A method for detecting and analyzing collision damage based on a bridge pier

Abstract

The application belongs to the technical field of pier collision damage detection, and specifically discloses a collision damage detection and analysis method based on a bridge pier, which comprises the following steps: a finite element model containing a pier, a pile foundation and soil around the pile is established, and the whole process of ship collision is simulated based on an explicit dynamic time-history analysis, and response parameters such as impact force, displacement and strain are directly obtained in numerical calculation, so that the risk of signal capture failure caused by the contingency and suddenness of the collision event is avoided, and at the same time, a plurality of detection sections are arranged along the pile body in the established finite element model, the relative slip amount of the pile and soil and the plastic deformation degree of the soil are extracted in real time during the collision process, so that the simulation analysis can truly reflect the progressive weakening effect of the soil around the pile on the constraint of the pile foundation during the collision process, the distortion problem of the boundary condition caused by the neglect of the participation of the pile and soil in the prior art is effectively solved, and the consistency of the collision damage evaluation of the bridge substructure and the actual service state is improved.

Description

Technical Field

[0001] This invention belongs to the field of bridge pier collision damage detection technology, and specifically discloses a collision damage detection and analysis method based on bridge piers. Background Technology

[0002] In recent years, with the increase in the density of waterway traffic and the increase in ship tonnage, ship-bridge collisions have become more frequent, threatening bridge safety. In particular, underwater pile foundations are often subject to concrete spalling and other defects due to long-term water erosion, resulting in a significant reduction in actual load-bearing capacity compared to their design specifications. Therefore, accurately assessing the damage status of bridges under ship impact is essential for ensuring waterway traffic safety.

[0003] Existing technologies already include methods for detecting and assessing bridge collision damage. For example, Chinese invention patent CN119470863B discloses a method, system, and medium for assessing bridge damage caused by ship collisions. By deploying an array of acceleration sensors at different heights and locations on the bridge piers, the system collects acceleration response signals during the impact process and generates a time series matrix. Then, it plots the time-frequency coherence spectrum under different basis functions and determines the location and extent of the damage by calculating the trajectory curve of the time-frequency coherence loss factor.

[0004] However, the above approach relies on deploying a large number of sensors on existing bridges to acquire measured data and then using signal processing to invert the damage state. Because impact events are sporadic and sudden, there is considerable uncertainty as to whether the sensor array can completely capture effective acceleration signals at the moment of impact, making it prone to misjudgment due to signal distortion or noise interference.

[0005] Furthermore, the aforementioned approach only obtains macroscopic response data after the impact, failing to reflect the involvement of the surrounding soil, thus causing the analysis results to be disconnected from the service environment of the bridge substructure. In fact, during ship impacts, the surrounding soil undergoes progressive yielding, plastic zone expansion, and even the formation of soil wedges as the impact load is applied. These evolutions directly affect the lateral restraint state and free segment length of the pile foundation, thereby altering the dynamic response and damage mode of the pier.

[0006] Existing technologies neglect the dynamic participation of the soil around the pile, failing to accurately reflect the pile-soil interaction during the collision process, resulting in significant discrepancies between damage assessment results and actual conditions. Summary of the Invention

[0007] To solve the above-mentioned technical problems, or at least partially solve them, the present invention provides a collision damage detection and analysis method based on bridge piers.

[0008] The objective of this invention can be achieved through the following technical solution: a collision damage detection and analysis method based on bridge piers, comprising the following steps: establishing a finite element model including the bridge pier, pile foundation and surrounding soil, and setting the collision point between the ship and the bridge pier in the model.

[0009] The impact process is divided into continuous time segments. At the end of each time segment, the instantaneous impact force on the pier is calculated, and the impact force drives the deformation response of the pier and pile foundation.

[0010] Multiple detection sections were set along the pile body, and the relative slippage between the pile and the soil and the degree of plastic deformation of the soil were obtained at the end of each time segment.

[0011] Based on the relative slippage between the pile and the soil at each cross-section and the degree of plastic deformation of the soil, the failure state of the soil is judged segment by segment from the top of the pile to the bottom of the pile, and the shallowest depth of the failed pile segment is taken as the current virtual ground line.

[0012] Adjust the lateral support conditions of the pile foundation according to the current virtual ground line depth, and enter the next time segment to calculate the instantaneous impact force and solve the structural deformation response.

[0013] The calculation stops when the virtual ground line depth and the residual displacement at the top of the pile no longer change for multiple consecutive time segments, and the damaged area of ​​the bridge pier is output.

