A Method and System for Simulating the Mechanical Properties of Prestressed Composite Slabs Based on Digital Twins

Abstract

This invention discloses a method and system for simulating the mechanical properties of prestressed composite slabs based on digital twins, relating to the field of mechanical performance simulation technology for prefabricated building structures. The method establishes an initial twin model of the prestressed composite slab, including prestressing tendons, a detection chain of the composite surface, and support boundaries; obtains the stage response sequence and decomposes it into loading stroke and return stroke; extracts the slip initiation point that deviates from the cooperative trend from the loading stroke, and extracts the return stagnation segment that retains relative displacement from the return stroke; projects the crack extension path onto the continuous detection segment to generate an interface event chain; performs adjacency compression on the interface event chain along the load direction to reconstruct the shear force transmission breakpoint; forms segmented contact boundaries based on the breakpoint and updates the model, outputting candidate values ​​of shear bearing capacity and shear force discontinuity locations. This invention can accurately identify the local shear force transmission interruption locations on the composite surface, improving the accuracy of shear performance simulation of prestressed composite slabs.

Description

Technical Field

[0001] This invention relates to the field of mechanical performance simulation technology for prefabricated building structures, specifically to a method and system for simulating the mechanical performance of prestressed composite slabs based on digital twins. Background Technology

[0002] Prestressed composite slabs are commonly used floor components in prefabricated buildings, formed by a precast base slab and a cast-in-place concrete layer bonded together at the interface. During construction, load transfer, and service life, shear forces must be transferred between the precast base slab and the cast-in-place layer through the interface to ensure their coordinated operation. The bond state, slip behavior, and crack penetration of the interface directly affect the shear performance of the prestressed composite slab.

[0003] In existing technologies, the mechanical performance analysis of prestressed composite slabs or similar composite components mainly employs a combination of experimental testing and finite element simulation or digital twin model correction. A typical method involves establishing a computational model based on load, deflection, crack width, interface slip, or material parameters. By comparing measured data with simulation results, the model parameters are inverted and corrected to assess the load-bearing capacity of the component under specific working conditions. For the stress problem of the composite surface, existing simulation methods typically simplify the composite surface to a bonded contact boundary or a slip contact boundary, reflecting the relative displacement influence between the precast slab and the cast-in-place layer in the model.

[0004] However, existing technologies have the following drawbacks: First, existing simulation methods focus more on parameter corrections for the overall bearing capacity or overall slip of the composite surface, making it difficult to accurately identify the location of local shear force transmission interruptions. In actual use of prestressed composite slabs, after load reduction or transfer, some composite surface sections may still retain residual relative displacement, preventing these sections from fully recovering their shear force transmission capacity. Existing methods typically treat the composite surface as continuously transmitting force or experiencing overall slip, failing to reflect this phenomenon of local shear force transmission interruption.

[0005] Second, existing interface models often treat the composite surface as a continuous force transmission, overall slip, or uniform contact boundary, failing to establish segmented contact boundaries based on slip initiation points, residual slip, and crack penetration states. When the composite surface experiences local slippage, return slip, and crack penetration under load cycles, the shear force transmission state differs across different sections. Existing methods lack a mechanism for segmenting the composite surface along its length, leading to discrepancies between simulated boundaries and actual force transmission states.

[0006] Third, existing data processing methods often focus only on slip or crack condition at a single stage, making it difficult to identify shear force transfer anomalies by comparing the loading and return strokes. During the load increase phase, adjacent consecutive test segments may exhibit a coordinated deformation trend; however, when a segment deviates from this coordinated trend and retains residual displacement during the return stroke, a shear force transfer breakpoint may have formed at that location. Existing methods lack systematic correlation analysis between the loading and return strokes, leading to inaccurate identification of shear force transfer breakpoints.

[0007] Fourth, existing digital twin model correction methods typically use the error between measured and simulated results as the objective function to uniformly correct the contact boundaries of the overlapping surfaces. They fail to perform adjacency compression of the interface event chain and reconstruct shear force transmission breakpoints based on the load direction. When the slip initiation point, return retention segment, and crack projection segment are consecutively adjacent in the load direction and point to the same crack penetration location, this segment forms an abnormal shear force transmission group and ultimately transforms into a shear force transmission breakpoint. Existing methods lack analysis of the spatial correlation and causal transmission of such interface events, causing the simulated boundary update to fail to reflect the true force transmission state.

[0008] Therefore, a technical solution is needed that can identify shear force transmission breakpoints and form segmented contact boundaries based on the slip behavior, residual slip, and crack penetration state of the composite surface at different stages, thereby accurately simulating the shear resistance of prestressed composite slabs. Summary of the Invention

[0009] The purpose of this invention is to provide a method and system for simulating the mechanical properties of prestressed composite slabs based on digital twins, in order to solve the problems in the prior art that make it difficult to accurately identify the location of the interruption of local shear force transmission on the composite surface, cannot form segmented contact boundaries, lack system correlation analysis of loading stroke and return stroke, and the simulation boundary update cannot reflect the real force transmission state.

[0010] To achieve the above objectives, the present invention provides a method for simulating the mechanical properties of prestressed composite slabs based on digital twins, comprising: For prestressed composite slabs with a composite surface formed by a precast base slab and a cast-in-place layer, an initial twin model is established, including prestressing tendons, a composite surface detection chain, and support boundaries. This initial twin model provides the geometric basis, material parameters, and initial contact boundary conditions for subsequent boundary updates and shear performance simulations.

[0011] Obtain the stage response sequence of the prestressed composite slab during the construction or service phase. The stage response sequence is a data sequence formed by organizing the detection data of different load stages (load application, load reduction, and load transfer) according to the sequence of continuous detection segments and stages, including the relative displacement of the composite surface, crack propagation state, and slab deflection state.

[0012] The stage response sequence is decomposed along the length of the overlapping surface into loading stroke and return stroke of continuous detection segments. The loading stroke corresponds to the response data of the load increase stage, and the return stroke corresponds to the response data of the load decrease or load transfer stage. An intra-segment correspondence between the loading stroke and the return stroke is established within each continuous detection segment.

[0013] The slip start point, where the relative displacement breaks away from the cooperative deformation trend of adjacent continuous detection segments, is extracted from the loading stroke. The return stroke, where the relative displacement is still retained after the load is reduced or transferred, is extracted from the return stroke. The slip start point indicates that the continuous detection segment is the first to break away from the cooperative deformation trend of adjacent segments during loading, and the return stroke retention segment indicates that the continuous detection segment retains residual relative displacement after unloading.

[0014] The extension path of the crack through the composite surface is projected onto the continuous detection segment, generating an interface event chain consisting of the slip initiation point, the return retention segment, and the crack projection segment. The interface event chain is a sequence of events that spatially links key events occurring on the composite surface, reflecting the abnormal force distribution along the length of the composite surface.

[0015] The interface event chain is compressed along the load direction to reconstruct the shear force transmission breakpoint of the composite surface. Slip start points and return retention segments that are consecutively adjacent and point to the same crack projection segment are compressed into a shear force transmission anomaly group. The end of the anomaly group closest to the crack projection segment is taken as the shear force transmission breakpoint, forming a shear force transmission breakpoint sequence.

[0016] Based on the shear force transmission breakpoints, segmented contact boundaries are formed, and the initial twin model is updated using these segmented contact boundaries. Shear performance simulation is then performed on the prestressed composite slab, outputting candidate values ​​for shear bearing capacity and the location of shear force discontinuity. The segmented contact boundaries include continuous force transmission boundaries, return energy dissipation boundaries, and discontinuous force transmission boundaries, corresponding to different force transmission states of the composite surface, respectively.

[0017] Furthermore, obtaining the stage response sequence formed by the prestressed composite slab during the construction or use stage includes: grouping the relative displacement of the composite surface, crack extension state, and slab deflection state into the same segment according to the stage sequence of load application, load reduction, and load transfer; grouping the states formed by the same continuous detection segment at different stages into the same response unit; and connecting the response units according to the arrangement order of the continuous detection segments along the length direction of the composite surface to form a stage response sequence.

[0018] Furthermore, the stage response sequence is decomposed along the length direction of the overlapping surface into loading stroke and return stroke of continuous detection segments, including: generating the loading stroke with the segment response unit corresponding to the load increase stage; generating the return stroke with the segment response unit corresponding to the load decrease or load transfer stage; establishing an intra-segment correspondence between the loading stroke and the return stroke within each continuous detection segment; and using the intra-segment correspondence as the basis for extracting the slip start point and the return dwell segment.

