Anti-seismic property analysis method for bridge body structure of wind and rain bridge

Abstract

The invention discloses an anti-seismic property analysis method for a wind and rain bridge body structure. By constructing a finite element model of the wind and rain bridge, the mechanical response of the wind and rain bridge under the action of static load and seismic waves is simulated. The method specifically comprises the following steps: constructing a finite element model comprising a pier, a bridge floor, a wooden support and a rubber shock insulation layer; carrying out static analysis to obtain bearing capacity, deflection and stress distribution; carrying out dynamic analysis, including modal analysis and seismic response analysis, to determine a key response spectrum; and the arrangement scheme of the rubber shock insulation layer is optimized to improve the anti-seismic performance. According to the method, through refined finite element analysis and in combination with the rubber shock insulation technology, the anti-seismic performance of the wind and rain bridge is remarkably improved, and the historical and cultural values of the wind and rain bridge are kept to the maximum extent. The method provides a scientific basis and technical support for improving the anti-seismic property of a traditional wood structure building, and has important engineering application value and culture protection significance.

Description

Technical Field

[0001] The present invention relates to the technical field of earthquake-resistant building structures, and in particular to a method for analyzing the earthquake-resistant performance of a wind and rain bridge structure. Background Art

[0002] Wind and rain bridges are a unique wooden structure unique to the Dong ethnic group. Composed of a bridge, tower, and pavilion, they are joined using mortise and tenon joints, eliminating the need for nails or rivets. The piers are mostly hexagonal columns, with sharp angles upstream and downstream to mitigate flooding. The bridge body utilizes a cantilever bracket system with a simply supported beam, topped by a tiled corridor, serving as a transportation hub, shelter from the rain, and a resting area. Widely distributed across Hunan, Guizhou, and Guangxi, wind and rain bridges are representative of Dong architectural art, blending mechanics and aesthetics. The pavilions and corridors are intricately painted and carved, embodying the harmonious coexistence of traditional Dong craftsmanship with the natural environment.

[0003] In the area of ​​ancient bridge preservation, existing research has developed a multi-dimensional, systematic conservation strategy. In terms of material optimization, dynamic monitoring of wood moisture content reveals the spatiotemporal heterogeneity of its moisture absorption behavior, providing data support for climate-responsive structural design. Composite materials such as glulam are being used to improve seismic strength and load transfer efficiency, overcoming the mechanical limitations of traditional timber structures. In the area of ​​structural restoration, traditional construction techniques are integrated with finite element analysis to establish a systematic restoration process: damage identification – mechanism modeling – performance adaptation. A quantitative safety assessment system has been developed for wooden arch bridges, employing a weighted distribution algorithm and numerical simulation to accurately determine risk levels. In terms of disaster prevention and control, fire dynamics simulations are used to analyze fire spread patterns and develop fire-retardant technologies that balance architectural characteristics and cultural value. These multi-dimensional measures, encompassing dynamic monitoring, scientific assessment, technical restoration, material innovation, and disaster prevention and control, form a closed-loop cultural heritage conservation system that balances authenticity and sustainability.

[0004] Modern bridge seismic isolation technology, centered around multi-dimensional collaborative protection, offers significant versatility. Rubber isolation methods dissipate seismic energy through shear deformation, reducing structural response. Viscous dampers, metal yield dampers, and other methods utilize material hysteresis or fluid friction to dissipate energy. Global stiffness enhancement methods improve seismic resistance through prestressing, carbon fiber reinforcement, or steel-concrete composite structures. Damping performance can also be enhanced through material modification, with intelligent control technologies enabling real-time adjustment of damping parameters. In particular, for rubber isolation bearings, a parameter optimization framework based on the Mooney-Rivlin hyperelastic constitutive model precisely regulates the stiffness characteristics of the isolator through material-structure collaborative design. Compression-shear hybrid finite element models improve the accuracy of predicting the vibration response of sandwich structures through the multimodal damping coupling mechanism of viscoelastic interlayers. The multiscale design theory of high-damping rubber materials, combined with vulcanization modification and filler reinforcement strategies, constructs a hyperelastic-viscoelastic constitutive fusion model, overcoming the temperature sensitivity challenge of traditional isolation bearings. These methods form a full-chain technical system from material property optimization, multi-physical field coupling to engineering application verification.

[0005] In summary, as traditional wooden structures with significant cultural value, wind and rain bridges require seismic performance analysis and preservation strategies that consider both structural safety and cultural heritage. Existing research, in terms of cultural heritage preservation, finite element analysis techniques, and modern bridge seismic mitigation technology, provides a solid foundation for seismic performance analysis methods for wind and rain bridge structures. Summary of the Invention

[0006] The present invention aims to provide a method for analyzing the seismic performance of the wind and rain bridge structure. By optimizing the arrangement and thickness selection of the rubber isolation layer, the seismic performance of the wind and rain bridge can be improved while taking into account cultural heritage and economic efficiency.