[0014] Combining all the above technical solutions, the positive effects of this invention are as follows: 1. This invention establishes a finite element model including bridge piers, pile foundations and surrounding soil, and simulates the entire process of ship collision based on explicit dynamic time history analysis. The impact force, displacement, strain and other response parameters are directly obtained in numerical calculation without the need to deploy any physical sensors on the bridge. This avoids the risk of signal acquisition failure due to the sporadic and sudden nature of the collision event, and eliminates the influence of sensor signal distortion and environmental noise interference on the detection results.

[0015] 2. This invention sets up multiple detection sections along the pile body in the established finite element model, and extracts the relative slippage between the pile and the soil and the degree of plastic deformation of the soil in real time during the impact process. This enables the simulation analysis to truly reflect the gradual weakening effect of the soil around the pile on the pile foundation during the collision process, effectively solving the problem of boundary condition distortion caused by ignoring the participation of pile and soil in the prior art, thereby improving the consistency between the collision damage assessment of the bridge substructure and the actual service condition on site. Attached Figure Description

[0016] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0017] Figure 1This is a diagram illustrating the implementation steps of the method of the present invention;

[0018] Figure 2 This is a flowchart illustrating the process of determining the soil failure state segment by segment from the pile top to the pile bottom in this invention.

[0019] Figure 3 This is a flowchart illustrating the process of determining the current virtual ground line in this invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] During a ship-bridge collision, the impact load generates a transient impact effect on the pier and substructure, causing structural deformation and localized damage. If damage assessment is not conducted in a timely manner, it can easily lead to the accumulation of potential safety hazards to the bridge.

[0022] Traditional detection methods involve deploying arrays of acceleration sensors at different heights and locations on the bridge piers to collect acceleration response signals during the impact process. The location and extent of damage are then determined based on the time-frequency coherence loss factor trajectory curve. However, ship collisions are short-duration, highly stochastic dynamic processes, and sensor arrays face challenges in practical engineering, such as signal acquisition failures and environmental noise interference. Furthermore, during a collision, the impact load on the pier is transferred to the pile foundation through the abutment and further acts on the surrounding soil, inducing plastic yielding. Traditional monitoring methods focus only on the dynamic response of the pier itself, neglecting the dynamic participation of the surrounding soil during the collision process, leading to a disconnect between the assessment results and the actual service condition of the bridge substructure.

[0023] To address the aforementioned technical problems, this invention fully considers the collaborative work of bridge piers, pile foundations, and surrounding soil during the collision process, and proposes the following technical solutions.

[0024] See Figure 1 A collision damage detection and analysis method based on bridge piers includes the following steps: S1, establishing a finite element model including the bridge pier, pile foundation and surrounding soil, and setting the collision point between the ship and the bridge pier in the model.

[0025] Given that physical sensor monitoring methods suffer from signal capture uncertainty and cannot reflect pile-soil interaction, this invention constructs a three-dimensional finite element model to map the geometry, material properties, and boundary conditions of the actual bridge pier structure into a numerical calculation environment, thereby enabling controllable and repeatable simulation analysis of the entire ship collision process in virtual space.

[0026] In specific implementation, S1 further includes the following sub-steps: S11, establishing a finite element model that includes the bridge piers, pile foundations and the soil around the piles.

[0027] S111. Construct three-dimensional solid models of the bridge piers, pile foundations, and surrounding soil in computer software. The bridge piers and pile foundations adopt elastoplastic damage constitutive models that can describe the compressive yielding, tensile cracking, and stiffness degradation of concrete to accurately simulate the nonlinear response of structural materials under impact loads. The surrounding soil adopts Mohr-Coulomb or modified Cambridge constitutive models that can reflect soil compaction hardening and shear failure to capture the plastic deformation and strength decay of the soil under impact loads.

[0028] S112. Considering that the pile body and the surrounding soil will undergo relative displacement or even separation during the collision process, the contact between the outer surface of the pile foundation and the corresponding hole wall of the soil around the pile is set to a surface-to-surface contact type that allows normal separation and tangential sliding, and a friction coefficient is assigned to the contact surface. This setting is used to transmit the normal pressure and tangential friction force between the pile and the soil in numerical calculations, while allowing the two to separate when the separation condition is reached, so as to realistically simulate the dynamic interaction between the pile and the soil.

[0029] S113. Based on the establishment of the above model and the completion of the contact definition, a fixed displacement constraint is applied to the outer boundary of the soil model to restrict its movement in the horizontal and vertical directions in order to simulate the infinite domain effect of the far-field soil. At the same time, an equivalent vertical pressure calculated from the self-weight of the bridge superstructure and the normal service load is applied to the top of the pier to reflect the axial stress conditions under actual service conditions.

