Method and system for evaluating masonry wall collapse and scattering, and method for establishing evaluation model thereof

Abstract

The application discloses a method for establishing a masonry wall breaking and scattering evaluation model, comprising the following steps: constructing a masonry sample composed of typical blocks and a real masonry wall; carrying out SHPB experiments on the masonry sample to obtain dynamic constitutive curves and breaking block size distribution characteristics under different strain rates; carrying out full-size explosion impact tests on the real masonry wall to obtain basic laws of masonry wall impact breaking and scattering and accumulation of broken block groups; constructing a block-joint binary structure mechanical model; introducing a continuous-discontinuous element method to carry out numerical simulation of the breaking and scattering laws of the masonry wall under different parameters; and inputting the numerical simulation results and the full-size explosion impact test results into a BP neural network for machine learning to construct the masonry wall breaking and scattering evaluation model. The application further discloses a masonry wall breaking and scattering evaluation method and system. The application can quantitatively evaluate the damage and breaking conditions and the breaking and scattering conditions of the wall, and meets the dual requirements of calculation accuracy and calculation efficiency.

Description

Technical Field

[0001] This invention relates to the field of evaluation technology for the blast resistance performance of civil engineering and building structures, and particularly to a method, system and evaluation model for assessing the breakage and scattering of masonry walls. Background Technology

[0002] Industrial explosions pose a significant risk of damage due to the fragmentation of masonry structures, resulting in severe losses. Petrochemical plant areas contain numerous masonry buildings (such as old control rooms and office buildings). These structures generally have weak impact resistance and are highly susceptible to damage and fragmentation in plant explosions, primarily involving gas cloud combustion. Related investigations show that fragmentation formations travel long distances and possess high impact energy, causing substantial personal injury and property damage in numerous accidents.

[0003] Current assessment models for masonry wall fragmentation and scattering can be broadly categorized into two types: empirical formulas and numerical simulations. Empirical formulas are often based on extensive field experiments, summarizing and refining experimental data to create assessment models for specific walls under specific impact loads. While simple and easy to use, these methods have significant limitations in terms of the assessment objects and scenarios, and the assessment results often differ considerably from actual results. Numerical simulations, based on rigorous mechanical equations and numerical solution strategies, can accurately calculate the damage and fracture process of masonry walls under different explosive impact loads, as well as the scattering process of the fragmented debris. However, these methods require complex computational models, are extremely time-consuming, and cannot provide rapid assessments of masonry wall fragmentation and scattering.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] One of the objectives of this invention is to provide a method, system, and method for establishing an evaluation model for the assessment of broken and scattered masonry walls, thereby improving the problems of low calculation accuracy of empirical formula methods and long calculation time of numerical simulation methods in the prior art.

[0006] To achieve the above objectives, according to a first aspect of the present invention, the present invention provides a method for establishing an assessment model for the breakage and scattering of masonry walls, comprising the following steps: constructing masonry specimens composed of typical masonry blocks and a real masonry wall; conducting SHPB experiments on the masonry specimens to obtain dynamic constitutive curves and fragment size distribution characteristics under different strain rates; conducting full-scale explosive impact tests on the real masonry wall to obtain the basic laws of impact breakage and fragment scattering and accumulation of masonry walls; based on the data obtained from the SHPB experiments and the full-scale explosive impact tests, constructing a block-joint binary structural mechanical model, including a block-masonry impact breakage mechanical model and a fragment scattering and accumulation mechanical model; introducing the block-joint binary structural mechanical model into the continuous-discontinuous element method to conduct numerical simulations of the breakage and scattering laws of masonry walls under different parameters; and inputting the numerical simulation results and the results of the full-scale explosive impact tests into a BP neural network for machine learning to construct an assessment model for the breakage and scattering of masonry walls.

[0007] Furthermore, in the above technical solutions, typical blocks include sintered brick blocks, ordinary concrete blocks, and aerated concrete blocks.

[0008] Furthermore, the above technical solution combines numerical methods for the propagation process of gas cloud combustion and explosion with a three-dimensional full-size masonry wall model for numerical simulation.