[0007] To achieve the above-mentioned object, the present invention provides the following technical solution: a method for analyzing the seismic performance of a wind and rain bridge structure, comprising the following steps:

[0008] Step 1: Construct a finite element model of the wind and rain bridge structure. The model is based on the structural characteristics of an actual wind and rain bridge, including piers, bridge deck, wooden supports, and rubber isolation layers.

[0009] Step 2: Performing static analysis on the finite element model to obtain the load-bearing capacity, deflection, and stress distribution of the model under static load;

[0010] Step 3: Performing dynamic analysis on the finite element model, including modal analysis and seismic response analysis, to obtain the key response spectrum of the model under the action of seismic waves;

[0011] Step 4: Based on the results of static and dynamic analysis, optimize the layout of the rubber isolation layer to improve the seismic performance of the wind and rain bridge structure.

[0012] Specifically, the establishment of the finite element model includes: establishing a geometric model based on the actual structural characteristics of the wind and rain bridge; meshing the geometric model, using coarse meshes for the pier part and the rubber isolation layer, using fine meshes for the wooden support part, and selecting different mesh sizes for the bridge deck according to the long side and short side; setting the material properties of the model, including parameters such as the density, elastic modulus, and Poisson's ratio of wood, concrete, and rubber; defining the load arrangement and interaction settings of the model, including superstructure loads, crowd loads, self-weight loads, dynamic loads, and the connection methods between the piers and wooden supports, and between the wooden supports and the bridge deck.

[0013] Specifically, the static analysis includes: calculating the volume and mass of the wind and rain bridge model's superstructure and converting them into loads applied to the bridge deck; applying crowd loads and deadweight loads, and combining the loads according to relevant standards; applying static loads to the model to obtain the model's longitudinal displacement and stress distribution.

[0014] Specifically, the dynamic analysis includes: performing modal analysis on the model to determine the natural frequency and modal shape of the structure; calculating the damping coefficient of the structure based on the modal analysis results; inputting seismic waves as dynamic loads, performing seismic response analysis on the model, and obtaining the acceleration response, displacement response, and stress change of the model under the action of seismic waves.

[0015] Specifically, the optimization of the layout scheme of the rubber isolation layer includes: setting different rubber isolation layer layout schemes, including full layout, two-end layout, middle layout and span layout; performing finite element analysis on the model of each layout scheme, and comparing the vibration reduction effect and displacement response under different schemes; selecting the layout scheme with the best shock absorption effect and controllable displacement response as the final rubber isolation layer layout scheme.

[0016] Specifically, the thickness selection of the rubber isolation layer includes: selecting multiple rubber isolation layers of different thicknesses within a certain thickness range for parametric analysis; performing finite element analysis on the rubber isolation layer models of each thickness to obtain the acceleration response and displacement response under different thicknesses; and determining the optimal rubber isolation layer thickness based on the analysis results so that the structure achieves the best shock absorption effect at this thickness.

[0017] The principle and beneficial effects of this technical solution:

[0018] The principle of this technical solution is based on the finite element analysis method, combined with rubber isolation technology, to optimize the seismic performance of the wind and rain bridge structure. A finite element model of the wind and rain bridge is established to accurately simulate key structural components such as piers, bridge decks, wooden supports, and rubber isolation layers. In the static analysis, the bearing capacity and stress distribution of the model under the action of superstructure loads, crowd loads, and deadweight loads are calculated to identify stress concentration areas. The dynamic analysis determines the natural frequency and modal shape of the structure through modal analysis, and then inputs seismic waves for response analysis to obtain the acceleration, displacement, and stress changes of the structure under earthquake action. By comparing the finite element analysis results of different rubber isolation layer arrangements and thicknesses, the optimal isolation scheme is selected to significantly reduce the seismic response of the structure.

[0019] By optimizing the layout and thickness of the rubber isolation layer, the acceleration and displacement responses of the wind and rain bridge under earthquakes were effectively reduced, significantly improving the structure's seismic resistance and reducing the risk of earthquake damage to the bridge structure. While improving the seismic performance, the uniqueness of the wind and rain bridge as a cultural heritage of the Dong ethnic group was fully considered, and rubber isolation technology was adopted to avoid large-scale changes to the bridge's appearance and structural form, thereby preserving its historical and cultural value to the greatest extent possible. By comparing different layout schemes, the isolated span layout (Plan 4) was selected as the optimal solution. This solution achieved good shock absorption while reducing material consumption, and has high engineering economy and practicality. Using finite element analysis methods, combined with modal analysis and seismic response analysis, the seismic performance of the wind and rain bridge was systematically evaluated, providing a scientific basis for the optimized design of the rubber isolation layer, making the entire seismic performance improvement process highly scientific and systematic.