[0030] S114. After completing the above geometric modeling, material assignment, contact definition, and boundary load application, perform a ground stress equilibrium analysis on the entire model. Specifically, first apply a gravity load to the model to perform a static analysis, calculate the stress distribution of the soil under its own weight, and import this stress field as the initial stress condition into the original model. At the same time, apply the equivalent vertical pressure at the top of the pier. If the check finds that the soil still has displacement, iteratively correct the stress field until the displacement of each node of the soil is less than the preset tolerance. At this time, the model is in the initial equilibrium state, which can be used as the starting state for collision analysis. The purpose is to eliminate the initial deformation caused by the soil's own weight and avoid false displacement caused by self-weight settlement.

[0031] S12. After establishing the model, in order to simulate the actual working condition of a ship colliding with a bridge pier, it is necessary to set the location of the collision point between the ship and the bridge pier. In the finite element model, the ship's geometry, collision location, and initial velocity directly determine the application method of the collision load and the structural response. Therefore, based on the actual navigation conditions of the waterway where the bridge is located and the structural characteristics of the bridge pier, the following steps are taken: S121. Based on the statistical data of representative ship types in the waterway where the bridge is located, obtain the ship's length, width, and full-load draft parameters. Since the stiffness of the ship's steel hull is much greater than that of the bridge pier's concrete, the deformation of the ship itself during the collision can be ignored. Therefore, the ship model is simplified to a rigid body.

[0032] S122. On the side of the bridge pier facing the oncoming vessel, based on the highest navigable water level and the vessel's full-load draft in the bridge design data, determine the impact height range with the sum of the lowest navigable water level and draft as the lower limit and the highest navigable water level as the upper limit. This range represents the most likely collision area when the vessel is navigating normally under different water level conditions, ensuring the comprehensiveness of the working condition settings.

[0033] S123. Within the above-mentioned height range, the height position with the smallest horizontal cross-sectional dimension of the pier is selected as the impact point; if the cross-sectional dimension does not change within the entire height range, the center height of the connection node between the pier and the crossbeam is selected as the impact point. This is because the point with the smallest cross-section or the connection node is the weak link of the pier's lateral stiffness. Applying impact load at these locations can obtain an upper limit estimate of the structural response, providing the most unfavorable working condition for bridge safety assessment.

[0034] S124. Based on the statistical values ​​of the actual sailing speeds of representative ship types in the waterway, set the magnitude and direction of the ship's speed when it collides with the bridge pier, so that the ship model moves along a straight line towards the determined impact point with this initial velocity. This setting is used to impart initial kinetic energy to the ship in explicit dynamic time history analysis, thereby simulating the dynamic application process of the impact load.

[0035] S2. Divide the impact process into continuous time segments, calculate the instantaneous impact force on the pier at the end of each time segment, and use the impact force to drive the deformation response of the pier and pile foundation.

[0036] With the establishment of the finite element model in S1 and the setting of the impact conditions, the conditions for conducting collision simulation are met. Since the collision of a ship with a bridge pier is a highly nonlinear, short-term, and violent dynamic process, the contact force, deformation, and energy conversion change rapidly. Therefore, it is necessary to discretize the total collision time into several continuous time segments and calculate the instantaneous impact force at the end of each segment in order to track the collision process.

[0037] As an optional embodiment of the present invention, S2 is implemented according to the following process: S21, divide the contact surface of the bridge pier model facing the oncoming ship into quadrilateral grid cells. The grid cell is a basic unit that discretizes a continuous entity into a finite number of basic computational subdomains. Adjacent cells share boundaries to ensure displacement coordination. The area of ​​each cell is pre-calculated based on the quadrilateral side length.

[0038] S22. According to the stability criterion of explicit dynamics, the maximum allowable time step is equal to the size of the smallest mesh element in the global finite element model divided by the longitudinal wave velocity of the stress wave in the material, and then multiplied by a safety factor less than 1, usually taken as 0.8 to 0.9. This is used as the fixed duration of each time segment, which can ensure that the calculation process is stable and that the details of the propagation of the stress wave in the smallest element are not missed.

[0039] It is important to note that the smallest element in the global finite element model can appear anywhere in the pier, pile foundation, abutment, or soil, rather than being limited to the contact surface.