[0009] Furthermore, in the above technical solution, when performing numerical simulation of the gas cloud combustion and explosion propagation process, the second-order finite volume method is used for gas flow calculation and analysis; the chemical reaction source term is handled by combining the splitting operator and the relaxation time step to simulate the rigidity problem of the chemical reaction; the Kurganov algorithm, the MUSCL method, and the second-order and third-order Runge-Kutta methods are used to ensure that the spatiotemporal calculation accuracy is at least second-order; the submerged boundary method is used to calculate the gas-solid coupling effect; and a multi-core CPU parallel strategy is adopted.

[0010] Furthermore, in the above technical solution, the dynamic constitutive curves under different strain rates include the block damage and breakage constitutive curve and the fracture friction constitutive curve of the joint.

[0011] Furthermore, in the above technical solution, the construction of the mechanical model of the scattered accumulation of broken blocks includes: collecting high-speed photography data of the actual scattering process of masonry walls; analyzing the high-speed photography data to obtain the spatiotemporal motion law of masonry fragments under the airflow; and carrying out CFD numerical simulation of a single complex-shaped block under different flow velocities to establish the correspondence between gas velocity, broken block shape, and broken block resistance, and to form a calculation model of the force and torque of the broken blocks.

[0012] Furthermore, in the above technical solution, the mechanical model is introduced into the continuous-discontinuous element method to conduct numerical simulation of the fragmentation and scattering law of masonry walls under different parameters. This includes: using blocks to represent the continuous medium properties of the material, and using the interface between blocks to represent the discontinuous medium properties; using nodal fracture mode and adaptive fracture mode to describe the process of internal crack interaction and penetration of masonry blocks; using a half-plane algorithm to quickly identify the three-dimensional block contact state; using a rigid body inelastic collision model with momentum conservation and energy loss to describe the contact and collision process between fragments; using a rebound coefficient to represent the energy loss during the fragment collision process; and using a complex block air resistance model considering shape and velocity to describe the process of fragments scattering and accumulating under high-speed airflow.

[0013] Furthermore, in the above technical solution, the parameters include gas source type, gas source location, gas source volume, gas source concentration, block type, block arrangement, joint thickness, joint strength, and wall thickness; the masonry wall breakage and scattering pattern includes the degree of damage and breakage of the masonry wall, the scattering distance of the broken blocks, and the accumulation range.

[0014] Furthermore, the method for establishing the masonry wall breakage and scattering assessment model in the above technical solution also includes the following steps: verifying the constructed masonry wall breakage and scattering assessment model through relevant accidents.

[0015] According to a second aspect of the present invention, the present invention provides a method for assessing the breakage and scattering of masonry walls based on a masonry wall breakage and scattering assessment model, comprising the following steps: obtaining the current state parameters of the masonry wall; and inputting the obtained state parameters into a pre-established masonry wall breakage and scattering assessment model to generate an assessment result, wherein the masonry wall breakage and scattering assessment model is established using any one of the above-described technical solutions.

[0016] Furthermore, in the above technical solution, the current state parameters of the masonry wall include gas source type, gas source location, gas source volume, gas source concentration, block type, block arrangement, joint thickness, joint strength, and wall thickness.

[0017] Furthermore, in the above technical solution, the evaluation results include the degree of damage and breakage of the masonry wall, the distance the broken pieces scatter, and the accumulation range.

[0018] Furthermore, the above technical solution for assessing the breakage and scattering of masonry walls also includes: determining the warning level based on the assessment results and issuing warning information corresponding to the warning level.

[0019] According to a third aspect of the present invention, the present invention provides a masonry wall breakage and scattering assessment system based on a masonry wall breakage and scattering assessment model, comprising: a data acquisition unit for acquiring current state parameters of the masonry wall; and an assessment unit for inputting the acquired state parameters into a pre-established masonry wall breakage and scattering assessment model to generate an assessment result, wherein the masonry wall breakage and scattering assessment model is established using any one of the above-described technical solutions.