[0019] Furthermore, extracting the slip start point where the relative displacement deviates from the cooperative trend of adjacent continuous detection segments from the loading stroke, and extracting the return travel segment that retains relative displacement after load reduction or load transfer from the return stroke, includes: comparing the relative displacement change direction of adjacent continuous detection segments in the loading stroke along the length direction of the overlapping surface; taking the continuous detection segment where the relative displacement change direction changes from a common change of adjacent segments to a single segment offset as the slip start point; tracing the relative displacement fall process of the slip start point and its adjacent continuous detection segments along the return stroke; and taking the continuous detection segment that retains relative displacement within the segment after the end of the return stroke as the return travel segment.

[0020] Furthermore, the extension path of the crack through the composite surface is projected onto the continuous detection segment to generate an interface event chain consisting of the slip start point, the return retention segment, and the crack projection segment. This includes: extracting the path position of the crack extending from the precast base plate to the composite surface and entering the cast-in-place layer; mapping the path position to the continuous detection segment in the composite surface detection chain to form the crack projection segment; and connecting the three types of segments into an interface event chain according to the sequential positions of the slip start point, the return retention segment, and the crack projection segment in the length direction of the composite surface.

[0021] Further, the interface event chain is compressed along the load direction to reconstruct the shear force transmission breakpoint of the composite surface, including: reading adjacent slip start points, return retention segments, and crack projection segments in the interface event chain along the load direction; compressing consecutive adjacent slip start points and return retention segments pointing to the same crack projection segment into a shear force transmission anomaly group; taking the end of the shear force transmission anomaly group closest to the crack projection segment as the shear force transmission breakpoint; arranging multiple shear force transmission breakpoints according to the load direction to form a shear force transmission breakpoint sequence.

[0022] Further, forming segmented contact boundaries based on the shear force transmission breakpoint includes: dividing the load along the load direction into a section before the shear force transmission breakpoint, an adjacent section, and a section after the shear force transmission breakpoint, using the shear force transmission breakpoint as the dividing point; converting the section before the shear force transmission breakpoint into a continuous force transmission boundary; converting the adjacent section into a return energy dissipation boundary; converting the section after the shear force transmission breakpoint into a discontinuous force transmission boundary; and forming segmented contact boundaries according to the arrangement order of the continuous force transmission boundary, the return energy dissipation boundary, and the discontinuous force transmission boundary on the composite surface.

[0023] Further, converting the adjacent section of the shear force transmission breakpoint into a return energy dissipation boundary includes: extracting the relative displacement growth process of the adjacent section of the shear force transmission breakpoint during the loading stroke and the relative displacement retention process during the return stroke; forming a loading force transmission state based on the relative displacement growth process; forming a return energy dissipation state based on the relative displacement retention process; and writing the loading force transmission state and the return energy dissipation state into the corresponding overlapping surface contact boundary in the initial twin model to obtain the return energy dissipation boundary.

[0024] Furthermore, the initial twin model is updated using the segmented contact boundary to simulate the shear performance of the prestressed composite slab, outputting candidate values ​​for shear bearing capacity and shear discontinuity locations. This includes: designating the composite surface segment corresponding to the continuous force transmission boundary as the segment where the precast base slab and cast-in-place layer are jointly stressed; designating the composite surface segment corresponding to the return energy dissipation boundary as the sliding energy dissipation segment that retains part of the shear force transmission; and designating the composite surface segment corresponding to the discontinuous force transmission boundary as the discontinuous segment where continuous shear force transmission stops. Shear simulation is performed along the load direction in the updated initial twin model, and candidate values ​​for shear bearing capacity and shear discontinuity locations are output based on the truncation locations of the continuous shear force transmission path in the discontinuous segments.

[0025] This invention also provides a digital twin-based simulation system for the mechanical properties of prestressed composite slabs, comprising a sensing interface, a memory, a processor, an initial model building unit, a response sequence forming unit, an event chain generation unit, a breakpoint reconstruction unit, and a boundary simulation unit. The sensing interface receives detection signals generated by the prestressed composite slab during construction or use. The memory stores the initial twin model, stage response sequences, and segmented contact boundaries. The processor invokes each unit to perform calculations. The initial model building unit establishes an initial twin model for the prestressed composite slab formed by a precast base slab and a cast-in-place layer, including prestressing tendons, a detection chain for the composite surface, and support boundaries. The response sequence forming unit obtains the stage response sequences generated by the prestressed composite slab during construction or use and extends the stage response sequences along the length of the composite surface. The direction is decomposed into the loading stroke and return stroke of the continuous detection segment; the event chain generation unit is used to extract the slip start point where the relative displacement deviates from the cooperative trend of the adjacent continuous detection segment from the loading stroke, and to extract the return retention segment where the relative displacement is still retained after the load decreases or the load is transferred from the return stroke. The extension path of the crack through the composite surface is projected to the continuous detection segment to generate an interface event chain composed of the slip start point, the return retention segment and the crack projection segment; the breakpoint reconstruction unit is used to perform adjacent compression on the interface event chain along the load direction to reconstruct the shear force transmission breakpoint of the composite surface; the boundary simulation unit is used to form a segmented contact boundary based on the shear force transmission breakpoint, and to update the initial twin model using the segmented contact boundary to simulate the shear performance of the prestressed composite slab, and output the candidate value of shear bearing capacity and the shear discontinuity position.

[0026] Based on the above steps, the technical effect of the present invention is as follows: First, by comparing the loading stroke and return stroke of the same continuous test segment, the slip start point and return retention segment can be located in the specific test segment, and the shear force transmission break point is no longer deduced solely from the overall slip amount or the overall bearing capacity.

[0027] Second, by incorporating the crack projection segment into the interface event chain, slippage, residual displacement, and crack penetration location can be grouped into the same spatial sequence; the breakpoints obtained through adjacent compression are used to generate continuous force transmission boundaries, return energy dissipation boundaries, and discontinuous force transmission boundaries, so that the contact boundary is updated in segments according to the state of the detection segment.

[0028] Third, the intra-segment correspondence preserves the response differences of the same detection segment during loading and unloading. When adjacent compression is performed, isolated slip points that are not spatially discontinuous with the crack projection segment can be excluded, reducing the false identification of breakpoints.

[0029] Fourth, after the return travel stagnation section is converted into the return travel energy dissipation boundary, the model can retain the residual relative displacement and the resulting tangential stiffness change in the corresponding detection section, thus avoiding the continued treatment of the overlapping surface that has already undergone local slippage as a fully cooperative section. Attached Figure Description

[0030] The accompanying drawings used in the embodiments of the present invention are briefly described below.

[0031] Figure 1 This is a flowchart illustrating a method for simulating the mechanical properties of prestressed composite slabs based on digital twins, as provided in an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of the initial twin model of a method for simulating the mechanical properties of prestressed composite slabs based on digital twins, provided in an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of the stage response sequence decomposition of a digital twin-based method for simulating the mechanical properties of prestressed composite slabs, as provided in an embodiment of the present invention.

[0034] Figure 4 This is a schematic diagram of the interface event chain generation for a method of simulating the mechanical properties of prestressed composite slabs based on digital twins, provided in an embodiment of the present invention.

[0035] Figure 5 This is a schematic diagram of the shear force transmission breakpoint and segmental contact boundary of a method for simulating the mechanical properties of prestressed composite slabs based on digital twins, provided in an embodiment of the present invention.

[0036] Figure 6 This is a schematic diagram of a prestressed composite slab mechanical performance simulation system based on digital twin, provided as an embodiment of the present invention. Detailed Implementation

[0037] The following describes the initial twin model establishment, stage response sequence processing, interface event chain generation, and segmented contact boundary update process in conjunction with specific implementation methods.

[0038] Example 1: A method for simulating the mechanical properties of prestressed composite slabs based on digital twins.

[0039] like Figure 1 As shown in the figure, this embodiment provides a method for simulating the mechanical properties of prestressed composite slabs based on digital twins. The method first establishes an initial twin model of the prestressed composite slab, then uses the detection data from the construction or service phase to form a phase response sequence, subsequently extracts interface events, reconstructs shear force transmission breakpoints, and updates the segmented contact boundaries accordingly to simulate shear performance.

[0040] S1: For a prestressed composite slab with a composite surface formed by a precast base slab and a cast-in-place layer, establish an initial twin model including prestressing tendons, a composite surface detection chain, and support boundaries.

[0041] like Figure 2 As shown, the initial twin model takes a prestressed composite slab as the object, including an upper cast-in-place layer, a lower precast base slab, prestressing tendons set in the precast base slab, a detection chain for the composite surface between the precast base slab and the cast-in-place layer, and two supporting boundaries. The detection chain for the composite surface is used to obtain the response state of a continuous detection segment along the length of the composite surface, and the supporting boundaries are used to characterize the constraint conditions of the prestressed composite slab.

[0042] Specifically, the establishment of the initial twin model includes the following steps: First, establish the geometric model of the prestressed composite slab. Based on the design drawings of the prestressed composite slab, create three-dimensional solid models of the precast base slab and the cast-in-place layer in finite element software. The precast base slab is modeled using solid elements, with a thickness of 60mm to 80mm; the cast-in-place layer is modeled using solid elements, with a thickness of 40mm to 60mm. The overlapping surface is located between the top surface of the precast base slab and the bottom surface of the cast-in-place layer, extending along the length and width directions of the composite slab.

