bending moment it bears. Old bridge piers often have insufficient seismic resistance but frequently experience high seismic responses due to the high stiffness of their original supports, creating a contradiction between capacity and demand. Summary of the Invention

[0005] This invention aims to address the aforementioned problems in the existing technology by providing a seismic toughness system for widened bridges that achieves coordinated operation between the old and new bridge sections, along with its design and construction method. The core concept of this invention lies in achieving a rational redistribution of seismic forces by actively adjusting the horizontal stiffness of the supports between the old and new bridge sections. This protects the structure of the old bridge while fully leveraging the seismic advantages of the new bridge, thereby comprehensively enhancing the overall seismic toughness of the widened bridge without requiring large-scale reinforcement of the old bridge piers.

[0006] To solve the above-mentioned technical problems, the technical solution proposed in this application is as follows:

[0007] This invention provides a seismic toughness system for widened bridges that enables cooperation between old and new spans, including an old bridge, a new bridge, and a wet joint connecting the old bridge and the new bridge; The old bridge includes the old bridge main beam, the old bridge bearing system, the old bridge cap beam, and the old bridge piers; wherein, the old bridge bearing system includes upper anchor bolts, upper steel plate, stainless steel plate, limiting steel plate, wear-resistant plate, bearing body, connecting steel plate, lower steel plate, and lower anchor bolts; the wear-resistant plate and the stainless steel plate form a sliding interface to reduce the horizontal stiffness of the old bridge bearing system; The new bridge includes a main girder, bearings, cap beams, and piers; the bearings are seismic isolation bearings designed to bear the main seismic loads. The horizontal stiffness of the old bridge bearing system and the new bridge bearing are tuned and configured so that the new bridge bears the main seismic load under seismic action, while the old bridge is in a low-damage working state, thus achieving collaborative seismic resistance between the old and new bridges.

[0008] Furthermore, the upper steel plate is welded to the stainless steel plate and the limiting steel plate; the wear-resistant plate is bonded to the top surface of the support body; the support body is composed of a rubber plate and a stiffening steel plate, and the rubber plate and the stiffening steel plate are connected by vulcanization; the connecting steel plate is connected to the support body by vulcanization; a round hole is provided in the middle of the lower steel plate, and the connecting steel plate is embedded in the round hole in the middle of the lower steel plate; round holes are provided at the four corners of the upper and lower steel plates; the upper anchor bolt passes through the round holes at the corners of the upper steel plate to connect the old bridge support system to the old bridge main beam; the lower anchor bolt passes through the round holes at the corners of the lower steel plate to connect the old bridge support system to the old bridge cap beam.

[0009] Furthermore, the wear-resistant plate is made of polymer material, and the coefficient of friction between it and the stainless steel plate is no greater than 0.03.

[0010] Furthermore, the wear-resistant plate, the support body, and the connecting steel plate have the same planar dimensions.

[0011] Furthermore, there is a clear distance between the support body and the limiting steel plate, and the clear distance is equal to the design horizontal displacement value of the old bridge support system.

[0012] Furthermore, the connecting steel plate and the lower steel plate have the same thickness.

[0013] Furthermore, the new bridge bearing is a seismic isolation bearing, which is selected from plate rubber bearings, lead-core rubber bearings, high-damping rubber bearings, or friction pendulum bearings.

[0014] Furthermore, the polymer material is ultra-high molecular weight polyethylene or polytetrafluoroethylene, and the coefficient of friction between the wear-resistant plate and the stainless steel plate is controlled by incorporating modified fillers or by surface treatment processes.