[0020] This proposal not only targets wind and rain bridges but also provides a new technical path for improving the seismic performance of other traditional wooden structures. It promotes the integration of engineering mechanics and cultural heritage protection, and has important demonstration and promotional value. This research provides guidance for further exploring the application of intelligent sensing materials in the protection of ancient bridges, building long-term health monitoring systems, and deepening research on the mechanisms of multi-hazard coupling. This will help promote the transformation of ancient bridge protection from passive reinforcement to active adaptation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a model diagram of the Wind and Rain Bridge;

[0022] Figure 2 This is the mesh division diagram of the local model and rubber isolation layer;

[0023] Figure 3 is the constitutive model diagram of concrete;

[0024] Figure 4 This is the test result diagram of rubber material;

[0025] Figure 5 This is the time history graph of the El-Centro earthquake wave;

[0026] Figure 6 is the longitudinal displacement cloud diagram of the model under static load;

[0027] Figure 7 is the stress distribution cloud diagram of the model under static load;

[0028] Figure 8 It is the stress concentration cloud diagram of the model under static load;

[0029] Figure 9 This is the maximum equivalent displacement diagram of the first 9 modes;

[0030] Figure 10 is the key mode equivalent displacement cloud map;

[0031] Figure 11 is the acceleration response cloud diagram of the model;

[0032] Figure 12 is the acceleration change diagram of the model;

[0033] Figure 13 is the lateral displacement change diagram of the model;

[0034] Figure 14 Figure 1 is a diagram of stress concentration locations and stress changes;

[0035] Figure 15 This is the layout and support numbering diagram of the rubber isolation layer;

[0036] Figure 16 This is a heat map of the acceleration reduction effect;

[0037] Figure 17 This is the lateral acceleration response diagram of Plan 4;

[0038] Figure 18 This is the longitudinal acceleration response diagram of Plan 4;

[0039] Figure 19 is the displacement response diagram of Plan 4;

[0040] Figure 20 It is the waterfall diagram of the lateral acceleration amplitude change;

[0041] Figure 21 is the maximum lateral acceleration amplitude diagram;

[0042] Figure 22 is the maximum longitudinal acceleration amplitude diagram;

[0043] Figure 23 is the maximum displacement amplitude diagram. DETAILED DESCRIPTION

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0045] Example: Seismic Performance Analysis of Chengyang Yongji Bridge

[0046] The Chengyang Yongji Bridge over the Linxi River in Sanjiang, Guangxi Zhuang Autonomous Region, was selected for analysis. The bridge is 64.4 meters long and 3.4 meters wide, featuring a "two platforms, three piers, and four arches" structure with stone piers and timber. The piers are flat hexagonal, constructed of bluestone, with sharp angles at each end to mitigate flooding. Its core force transmission system is a densely distributed cantilever bracket simply supported beam system. The bridge deck, comprised of five tower-style pavilions and 19 galleries, utilizes mortise and tenon joints, eliminating the need for nail reinforcement, to accommodate the required long span and enhance stability.

[0047] 1 Modeling

[0048] 1.1 Geometric model establishment and meshing

[0049] A three-span simply supported wind and rain bridge model was built with a total span of 76 meters and a deck width of 4.3 meters. There are wooden supports between the deck and the piers, connected by mortise and tenon joints. Figure 1 .

[0050] The piers and rubber isolation layer use a 500mm coarse grid, the wooden supports use a 100mm fine grid, the long side of the bridge deck uses a 500mm grid and the short side uses a 100mm grid. Figure 2 .

[0051] 1.2 Material properties

[0052] Key materials under investigation include wood, concrete and rubber.

[0053] 1.2.1 Wood

[0054] Wood is an anisotropic material and is mainly used in bridge decks and wooden supports. The density is ρw=500kg / m 3 , the parameters are shown in Table 1.

[0055] Table 1. Properties of wood.

[0056]

[0057] Note: Subscripts 1, 2, and 3 denote the longitudinal, radial, and chordal directions, respectively; E denotes the elastic modulus; Nu denotes the Poisson's ratio; G denotes the shear modulus; f denotes the yield stress; and R denotes the yield stress ratio in each direction. All moduli in Table 1 are in MPa.

[0058] 1.2.2 Concrete

[0059] Concrete material is mainly used in the pier part, and the density is selected as 2400kg / m 3 , elastic modulus 3×10 10 Pa, Poisson's ratio 0.2, and plastic damage model conforming to GB50010-2010, such as Figure 3 As shown, (a) is the strain-stress and strain-damage relationship during compression, and (b) is the strain-stress and strain-damage relationship during tension.