[0020] Furthermore, in the above technical solution, the masonry wall breakage and scattering assessment system also includes: an early warning unit, which is used to determine the early warning level based on the assessment results and issue early warning information corresponding to the early warning level.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention employs a high-precision shock wave calculation method to accurately calculate the natural gas combustion and explosion process, uses a block-joint binary structural mechanical model to accurately characterize the dynamic mechanical behavior of masonry walls, uses the continuous-discontinuous element method to accurately simulate the damage and breakage of masonry walls, uses the submerged boundary method to achieve dynamic coupling between shock waves and masonry walls, uses a block size statistical algorithm to achieve statistical analysis of broken blocks, uses a BP neural network to establish the intrinsic relationship between input parameters and output quantities, and constructs a rapid assessment model for the degree of masonry wall breakage and scattering under shock waves through training with tens of thousands of calculation cases.

[0023] 2. This invention combines numerical simulation with neural networks, enabling rapid assessment of broken and scattered masonry walls, thus meeting the dual requirements of computational accuracy and efficiency.

[0024] 3. This invention is mainly used for assessing the safety of masonry structures under accidental gas combustion and explosion. It can quantitatively evaluate the damage and cracking of the wall and the scattering of debris after breakage, and can provide a basis for the scientific design of new masonry building structures and the safety assessment of old masonry building structures.

[0025] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, and to make the above and other objects, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating a method for establishing an assessment model for broken and scattered masonry walls according to an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of fracture description in CDEM according to an embodiment of the present invention.

[0028] Figure 3 This is a typical solution process for CDEM according to an embodiment of the present invention.

[0029] Figure 4 This is a schematic diagram of the adhesive surface spring arrangement according to an embodiment of the present invention.

[0030] Figure 5 This is a schematic diagram of a masonry wall breakage and scattering assessment system based on a masonry wall breakage and scattering assessment model according to an embodiment of the present invention. Detailed Implementation

[0031] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0032] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0033] In this document, for ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” “above,” “up,” etc., are used to describe the relationship of one element or feature to another element or feature in the accompanying drawings. It should be understood that spatial relative terms are intended to encompass different orientations of an object in use or operation, in addition to those depicted in the figures. For example, if an object in the figure is flipped, an element described as “below” or “under” another element or feature would be oriented “above” that element or feature. Thus, the exemplary term “below” can encompass both the downward and upward orientations. An object may also have other orientations (rotated 90 degrees or other orientations), and the spatial relative terms used herein should be interpreted accordingly.

[0034] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0035] refer to Figure 1As shown, the method for establishing a masonry wall breakage and scattering assessment model according to a specific embodiment of the present invention includes the following steps: constructing masonry samples composed of typical masonry blocks and a real masonry wall; conducting SHPB experiments on the masonry samples to obtain dynamic constitutive curves and fragment size distribution characteristics under different strain rates; conducting full-scale explosive impact tests on the real masonry wall to obtain the basic laws of masonry wall impact breakage and fragment scattering and accumulation; based on the data obtained from the SHPB experiment and the full-scale explosive impact test, constructing a block-joint binary structural mechanical model, including a block-masonry impact breakage mechanical model and a fragment scattering and accumulation mechanical model; introducing the block-joint binary structural mechanical model into the continuous-discontinuous element method (CDEM) to conduct numerical simulation of the masonry wall breakage and scattering law under different parameters; and inputting the numerical simulation results and the results of the full-scale explosive impact test into a BP neural network for machine learning to construct a masonry wall breakage and scattering assessment model.

[0036] Furthermore, in one or more exemplary embodiments of the present invention, sintered bricks, ordinary concrete blocks and aerated concrete blocks can be selected as typical blocks to construct masonry samples and real masonry walls.

[0037] Furthermore, in one or more exemplary embodiments of the present invention, the continuous-discontinuous element method (CDEM), combined with numerical methods for the propagation process of gas cloud combustion and explosion and a three-dimensional full-size masonry wall model, is used to conduct numerical simulations of the wall fragmentation and scattering behavior under different parameter controls. The block-joint binary structural mechanical model is a mechanical model describing the fracture, fragmentation, movement, and accumulation of masonry and joints under the control of a series of mechanical equations. The three-dimensional full-size masonry wall model refers to a geometric model composed of many blocks and joints; describing the dynamic behavior of these block-joint assemblies requires the use of the block-joint binary structural mechanical model. The wall damage is mainly caused by the impact of the explosion shock wave; the main function of the numerical simulation of the gas cloud combustion and explosion propagation process is to accurately calculate the magnitude and duration of the impact force acting on the wall.