[0015] On the other hand, this application also claims protection for a design method for achieving a seismic toughness system for widened bridges that realizes the cooperation between old and new spans as described in any of the above claims, comprising the following steps: Step 1: Based on the as-built drawings of the old bridge and the preliminary design drawings of the new bridge, establish a seismic analysis model for the widened bridge and verify the seismic toughness of the old bridge; if the verification results do not meet the design specifications, proceed to the next steps. Step 2: In the seismic analysis model, the existing bearings of the old bridge are replaced with the bearing system of the old bridge to form a seismic toughness enhancement model; the bearing system of the old bridge is simulated using a constitutive relationship of a linear model and an ideal bilinear model in series. The horizontal stiffness K of the linear model is calculated using the following formula: K = GA / t Wherein, G is the shear modulus of the rubber sheet, A is the planar area of ​​the support body, and t is the total thickness of the rubber layer of the support body; The yield force F of the ideal bilinear model is calculated using the following formula: F = μN Where μ is the coefficient of friction between the wear-resistant plate and the stainless steel plate, and N is the dead load reaction force of the old bridge main beam; The initial stiffness K1 of the ideal bilinear model is calculated using the following formula: K1 = F / s Where s is the yield displacement, and the value of s ranges from 0.002m to 0.005m; Step 3: Perform calculation and analysis on the seismic toughness improvement model, and verify the seismic toughness of the old bridge and the new bridge respectively; If the seismic toughness of the old bridge does not meet the design specifications, it can be optimized by adjusting the horizontal stiffness of the old bridge bearing system. The horizontal stiffness of the old bridge bearing system should be determined based on the bending and shear bearing capacity of the old bridge piers to ensure that the old bridge piers do not suffer strength failure. If the seismic toughness of the new bridge does not meet the design specifications, it can be optimized by adjusting the horizontal stiffness of the new bridge bearings or increasing the size and reinforcement of the new bridge piers. The horizontal stiffness of the new bridge bearings should be determined based on the super bending moment and super shear force of the new bridge piers to ensure that the new bridge piers do not suffer shear failure and that the ductile deformation meets the specifications.

[0016] Furthermore, in the third step, adjusting the horizontal stiffness of the old bridge bearing system specifically involves: changing the total thickness t of the rubber layer of the bearing body, the shear modulus G of the rubber plate, the planar area A of the bearing body, or changing the friction coefficient μ between the wear-resistant plate and the stainless steel plate to achieve precise tuning of the horizontal stiffness of the old bridge until the seismic toughness of the old bridge meets the design specifications.

[0017] On the other hand, this application also claims protection for a construction method for achieving a seismic toughness system for widened bridges that integrates new and old spans as described in any of the above claims, comprising the following steps: Step 1: The old bridge bearing system is prefabricated in the factory. First, holes are made in the upper steel plate and the lower steel plate. Second, the upper steel plate is welded to the stainless steel plate and the limiting steel plate. Third, the wear-resistant plate is bonded to the top surface of the bearing body. Finally, the connecting steel plate is vulcanized to the bearing body. Step 2: Remove the existing supports of the old bridge on site; use jacks to lift the main beam of the old bridge and remove the existing supports of the old bridge. Step 3: On-site installation of the old bridge bearing system; First, clean, smooth, and drill holes at the corresponding bearing positions on the bottom of the old bridge main beam and the top of the old bridge cap beam, and apply structural adhesive; Second, install the assembly consisting of the upper steel plate, the stainless steel plate, and the limiting steel plate at the bottom of the old bridge main beam, and fix it with the upper anchor bolts; Third, install the assembly consisting of the connecting steel plate, the bearing body, and the wear-resistant plate, as well as the lower steel plate, on the top of the old bridge cap beam, and fix it with the lower anchor bolts; Finally, lower the old bridge main beam back to the designed position and remove the jacks; Step 4: On-site construction of the new bridge; from bottom to top, the new bridge piers and cap beams are cast in place, the new bridge supports are installed, and the new bridge main beams are hoisted. Step 5: Complete the widening of the bridge; use the wet joint to connect the old bridge main beam and the new bridge main beam into a whole, and construct the bridge deck system.

[0018] Furthermore, in the third step, after drilling holes in the bottom of the old bridge main beam and the top of the old bridge cap beam, injecting anchoring adhesive or epoxy resin structural adhesive into the holes, and then installing the upper and lower anchor bolts; after the old bridge main beam is lowered back to the design position, the old bridge support system needs to be dustproofed and sealed around its perimeter.

[0019] Furthermore, the system is applicable to the widening and renovation of existing beam bridges in high-intensity earthquake zones with seismic fortification intensity of VII, VIII, or IX, and achieves a synergistic improvement in the seismic toughness of the new and old bridges through stiffness tuning.