[0060] 1.2.3 Rubber

[0061] Rubber is a super elastic material used in the seismic isolation layer. The density is 930kg / m 3 , its tensile test data are as follows Figure 4 shown.

[0062] 1.3 Load arrangement and interaction setting

[0063] 1.3.1 Superstructure load (dead load)

[0064] The volume of each component of the wind and rain bridge superstructure was calculated using AutoCAD. The mass of each component was then converted into loads to be applied to the bridge deck. The mass calculation process is shown in Table 2.

[0065] Table 2. Mass calculation of the model superstructure (corridor and pavilion parts)

[0066]

[0067] There are 40 columns arranged in the superstructure of the model, with a cross-section of 0.3m*0.3m. Therefore, the contact area between the superstructure and the bridge deck can be obtained by formula (1).

[0068] S p =0.3×0.3×40=3.6(m 2 ) (1)

[0069] The load acting on the bridge deck by the superstructure can be obtained by formula (2).

[0070]

[0071] Where q1 represents the superstructure load acting on the bridge deck; m1, m2, and m3 represent the masses of the corridor and pavilion frames, the corridor and pavilion roofs, and the tiles, respectively, as shown in Table 1; S p represents the contact area between the model's superstructure (i.e., the corridor and pavilion) and the bridge deck, which is 3.6 square meters in this model; g represents the acceleration due to gravity, which is 9.8 m / s2.

[0072] 1.3.2 Crowd load (live load)

[0073] The method for determining the standard value of crowd load is shown in formula (3).

[0074]

[0075] Among them, Q crowd represents the crowd load, and L0 represents the maximum calculated span of the bridge.

[0076] The single span length of the model is less than 50m, so the crowd load standard is set to q2 = 3.0kN / m 2 .

[0077] 1.3.3 Load combinations

[0078] The combination coefficients of dead load and live load are γ G =1.3 and γ Q =1.5. The load combination method is shown in formula (4).

[0079] S=γ G G+γ Q Q (4)

[0080] Among them, S represents the load combination value, G represents the dead load, and Q represents the live load.

[0081] The calculation of load combination values ​​is shown in Table 3.

[0082] Table 3. Calculation of model load combination values

[0083]

[0084] 1.3.4 Self-weight load

[0085] AutoCAD was used to calculate the volume of each part of the model, thereby obtaining the mass of each part of the model. The material parameters of the lower structure of the model are shown in Table 4.

[0086] Table 4. Material parameters of the model substructure

[0087]

[0088] The self-weight load of the model can be obtained by formula (5).

[0089] G m =(97200+2380000)×9.8=2.43×10 7 (kg) (5)

[0090] 1.3.5 Dynamic load

[0091] Using El-Centro seismic waves, peak acceleration 0.35m / s 2 , input method see Figure 5 .

[0092] 1.3.6 Interaction

[0093] The bridge piers and wooden supports, as well as the wooden supports and the bridge deck, were initially bound together. A rubber isolation layer was added to the shock absorption model, with a small slip contact and a tangential friction coefficient of 0.75. A "hard" contact was used in the normal direction.

[0094] 1.4 Analysis step settings

[0095] Static analysis: duration 1 second, linearly increasing load.

[0096] Dynamic analysis: duration 36 seconds, with seismic wave input in the first 30 seconds and aftershock response observation in the last 6 seconds, and a time step of 0.01 seconds.

[0097] 2 Model stress analysis and seismic analysis

[0098] 2.1 Static analysis

[0099] When static loading is applied, the longitudinal displacement of the model changes as shown in Figure 6 , where the deformation scaling factor is 10, unit: mm. Finite element analysis shows that the maximum deflection of the model is 189.584 mm, located at the edge of the bridge deck mid-span. In a three-span simply supported beam bridge structure, each span has uniform stiffness distribution, symmetrical load transfer paths, and comparable load-bearing capacity, consistent with the mechanical characteristics of a simply supported beam bridge, where each span bears load independently, with weak coupling between spans.

[0100] The stress distribution during static loading is shown in Figure 7 , stress concentration area is shown Figure 8 , where the deformation scaling factor is 10, unit: MPa. Overall, the stresses at the supports and mid-span are relatively large. The stress concentration is mainly at the connection between the wooden supports and the bridge deck, with the maximum stress reaching 16.950 MPa. This is due to the geometric mutation and stiffness discontinuity in this area: a geometric transition zone is formed at the junction of the bridge deck and the pier, and the load transfer path changes suddenly. The discontinuous distribution of material stiffness prevents the stress from gradually weakening at the edge of the interface, forming a significant stress gradient. This stress concentration effect can be attributed to the local perturbation of Saint-Venant's principle, that is, the uniform stress field distribution is broken in the area where the cross-section changes sharply.