[0040] S23. The time period from the moment the ship model comes into contact with the bridge pier model until they completely separate is divided into multiple continuous time segments of fixed duration. Each time segment corresponds to an independent calculation step. Within this step, the state of the model is derived from the previous step, thus realizing continuous dynamic simulation of the collision process.

[0041] S24. At the end of each time segment, the explicit dynamics solver detects the geometric intrusion between each grid cell on the contact surface between the ship and the pier through contact search, i.e., the normal penetration distance. This penetration distance directly reflects the degree of mutual compression between the two objects in that time step and is the basic physical quantity for calculating the contact force. The larger the penetration distance, the more intense the compression at that cell.

[0042] S25. Multiply the normal penetration of each grid cell by a preset contact stiffness coefficient, then multiply by the area of ​​that grid cell to obtain the instantaneous normal contact force contributed by that grid cell. Finally, sum the instantaneous normal contact forces of all contact cells to obtain the instantaneous impact force on the pier at the end of this time segment: Specific expression In the formula Indicates the first Normal penetration of a grid cell Indicates the grid cell number, , This represents the preset contact stiffness coefficient, where the dimensions of the contact stiffness coefficient are force / length³, and it represents the pressure required to generate a unit normal penetration amount per unit contact area. Indicates the first The area of ​​a grid cell.

[0043] It should be noted that the instantaneous impact force calculated at the end of each time segment is the direct mechanical cause of the deformation response of the bridge pier pile foundation. It is under the action of this impact force that the bridge pier undergoes horizontal displacement, which is transmitted to the pile foundation through the pile cap, thereby causing pile bending deformation, pile-soil relative slippage, and accumulation of soil plastic strain. Therefore, the amount of pile-soil relative slippage and the degree of soil plastic deformation obtained in subsequent steps are essentially quantitative representations of the structural response induced by the instantaneous impact force in the current time segment.

[0044] S3. Set up multiple detection sections along the pile body, and at the end of each time segment, obtain the relative slippage between the pile and the soil and the degree of plastic deformation of the soil at each section.

[0045] After the time segment is divided, in order to track the evolution of pile-soil interaction induced by impact force in real time during the collision process, data monitoring and extraction can be carried out in two stages.

[0046] Phase 1: To obtain the mechanical response of the pile and surrounding soil during the collision process, a series of virtual detection sections are set up along the pile to establish observation points at different depths of the pile. The specific steps are as follows: 11) The entire finite element model of the pier, pile foundation, and surrounding soil is meshed, including the interior and surface of the model. The vertex of each mesh element is defined as a node, and adjacent elements share nodes. At the same time, a global Cartesian coordinate system is established in the model, and the spatial coordinates of all nodes are based on the coordinate system definition.

[0047] 12) Based on the pre-divided grid cells, multiple transverse horizontal sections are taken along the centerline of the pile from the top to the bottom of the pile as detection sections with varying spacing. That is, the section spacing is smaller near the pile top and larger near the pile bottom. This is because the collision load mainly acts on the area near the pile top, and the response change in the upper part of the pile is more drastic, requiring denser sections to capture stress wave propagation and deformation gradient; the response in the lower part of the pile is relatively gentle, so the sections can be sparsely distributed to reduce the amount of data.

[0048] 13) On the horizontal plane where each test section is located, select the outermost node on the impact side of the pile as a virtual test point for tensile deformation, and select the outermost node on the same horizontal plane on the back impact side of the pile as a virtual test point for compression deformation. These two types of test points are used to monitor the deformation evolution of the impact side under tension and the back impact side under compression, respectively.

[0049] 14) At the same horizontal plane of each detection section, on the side of the soil facing the impact direction of the pile, select a soil grid cell at a set distance from the outermost node of the pile body. Take the average value of the coordinates of the eight vertices of the soil grid cell to obtain the center point of the soil cell. Use this center point as the soil detection point to capture the horizontal displacement and plastic deformation of the soil around the pile during the collision process, and reflect the real-time state of the soil constraint on the pile foundation.

[0050] The second stage: During the collision process, when plastic deformation occurs in the soil surrounding the pier piles and slippage occurs between the piles and the soil, it indicates that the soil above the corresponding depth can no longer effectively restrain the pile foundation. If the boundary conditions are not updated in time and subsequent calculations are still performed based on the initial elastic support, the length of the free segment of the pile foundation will be underestimated, and the horizontal displacement and internal force response of the pier will be underestimated, thus causing the damage assessment results to deviate from reality. Therefore, it is necessary to dynamically update the lateral support conditions of the pile foundation. This dynamic boundary update directly affects the internal force distribution and deformation mode of the pier and pile foundation, and is a necessary step in collision damage analysis.