[0020] Compared with the prior art, the present invention achieves the following beneficial technical effects: This invention, through the concept of stiffness tuning, replaces the existing bearings of the old bridge with a low-friction sliding bearing system, significantly reducing the horizontal lateral stiffness of the old bridge. This means that under seismic loads, the old bridge section is no longer the primary load-bearing structure, transmitting only a small amount of seismic force through friction, while the new bridge section, with its more robust seismic design and greater stiffness, bears the main seismic load. This system balances the protection of the old bridge with the performance of the new bridge, eliminating the need for large-scale reinforcement of the old bridge piers and avoiding the limitations of traditional reinforcement methods, such as significant construction interference, long construction periods, and increased structural weight. It perfectly suits the "coexistence of old and new, and collaborative widening" characteristics of widened bridges. This invention can be widely applied to the widening and reconstruction of existing bridges in high-intensity seismic zones, especially in areas with seismic fortification intensities of VII, VIII, or IX, achieving a synergistic improvement in the seismic toughness of the old and new bridges through stiffness tuning. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic cross-sectional view of a seismic toughness system for widened bridges that achieves cooperation between old and new spans, according to the present invention.

[0023] Figure 2 for Figure 1 Detailed drawing of the bearing system 12 of the old bridge.

[0024] Figure 3 for Figure 2 The AA section sectional view of the old bridge bearing system is shown.

[0025] Figure 4 for Figure 2 The BB section sectional view of the old bridge bearing system is shown.

[0026] Figure 5 for Figure 2 Elevation structural diagram of the central support body 6.

[0027] Figure 6 for Figure 5 The CC section sectional view of the support body shown.

[0028] Explanation of the reference numerals in the figure: 1-Upper anchor bolt; 2-Upper steel plate; 3-Stainless steel plate; 4-Limiting steel plate; 5-Wear-resistant plate; 6-Bearing body; 61-Rubber plate; 62-Reinforcing steel plate; 7-Connecting steel plate; 8-Lower steel plate; 9-Lower anchor bolt; 10-Old bridge pier; 11-Old bridge main beam; 12-Old bridge bearing system; 13-Old bridge cap beam; 21-Wet joint; 31-New bridge main beam; 32-New bridge bearing; 33-New bridge cap beam; 34-New bridge pier. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] like Figure 1As shown, the widened bridge consists of an old bridge, a new bridge, and a wet joint 21 connecting the old and new bridges. The old bridge includes the old bridge main girder 11, the old bridge bearing system 12, the old bridge cap beam 13, and the old bridge piers 10; the new bridge includes the new bridge main girder 31, the new bridge bearings 32, the new bridge cap beam 33, and the new bridge piers 34. The structure of the old bridge bearing system 12 is as follows... Figures 2 to 6 As shown, it includes an upper anchor bolt 1, an upper steel plate 2, a stainless steel plate 3, a limiting steel plate 4, a wear-resistant plate 5, a bearing body 6, a connecting steel plate 7, a lower steel plate 8, and a lower anchor bolt 9. The wear-resistant plate 5 is bonded to the top surface of the bearing body 6, forming a sliding interface with the stainless steel plate 3. This sliding interface can significantly reduce the horizontal stiffness of the old bridge bearing system 12. The new bridge bearing 32 adopts a seismic isolation bearing, such as a lead-core rubber bearing, which has a large horizontal deformation capacity and energy dissipation capacity, and can bear the main seismic load during an earthquake. By coordinating the low horizontal stiffness characteristics of the old bridge bearing system 12 with the high energy dissipation characteristics of the new bridge bearing 32, that is, by tuning the horizontal stiffness of the two, the new bridge bears the main seismic load under earthquake action, while the old bridge is in a low-damage working state, thus achieving the goal of coordinated seismic resistance between the old and new bridges. In this embodiment, the vertical load of the old bridge main beam 11 is transferred to the wear-resistant plate 5 and the support body 6 through the upper steel plate 2 and the stainless steel plate 3, and then to the old bridge cap beam 13 through the connecting steel plate 7 and the lower steel plate 8. When the horizontal force is small, the restoring force is provided by the shear deformation of the support body 6. When the horizontal force exceeds the static friction between the wear-resistant plate 5 and the stainless steel plate 3, the upper stainless steel plate 3 and the lower wear-resistant plate 5 slide relative to each other, which greatly reduces the transmission of the horizontal force to the old bridge piers and abutments, thereby protecting the old bridge structure.