[0038] Furthermore, in one or more exemplary embodiments of the present invention, in order to improve the numerical simulation accuracy of the gas cloud combustion and explosion propagation process, a second-order finite volume method is used for high-precision calculation and analysis of gas flow; a method combining splitting operators and relaxation time steps is used to process the chemical reaction source term to accurately simulate the rigidity problem of chemical reaction; the Kurganov algorithm, the MUSCL method, and second-order and third-order Runge-Kutta methods are used to ensure that the spatiotemporal calculation accuracy is at least second-order; the submerged boundary method is used to achieve high-precision calculation of gas-solid coupling; and a multi-core CPU parallel strategy is adopted to achieve efficient simulation of the gas combustion and explosion process.

[0039] Furthermore, in one or more exemplary embodiments of the present invention, the construction of the block-joint binary structural mechanical model includes a quantitative description of the wall fracture process under impact load, and a quantitative description of the dispersion and accumulation process of the broken block group under high-speed airflow. To accurately describe the wall fracture process, it is necessary to fully understand the dynamic mechanical effects of the masonry wall. Specifically, in-depth analysis is conducted on data from SHPB experiments and real-scale wall impact fracture experiments, focusing on the dynamic stress-strain relationship of the blocks and masonry structure under different strain rates, as well as the influence of strain rate on the size of the broken blocks. Through in-depth analysis of experimental data, combined with the basic theories of impact dynamics and fracture mechanics, a block damage and fracture constitutive model considering the strain rate effect and a joint fracture friction constitutive model are constructed.

[0040] Furthermore, in one or more exemplary embodiments of the present invention, in order to accurately describe the scattering and accumulation process of broken blocks, constructing a mechanical model of the scattering and accumulation of broken block groups includes: acquiring high-speed photography data of the actual scattering process of masonry walls; analyzing the high-speed photography data to obtain the spatiotemporal motion law of masonry fragments under airflow; then conducting CFD numerical simulations of a single complex-shaped block at different flow velocities to comprehensively establish the correspondence between gas velocity, broken block shape, and broken block resistance, forming calculation formulas for the force and torque of broken blocks considering the shape and velocity of broken blocks, and finally constructing a mechanical model of the scattering and accumulation of broken block groups.

[0041] Furthermore, in one or more exemplary embodiments of the present invention, a binary structural mechanical model of masonry blocks and joints is introduced into the continuous-discontinuous element method to numerically simulate the fragmentation and scattering law of masonry walls under different parameters. Exemplarily, blocks are used to represent the continuous medium properties of the material, and interfaces between blocks are used to represent the discontinuous medium properties; nodal fracture mode and adaptive fracture mode are used to describe the process of internal crack interaction and penetration within the blocks; a half-plane algorithm is used for rapid identification of the three-dimensional block contact state; a rigid inelastic collision model with momentum conservation and energy loss is used to describe the contact and collision process between fragments; a rebound coefficient is used to characterize the energy loss during the fragment collision process; and a complex block air resistance model considering shape and velocity is used to describe the process of fragment scattering and accumulating under high-speed airflow.

[0042] Furthermore, in one or more exemplary embodiments of the present invention, the assessment model for masonry wall breakage and scattering is mainly used to answer the questions of what kind of gas source conditions, what kind of wall structure, will produce what kind of broken pieces, and how far the broken pieces will scatter. Exemplarily, more than ten thousand numerical simulations under different parameters are conducted to analyze the influence of parameters such as gas source type, gas source location, gas source volume, gas source concentration, block type, block arrangement, joint thickness, joint strength, and wall thickness on the degree of damage and breakage of the masonry wall, the scattering distance of the broken pieces, and the accumulation range. Using a BP neural network algorithm, an implicit functional relationship between the input parameters and the output results is formed, resulting in a masonry wall breakage and scattering assessment model that highly integrates numerical simulation and neural network.

[0043] Furthermore, in one or more exemplary embodiments of the present invention, the method for establishing a masonry wall breakage and scattering assessment model may also include verifying the constructed masonry wall breakage and scattering assessment model through relevant domestic and international accidents.