[0101] To address stress concentration, a multi-scale collaborative optimization strategy can be employed. For geometric optimization, a gradient transition design is employed, introducing a curved gradient transition structure instead of a right-angle connection to reduce stress concentration in areas with sudden cross-sectional changes. Furthermore, a gradient composite interlayer is placed in the connection area, leveraging the directional alignment of high-strength fibers to achieve a smooth stiffness transition and mitigate the impact of sudden stiffness changes in the material.

[0102] 2.2 Modal analysis and damping coefficient calculation

[0103] The model was subjected to nine modal analyses to determine the natural frequencies and mode shapes of the structure. Figure 9 The maximum equivalent displacements in nine modes are shown, including (a) the first mode (f1 = 3.6898 Hz) and (b) the second mode (f2 = 3.6948 Hz). The deformation scaling factor is 40,000, and the unit is mm. Figure 10 The response contours under key modes are displayed, which intuitively presents the vibration characteristics of the structure and provides an important basis for evaluating the structural dynamic performance and potential resonance risks.

[0104] The relationship between structural damping, mass and stiffness can be expressed by formula (6):

[0105] [C]=α[M]+β[K] (6)

[0106] Where C, M, and K represent the damping, mass, and stiffness of the model, respectively.

[0107] The damping coefficients α and β can be calculated using formulas (7) and (8):

[0108]

[0109] Where ξ represents the material damping ratio, which is 0.05 for concrete and 0.03 for wood respectively; f i and f j are the frequencies of the first and second modes in the modal analysis, respectively.

[0110] The calculation of damping coefficients α and β is shown in Table 5.

[0111] Table 5. Calculation of damping coefficients α and β.

[0112]

[0113] 2.3 Earthquake response analysis

[0114] Select two time nodes, 18 seconds (during the earthquake wave action process) and 36 seconds (aftershock stage after the earthquake wave action is completed), and derive the horizontal acceleration response cloud map in the earthquake wave direction (see Figure 11 , a is 18 seconds, b is 36 seconds, unit: mm / s 2 The acceleration changes at the mid-span position of the middle span and the side span are shown in Figure 12 , where (a) is the lateral acceleration, (b) is the longitudinal acceleration, and the lateral displacement change is shown in Figure 13 .

[0115] Under the excitation of the El-Centro earthquake wave, the lateral acceleration responses of the middle span and the side span are consistent, with the maximum values ​​of 829.205 mm / s 2 and 936.926 mm / s 2The longitudinal acceleration response and lateral displacement parameters showed significant differences: the maximum longitudinal acceleration of the side span was 154.30 mm / s 2 (for the middle span 391.89mm / s 2 The maximum lateral displacement is 0.2648 mm (50.20% of the 0.5275 mm in the middle span). This difference stems from the asymmetry of the longitudinal constraints. The middle span is located at the center of the continuous structure, with stronger longitudinal constraints and greater stiffness, which leads to the concentration of seismic energy. The side spans weaken the longitudinal constraints due to the end boundary conditions (such as sliding supports and free end effects), forming a flexible deformation mechanism and reducing the inertial force and displacement response. In addition, differences in structural mass distribution or the coupling of seismic wave spectrum characteristics with the longitudinal natural frequency may exacerbate this asymmetric response.

[0116] The stress concentration locations and stress changes of the model are shown in Figure 14 . The model mainly shows the characteristics of connection node failure and overall fragile performance under strong earthquakes. During the earthquake, the maximum stress of the connection node reached 17.0341MPa, which was aggravated compared with static load. The mortise and tenon joints between independent spans are prone to cumulative slip deformation under repeated ground vibrations, and the anisotropy of timber components exacerbates the stress relaxation effect in the node area. The composite vibration mode of the bridge deck includes lateral bending and longitudinal torsion, resulting in the formation of a weak interface of biaxial tension in the mid-span area. With the input of seismic energy, the geometric mutation zone at the junction of the bridge deck and the abutment first cracked, causing local stiffness degradation. The non-cooperative deformation between multiple spans further amplifies the difference in support displacement, which may eventually lead to collision.

[0117] 3. Analysis of rubber isolation layer layout and shock absorption effect

[0118] 3.1 Plan formulation

[0119] The seismic isolation performance of the wind and rain bridge was optimized by installing rubber isolation bearings. This solution not only ensures the stress safety of the wooden structure, but also maintains the authenticity of the cultural heritage. The layout method of the rubber isolation layer and the point numbering of the bridge bearings are as follows: Figure 15 shown.

[0120] First, the seismic performance of a 100 mm thick rubber isolation layer was analyzed. Four schemes were selected: full layout (Plan 1), two-end layout (Plan 2), middle layout (Plan 3), and every-span layout (Plan 4). The specific layout methods are shown in Table 6.