[0031] In one embodiment of this application, the specific construction of the old bridge bearing system 12 is described in detail. For example... Figures 2 to 6As shown, the upper steel plate 2 is welded to the stainless steel plate 3 and the limiting steel plate 4. The stainless steel plate 3 is fully welded to the central area of ​​the lower surface of the upper steel plate 2. The limiting steel plate 4 consists of four pieces, each welded to one of the four edges of the lower surface of the upper steel plate 2, forming a space to accommodate the lower components. The wear-resistant plate 5 is bonded to the top surface of the support body 6 with a special structural adhesive. The support body 6 is formed by alternating layers of rubber plates 61 and reinforcing steel plates 62, combined through a high-temperature vulcanization process. This structure provides vertical load-bearing capacity and horizontal shear deformation capacity. The connecting steel plate 7 is firmly bonded to the bottom of the support body 6 through a vulcanization process. A circular hole is opened in the middle of the lower steel plate 8 to accommodate the connecting steel plate 7. The connecting steel plate 7 is embedded in the circular hole and can be fixed by transition fit or welding. Circular holes are also opened at the four corners of the lower steel plate 8 for the lower anchor bolts 9 to pass through. Both the upper steel plate 2 and the lower steel plate 8 have circular holes at the four corners. The upper anchor bolt 1 passes through the corner hole of the upper steel plate 2, anchoring the upper component to the bottom of the old bridge main beam 11; the lower anchor bolt 9 passes through the corner hole of the lower steel plate 8, anchoring the lower component to the top of the old bridge cap beam 13. The above structure ensures the integrity and reliability of the old bridge bearing system 12, and the connection method of each component ensures the effective transfer of vertical loads and the realization of horizontal sliding function.

[0032] In one embodiment of this application, the wear-resistant plate 5 is made of a polymer material, such as ultra-high molecular weight polyethylene or polytetrafluoroethylene. Laboratory tests have shown that the coefficient of sliding friction between this material and the stainless steel plate 3 is no greater than 0.03, for example, controllable at 0.02 or 0.025. This low coefficient of friction is a key parameter for reducing the horizontal stiffness of the old bridge bearing system 12. When the horizontal force exceeds the yield force F = μN, determined by the coefficient of friction μ and the constant load reaction force N, the sliding interface is activated, allowing the old bridge to transmit only limited frictional force, thereby protecting the old bridge piers.

[0033] In one embodiment of this application, the wear-resistant plate 5, the support body 6, and the connecting steel plate 7 have the same planar dimensions. For example, all three have a planar dimension of 500mm × 500mm and are center-aligned. This design with equal planar dimensions ensures that the vertical load is evenly distributed from top to bottom, avoiding local stress concentration and improving the load-bearing stability and durability of the support.

[0034] In one embodiment of this application, a specific clearance is maintained between the four side walls of the bearing body 6 and the inner side wall of the corresponding limiting steel plate 4. This clearance is precisely equal to the design horizontal displacement value of the old bridge bearing system 12. For example, if the design horizontal displacement is determined to be 100mm based on seismic analysis, then the clearance is set to 100mm. Under normal use and minor earthquakes, the bearing body 6 deforms freely within the clearance range; when the horizontal displacement exceeds the design value, the side walls of the bearing body 6 contact the limiting steel plate 4, providing limiting protection and preventing beam collapse.

[0035] In one embodiment of this application, the connecting steel plate 7 and the lower steel plate 8 have the same thickness. For example, both are made of 20mm thick Q345 steel. The same thickness ensures that after the connecting steel plate 7 is inserted into the central circular hole of the lower steel plate 8, its upper surface is flush with the upper surface of the lower steel plate 8, forming a flat bearing surface, which facilitates installation and ensures uniform stress distribution.

[0036] In one embodiment of this application, the new bridge bearing 32 is selected as a seismic isolation bearing. The specific type can be chosen from plate rubber bearings, lead-core rubber bearings, high-damping rubber bearings, or friction pendulum bearings according to engineering needs. Lead-core rubber bearings have the characteristics of high initial stiffness and strong energy dissipation capacity after yielding; high-damping rubber bearings achieve energy dissipation through the damping characteristics of the rubber material itself; and friction pendulum bearings achieve self-resetting function through the geometric effect of the sliding surface. All of the above types of bearings can bear the main seismic loads, realizing the seismic resistance function of the new bridge.

[0037] In one embodiment of this application, the wear-resistant plate 5 is made of ultra-high molecular weight polyethylene or polytetrafluoroethylene. To further reduce the coefficient of friction, modified fillers, such as nano-sized molybdenum disulfide, can be incorporated during material preparation to reduce the coefficient of friction from 0.02 to 0.015; or surface treatment processes, such as laser etching to form a microtexture, can be used to reduce the coefficient of friction to 0.012. These control methods can be flexibly selected according to design requirements to achieve precise tuning of the horizontal stiffness of the old bridge bearing system 12.