[0051] Based on the above, in order to determine soil failure and update pile foundation boundary conditions in real time after setting the detection section, it is necessary to obtain the relative slip of pile and soil and the degree of plastic deformation of soil at each section after each time segment. The specific steps are as follows: 21) At the end of each time segment, select the virtual detection point of tensile deformation on the impact surface at each detection section and read the horizontal displacement value of the point; at the same time, read the horizontal displacement value of the soil detection point at the same depth, subtract the two to obtain the relative slip of pile and soil at the section. The slip is used to determine whether there is significant relative movement between the pile and the soil. When the slip increases sharply, it indicates that the soil constraint on the section has been basically lost.

[0052] 22) Read the equivalent plastic strain value automatically accumulated by the soil constitutive model based on the stress history within that time segment from the soil test point at the same test section. This value is used to determine whether the soil has entered the plastic yielding stage, providing a quantitative basis for subsequent determination of the soil failure location.

[0053] S4. Based on the relative slippage between the pile and the soil and the degree of plastic deformation of the soil at each section, determine the soil failure state segment by segment from the top of the pile to the bottom of the pile, and take the shallowest depth of the failed pile segment as the current virtual ground line.

[0054] During the collision, the soil gradually loses its lateral restraint on the pile from near the pile top, forming a downward-expanding failure zone. The shallowest depth of this failure zone is the virtual ground line. To determine this depth in real time, follow these steps: See Figure 2As shown, S41, starting from the first detection section closest to the pile top, two conditions are judged in sequence: a) Plastic deformation condition: extract the equivalent plastic strain value of the soil in this section. If it exceeds the initial deformation value, the first condition is met. The initial deformation value is the equivalent plastic strain value corresponding to the initial yield stress defined in the soil material constitutive model. It is usually 0. Exceeding this value indicates that the soil has undergone irreversible plastic damage.

[0055] b) Slippage growth rate condition: Extract the relative slippage between pile and soil in two consecutive time segments of the cross section, subtract the slippage of the previous segment from the slippage of the current segment, and then divide by the duration of the time segment to obtain the current slippage growth rate. If the current segment growth rate exceeds the set multiple of the previous segment growth rate, such as 2 times, it indicates that the slippage is accelerating and the soil constraint is rapidly lost.

[0056] It should be noted that, since the first time segment lacks data from the previous segment, it is impossible to calculate the growth rate comparison. Therefore, the slip growth condition can only be determined from the second time segment onwards.

[0057] When both conditions are met, the soil at that section begins to fail, indicating that the soil at that depth can no longer provide effective lateral support for the pile foundation.

[0058] S42. For the section where soil failure has been marked, further examine the adjacent sections below and extract the principal strain components of the soil mesh elements in the vertical plane in two orthogonal directions. These principal strain components are automatically output by the explicit dynamic solver at the end of each time segment. Calculate the angle between the maximum principal strain direction and the vertical direction. If the angle exceeds the critical angle such as 45°, it indicates that a significant shear zone has been formed in the soil, that is, the soil wedge has participated in the stress. Mark the adjacent section as the section where the soil wedge participates.

[0059] See Figure 3 As shown in S43, when three consecutive adjacent sections are marked as sections where soil begins to fail or where soil wedges participate, the shallowest section is selected. The horizontal displacement of the pile body at the shallowest section and its adjacent sections above and below can be measured from the virtual detection point of tensile deformation on the impact surface at each section. The displacement difference between this section and the upper section and the displacement difference between this section and the lower section are calculated respectively.

[0060] If the two displacement differences have opposite signs, for example, the upper displacement difference is positive and the lower displacement difference is negative, it indicates that the bending shape of the pile body at that section has changed direction, that is, from being tensile on the frontal side to being tensile on the rearal side or vice versa. The depth of this section is recorded as the current virtual ground line for subsequent dynamic adjustment of the lateral support conditions of the pile foundation.

[0061] If the two displacement differences have the same sign, slide down one section and take the shallowest section from the next set of three consecutive marked sections. Repeat the above displacement difference sign judgment, and so on, until a section that satisfies the opposite sign condition is found. If a section that satisfies the condition is not found when sliding to the bottom of the pile, the shallowest section from the last set of three consecutive marked sections is taken as the current virtual ground line.

[0062] It should be noted that soil mesh elements refer to the mesh elements divided into the soil around the pile in the finite element model.