[0043] Second, establish a prestressed tendon model. Prestressed tendons are arranged within the precast base slab, modeled using truss elements or solid elements. The location, diameter, and prestress value of the prestressed tendons are determined according to the design drawings. For example, for a prestressed composite slab with a span of 6m, prestressed steel strands with a diameter of 7mm are arranged along the length of the precast base slab at a spacing of 150mm, with an applied prestress value of 1200MPa. In the finite element model, prestress is applied to the prestressed tendons using either the cooling method or the initial strain method, inducing prestress in the precast base slab.

[0044] Third, establish a joint surface inspection chain. The joint surface inspection chain is a sequence of continuous inspection segments arranged along the length of the joint surface, used to monitor the relative displacement, crack propagation, and deflection of the joint surface. Specifically, the joint surface is divided into n equal continuous inspection segments along its length, and the length of each continuous inspection segment is... The measurement is determined based on the span of the composite slab and the required testing accuracy. For example, for a prestressed composite slab with a span of 6m, the composite surface is divided into 30 consecutive testing segments along its length, and the length of each consecutive testing segment is determined. mm.

[0045] In the finite element model, node pairs are set on the upper and lower surfaces of the overlapping surface of each continuous detection segment to monitor the relative displacement of the overlapping surface. The relative displacement between node pairs is calculated using the difference in node coordinates. The continuous detection segments are numbered k sequentially from the support end towards the mid-span as 1, 2, ..., n.

[0046] Fourth, establish the support boundaries. Based on the support conditions of the prestressed composite slab, apply constraints at the support locations of the model. For simply supported boundaries, constrain vertical displacement at the support locations and, based on model stability, constrain necessary horizontal displacement, while releasing angular degrees of freedom. For fixed supported boundaries, constrain displacement in all directions at the support locations and, according to the actual support construction, constrain or release angular freedom. The constrained degrees of freedom of the above support boundaries are consistent with the actual support form to avoid mistakenly constructing simply supported boundaries as fixed supported boundaries.

[0047] Fifth, define material parameters. The concrete materials for the precast base slab and cast-in-place layers are modeled using an elastoplastic constitutive model, and the elastic modulus of the concrete is... The elastic modulus is determined based on the concrete strength grade, for example, C40 concrete. MPa, Poisson's ratio ν=0.2. The material of the prestressing tendon adopts an ideal elastic-plastic model, with an elastic modulus of MPa. MPa, yield strength MPa.

[0048] Sixth, define the initial contact boundary of the composite surface. In the initial twin model, the composite surface is modeled using contact elements, which are used to simulate the normal contact and tangential friction behavior between the precast slab and the cast-in-place layer. The normal stiffness of the contact element is determined based on the elastic modulus of concrete, the area of ​​the contact element, and the normal characteristic length; when normalized, the normal stiffness can be expressed as... ,in This is the equivalent characteristic length normal to the overlapping surface, with the unit diameter consistent with the contact stiffness definition in the finite element software. Tangential friction coefficient. The coefficient of friction is determined based on the surface roughness of the mating surfaces or calibration results of similar test pieces. For example, for mating surfaces with roughened surfaces, the coefficient of friction is... In the initial state, all continuous detection segments of the overlapping surface use the same contact parameters and have not yet been segmented according to the actual stress state.

[0049] After establishing the initial twin model, the model includes the precast base slab, cast-in-place layer, prestressed tendons, composite surface detection chain, and support boundary, providing a foundation for subsequent stage response sequence acquisition and boundary update.

[0050] S2: Obtain the phase response sequence formed by the prestressed composite slab during the construction or use phase.

[0051] The stage response sequence is a data sequence formed by organizing the test data of prestressed composite slabs at different load stages according to the sequence of continuous test segments and stages.

[0052] Specifically, obtaining the phased response sequence includes the following steps: First, determine the load stages. Based on the stress process of the prestressed composite slab, the load application process is divided into the load application stage, the load reduction stage, and the load transfer stage. The load application stage refers to the process from an initial unloaded state to reaching the maximum load; the load reduction stage refers to the process of gradually unloading from the maximum load state; and the load transfer stage refers to the process of the load application location changing. For example, in the construction stage, the load application stage corresponds to the process of pouring and curing the cast-in-place concrete, and the load transfer stage corresponds to the process of transferring the construction load from one area to another.

[0053] Second, data collection and testing. At each loading stage, sensors or measuring devices are used to collect data on the relative displacement of the composite surface, crack propagation status, and plate deflection status. The relative displacement of the composite surface is measured by displacement sensors arranged on the upper and lower surfaces of the composite surface, with the sensor positions corresponding to the positions of consecutive detection segments in the composite surface detection chain. Crack propagation status is obtained through crack observation or image recognition methods, recording the crack initiation position, propagation path, and crack width. Plate deflection status is measured by displacement sensors or laser rangefinders arranged on the plate surface.

[0054] Third, same-segment aggregation. Following the stages of load application, load reduction, and load transfer, the relative displacement of the composite surface, crack propagation status, and plate deflection status are aggregated within the same segment. Same-segment aggregation refers to combining the detection data of the same continuous detection segment at different load stages to form a complete response history for that continuous detection segment.

[0055] Specifically, for the continuous detection segment numbered k, the relative displacement of the overlapping surface collected during the load application stage is: The relative displacement of the overlapping surface collected during the load reduction phase is The relative displacement of the overlapping surface collected during the load transfer phase is Simultaneously, the crack propagation status of this continuous detection segment at each stage was recorded. , , and plate deflection state , , .

[0056] Fourth, segment response units are formed. The states of the same continuous detection segment at different stages are grouped into the same segment response unit. A segment response unit is a data structure containing the response data of the continuous detection segment at all load stages. For the continuous detection segment numbered k, its segment response unit... include: ; The data in the segment response unit is arranged in the order of the load stages, which facilitates subsequent decomposition into loading stroke and return stroke.

[0057] Fifth, connect to form a staged response sequence. Following the arrangement order of the continuous detection segments along the length of the overlapping surface, connect the response units to form a staged response sequence. The staged response sequence S is represented as: ; in, The continuous detection section corresponding to the support end, This corresponds to a continuous detection segment at the mid-span or another support end. The stage response sequence S contains the response data of all continuous detection segments at all load stages, providing a data basis for subsequent loading and return stroke breakdown.

[0058] S3: Decompose the stage response sequence along the length of the overlapping surface into the loading stroke and return stroke of the continuous detection segment.

[0059] The purpose of disassembly is to separate the load increase process from the load decrease process in order to identify the slip start point and the return stagnation section.

[0060] like Figure 3 As shown, the stage response sequence is organized along the length of the overlapping surface and decomposed into loading stroke and return stroke. The loading stroke corresponds to the response data generated during the load increase stage, while the return stroke corresponds to the response data generated during the load decrease or load transfer stage. By establishing the intra-segment correspondence between the loading stroke and return stroke within the same continuous detection segment, a data foundation is provided for subsequent identification of the slip start point and the return dwell segment.

[0061] Specifically, breaking down the load trip and return trip involves the following steps: First, generate the loading stroke. The loading stroke is generated based on the segment response unit corresponding to the load increase stage. For the continuous detection segment numbered k, its loading stroke... This includes the relative displacement, crack propagation state, and plate deflection state of this segment during the load application stage: ; The loading stroke reflects the response change of this continuous detection segment as the load gradually increases. When the load increases, if the bonding surfaces maintain good adhesion, the relative displacement... The value should be kept small; if slippage occurs at the overlapping surfaces, the relative displacement... It will increase significantly.

[0062] Second, generate the return stroke. The return stroke is generated using the segment response unit corresponding to the load reduction or load transfer stage. For the continuous detection segment numbered k, its return stroke... This includes the relative displacement, crack propagation state, and plate deflection state of this segment during the load reduction and load transfer phases: ; The return stroke reflects the response recovery of the continuous detection segment during load reduction or transfer. If no slippage occurs on the overlapping surface during loading, the relative displacement during the return stroke should recover to near zero; if slippage occurs on the overlapping surface during loading, residual relative displacement may still remain during the return stroke.

[0063] Third, establish intra-segment correspondences. Within each continuous detection segment, establish intra-segment correspondences between the loading and return strokes. These correspondences are used to associate the response data of the same continuous detection segment during the loading and unloading processes, facilitating subsequent identification of the slip start point and the return dwell segment.

[0064] Specifically, for a continuous detection segment numbered k, the intra-segment correspondence is... Represented as: ; intra-segment correspondence Loading stroke of the continuous detection segment and return trip By linking them together, it becomes possible to compare the relative displacement changes of this segment during the loading and unloading processes.