[0038] In one embodiment of this application, a design method for achieving the aforementioned seismic toughness system is described in detail. Taking a simply supported beam bridge on an actual highway that needs widening as an example, the original bridge has a 20-meter span and double-column piers. First, based on the as-built drawings of the old bridge and the preliminary design drawings of the new bridge, a seismic analysis model of the entire bridge is established using finite element software. The old bridge piers, cap beams, etc., are simulated according to their actual reinforcement and cross-sectional dimensions in the model, and time history analysis is performed by inputting the design ground motion parameters. The verification results show that the bending moment demand of the old bridge piers under seismic loading exceeds their bending bearing capacity, and the displacement ductility coefficient does not meet the requirements of current specifications, necessitating seismic reinforcement. Second, based on the original model, the supports of the old bridge are replaced with the old bridge support system 12, forming a seismic toughness enhancement model. The old bridge support system 12 is simulated using nonlinear connection elements, and its constitutive relation is set as a series connection of a linear model and an ideal bilinear model. The horizontal stiffness K of the linear model is calculated using the following formula: K = GA / t, where G is the shear modulus of the rubber plate 61, taken as 1.0 MPa; A is the planar area of ​​the support body 6, taken as 0.2 m²; t is the total thickness of the rubber layer of the support body 6, taken as 0.05 m, resulting in K = 4000 kN / m. The yield force F of the ideal bilinear model is calculated using the following formula: F = μN, where μ is the friction coefficient between the wear-resistant plate 5 and the stainless steel plate 3, taken as 0.02; N is the dead load reaction force of the old bridge main beam 11, taken as 1000 kN, resulting in F = 20 kN. The initial stiffness K1 of the ideal bilinear model is calculated using the following formula: K1 = F / s, where s is the yield displacement, taken as 0.003 m, resulting in K1 ≈ 6667 kN / m. In the third step, the updated model is calculated and analyzed to verify the seismic toughness of the old bridge and the new bridge respectively. Regarding the old bridge, because the old bridge bearing system 12 entered a sliding state after the horizontal force exceeded 20kN, the seismic shear force transmitted to the old bridge piers was significantly reduced. The bending moment requirement and displacement ductility coefficient of the old bridge piers both decreased to within the code limits, meeting the seismic toughness requirements. According to design principles, the bending and shear bearing capacities of the old bridge piers 10 were further verified, confirming that the piers themselves would not suffer strength failure under the current seismic force. Regarding the new bridge, the new bridge bearings 32 and piers 34 bore most of the seismic load. Verification revealed that the displacement at the top of the new bridge piers was too large. According to design principles, the horizontal stiffness of the new bridge bearings 32 was adjusted, replacing the ordinary plate rubber bearings with high-damping rubber bearings, increasing the damping ratio. Simultaneously, based on the ultra-high bending moment and ultra-high shear force requirements of the new bridge piers 34, the reinforcement of the new bridge piers 34 was appropriately increased. After the adjustments, the displacement and internal forces of the new bridge both met the code requirements, and the piers did not experience shear failure, with ductility deformation meeting the requirements.

[0039] In one embodiment of this application, a detailed description is provided of the specific method for adjusting the horizontal stiffness of the old bridge bearing system 12. When the seismic toughness calculation results of the old bridge indicate that further reduction in seismic response is still needed, adjustments can be made using one or a combination of the following methods: changing the total thickness t of the rubber layer of the bearing body 6, for example, increasing t from 0.05m to 0.08m, thus reducing the horizontal stiffness K to 2500kN / m; changing the shear modulus G of the rubber plate 61, for example, by selecting a rubber material with a lower modulus; changing the planar area A of the bearing body 6; or changing the friction coefficient μ between the wear-resistant plate 5 and the stainless steel plate 3, for example, reducing μ from 0.02 to 0.01 through surface treatment, thus reducing the yield force F to 10kN. Through multiple rounds of iterative optimization, the horizontal stiffness of the old bridge can be precisely tuned until the seismic toughness of the old bridge fully meets the specifications, and the old bridge piers 10 do not experience strength failure.