[0063] S5. Adjust the lateral support conditions of the pile foundation according to the current virtual ground line depth, and proceed to the next time segment to calculate the instantaneous impact force and solve the structural deformation response.

[0064] When the soil fails, the lateral constraint of the surrounding soil on the pile will weaken or even disappear. To accurately reflect this mechanical behavior, it is necessary to dynamically adjust the lateral support conditions of the pile foundation according to the current virtual ground line depth to ensure that the structural response calculation of subsequent time segments is consistent with the actual stress state. The specific operation is as follows: cancel all pile-soil contact relationships from the current virtual ground line depth to the pile top, making this section of the pile foundation a free section without soil support. This operation is used to simulate the actual situation of the loss of lateral constraint of the pile body after the complete failure of the soil, and to avoid overestimating the lateral stiffness of the pile foundation.

[0065] The lateral support stiffness of the soil at each test section within the pile segment between the current virtual ground line and the previous virtual ground line is reduced proportionally by the degree of plastic deformation. This ratio is defined as the ratio of the equivalent plastic strain to the ultimate plastic strain of the current section, and its value is between 0 and 1. The ultimate plastic strain refers to the equivalent plastic strain value corresponding to the complete failure of the soil material under monotonic loading conditions. It is usually given directly by the input parameters of the soil constitutive model. The greater the degree of plastic deformation, the closer the reduction factor is to 1, and the more significant the reduction in lateral support stiffness. This is used to simulate the transitional state of partial soil failure and gradual decrease in bearing capacity.

[0066] It should be noted that in the initial state before the collision, the soil has not yet failed, and the entire surrounding soil provides complete lateral support to the pile foundation. The virtual ground line at this time is the initial ground line, which is the depth of the soil surface. Therefore, when the soil failure is first determined and the first current virtual ground line is obtained, the previous virtual ground line is taken as the initial ground line.

[0067] The pile segments below the current virtual ground line and up to the pile bottom are kept with their original, unweakened support to simulate the complete constraint of the pile foundation by the unaffected soil deep inside.

[0068] After all support conditions are updated, the next time segment will begin. In this segment, the explicit dynamic solver will recalculate the contact penetration based on the new positions of the ship and the pier, automatically determine the instantaneous impact force at that moment, and solve the structural deformation response in conjunction with the updated pile foundation lateral support conditions.

[0069] S6. When the depth of the virtual ground line and the residual displacement of the pile top no longer change for multiple consecutive time segments, stop the calculation and output the pier damage area.

[0070] In explicit dynamic time history analysis, the collision process does not continue indefinitely. When the soil failure area no longer expands downward and the residual displacement at the pile top tends to stabilize, it indicates that the structural response has entered the convergence stage. At this point, the calculation can be terminated and the final damage result can be output.

[0071] S61. Therefore, a clear stopping condition needs to be set. The specific determination steps are as follows: S611. At the end of each time segment, if the current segment meets the condition in S43, then update the virtual ground line depth. If not, the virtual ground line depth remains the value of the previous segment. Compare the current virtual ground line depth with the depth of the previous time segment and calculate the absolute value of the depth change. This change value reflects the expansion trend of the soil failure zone.

[0072] S612. Extract the horizontal displacement value of the virtual detection point of tensile deformation at the top of the pile, take the average horizontal displacement of the most recent preset number (e.g., five) time segments as the current residual displacement, calculate the absolute value of the change between the current residual displacement and the residual displacement of the same number of time segments before, and this change value reflects the convergence trend of structural deformation.

[0073] S613. When the absolute value of the change in the depth of the virtual ground line and the absolute value of the change in the residual displacement at the top of the pile are both less than their respective preset allowable values, it indicates that the soil failure has tended to stabilize and the structural deformation has entered a convergent state. When the above state is maintained continuously for no less than a preset number of time segments, it is determined that the collision response has reached the final equilibrium state, and further calculation will not generate new effective information.

[0074] The preset quantity mentioned above can be determined based on the total number of time segments in the model. The allowable value for the change in the depth of the virtual ground line can be set according to the minimum mesh element size of the full finite element model, such as taking a certain proportion of the element characteristic length. The allowable value for the change in the residual displacement at the top of the pile can be determined by scaling the deformation limit in the bridge span or design specifications.

[0075] S62. After terminating the calculation, the simulated collision damage results can be output.