[0121] Table 6. Rubber isolation layer layout scheme.

[0122]

[0123] Note: “√” indicates that a rubber isolation layer is arranged on this bearing.

[0124] 3.2 Analysis of shock absorption effect and comparison of solutions

[0125] Finite element analysis was performed on the models of each solution. The maximum vibration amplitude is shown in Table 7, and the vibration reduction efficiency is shown in Table 8.

[0126] Table 7. Maximum amplitude results of each scheme.

[0127]

[0128] Table 8. Vibration reduction effect of each solution.

[0129]

[0130] According to Table 8, a reasonable arrangement of rubber isolation bearings can significantly reduce the structure's bidirectional acceleration response, but it can also increase the displacement response. Engineering evaluations show that the relative displacement of the structure under seismic excitation is within an acceptable range, and the displacement increase of the isolation system is far lower than the acceleration attenuation rate, demonstrating the effectiveness of this isolation scheme in controlling vibration energy.

[0131] Figure 16 The acceleration reduction effects of each plan were visually displayed in the form of a heat map. The results showed that Plan 2 and Plan 3 were not reasonable. Plan 2 only partially reduced the lateral acceleration of the side spans, but increased the acceleration of the middle span. Plan 3 had a poor lateral acceleration reduction effect (only 14.15%) and only reduced the longitudinal acceleration of the middle span. In contrast, Plan 1 and Plan 4 performed well, significantly reducing the bidirectional acceleration of both the middle and side spans, especially the longitudinal acceleration, with reduction rates of 80.72% and 73.39%, respectively.

[0132] Comparing the performance of Plan 1 and Plan 4, Plan 1 is slightly better but the difference is not significant. Plan 4 adopts half the support arrangement (2 / 4), which reduces the material consumption by 50%, and its displacement increase (30.88% and 71.68%) is much lower than Plan 1 (194.86% and 402.61%), indicating that Plan 4 has achieved an optimal balance between control performance and displacement cost, and has engineering economic advantages. The dynamic response of Plan 4 in lateral acceleration, longitudinal acceleration and displacement are shown in Figure 2. Figure 17 、 Figure 18 and Figure 19 , where (a) is the middle span and (b) is the side span.

[0133] 4. Analysis of rubber cushion thickness selection

[0134] 4.1 Overview of the Solution

[0135] Based on the technical and economic comparison results, the rubber isolation bearing system with a span-to-span arrangement offers the best overall benefits. This study, focusing on rubber isolation layers with a thickness of ≤100 mm, parametrically analyzes the quantitative relationship between thickness and isolation performance, providing theoretical support for engineering optimization design.

[0136] Initial finite element analysis using a 500mm coarse mesh and a 0.5-second time step revealed that thickness variations significantly affect acceleration amplitude at smaller thicknesses. Therefore, this study employed a refined approach for smaller thicknesses and a coarsened approach for larger thicknesses, selecting rubber isolation layers of 15, 20, 25, 30, 35, 40, 50, 60, 80, and 100mm thickness for analysis.

[0137] Based on sensitivity analysis, the nonlinear discretization principle was adopted to construct a thickness gradient sampling strategy: a 5mm arithmetic gradient was used in the 15-40mm range, a 10mm arithmetic gradient was used in the 40-60mm range, and a 20mm arithmetic gradient was used above 60mm to enhance the parameter resolution in key areas.

[0138] Since the longitudinal acceleration after shock absorption is significantly lower than the lateral acceleration, the shock absorption performance evaluation focuses on the optimal control of the lateral dynamic response.

[0139] 4.2 Conclusion Analysis

[0140] Finite element analysis shows that the lateral acceleration amplitude changes under different thicknesses are shown in Figure 20 , the maximum lateral and longitudinal acceleration amplitudes are shown in Figure 21 and Figure 22 , where (a) is the middle span and (b) is the side span.

[0141] The results show that the thickness of the isolation layer is non-monotonic with the acceleration amplitude. When the thickness is close to 80mm, the system reaches the optimal isolation state, and the lateral and longitudinal shock absorption efficiencies are 38.56% and 73.34% respectively. The 50mm thick rubber isolation layer has met 30% of the lateral acceleration shock absorption requirements, and the lateral and longitudinal shock absorption effects are 30.13% and 72.17% respectively; the 40mm thick rubber isolation layer can meet 20% of the lateral acceleration shock absorption requirements, and the lateral and longitudinal shock absorption effects are 21.71% and 69.10% respectively. The specific shock absorption conditions are shown in Table 9. The displacement response of each scheme is shown in Table 9. Figure 23 As shown, (a) is the middle span and (b) is the side span.