[0040] In one embodiment of this application, a construction method for achieving the aforementioned seismic toughness system is described in detail. The first step involves prefabricating the existing bridge bearing system 12 in a factory. In a specialized rubber bearing factory, holes are first drilled in the upper steel plate 2 and lower steel plate 8, anchor bolt holes are drilled at the four corners of the upper and lower steel plates 2 and 8, and a square hole matching the size of the connecting steel plate 7 is milled in the middle of the lower steel plate 8. Next, the upper steel plate 2 is welded to the stainless steel plate 3 and the limiting steel plate 4. Then, the wear-resistant plate 5 is bonded to the top surface of the bearing body 6 using a special structural adhesive. Finally, the connecting steel plate 7 is vulcanized and connected to the bearing body 6. The finished product is shipped after passing inspection. The second step involves dismantling the existing bridge bearings on-site. A construction platform and supports are erected, and multiple synchronous hydraulic jacks are positioned under the main beam 11 of the old bridge to lift the beam to an appropriate height in stages and synchronously. The existing bridge bearings are then removed, and debris is cleaned from the bottom of the beam and the surface of the bearing pad. The third step involves installing the existing bridge bearing system 12 on-site. First, the support installation positions at the bottom of the old bridge main beam 11 and the top of the old bridge cap beam 13 are cleaned, smoothed, and drilled, and structural adhesive is applied. Second, an assembly consisting of an upper steel plate 2, a stainless steel plate 3, and a limiting steel plate 4 is installed at the bottom of the old bridge main beam 11 and fixed with upper anchor bolts 1. Third, an assembly consisting of a connecting steel plate 7, a support body 6, and a wear-resistant plate 5, along with a lower steel plate 8, is installed at the top of the old bridge cap beam 13 and fixed with lower anchor bolts 9. Finally, the old bridge main beam 11 is slowly lowered back to its designed position, and the jacks are removed. Fourth, the new bridge is constructed on-site. The foundation construction of the new bridge pier 34 is carried out on one side of the old bridge, including reinforcing steel binding, formwork erection, and in-situ concrete pouring, which is then cured to the design strength. New bridge supports 32 are installed on the top surface of the new bridge cap beam 33. The prefabricated new bridge main beam 31 is hoisted and precisely positioned onto the new bridge supports 32. Fifth, the widening of the bridge is completed. The steel bars of the wet joint 21 between the old bridge main beam 11 and the new bridge main beam 31 are tied and connected to the reserved steel bars of the beams on both sides; the wet joint concrete is poured with formwork and the formwork is removed after the concrete reaches the design strength; finally, the bridge deck paving, guardrails, expansion joints and other bridge deck ancillary facilities are constructed to complete the widening and renovation construction.

[0041] In one embodiment of this application, details of the construction process are supplemented. During the third step of on-site installation of the old bridge bearing system 12, holes are drilled at the bottom of the old bridge main beam 11 and the top of the old bridge cap beam 13. Reinforcing adhesive (such as epoxy resin structural adhesive) is injected into the holes before installing the upper anchor bolts 1 and lower anchor bolts 9 to enhance the bond strength between the anchor bolts and the concrete. After the old bridge main beam 11 is lowered to its designed position, the perimeter of the old bridge bearing system 12 is sealed with a dustproof sealant. Weather-resistant sealant is used to fill the gaps around the bearing to prevent dust, moisture, and other debris from intruding into the sliding interface, ensuring the long-term performance of the bearing.

[0042] In one embodiment of this application, the application scenario of the system of the present invention is described. An existing highway bridge located in a seismic fortification intensity zone of degree VIII needs to be widened and renovated. The original bridge is a 20-meter span simply supported beam bridge with low reinforcement ratio of piers and columns, resulting in insufficient seismic performance. The widening and renovation is carried out using the seismic toughness enhancement system of the present invention, which achieves cooperation between the old and new spans: the old bridge is replaced with the old bridge bearing system 12, and the new bridge uses lead-core rubber bearings. Through stiffness tuning design, the new bridge bears the main seismic load, while the old bridge is in a low-damage working state. After the renovation, the seismic toughness of the entire bridge is significantly improved, meeting the seismic fortification requirements of degree VIII. In another embodiment, a bridge located in a seismic fortification intensity zone of degree IX is widened and renovated using the system of the present invention, which also achieves good seismic performance. It can be seen that the system of the present invention is particularly suitable for the widening and renovation projects of existing beam bridges in high-intensity seismic zones of degree VII, VIII, or IX, achieving a synergistic improvement in the seismic toughness of the old and new bridges through stiffness tuning.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A seismic toughness system for widened bridges that achieves cooperation between old and new spans, characterized in that, Includes the old bridge, the new bridge, and the wet joint connecting the old bridge and the new bridge (21). The old bridge includes the old bridge main beam (11), the old bridge bearing system (12), the old bridge cap beam (13), and the old bridge piers (10); wherein, the old bridge bearing system (12) includes an upper anchor bolt (1), an upper steel plate (2), a stainless steel plate (3), a limiting steel plate (4), a wear-resistant plate (5), a bearing body (6), a connecting steel plate (7), a lower steel plate (8), and a lower anchor bolt (9); a sliding interface is formed between the wear-resistant plate (5) and the stainless steel plate (3) to reduce the horizontal stiffness of the old bridge bearing system (12); The new bridge includes a main beam (31), bearings (32), cap beams (33), and piers (34); wherein the bearings (32) are seismic isolation bearings to bear the main seismic loads. The horizontal stiffness of the old bridge bearing system (12) and the new bridge bearing (32) are tuned and configured so that the new bridge bears the main seismic load under seismic action and the old bridge is in a low-damage working state, thus realizing the new and old bridges working together to resist earthquakes.