[0065] Fourth, the intra-segment correspondences are used as the basis for the travel calculation. The intra-segment correspondences of all continuous detection segments are used as the basis for extracting the slip start point and return dwell segment. The travel basis includes the loading travel and return travel of all continuous detection segments, and the correspondences between them: ; The travel baseline M provides data support for the subsequent extraction of the slip start point and return dwell segment.

[0066] S4: Extract the slip start point from the loading stroke where the relative displacement deviates from the cooperative trend of adjacent continuous detection segments, and extract the return stroke where the relative displacement is still retained after the load is reduced or transferred.

[0067] Specifically, extracting the slip start point and the return dwell segment includes the following steps: First, compare the direction and magnitude of the relative displacement changes. Compare the direction and magnitude of the relative displacement increments of adjacent continuous detection segments along the length of the overlapping surface during the loading stroke. The direction of the relative displacement increment is determined by the sign of the relative displacement increment between adjacent load steps, and the magnitude of the increment is determined by the absolute value of the relative displacement increment or the difference in increments between adjacent segments.

[0068] For the continuous detection segment numbered k, during the loading stroke, the relative displacement changes from the initial state. Gradually increase to the maximum load state Direction of displacement Defined as: ; if or This indicates that the relative displacement of the continuous detection segment changes along the corresponding positive or negative direction during the loading process; if This indicates that the relative displacement of the continuous detection segment remains essentially unchanged during loading, and the overlapping surface remains in an adhesive state. The positive measurement direction is predetermined by the sensor arrangement direction, and the positive and negative signs are not directly limited to fixed upward and downward sliding directions.

[0069] For adjacent consecutive detection segments k and k+1, calculate the difference in their relative displacement direction: ; if Smaller, and If the sign of the relative displacement increment is consistent with that of adjacent continuous detection segments, it indicates that the adjacent continuous detection segments exhibit a cooperative deformation trend; if Larger, or If the sign of the relative displacement increment is inconsistent with that of the adjacent continuous detection segments, it indicates that there is a deviation in amplitude or direction between the adjacent continuous detection segments, and a certain segment has deviated from the cooperative trend.

[0070] Second, identify the slip start point. The continuous detection segment where the relative displacement change direction changes from a shared change between adjacent segments to a single-segment offset is identified as the slip start point. The criteria for determining the slip start point are: when and If the relative displacement increment sign of continuous detection segment k deviates from the direction of adjacent continuous detection segments, and this magnitude deviation or direction deviation continues for more than two load steps, then continuous detection segment k will be identified as the slip start point.

[0071] In the above determination, Used to characterize the deviation of displacement increment amplitude between adjacent consecutive detection segments; relative displacement increment direction through and , The determination is based on whether they are consistent. When there is only a deviation in amplitude but no reversal in direction, it is determined by... Exceed As the basis for identifying the slip start point; when there is a direction reversal, the direction reversal and amplitude deviation are used together as the basis for identifying the slip start point.

[0072] in, The co-trend threshold is used to determine whether adjacent consecutive detection segments exhibit co-deformation. The value is determined based on the resolution of the relative displacement sensor on the composite surface, the no-load noise amplitude, and the length of the continuous detection section. It should be no less than twice the relative displacement measurement accuracy, and calibrated by combining the displacement increment difference between adjacent sections of the uncracked test section under the same load step. When measured calibration data is lacking, [the following can be used]. Set to three times the standard deviation of the displacement increment difference between adjacent segments. For example, when the relative displacement measurement accuracy is 0.01 mm and the standard deviation of the displacement increment difference between adjacent segments in the uncrackled test segment does not exceed 0.015 mm, Take 0.05mm.

[0073] The slip initiation point indicates that the continuous detection segment is the first to break away from the cooperative deformation trend of adjacent segments during loading, indicating local slippage. The set of slip initiations is denoted as... .

[0074] Third, track the relative displacement recovery process. Track the relative displacement recovery process of the slippage starting point and its adjacent continuous detection segments along the return stroke. The relative displacement recovery process refers to the process in which the relative displacement of the continuous detection segments gradually decreases from its maximum value during the load reduction or load transfer phase.

[0075] For the slip start point During the return stroke, the relative displacement changes from the maximum load state. From the completion of unloading or the stabilization of load transfer to... To eliminate non-zero references caused by initial assembly deviations, pre-cavitation, temperature drift, or shrinkage, the initial relative displacement is first used. As a baseline, the relative displacement fallback and residual relative displacement are calculated. The relative displacement fallback is defined as: ; The residual relative displacement difference is defined as The residual relative displacement amplitude is .if This indicates that the relative displacement of the continuous detection segment is basically recovered during the unloading process, and the slippage of the overlapping surface is recoverable slippage; if This indicates that the relative displacement of the continuous detection segment was not fully recovered during the unloading process, and the overlapping surface retained residual relative displacement.

[0076] Fourth, identify the return travel delay segment. The continuous detection segment that retains relative displacement within the segment after the return journey is defined as the return travel delay segment. The criteria for determining the return travel delay segment are as follows: After unloading is complete or the load transfer is stable Furthermore, the residual relative displacement did not recover to its original value within two adjacent sampling windows. In the following cases, the continuous detection segment k will be identified as the return delay segment.

[0077] in, The residual relative displacement threshold is used to determine whether the continuous detection segment still retains a significant relative displacement relative to the initial reference after unloading. The value is determined based on the zero-point drift of the relative displacement sensor on the overlapping surface, the stabilization time after unloading, the no-load repeatability measurement error, and the necessary temperature correction results. It should be no less than the larger of the upper limit of the zero-point drift and twice the measurement resolution. For example, when the upper limit of the zero-point drift is 0.015 mm and the measurement resolution is 0.01 mm, Take 0.02mm.

[0078] For the sake of a unified understanding, in this article , and These represent the relative displacements of the continuous detection segment k in the initial state, the maximum load state, and the state after unloading or load transfer stabilization, respectively, in mm; , , and All values ​​are derived from the relative displacement difference, and the unit is mm. This represents the magnitude of the residual relative displacement, in mm. and All values ​​are displacement thresholds, in mm.

[0079] The return retention section indicates that the continuous test section retains residual relative displacement after the load is reduced or transferred, and the overlapping surface has not fully recovered to the bonded state, thus weakening the shear force transfer capacity of this section. The set of return retention sections is denoted as... .

[0080] S5: Project the extension path of the crack through the overlapping surface to the continuous detection segment, generating an interface event chain consisting of the slip start point, the return retention segment, and the crack projection segment.

[0081] The interface event chain is a sequence of events that links key events (slippage, residual slippage, crack penetration) occurring on the overlapping surface according to their spatial location.

[0082] Specifically, generating a UI event chain includes the following steps: First, extract the crack propagation path. This involves identifying the location where the crack extends from the precast base slab to the composite surface and into the cast-in-place layer. The crack propagation path is obtained through crack observation or image recognition methods.

[0083] During the stress process of prestressed composite slabs, cracks typically first appear in the tension zone of the precast base slab. As the load increases, the cracks extend upwards to the composite surface and may further extend into the cast-in-place layer. The location where cracks cross the composite surface has a significant impact on the shear force transfer at that location, as cracks weaken the bond strength of the composite surface, causing the shear force transfer to be interrupted at that point.

[0084] For each crack, record its starting position. (Usually located on the bottom or side of the precast base plate), at the point where it passes through the overlapping surface. and finish line (Located inside or on top of the cast-in-place layer). The crack propagation path is represented by a line segment, with the coordinates of the endpoints of the line segment being... and , where the y-coordinate represents the vertical position.

[0085] Second, the crack projection segment is formed by mapping. The location where the crack crosses the overlapping surface is determined. The crack projection segment is formed by mapping the continuous detection segments in the overlapping surface detection chain. The mapping method is as follows: For the location where the crack passes through the overlapping surface Find the consecutive detection segment numbers containing that location. Specifically, if the length range of the continuous detection segment k is... ,and The crack projection segment number corresponding to this crack is: .

[0086] A crack projection segment represents a continuous detection segment on the overlapping surface where a crack extends through. The set of crack projection segments is denoted as... .

[0087] Third, connect to form an interface event chain. According to the sequential positions of the slip start point, return retention segment, and crack projection segment on the load direction coordinate, connect the three types of segments to form an interface event chain; when the direction of the continuous detection segment number is consistent with the direction of the load, they can be directly connected according to the sequential order of the continuous detection segment numbers.

[0088] The UI event chain E is represented as: ; in, This represents the i-th UI event. It can be the slip start point, the return retention section, or the crack projection section. The events in the interface event chain E are arranged from upstream to downstream according to their position on the load direction coordinate; when the numbering direction is consistent with the load direction, it can be equivalent to arranging the continuous detection segments in the overlapping surface length direction from smallest to largest.