[0044] The method for assessing the breakage and scattering of masonry walls based on a masonry wall breakage and scattering assessment model according to a specific embodiment of the present invention includes the following steps: obtaining the current state parameters of the masonry wall; and inputting the obtained state parameters into a pre-established masonry wall breakage and scattering assessment model to generate an assessment result, wherein the masonry wall breakage and scattering assessment model is established using any one of the methods described above.

[0045] Furthermore, in one or more exemplary embodiments of the present invention, the current state parameters of the masonry wall include gas source type, gas source location, gas source volume, gas source concentration, block type, block arrangement, joint thickness, joint strength, and wall thickness, which are used as model inputs. Furthermore, in one or more exemplary embodiments of the present invention, the evaluation results include the degree of damage and fragmentation of the masonry wall, the distance the fragmented blocks scatter, and the accumulation range.

[0046] Furthermore, in one or more exemplary embodiments of the present invention, the method for assessing the breakage and scattering of masonry walls further includes: determining a warning level based on the assessment results, and issuing a warning message corresponding to the warning level.

[0047] The following describes in more detail the method, system and evaluation model establishment method for assessing broken masonry walls, and the present invention through specific embodiments. It should be understood that the embodiments are merely exemplary and the present invention is not limited thereto.

[0048] Example 1

[0049] This embodiment illustrates the core algorithm of the chemical reaction fluid part in the method for establishing a masonry wall breakage and scattering assessment model.

[0050] First, a mathematical and mechanical model of compressible chemical reaction fluid dynamics is established, as shown in equations (1-1) and (1-2). The compressible flow adopts the Euler equation (ignoring the influence of viscosity, since the influence of viscosity is generally very small and can be ignored in large-scale shock waves), and the chemical reaction flow considers a single-step reaction model of combustibles.

[0051]

[0052]

[0053] Among them, U=(ρ,ρu,ρv,ρw,E,ρz i ) T ,

[0054] F=(ρu,ρu 2 +p,ρuv,ρuw,u(E+p),ρuz i ) T ,

[0055] G=(ρv,ρuv,ρv 2 +p,ρvw,v(E+p),ρvz i ) T ,

[0056] H=(ρw,ρuw,ρvw,ρw 2 +p,w(E+p),ρwz i ) T , which represent the conserved variables and the flux in the three directions, respectively.

[0057] S=(0,0,0,0,0,ω i ) T It mainly characterizes the source terms of chemical reactions.

[0058] The mathematical characteristics of equation (1-1) are shown in equation (1-3). The Euler equation is a strictly nonlinear hyperbolic partial differential equation, where the eigenvalues ​​of matrix A are uc,u,u,u,u,u+c, where c is the speed of sound. Under high-speed flow conditions, shock waves are generated. As these shock waves propagate towards the combustible material region, they induce rapid chemical reactions, driving deflagration into detonation. Therefore, the computational model needs to be capable of capturing shock waves and handling rapid chemical reactions.

[0059]

[0060] The governing equations (1-1) are solved using the finite volume method based on orthogonal grids. All physical quantities are defined at the grid center, and two layers of virtual grids are added around the perimeter to handle boundary conditions. The grid numbers range from -1 to Icells and -1 to Jcells, where (1, Icells) * (1, Jcells) is the computational domain. The physical quantities stored at the grid center include state variables such as density, velocity, pressure, temperature, and chemical reaction progress.

[0061] High-resolution computational methods are employed for shock wave capture, and operator splitting methods are used for detailed chemical reaction calculations. For some large-scale, fast, and efficient computational problems, a projection method (time-step relaxation) is used to handle time-step rigidity problems. Structured finite volume elements are used to construct the simulation domain; these elements are simple to generate, convenient for handling solid structures, and highly suitable for high-performance computing. The values ​​of field variables are defined as the average values ​​of physical quantities across the mesh, such as... The field variables need to be updated through the flux difference at the grid boundary and the chemical reaction steps.

[0062] The numerical calculation format is shown in equation (1-4).

[0063]

[0064] in, and Let S be the numerical flux at the grid boundary, and S be the chemical reaction source term. Flux construction is the core module of the entire numerical simulation, requiring special processing to capture the shock wave. The Kurganov approximate Riemann solver is used for numerical flux calculation. The MUSCL method is employed spatially to achieve second-order spatial accuracy. Second-order and third-order Runge-Kutta methods are used for time discretization to ensure at least second-order accuracy in the time direction. The basic flux construction formula is shown in equation (1-5), where... This represents the flux value at the boundary of a cell in any direction.