2. The seismic toughness system for widened bridges that achieves cooperation between old and new spans as described in claim 1, characterized in that, The upper steel plate (2) is welded to the stainless steel plate (3) and the limiting steel plate (4); the wear-resistant plate (5) is bonded to the top surface of the support body (6); the support body (6) is composed of a rubber plate (61) and a stiffening steel plate (62), and the rubber plate (61) and the stiffening steel plate (62) are connected by vulcanization; the connecting steel plate (7) is connected to the support body (6) by vulcanization; a round hole is provided in the middle of the lower steel plate (8). The connecting steel plate (7) is embedded in the round hole in the middle of the lower steel plate (8); the upper steel plate (2) and the lower steel plate (8) are provided with round holes at the four corner points; the upper anchor bolt (1) passes through the round hole at the corner point of the upper steel plate (2) to connect the old bridge bearing system (12) to the old bridge main beam (11); the lower anchor bolt (9) passes through the round hole at the corner point of the lower steel plate (8) to connect the old bridge bearing system (12) to the old bridge cap beam (13).

3. The seismic toughness system for widened bridges that achieves cooperation between old and new spans as described in claim 2, characterized in that, The wear-resistant plate (5) is made of polymer material and the coefficient of friction between it and the stainless steel plate (3) is no greater than 0.

03.

4. The seismic toughness system for widened bridges that achieves cooperation between old and new spans as described in claim 2, characterized in that, The wear-resistant plate (5), the support body (6), and the connecting steel plate (7) have the same planar dimensions.

5. The seismic toughness system for widened bridges that achieves cooperation between old and new spans as described in claim 2, characterized in that, There is a clear distance between the bearing body (6) and the limiting steel plate (4), which is equal to the design horizontal displacement value of the old bridge bearing system (12).

6. The seismic toughness system for widened bridges that achieves cooperation between old and new spans as described in claim 2, characterized in that, The connecting steel plate (7) and the lower steel plate (8) have the same thickness.

7. The seismic toughness system for widened bridges that achieves cooperation between old and new spans as described in claim 1, characterized in that, The new bridge bearing (32) is a seismic isolation bearing, which is selected from plate rubber bearings, lead-core rubber bearings, high-damping rubber bearings or friction pendulum bearings.

8. The seismic toughness system for widened bridges that achieves cooperation between old and new spans as described in claim 3, characterized in that, The polymer material is ultra-high molecular weight polyethylene or polytetrafluoroethylene, and the friction coefficient between the wear-resistant plate (5) and the stainless steel plate (3) is controlled by adding modified fillers or surface treatment processes.