[0089] Specifically, the set of sliding origins Return journey delay section collection and the set of crack projection segments Merge and sort according to the load direction coordinates corresponding to each event to form the interface event chain E. Each interface event This includes the event type (slippage start point, return travel segment, or crack projection segment), event location (continuous detection segment number), and the corresponding load direction coordinates.

[0090] The interface event chain E reflects the key events that occur along the length of the overlapping surface and their spatial distribution, providing an event basis for subsequent shear force transmission breakpoint reconstruction.

[0091] like Figure 4 As shown, for example, continuous detection segments in the composite surface detection chain are read along the load direction, and the slip start point extracted during the loading stroke, the return retention segment extracted during the return stroke, and the crack projection segment obtained by projecting the crack after it passes through the composite surface are connected according to their sequential relationship in the load direction coordinates, thereby forming an interface event chain. The crack path in the figure represents the extension direction of the crack through the composite surface, and the projection arrow indicates that the crack path is mapped to the corresponding continuous detection segment in the composite surface detection chain.

[0092] S6: Perform adjacency compression on the interface event chain along the load direction to reconstruct the shear force transmission breakpoint of the overlapping surface.

[0093] The shear force transmission breakpoint is the location where the shear force transmission capacity on the composite surface decreases or is interrupted, and it is a key basis for determining the segmented contact boundary.

[0094] Specifically, reconstructing the shear force transmission breakpoint includes the following steps: First, read adjacent interface events. Read the adjacent slip start point, return travel segment, and crack projection segment in the interface event chain along the load direction. The load direction is usually from the support to the mid-span or from one support to the other. When the direction of the continuous detection segment number is inconsistent with the load direction, first convert the continuous detection segment number k to load direction coordinates. Then according to The size determines the upstream and downstream sides.

[0095] For UI event chain Read adjacent event pairs sequentially according to their position on the load direction coordinate s. Determine whether two events satisfy the adjacency compression condition. If it is bidirectional loading or mid-span symmetrical loading, establish interface event chains according to the corresponding principal shear flow directions and perform adjacency compression.

[0096] Second, identify groups of anomalous shear force transmission. Slip start points and return retention sections that are consecutively adjacent and point to the same crack projection segment are compressed into a single group of anomalous shear force transmission.

[0097] Continuous adjacency refers to two events being adjacent in the interface event chain, and the interval between their corresponding consecutive detection segment numbers or the coordinate distance along the load direction does not exceed a threshold. . Based on the crack observation and positioning error, and the length of the continuous detection section The value is determined by the direction of the load and is taken as the integer part of the number of segments for calculating the crack location error; for example, when the crack location error does not exceed 400mm and When mm, A value of 2 indicates that the consecutive detection segment numbers corresponding to the event differ by no more than 2 segments or the coordinate distance in the load direction does not exceed 2. .

[0098] Pointing to the same crack projection segment means that the slip initiation point or return retention segment is located upstream of a certain crack projection segment in the direction of load application, and there are no other crack projection segments between them. Specifically, for the slip initiation point or return retention segment... If a crack projection segment exists , making And in the coordinate range of the load direction If there are no other crack projection segments within, then it is considered... point to When the direction of the numbering is consistent with the direction of the load, the above conditions can be equivalently expressed as follows: .

[0099] For consecutively adjacent slip start points and return travel segments pointing to the same crack projection segment in the interface event chain, they are compressed into a single shear force transmission anomaly group G. Shear force transmission anomaly group G includes: ; in, Number the upstream slip start point or return delay segment in the anomaly group. Number the downstream slip start point or return delay segment in the anomaly group. This is the number of the crack projection segment pointed to by the anomaly group.

[0100] Third, determine the shear force transmission breakpoint. The end of the shear force transmission anomaly group closest to the crack projection segment is taken as the shear force transmission breakpoint. The location of the shear force transmission breakpoint... Defined as: ; This means that the shear force transmission breakpoint is located at the slip initiation point or return retention section closest to the crack projection segment in the shear force transmission anomaly group. This location is a critical point where the shear force transmission capacity of the composite surface decreases significantly, because slip or residual slip has occurred at this location, and it is also close to the crack penetration point, resulting in a significant weakening of the shear force transmission capacity of the composite surface at this location and in its downstream section.

[0101] Fourth, arrange and merge the shear force transfer breakpoint sequence. Multiple shear force transfer breakpoints are arranged according to the load direction to form a shear force transfer breakpoint sequence, and overlap checks are performed on adjacent sections of adjacent breakpoints. The shear force transfer breakpoint sequence B is represented as: ; in, The number of the continuous detection segment for the i-th shear force transmission breakpoint is given. The breakpoints in the shear force transmission breakpoint sequence B are arranged from upstream to downstream according to the load direction coordinates. When the numbering direction is consistent with the load direction, the breakpoints can be arranged from smallest to largest according to the continuous detection segment number.

[0102] The shear force transmission breakpoint sequence B reflects the location distribution of shear force transmission interruptions along the length of the composite surface. If the adjacent sections of two adjacent shear force transmission breakpoints overlap, the overlapping part is incorporated into the adjacent section of the downstream breakpoint, or the boundary type is determined preferentially according to the breakpoint with larger residual relative displacement and closer crack projection distance. This results in a table of non-conflicting breakpoint sections, providing a breakpoint basis for the subsequent formation of segmented contact boundaries.

[0103] S7: Based on the shear force transmission discontinuity, segmented contact boundaries are formed, and the initial twin model is updated using the segmented contact boundaries. The shear performance of the prestressed composite slab is simulated, and candidate values ​​of shear bearing capacity and shear discontinuity locations are output.

[0104] Specifically, forming segmented contact boundaries and updating the model includes the following steps: First, divide the area into three categories. Using the sequence of shear force transfer breakpoints as the boundary, divide the area along the load direction into three segments: the segment before the shear force transfer breakpoint, the segment adjacent to the shear force transfer breakpoint, and the segment after the shear force transfer breakpoint. When there are multiple shear force transfer breakpoints, generate non-overlapping boundary segments sequentially according to the breakpoint segment table.

[0105] For the shear force transmission breakpoint Define the following three types of segments: (1) Shear force transfer breakpoint upstream section: This refers to the continuous test section upstream of the current shear force transfer breakpoint that has not yet been occupied by the adjacent or downstream section of the previous breakpoint. These sections do not experience significant slippage during loading, and the overlapping surfaces maintain good adhesion. When the current breakpoint is the first breakpoint, the upstream section can be represented as... If there are other breakpoints before the current breakpoint, the preceding segment starts after the end position of the segment following the previous breakpoint. The number of transition sections between the front section and the breakpoint is based on the length of the continuous detection section. The error in crack projection positioning is determined, and its value is at least 1; when When the crack projection positioning error does not exceed one detection segment length and the crack diameter is mm, the error is within mm. Take 1.

[0106] (2) Adjacent Sections of Shear Force Transmission Discontinuity: These refer to the continuous monitoring sections near the current shear force transmission discontinuity. These sections slip during loading and retain residual relative displacement during unloading. The range of the adjacent sections can be represented as follows: When the range overlaps with the adjacent segment of the adjacent breakpoint, it is merged according to the priority in the breakpoint segment table to ensure that only one boundary type is written for the same continuous detection segment. The number of transition sections between the breakpoint and the subsequent section is determined based on the number of consecutive sections where the downstream shear force decreases after the crack penetrates, and the value is at least 1; when the shear force decrease rate of the adjacent downstream section exceeds the set decrease ratio and When mm, Take 1.

[0107] The set reduction ratio is the percentage decrease in interface shear force downstream of the fault point relative to the average interface shear force in the continuous force-transmitting section upstream of the fault point. This reduction ratio is determined based on the shear force-slip curve of similar specimens or the interface damage initiation point in the constitutive model, and is preferably between 30% and 50%. When the shear force reduction ratio of two consecutive downstream test sections both reach the selected value within this range, these test sections are included in the calculation. .

[0108] (3) Segment downstream of the shear force transmission breakpoint: This refers to the continuous monitoring segment downstream of the current shear force transmission breakpoint and not re-divided by adjacent segments of subsequent breakpoints. These segments are located downstream of the crack penetration point, where the continuous shear force transmission path of the composite surface is interrupted. When the current breakpoint is the last breakpoint, the range of the downstream segment can be represented as follows: When there are other breakpoints after the current breakpoint, the subsequent segment extends to the position before the start of the segment adjacent to the next breakpoint.

[0109] Second, the boundary is converted into three types. The section before the shear force transmission discontinuity is converted into a continuous force transmission boundary; the section adjacent to the shear force transmission discontinuity is converted into a return energy dissipation boundary; and the section after the shear force transmission discontinuity is converted into a discontinuous force transmission boundary.