[0076] Considering that the main damage to bridge piers during collisions is concrete cracking and crushing, the collision damage result output by this invention represents the damaged area of ​​the bridge pier. The specific implementation is as follows: S621. After stopping the calculation, extract the horizontal displacement difference of the tensile deformation detection points on the impact surface at two adjacent detection sections from the key areas of the bridge pier, namely the connection between the pier bottom and the abutment, and the connection between the transverse beam and the pier column. Divide this difference by the distance between the two sections to obtain the average tensile strain, which reflects the average tensile deformation degree of the concrete. If the average tensile strain exceeds the set limit tensile strain, it is determined that a through tensile crack has appeared in that section, and the section between the two adjacent detection sections is marked as the damaged area.

[0077] S622. Extract the horizontal displacement difference between the back-impact compression deformation detection points at two adjacent detection sections, divide it by the distance between the two sections, and obtain the average compressive strain, which reflects the average compressive deformation degree of the concrete. If the average compressive strain exceeds the set limit compressive strain, it is determined that the concrete in this section has been crushed, and the section between the two adjacent detection sections is marked as the damaged area.

[0078] The determination of the ultimate tensile strain and ultimate compressive strain is as follows: based on the failure criterion in the constitutive model of concrete material, the ultimate tensile strain is usually taken as the strain value corresponding to the peak tensile stress of concrete (e.g., 0.0001 to 0.0002), and the ultimate compressive strain is taken as the strain value corresponding to the peak compressive stress of concrete (e.g., 0.002 to 0.003).

[0079] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0080] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0081] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0082] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A collision damage detection and analysis method based on bridge piers, characterized in that, Includes the following steps: Establish a finite element model that includes the bridge piers, pile foundations and surrounding soil, and set the location of the impact point between the ship and the bridge pier in the model; The impact process is divided into continuous time segments. At the end of each time segment, the instantaneous impact force on the pier is calculated, and the impact force drives the deformation response of the pier and pile foundation. Multiple detection sections were set along the pile body, and the relative slippage between the pile and the soil and the degree of plastic deformation of the soil were obtained at the end of each time segment. Based on the relative slippage between the pile and the soil and the degree of plastic deformation of the soil at each section, the failure state of the soil is judged segment by segment from the top of the pile to the bottom of the pile, and the shallowest depth of the failed pile segment is taken as the current virtual ground line. Adjust the lateral support conditions of the pile foundation according to the current virtual ground line depth, and proceed to the next time segment to calculate the instantaneous impact force and solve the structural deformation response; The calculation stops when the virtual ground line depth and pile top residual displacement no longer change for multiple consecutive time segments, and the pier damage area is output. The process of judging the soil failure state segment by segment from the pile top to the pile bottom, and taking the shallowest depth of the failed pile segment as the current virtual ground line, specifically includes the following: Starting from the test section closest to the pile top, the following judgments are made sequentially: a) Extract the value of the plastic deformation of the soil at the cross section. If it exceeds the initial deformation value, then the first condition is met. b) Extract the relative slippage between pile and soil in two consecutive time segments of the cross section, calculate the slippage growth rate, and if the slippage growth rate of the current segment exceeds the set multiple of the growth rate of the previous segment, then the second condition is met. When both conditions are met, the soil at that section begins to fail. For the marked section, check the adjacent section below and calculate the angle between the direction of the maximum principal strain of the soil and the vertical direction. If it exceeds the critical angle, mark it as a section in which the soil wedge participates. When three consecutive adjacent cross sections are marked as soil failure or soil wedges are involved in the cross section, the shallowest cross section is selected, and the direction of displacement change is calculated using the horizontal displacement of the pile body of the shallowest cross section and the adjacent cross sections above and below. If the difference in horizontal displacement of the pile body at the shallowest section has the opposite sign to the difference in horizontal displacement at the upper adjacent section and the lower adjacent section, then the depth of the shallowest section is recorded as the current virtual ground line. If the signs are the same, continue to check three consecutive marked sections until a section depth that satisfies the condition of opposite signs is found as the current virtual ground line.

2. The collision damage detection and analysis method based on bridge piers as described in claim 1, characterized in that: The steps for establishing a finite element model that includes bridge piers, pile foundations, and surrounding soil are as follows: Three-dimensional solid models of the bridge pier, pile foundation and surrounding soil were constructed respectively. The contact surface between the pile foundation and the soil was set to a separable and sliding state and the friction characteristics were set. Movement is restricted at the outer boundary of the soil model, and vertical pressure is applied to the top of the pier; The model is initially balanced to serve as the starting state for collision analysis.