9. A design method for implementing the seismic toughness system of a widened bridge achieving new and old span coordination as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Step 1: Based on the as-built drawings of the old bridge and the preliminary design drawings of the new bridge, establish a seismic analysis model for the widened bridge and verify the seismic toughness of the old bridge; if the verification results do not meet the design specifications, proceed to the next steps. Step 2: In the seismic analysis model, the existing bearings of the old bridge are replaced with the old bridge bearing system (12) to form a seismic toughness enhancement model; the old bridge bearing system (12) is simulated using a constitutive relationship of a linear model and an ideal bilinear model connected in series. The horizontal stiffness K of the linear model is calculated using the following formula: K = GA / t Wherein, G is the shear modulus of the rubber plate (61), A is the planar area of ​​the support body (6), and t is the total thickness of the rubber layer of the support body (6). The yield force F of the ideal bilinear model is calculated using the following formula: F = μN Wherein, μ is the coefficient of friction between the wear-resistant plate (5) and the stainless steel plate (3), and N is the dead load reaction force of the old bridge main beam (11); The initial stiffness K1 of the ideal bilinear model is calculated using the following formula: K1 = F / s Where s is the yield displacement, and the value of s ranges from 0.002m to 0.005m; Step 3: Perform calculation and analysis on the seismic toughness improvement model, and verify the seismic toughness of the old bridge and the new bridge respectively; If the seismic toughness of the old bridge does not meet the design specifications, it can be optimized by adjusting the horizontal stiffness of the old bridge bearing system (12). The horizontal stiffness of the old bridge bearing system (12) should be determined according to the bending bearing capacity and shear bearing capacity of the old bridge pier (10) to ensure that the old bridge pier (10) does not suffer strength failure. If the seismic toughness of the new bridge does not meet the design specifications, it can be optimized by adjusting the horizontal stiffness of the new bridge support (32) or increasing the size and reinforcement of the new bridge pier (34). The horizontal stiffness of the new bridge support (32) should be determined according to the super bending moment and super shear force of the new bridge pier (34) to ensure that the new bridge pier (34) does not suffer shear failure and that the ductile deformation meets the specifications.

10. The design method for a seismic toughness system of a widened bridge achieving cooperation between old and new spans, as described in claim 9, is characterized in that... In the third step, adjusting the horizontal stiffness of the old bridge bearing system (12) specifically involves: changing the total thickness t of the rubber layer of the bearing body (6), the shear modulus G of the rubber plate (61), the planar area A of the bearing body (6), or changing the friction coefficient μ between the wear-resistant plate (5) and the stainless steel plate (3) to achieve precise tuning of the horizontal stiffness of the old bridge until the seismic toughness of the old bridge meets the design specifications.

11. A construction method for implementing the seismic toughness system of a widened bridge achieving new and old span coordination as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Step 1: The old bridge bearing system (12) is prefabricated in the factory; first, holes are made in the upper steel plate (2) and the lower steel plate (8); second, the upper steel plate (2) is welded to the stainless steel plate (3) and the limiting steel plate (4); third, the wear-resistant plate (5) is bonded to the top surface of the bearing body (6); finally, the connecting steel plate (7) is vulcanized to the bearing body (6); Step 2: Remove the existing supports of the old bridge on site; use jacks to lift the main beam (11) of the old bridge and remove the existing supports of the old bridge; Step 3: Install the old bridge support system (12) on site; First, clean, grind and drill holes at the positions corresponding to the supports at the bottom of the old bridge main beam (11) and the top of the old bridge cap beam (13), and apply structural adhesive; Second, install the assembly consisting of the upper steel plate (2), the stainless steel plate (3) and the limiting steel plate (4) at the bottom of the old bridge main beam (11), and fix it with the upper anchor bolt (1); Third, install the assembly consisting of the connecting steel plate (7), the support body (6) and the wear-resistant plate (5) and the lower steel plate (8) at the top of the old bridge cap beam (13), and fix it with the lower anchor bolt (9); Finally, lower the old bridge main beam (11) back to the design position and remove the jacks; Step 4: Construct the new bridge on site; from bottom to top, cast the new bridge piers (34) and the new bridge cap beams (33) in place, install the new bridge supports (32), and hoist the new bridge main beams (31). Step 5: Complete the widening of the bridge construction; use the wet joint (21) to connect the old bridge main beam (11) and the new bridge main beam (31) into a whole, and construct the bridge deck system.

12. The construction method for a widened bridge seismic toughness system that achieves cooperation between old and new spans, as described in claim 11, is characterized in that... In the third step, after drilling holes in the bottom of the old bridge main beam (11) and the top of the old bridge cap beam (13), the anchoring adhesive or epoxy resin structural adhesive is injected into the holes and then the upper anchor bolt (1) and lower anchor bolt (9) are installed. After the old bridge main beam (11) is lowered to the design position, the old bridge support system (12) needs to be dustproofed and sealed around its perimeter.

13. A seismic toughness system for widened bridges that achieves cooperation between old and new spans according to any one of claims 1 to 8, characterized in that, The system is applicable to the widening and renovation of existing beam bridges in high-intensity earthquake zones with seismic fortification intensity of VII, VIII or IX, and achieves synergistic improvement in seismic toughness of the new and old bridges through stiffness tuning.

Images