[0110] (1) Continuous force transmission boundary: The overlapping surface section corresponding to the continuous force transmission boundary maintains a good bond state, and the precast base plate and the cast-in-place layer are subjected to force together, with shear force continuously transmitted through the overlapping surface. In the finite element model, the continuous force transmission boundary is simulated using bonded contact elements or high-stiffness contact constraints. The normal stiffness and tangential stiffness of the contact elements are determined based on the elastic modulus of concrete, the area of ​​the contact element, the normal characteristic length, the length of the continuous detection section, and the roughness of the overlapping surface; the tangential friction coefficient... The determination is based on the surface treatment method of the overlapping surfaces or the calibration results of similar test pieces. For example, for overlapping surfaces with a roughened surface treatment, Take 0.6. Tangential slip in the continuous force transmission section is restricted, and whether normal separation is allowed is set according to the actual bonding and cracking state of the mating surface.

[0111] (2) Return energy dissipation boundary: The overlapping surface segment corresponding to the return energy dissipation boundary slips during loading and retains residual relative displacement during unloading. This segment exhibits energy dissipation characteristics under load cycles. The method for forming the return energy dissipation boundary is as follows: First, the relative displacement growth process of the adjacent segment at the shear force transfer breakpoint during the loading stroke and the relative displacement retention process during the return stroke are extracted. For the adjacent segment number k, its relative displacement during the loading stroke is... The relative displacement after the return journey is .

[0112] Secondly, the loading force transmission state is formed based on the relative displacement growth process. The loading force transmission state describes the shear force-relative displacement relationship of this section during the load increase process. To eliminate non-zero references caused by initial assembly deviations, pre-camber, temperature drift, or shrinkage, let... Represents the relative displacement with respect to the initial reference; when When the value is negative along the positive direction of measurement, Converted to a nonnegative scalar along the loading slip direction. The shear force-relative displacement relationship during the loading process is: (when ); in, Tangential stiffness, expressed in MPa / mm or N / mm, is the interfacial shear force calculated from the tangential contact force of the contact element during the loading stroke. and relative displacement relative to the initial reference The data is obtained by linear fitting; during fitting, the load step data is selected after the slip start point and before the formation of the residual displacement, and displacement rebound or sensor data is removed.

[0113] when When taking the interfacial shear stress, The unit is MPa. The unit is MPa / mm; when When taking the tangential contact force of the contact unit, The unit is N. The unit is N / mm. In one embodiment, the tangential contact force of the contact element is preferentially divided by the corresponding contact area to convert it into interfacial shear stress before fitting. This is to ensure that the stiffness parameters between different continuous test sections are comparable.

[0114] Secondly, the return energy dissipation state is formed based on the relative displacement retention process. The return energy dissipation state describes the shear force-relative displacement relationship of this section during the load reduction process. The return segment follows the aforementioned calculation relative to the initial datum and along the loading slip direction. and with This represents the residual relative displacement amplitude after unloading or load transfer stabilization; in this embodiment, the return segment uses the same equivalent tangential stiffness as the loading segment. In other implementations, the equivalent return stiffness can be fitted separately based on the return segment data. The shear force-relative displacement relationship during the return process is: (when hour); (when hour); Finally, the loading force transmission state and the return energy dissipation state are written into the corresponding overlapping surface contact boundary in the initial twin model to obtain the return energy dissipation boundary. In the finite element model, the return energy dissipation boundary is simulated using nonlinear contact elements, and the tangential constitutive relation of the contact elements adopts the above-mentioned piecewise linear model, which can reflect the energy dissipation and residual displacement during the loading-unloading process.

[0115] (3) Discontinuous force transmission boundary: The overlapping surface section corresponding to the discontinuous force transmission boundary is located downstream of the crack penetration point. The continuous shear force transmission path of the overlapping surface is interrupted here, and continuous shear force transmission ceases in this section. Limited shear force can only be transmitted through friction or local contact. In the finite element model, the discontinuous force transmission boundary is simulated using friction contact elements. The normal stiffness of the contact elements is maintained or appropriately modified according to the same unit system, and the tangential stiffness is written according to the reduction ratio of the tangential stiffness of the continuous force transmission boundary; the reduction ratio and the tangential friction coefficient are also considered. The shear force reduction rate in the downstream section after crack penetration or the inversion results of similar specimens are used to determine the shear force. For example, when the shear force in the downstream section drops to less than 50% of that in the continuous force transmission section... With a value of 0.3, the contact element is allowed to slide tangentially.

[0116] Tangential stiffness reduction ratio Defined as the ratio of the tangential stiffness of the discontinuous force transmission boundary to the tangential stiffness of the continuous force transmission boundary. ,in This represents the average interfacial shear force in the downstream section after the crack has penetrated. This refers to the average interfacial shear force in the continuous force-transmitting section before the crack penetrates or upstream of the break; when When the value is less than 0.5, this section is written into the discontinuous force transmission boundary, and... Inversion values ​​of similar specimens or Sure.

[0117] Third, segmented contact boundaries are formed. Segmented contact boundaries are formed according to the arrangement order of continuous force transmission boundaries, return energy dissipation boundaries, and discontinuous force transmission boundaries on the composite surface. Segmented contact boundaries are boundary conditions composed of multiple contact boundary segments of different types, reflecting the segmented force transmission state of the composite surface along its length.

[0118] The segmented contact boundary is represented as follows: ; in, For the continuous force transmission boundary section, This is the return energy consumption boundary segment. This refers to the discontinuous force transmission boundary segment. Each boundary segment includes the boundary type, boundary range (the range of continuous detection segment numbers), and boundary parameters (stiffness, friction coefficient, constitutive relation).

[0119] Fourth, update the initial twin model. Update the initial twin model using the segmented contact boundary. The update process is as follows: The overlapping surface section corresponding to the continuous force transmission boundary is taken as the section where the precast base plate and the cast-in-place layer are jointly stressed, and the contact unit of this section adopts the bonded contact boundary condition. The overlapping surface section corresponding to the return energy dissipation boundary is regarded as the sliding energy dissipation section that retains part of the shear force transmission. The contact element of this section adopts nonlinear contact boundary conditions to reflect the energy dissipation of the loading-unloading process. The overlapping surface section corresponding to the discontinuous force transmission boundary is taken as the discontinuous section where continuous shear force transmission stops, and the contact element of this section adopts the frictional contact boundary condition.

[0120] In the updated initial twin model, the contact boundary of the overlapping surface is no longer a uniform single boundary condition, but a segmented contact boundary formed according to the actual stress state, which can more accurately reflect the true force transmission state of the overlapping surface.

[0121] Fifth, shear performance simulation is performed. Shear simulation is conducted along the load direction in the updated initial twin model, and candidate values ​​of shear bearing capacity and shear discontinuity locations are output based on the cutoff locations of the continuous shear force transmission path in the discontinuous section.

[0122] Specifically, the shear performance simulation includes the following steps: First, apply loads. Apply vertical loads to the prestressed composite slab. The loads can be concentrated or uniformly distributed, and the location of the load application is determined according to the actual working conditions. Gradually increase the loads until the prestressed composite slab reaches its ultimate shear capacity.

[0123] Secondly, the shear force distribution is calculated. In each load step, the shear force of each continuous detection segment on the composite surface is calculated. The shear force on the composite surface is calculated using the tangential contact force of the contact elements. For the segment corresponding to the continuous force transmission boundary, the shear force is continuously transmitted, resulting in a larger shear force value; for the segment corresponding to the return energy dissipation boundary, the shear force is partially transmitted, resulting in a lower shear force value; for the segment corresponding to the discontinuous force transmission boundary, the shear force transmission is interrupted, resulting in a significant decrease in shear force value.

[0124] Third, identify the location of shear force discontinuity. Trace the shear force distribution along the load direction to identify the cutoff point of the shear force transmission path. The location of shear force discontinuity is defined as the position where the shear force on the composite surface transitions from a continuous transmission state to a discontinuous transmission state. This typically corresponds to the starting point of the discontinuous force transmission boundary, i.e., the location of the shear force transmission break. .

[0125] Fourth, calculate candidate values ​​for shear bearing capacity. Candidate values ​​for shear bearing capacity are the load values ​​at which the prestressed composite slab meets the shear limit criterion at the location of discontinuous shear force. The shear limit criterion includes a primary criterion and an auxiliary criterion: the primary criterion is that the finite element material constitutive model enters a shear damage failure state, or the overall load-displacement curve reaches its peak and then enters a stable decreasing stage; the auxiliary criterion is that the interface shear force at the starting position of the discontinuous force transmission boundary no longer increases for three consecutive load steps, or the relative displacement at that position exceeds [a certain value]. The preset multiple. When the main criterion is met, the external load of the corresponding load step is used as a candidate value for shear bearing capacity. When only the auxiliary criterion is met, the corresponding load step is taken as a candidate load step and confirmed in conjunction with the subsequent main criterion or test failure state.