[0142] Table 9. Shock absorption

[0143]

[0144] The displacement response of the middle span is relatively average, and the optimal effect is achieved when the thickness parameter is about 40 mm, while the vibration reduction effect of the side span decreases roughly monotonically.

[0145] 5 Conclusion

[0146] The Dong ethnic group's wind and rain bridges are a classic example of wooden architecture from southwestern China's ethnic minorities. Combining the techniques of through-beam timber construction with ethnic decorative art, they hold significant cultural heritage value and engineering research significance. This study, drawing on the Yongji Bridge in Chengyang, Guangxi Zhuang Autonomous Region, constructed a model of the Dong ethnic group's wind and rain bridge. Using ABAQUS finite element analysis, a three-stage numerical simulation was conducted to systematically evaluate its structural performance, encompassing static load-bearing capacity, dynamic seismic performance, time-course analysis, and design of a seismic optimization scheme. The study established the dual objectives of "structural safety and cultural heritage," employing a rubber isolation scheme to minimize the impact on the building's exterior. The main conclusions are as follows:

[0147] Static loading analysis: The maximum deflection of the three-span simply supported beam bridge model was 189.584 mm, occurring at the mid-span edge of the bridge deck. The interspan stiffness distribution was uniform, and the load transfer path was symmetrical, consistent with the mechanical properties of a simply supported beam bearing independent loads. The model exhibited significant stress concentration, with a maximum stress of 16.950 MPa, concentrated at the junction of the wooden supports and the bridge deck. This was primarily due to geometric abruptness and stiffness discontinuity. Curved transitions and high-strength fiber layers are recommended to reduce stress concentration and improve structural durability.

[0148] Dynamic loading analysis: Under the excitation of the El-Centro earthquake wave, the lateral dynamic response of the structure showed significant spatial distribution characteristics. The peak lateral acceleration of the middle span and the side span were 829.205 mm / s respectively. 2 and 936.926 mm / s 2 , showing consistent characteristics, indicating that the lateral stiffness distribution is uniform and the excitation by the lateral component of the earthquake wave is similar. The longitudinal response shows significant asymmetry, with the peak longitudinal acceleration of the middle span being 391.89 mm / s 2 , the side span is only 154.30mm / s 2 (39.37%), and the peak lateral displacements were 0.5275mm and 0.2648mm (50.20%) respectively. This difference is due to the asymmetric distribution of longitudinal constraints. The middle span is reinforced by the constraints of the adjacent spans due to the continuous structure center position, forming a stiffness concentration area, which leads to the accumulation of seismic energy; the side spans are affected by the end sliding supports and free end effects, and the longitudinal constraints are weakened. The flexible deformation mechanism reduces the inertial force and displacement response. Under earthquake action, the maximum stress of the connection node reaches 17.0341MPa, which is aggravated compared with static load. Node cumulative damage and material anisotropy are the main causes of failure. It is necessary to optimize the node structure and constraint conditions to improve the overall seismic performance.

[0149] Comparison of Rubber Isolation Layer Layout Schemes: Four rubber isolation layer layout schemes were compared: full layout (Plan 1), two-end layout (Plan 2), middle layout (Plan 3), and separated span layout (Plan 4). Plans 2 and 3 had significant drawbacks: Plan 2 resulted in an increase in the lateral acceleration of the middle span, while Plan 3 reduced the longitudinal acceleration by only 14.15%, and the vibration reduction effect was limited to a localized area. Plans 1 and 4 demonstrated overall optimization performance, with longitudinal acceleration reductions of 80.72% and 73.39%, respectively, and similar bidirectional acceleration control efficiencies. Economic analysis showed that Plan 4 significantly outperformed Plan 1 in displacement response control by reducing the number of supports by 50% (2 / 4 layout). The results indicate that the separated span layout strategy (Plan 4) achieves the optimal balance between vibration reduction efficiency, displacement cost, and material economy, providing a technical path for engineering practice that balances performance and cost.

[0150] Analysis of Rubber Isolation Layer Thickness: Through sensitivity analysis, a nonlinear discretization sampling strategy was constructed: a 5mm asymptotic gradient was used in the 15-40mm range, a 10mm asymptotic gradient was used in the 40-60mm range, and a 20mm gradient was used above 60mm. Results show that when the isolation layer thickness approaches 80mm, the system reaches optimal isolation, with lateral and longitudinal damping efficiencies of 38.56% and 73.34%, respectively. In engineering applications, a thickness of 50mm can meet 30% of the lateral acceleration damping requirement (30.13% lateral and 72.17% longitudinal), while a thickness of 40mm can meet 20% of the lateral acceleration damping requirement (21.71% lateral and 69.10% longitudinal). Displacement response analysis shows that optimal control of mid-span displacement is achieved at a thickness of 40mm, while the damping efficiency of the side spans decreases monotonically with increasing thickness.