3. The collision damage detection and analysis method based on bridge piers as described in claim 1, characterized in that: The steps for determining the location of the impact point between the ship and the bridge pier are as follows: Based on the representative ship type of the waterway where the bridge is located, determine the ship's length, width, and full-load draft, and simplify the ship into a rigid body model; On the side of the bridge pier facing the ship, the impact height range is determined with the sum of the lowest navigable water level and the draft as the lower limit and the highest navigable water level as the upper limit, and the height position with the smallest horizontal cross-sectional dimension of the bridge pier within the height range is selected as the impact point. Set the magnitude and direction of the ship's impact speed so that the ship moves in a straight line toward the point of impact at that speed.

4. The collision damage detection and analysis method based on bridge piers as described in claim 1, characterized in that: The calculation of the instantaneous impact force on the bridge pier is as follows: The contact surface of the bridge pier model with the ship is divided into grid cells, each cell having a preset area; Based on the size of the smallest mesh element and the stress wave velocity in the full model, the maximum allowable time step is determined according to the stability criterion and used as the fixed duration of each time segment; The period from the moment the ship model comes into contact with the bridge pier model until they are completely separated is divided into multiple continuous time segments of fixed duration. At the end of each time segment, the normal penetration of each mesh cell is calculated using an explicit dynamic solver, and expressed as follows: Calculate the instantaneous impact force on the bridge pier In the formula Indicates the first Normal penetration of a grid cell Indicates the grid cell number, , This represents the preset contact stiffness coefficient. Indicates the first The area of ​​a grid cell.

5. The collision damage detection and analysis method based on bridge piers as described in claim 1, characterized in that: The process of setting multiple detection sections along the pile body is carried out according to the following steps: The finite element model of the bridge piers, pile foundations and surrounding soil is divided into mesh elements. The vertex of each mesh element is defined as a node, and adjacent elements share nodes. Multiple detection sections are set along the centerline of the pile from the top to the bottom at varying intervals, with the section spacing at the top of the pile being smaller than that at the bottom of the pile. On the horizontal plane of each test section, the outermost node of the frontal impact surface is selected as the tensile deformation test point, and the outermost node of the rear impact surface is selected as the compressive deformation test point. At the same horizontal plane of each test section, the center point of the soil grid cell at a set distance from the pile body is selected as the soil test point on the side of the soil facing the impact direction.

6. The collision damage detection and analysis method based on bridge piers as described in claim 5, characterized in that: The steps for obtaining the relative slippage between the pile and the soil and the degree of plastic deformation of the soil at each cross-section are as follows: At the end of each time segment, the horizontal displacement of the tensile deformation detection point on the impact surface at each detection section and the horizontal displacement of the soil detection point at the same depth are read, and the relative slip of the pile and soil is obtained by subtracting the two. Read the degree of plastic deformation value automatically accumulated by the constructed soil model based on the stress history from the soil detection points.

7. The collision damage detection and analysis method based on bridge piers as described in claim 1, characterized in that: The specific steps for adjusting the lateral support conditions of the pile foundation based on the current virtual ground line depth are as follows: Cancel all pile-soil contact relationships from the current virtual ground line to the top of the pile; The degree of soil plastic deformation at each test section within the pile segment between the current virtual ground line and the previous virtual ground line is reduced by the lateral support stiffness based on the ratio of the equivalent plastic strain to the ultimate plastic strain of the current section. Maintain the original support for the pile segment below the current virtual ground line down to the pile bottom.

8. The collision damage detection and analysis method based on bridge piers as described in claim 5, characterized in that: The decision to stop the calculation is executed according to the following procedure: Record the current virtual ground line depth at the end of each time segment and calculate the absolute value of the depth change compared to the previous time segment; Extract the horizontal displacement of the virtual detection point of tensile deformation at the top of the pile, and take the average horizontal displacement of the most recent preset number of time segments as the current residual displacement. Calculate the absolute value of the change between the current residual displacement and the residual displacement of the same number of time segments before it. The calculation stops when the absolute values ​​of the virtual ground line depth change and the absolute values ​​of the pile top residual displacement change are both less than their respective allowable values ​​and are maintained for multiple consecutive time segments.

9. The collision damage detection and analysis method based on bridge piers as described in claim 5, characterized in that: The implementation process for the damaged area of ​​the output pier is as follows: After the calculation is stopped, the horizontal displacement difference between the frontal and rear impact detection points of two adjacent detection sections is extracted from the key area of ​​the pier. The difference is then divided by the distance between the two sections to obtain the average tensile strain and average compressive strain. If the average tensile strain exceeds the ultimate tensile strain or the average compressive strain exceeds the ultimate compressive strain, the section between two adjacent test sections will be marked as the damaged area.

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