[0126] Among them, the interface shear force no longer increases for three consecutive load steps means that the absolute value of the interface shear force increment in adjacent load steps is less than 2% of the average interface shear force in the upstream continuous force transmission section; the relative displacement exceeds The preset multiple refers to the residual relative displacement of this position relative to the initial reference exceeding... Furthermore, at least two sampling windows are required. If the finite element material constitutive model has a shear damage variable, then a shear damage variable of 0.8 is used as the criterion for the material constitutive model to enter the shear damage failure state; if no shear damage variable is set, then the peak value of the overall load-displacement curve and the subsequent decrease in bearing capacity are used as the confirmation criteria.

[0127] Fifth, output results. Output candidate values ​​for shear bearing capacity. and shear discontinuity position The location of shear force discontinuity is the length-direction coordinate of the continuous detection segment corresponding to the shear force transmission breakpoint, for example... .

[0128] Candidate values ​​for shear bearing capacity and the location of shear discontinuity reflect the shear performance of prestressed composite slabs under the condition of local shear force transmission interruption at the composite surface. This is more accurate than the results obtained by traditional methods that assume continuous force transmission at the composite surface, and can provide a more reliable basis for the design and safety assessment of prestressed composite slabs.

[0129] like Figure 5As shown, for example, adjacent slip start points and return retention segments pointing to the same crack projection segment in the interface event chain are compressed into a shear force transmission anomaly group, and the shear force transmission breakpoint is determined by the end of this anomaly group closest to the crack projection segment. Subsequently, using the shear force transmission breakpoint as the boundary position, the overlapping surface is divided into continuous force transmission boundary, return energy dissipation boundary, and discontinuous force transmission boundary, and the initial twin model is updated using the segmented contact boundaries.

[0130] Example 2: System Example.

[0131] like Figure 6 As shown, this embodiment provides a digital twin-based simulation system for the mechanical properties of prestressed composite slabs, which is used to perform the method described in Embodiment 1.

[0132] The system includes a sensing interface, memory, processor, initial model building unit, response sequence forming unit, event chain generation unit, breakpoint reconstruction unit, and boundary simulation unit.

[0133] The sensing interface is used to receive detection signals generated during the construction or service phases of the prestressed composite slab. The sensing interface includes analog signal input interfaces and digital signal input interfaces. The analog signal input interface receives signals from analog sensors such as displacement sensors and strain sensors; these signals are converted into digital signals via an analog-to-digital converter. The digital signal input interface receives signals from digital sensing devices such as digital displacement gauges and image acquisition equipment. The sensing interface supports multi-channel synchronous acquisition; the sampling frequency and acquisition accuracy are determined based on the relative displacement threshold. Residual relative displacement threshold And the load step duration is determined.

[0134] The memory is used to store the initial twin model, stage response sequences, and segmented contact boundaries. The memory is non-volatile, and its capacity is determined based on the number of consecutive detection segments, the number of load steps, and the size of the finite element model file. The data in the memory is organized into different data files according to data type; for example, the initial twin model is stored as a finite element model file (.inp or .k file), the stage response sequences are stored as time-series data files (.csv or .mat files), and the segmented contact boundaries are stored as boundary condition files.

[0135] The processor is used to invoke each unit to perform computational processing. The processor is a central processing unit or graphics processing unit capable of running finite element preprocessing scripts, event chain identification programs, and finite element solvers. The processor schedules the computational tasks of each functional unit through the operating system and allocates parallel computing resources according to the number of consecutive detection segments and the number of load steps.

[0136] The initial model building unit is used to create an initial twin model of a prestressed composite slab formed by a precast base slab and a cast-in-place layer, including prestressing tendons, a detection chain for the composite surface, and support boundaries. The initial model building unit includes a geometric modeling module, a material definition module, a mesh generation module, and a boundary condition setting module. The geometric modeling module creates a 3D geometric model based on the design drawings of the prestressed composite slab; the material definition module defines the material parameters of the precast base slab, cast-in-place layer, and prestressing tendons; the mesh generation module divides the geometric model into finite element meshes; and the boundary condition setting module sets the support boundaries and initial contact boundaries. The initial model building unit generates the initial twin model file using a finite element preprocessing program.

[0137] The response sequence formation unit is used to obtain the stage response sequence formed by the prestressed composite slab during the construction or service phase, and decomposes the stage response sequence along the length of the composite surface into the loading stroke and return stroke of continuous detection segments. The response sequence formation unit includes a data acquisition module, a data aggregation module, and a stroke decomposition module. The data acquisition module reads the detection signals from the sensor interface and converts them into data on the relative displacement of the composite surface, crack propagation status, and slab deflection status. The data aggregation module aggregates the data according to the load stage and continuous detection segments, forming segment response units and stage response sequences. The stroke decomposition module decomposes the stage response sequence into loading stroke and return stroke, and establishes the correspondence within each segment. The response sequence formation unit can be implemented using a numerical calculation program.

[0138] The event chain generation unit extracts the slip start point from the loading stroke, indicating a departure from the cooperative trend of adjacent continuous detection segments; extracts the return travel segment from the return stroke, indicating a retention segment that retains relative displacement after load reduction or transfer; and projects the extension path of the crack across the composite surface onto the continuous detection segment, generating an interface event chain consisting of the slip start point, the return travel segment, and the crack projection segment. The event chain generation unit includes a slip start point identification module, a return travel segment identification module, a crack projection module, and an event chain connection module. The slip start point identification module identifies the slip start point by comparing the direction and increment of relative displacement changes in adjacent continuous detection segments; the return travel segment identification module identifies the return travel segment by tracking the residual relative displacement relative to the initial reference; the crack projection module maps the crack extension path onto the continuous detection segment to form the crack projection segment; and the event chain connection module connects the three types of events according to the load direction coordinates to form an interface event chain. The event chain generation unit can be implemented using a numerical calculation program.

[0139] The breakpoint reconstruction unit is used to compress the interface event chain along the load direction to reconstruct the shear force transmission breakpoints of the composite surface. The breakpoint reconstruction unit includes an event reading module, an anomaly group identification module, and a breakpoint determination module. The event reading module reads adjacent events in the interface event chain along the load direction coordinates; the anomaly group identification module compresses consecutively adjacent slip initiation points and return retention sections pointing to the same crack projection segment into shear force transmission anomaly groups; the breakpoint determination module determines the shear force transmission breakpoints based on the end of the anomaly group closest to the crack projection segment, and arranges and merges them to form a shear force transmission breakpoint sequence. The breakpoint reconstruction unit can be implemented using a numerical calculation program.

[0140] The boundary simulation unit is used to form segmented contact boundaries based on shear force transmission discontinuities, and to update the initial twin model using these segmented contact boundaries. It simulates the shear performance of the prestressed composite slab, outputting candidate shear capacity values ​​and shear force discontinuity locations. The boundary simulation unit includes a segment division module, a boundary transformation module, a model update module, and a shear simulation module. The segment division module divides the slab into three non-overlapping segments based on the shear force transmission discontinuity sequence. The boundary transformation module converts these three segments into continuous force transmission boundaries, return energy dissipation boundaries, and discontinuous force transmission boundaries. The model update module updates the contact boundary conditions of the initial twin model using the segmented contact boundaries. The shear simulation module calls the finite element solver to simulate shear performance, calculating candidate shear capacity values ​​and shear force discontinuity locations. The boundary simulation unit can be implemented through a numerical calculation program and a finite element solver interface.

[0141] The system's workflow is as follows: (1) The sensing interface receives the detection signal of the prestressed composite slab; (2) The processor calls the initial model building unit to build the initial twin model and stores the model in memory; (3) The processor calls the response sequence forming unit to obtain the stage response sequence and decomposes it into loading stroke and return stroke, and stores the data in the memory; (4) The processor calls the event chain generation unit to extract the sliding start point, return stagnation segment and crack projection segment, generate the interface event chain, and store the data in the memory; (5) The processor calls the breakpoint reconstruction unit to perform adjacency compression on the interface event chain, reconstruct the shear force transmission breakpoint, and store the data in the memory; (6) The processor calls the boundary simulation unit to form a segmented contact boundary, updates the initial twin model, performs shear performance simulation, and outputs candidate values ​​of shear bearing capacity and shear discontinuity location.

[0142] With the cooperation of the above units, the system can perform processing in the order of detection data acquisition, response sequence formation, breakpoint reconstruction and boundary simulation, so that the update process of segmented contact boundary corresponds to the acquired overlapping surface response data.

[0143] This invention processes the loading stroke, return stroke, and crack projection segment in the same detection segment sequence, making the determination of the shear force transmission breakpoint dependent on the relative displacement residue, crack penetration location, and adjacency relationship in the load direction.