[0151] This study systematically reveals the mechanical response laws and failure mechanisms of traditional wooden structures under static and dynamic loads by establishing a refined finite element model of the Dong ethnic group's wind and rain bridge. It also proposes a seismic optimization strategy under the dual constraints of "structural safety and cultural heritage," providing a scientific and operational technical approach for the protection of historical buildings. The study confirms that the gradient design based on rubber isolation technology can significantly improve seismic performance while maintaining the authenticity of the building's appearance to the greatest extent, resolving the contradiction between traditional reinforcement technology and cultural heritage protection principles. Through multi-scale parameter optimization and nonlinear discretization sampling methods, a quantitative correlation model between isolation layer thickness and shock absorption efficiency was constructed, providing a universal theoretical framework for the seismic design of traditional buildings and promoting the interdisciplinary integration of engineering mechanics and cultural heritage protection.

[0152] Future research directions include: further exploring the application of intelligent sensing materials in the protection of ancient bridges, developing environmentally adaptive seismic isolation devices to cope with complex load environments; building a long-term health monitoring system based on the Internet of Things to achieve damage warning and dynamic maintenance; deepening the research on the mechanism of multi-hazard coupling, establishing a comprehensive protection system that takes into account earthquakes, floods, and biological erosion, and promoting the transformation of ancient bridge protection from passive reinforcement to active adaptation.

[0153] The above is only an embodiment of the present invention, and common knowledge such as the specific technical solutions or characteristics in the solution is not described in detail here. For those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A method for analyzing the seismic performance of a wind and rain bridge structure, characterized in that: The following steps are involved: Step 1: Construct a finite element model of the wind and rain bridge structure. The model is based on the structural characteristics of an actual wind and rain bridge, including piers, bridge deck, wooden supports, and rubber isolation layers. Step 2: Performing static analysis on the finite element model to obtain the load-bearing capacity, deflection, and stress distribution of the model under static load; Step 3: Performing dynamic analysis on the finite element model, including modal analysis and seismic response analysis, to obtain the key response spectrum of the model under the action of seismic waves; Step 4: Based on the results of static and dynamic analysis, optimize the layout of the rubber isolation layer to improve the seismic performance of the wind and rain bridge structure.

2. The method for analyzing the seismic performance of a wind and rain bridge structure according to claim 1 is characterized in that: Establishing the finite element model includes: establishing a geometric model based on the actual structural characteristics of the wind and rain bridge; meshing the geometric model, using a coarse mesh for the piers and rubber isolation layer, a fine mesh for the wooden supports, and selecting different mesh sizes for the bridge deck based on the long and short sides; setting the material properties of the model, including parameters such as the density, elastic modulus, and Poisson's ratio of wood, concrete, and rubber; and defining the load arrangement and interaction settings of the model, including superstructure loads, crowd loads, deadweight loads, dynamic loads, and the connection methods between the piers and wooden supports, and between the wooden supports and the bridge deck.

3. The method for analyzing the seismic performance of a wind and rain bridge structure according to claim 1 is characterized in that: The static analysis includes: calculating the volume and mass of the wind and rain bridge model's superstructure and converting them into loads applied to the bridge deck; applying crowd loads and deadweight loads, and combining the loads according to relevant standards; and applying static loads to the model to obtain the model's longitudinal displacement and stress distribution.

4. The method for analyzing the seismic performance of a wind and rain bridge structure according to claim 1 is characterized in that: The dynamic analysis includes: performing modal analysis on the model to determine the natural frequency and modal shape of the structure; calculating the damping coefficient of the structure based on the modal analysis results; inputting seismic waves as dynamic loads, performing seismic response analysis on the model, and obtaining the acceleration response, displacement response and stress change of the model under the action of seismic waves.

5. The method for analyzing the seismic performance of a wind and rain bridge structure according to claim 1 is characterized in that: The optimization of the rubber isolation layer layout scheme includes: setting different rubber isolation layer layout schemes, including full layout, two-end layout, middle layout, and span-interval layout; performing finite element analysis on the models of each layout scheme, comparing the vibration reduction effect and displacement response under different schemes; and selecting the layout scheme with the best vibration reduction effect and controllable displacement response as the final rubber isolation layer layout scheme.

6. The method for analyzing the seismic performance of a wind and rain bridge structure according to claim 1 is characterized in that: The thickness selection of the rubber isolation layer includes: selecting multiple rubber isolation layers of different thicknesses within a certain thickness range for parametric analysis; performing finite element analysis on the rubber isolation layer models of each thickness to obtain the acceleration response and displacement response under different thicknesses; and determining the optimal rubber isolation layer thickness based on the analysis results so that the structure achieves the best shock absorption effect at this thickness.

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