[0144] Compared with the prior art, the present invention has the following technical effects: Compared with setting the overlapping surface as a continuous force transmission boundary or an overall slip boundary, the above processing can write the detection segment that still retains residual relative displacement after local slip into the return energy dissipation boundary, and write the detection segment where the continuous shear force transmission is blocked after the crack is connected into the discontinuous force transmission boundary, so that the contact parameters of the overlapping surface in the finite element model are updated according to the state of the detection segment.

[0145] The above embodiments are used to illustrate the implementation process of the present invention. Without changing the relationship between the formation of the stage response sequence, the generation of the interface event chain, the reconstruction of the shear force transmission breakpoint, and the update of the segmented contact boundary, the specific parameters can be adjusted according to the size of the prestressed composite slab, the support method, and the testing equipment.

Claims

1. A method for simulating the mechanical properties of prestressed composite slabs based on digital twins, characterized in that, include: For prestressed composite slabs with a composite surface formed by a precast base slab and a cast-in-place layer, an initial twin model including prestressing tendons, a composite surface detection chain, and support boundaries is established. Obtain the phase response sequence formed by the prestressed composite slab during the construction or use phase; The stage response sequence is decomposed along the length of the overlapping surface into the loading stroke and return stroke of a continuous detection segment; Extract the slip start point where the relative displacement deviates from the cooperative trend of adjacent continuous detection segments from the loading stroke, and extract the return stagnation segment where the relative displacement is still retained after the load is reduced or the load is transferred from the return stroke. The extension path of the crack through the overlapping surface is projected onto the continuous detection segment, generating an interface event chain consisting of the slip start point, the return retention segment, and the crack projection segment; Adjacent compression is performed on the interface event chain along the load direction to reconstruct the shear force transmission breakpoint of the overlapping surface; Based on the shear force transmission breakpoint, segmented contact boundaries are formed, and the initial twin model is updated using the segmented contact boundaries. The shear performance of the prestressed composite slab is simulated, and candidate values ​​of shear bearing capacity and shear force discontinuity locations are output.

2. The method for simulating the mechanical properties of prestressed composite slabs based on digital twins according to claim 1, characterized in that, Obtaining the stage response sequence of the prestressed composite slab during the construction or service phase includes: According to the stage sequence of load application, load reduction and load transfer, the relative displacement of the composite surface, the crack extension state and the plate deflection state are grouped together in the same segment. The states formed at different stages of the same continuous detection segment are grouped into the same response unit; The response units are connected according to the arrangement order of the continuous detection segments along the length of the overlapping surface to form a stage response sequence.

3. The method for simulating the mechanical properties of prestressed composite slabs based on digital twins according to claim 1, characterized in that, The stage response sequence is decomposed along the length of the overlapping surface into loading and return strokes of continuous detection segments, including: The loading stroke is generated using the segment response unit corresponding to the load increase stage; The return stroke is generated using the segment response unit corresponding to the load reduction or load transfer stage. Establish an intra-segment correspondence between the loading stroke and the return stroke within each continuous detection segment; The correspondence within the segment is used as the basis for extracting the slip start point and the return delay segment.

4. The method for simulating the mechanical properties of prestressed composite slabs based on digital twins according to claim 1, characterized in that, Extract the slip start point where the relative displacement deviates from the cooperative trend of adjacent continuous detection segments from the loading stroke, and extract the return travel segment where the relative displacement is still retained after the load decreases or is transferred from the return stroke, including: Compare the relative displacement change direction of adjacent continuous detection segments during the loading stroke along the length direction of the overlapping surface; The continuous detection segment where the relative displacement change direction changes from the common change of adjacent segments to the single-segment offset is taken as the slip start point; The relative displacement of the sliding starting point and its adjacent continuous detection segments is traced along the return stroke. The continuous detection segment that retains the relative displacement within the segment after the return journey is completed is designated as the return retention segment.

5. The method for simulating the mechanical properties of prestressed composite slabs based on digital twins according to claim 1, characterized in that, Projecting the extension path of the crack through the overlapping surface onto the continuous detection segment generates an interface event chain consisting of the slip start point, the return retention segment, and the crack projection segment, including: Extract the path location of the crack extending from the precast base plate to the composite surface and into the cast-in-place layer; The path position is mapped to a continuous detection segment in the overlapping surface detection chain to form a crack projection segment; According to the sequential positions of the slip start point, the return retention segment, and the crack projection segment along the length of the overlapping surface, the three types of segments are connected into an interface event chain.

6. The method for simulating the mechanical properties of prestressed composite slabs based on digital twins according to claim 1, characterized in that, Adjacent compression is performed on the interface event chain along the load direction to reconstruct the shear force transmission breakpoint of the composite surface, including: Read the adjacent slip start point, return retention segment and crack projection segment in the interface event chain along the load action direction; The slip start point and the return retention segment that are consecutively adjacent and point to the same crack projection segment are compressed into a shear force transmission anomaly group; The end of the shear force transmission anomaly group closest to the crack projection segment is taken as the shear force transmission breakpoint. Multiple shear force transmission breakpoints are arranged according to the direction of load application to form a shear force transmission breakpoint sequence.

7. The method for simulating the mechanical properties of prestressed composite slabs based on digital twins according to claim 1, characterized in that, The segmented contact boundary is formed based on the shear force transmission breakpoint, including: Using the shear force transmission break point as the dividing point, the load direction is divided into the section before the shear force transmission break point, the section adjacent to the shear force transmission break point, and the section behind the shear force transmission break point. The section before the shear force transmission break point is converted into a continuous force transmission boundary; the section adjacent to the shear force transmission break point is converted into a return energy dissipation boundary; and the section after the shear force transmission break point is converted into a discontinuous force transmission boundary. The segmented contact boundary is formed according to the arrangement order of the continuous force transmission boundary, the return energy dissipation boundary, and the discontinuous force transmission boundary on the overlapping surface.

8. The method for simulating the mechanical properties of prestressed composite slabs based on digital twins according to claim 7, characterized in that, Converting the adjacent section of the shear force transmission breakpoint into a return energy dissipation boundary includes: Extract the relative displacement growth process of the adjacent section of the shear force transmission breakpoint during the loading stroke and the relative displacement retention process during the return stroke; The loading and force transmission state is formed according to the relative displacement growth process; the return energy consumption state is formed according to the relative displacement retention process. The loading force transmission state and the return energy consumption state are written into the corresponding overlapping surface contact boundary in the initial twin model to obtain the return energy consumption boundary.

9. The method for simulating the mechanical properties of prestressed composite slabs based on digital twins according to claim 1, characterized in that, The initial twin model is updated using the segmented contact boundary to simulate the shear performance of the prestressed composite slab, outputting candidate values ​​for shear bearing capacity and the location of shear discontinuity, including: The overlapping surface section corresponding to the continuous force transmission boundary is taken as the section where the precast base plate and the cast-in-place layer share the force. The overlapping surface section corresponding to the return energy dissipation boundary is regarded as the sliding energy dissipation section that retains part of the shear force transmission; The overlapping surface segment corresponding to the discontinuous force transmission boundary is taken as the discontinuous segment where continuous shear force transmission stops; in the updated initial twin model, shear simulation is performed along the load direction, and candidate values ​​of shear bearing capacity and shear discontinuity position are output based on the cutoff position of the continuous shear force transmission path of the discontinuous segment.

10. A system for simulating the mechanical properties of prestressed composite slabs based on digital twins, characterized in that, It includes a sensing interface, memory, processor, initial model building unit, response sequence forming unit, event chain generation unit, breakpoint reconstruction unit, and boundary simulation unit; The sensing interface is used to receive detection signals generated by the prestressed composite slab during the construction or use phases; the memory is used to store the initial twin model, the phase response sequence, and the segmented contact boundary; the processor is used to call each unit to perform calculations. The initial model building unit is used to build an initial twin model for a prestressed composite slab formed by a precast base slab and a cast-in-place layer, including prestressed tendons, a composite surface detection chain, and a support boundary. The response sequence forming unit is used to obtain the stage response sequence formed by the prestressed composite slab during the construction or use stage, and to decompose the stage response sequence into the loading stroke and return stroke of the continuous detection segment along the length direction of the composite surface. The event chain generation unit is used to extract the slip start point from the loading stroke where the relative displacement deviates from the cooperative trend of adjacent continuous detection segments, extract the return retention segment from the return stroke where the relative displacement is still retained after the load is reduced or the load is transferred, and project the extension path of the crack through the composite surface onto the continuous detection segment to generate an interface event chain composed of the slip start point, the return retention segment and the crack projection segment. The breakpoint reconstruction unit is used to perform adjacency compression on the interface event chain along the load direction to reconstruct the shear force transmission breakpoint of the overlapping surface. The boundary simulation unit is used to form segmented contact boundaries based on the shear force transmission discontinuity points, and to update the initial twin model using the segmented contact boundaries, to simulate the shear performance of the prestressed composite slab, and to output candidate values ​​of shear bearing capacity and shear force discontinuity locations.

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