[0065]

[0066] Chemical reactions typically occur on much smaller timescales than flow phenomena, and are thus termed rigid problems, requiring specialized multi-step iterative calculations. We employ a projection method to relax and calculate chemical reactions, achieving the goal of accurately handling chemical reactions on large scales.

[0067] For fixed structures, a novel solid boundary treatment scheme (red-black mesh scheme) efficiently handles the structure generation problem. A special spatial field variable construction method is used for the boundary conditions of the fluid and solid meshes, establishing the field variable distribution of the fluid mesh near the solid. This achieves the effect of handling fluid motion and solid interaction within a unified framework. The force distribution on the solid surface is obtained by interpolation of the flow field distribution and transmitted to the solid calculation module. The solid mesh portion is handled through parametric methods or user-defined methods, proving to be an efficient processing scheme.

[0068] Example 2

[0069] This embodiment illustrates the solid fracture solution algorithm in the method for establishing a masonry wall breakage and scattering assessment model.

[0070] The continuous-discontinuous element method (CDEM) was used to simulate and analyze the fracture process of masonry walls. Each element in the CDEM has independent nodes and faces, and adjacent elements are connected by a bonding interface. The elements represent the continuous medium properties of the material, such as elasticity, plasticity, and damage, while the bonding interface represents the discontinuous medium properties, such as fracture slip. The fracture description in the CDEM is as follows: Figure 2 As shown.

[0071] CDEM employs an explicit algorithm based on an incremental approach to solve dynamic problems, mainly comprising two parts: calculation of nodal resultant forces and calculation of nodal motions. The formula for calculating nodal resultant forces is:

[0072] F = F E +F e +F c +F r +F l (2-1)

[0073] In the formula: F is the resultant force at the nodes; F E For the nodal external force; F e Nodal forces contributing to the deformation of finite element elements; F c F represents the component of the contact force at the node. r F is the nodal damping force contributed by Rayleigh damping at the node. l This represents the local damping force at the node.

[0074] The formula for calculating nodal motion is:

[0075]

[0076] In the formula: a is the nodal acceleration; v is the nodal velocity; Δu is the nodal displacement increment; u is the nodal displacement; m is the nodal mass; Δt is the calculation time step.

[0077] The alternating calculation based on equations (2-1) and (2-2) constitutes the explicit solution process. A typical solution flow for CDEM is as follows: Figure 3 As shown.

[0078] Masonry structures are binary composites composed of blocks and mortar, and their dynamic response under shock wave action is extremely complex. To accurately characterize the damage and fracture process of masonry walls under impact loads, the HJC model and fracture energy model are introduced into CDEM. Solid elements are described using the HJC model, and the bond interface is described using the fracture energy model.

[0079] The HJC model is mainly used to describe the behavior of masonry elements under large strain, high strain rate and high pressure, and takes into account the impact of void collapse inside the masonry.

[0080] The expression for the yield stress in the HJC model is:

[0081]

[0082] In the formula, Where p is the normalized yield stress, D is the damage factor, and p is the normalized yield stress. * For normalization pressure; σ is the dimensionless equivalent strain rate; A is the normalized cohesive strength of the material; B is the normalized pressure hardening coefficient; n is the pressure hardening exponent; and C is the strain rate coefficient. In equation (2-3), σ... * With p * It increases infinitely as σ increases, but in reality σ * There exists a limit value, therefore a normalized maximum intensity S is introduced. max .

[0083] p * and The expression is

[0084]

[0085] Where, σ y For yield stress, f c ' is the unconfined compressive strength, p is the actual pressure, For the true strain rate, The reference strain rate is used.

[0086] The state equation of the HJC model can be divided into three stages: the linear elastic stage, the transition stage, and the compaction stage.

[0087] When p < p crush time (p) crush (This refers to the pressure at which the cavity collapses), and the material is in the elastic stage; the pressure p can be expressed as...

[0088] p = K elastic μ (2-5)

[0089] K elastic =p crush / μ crush Let μ be the elastic bulk modulus, and μ be the volumetric strain. crush The elastic limit volumetric strain is given.

[0090] When p crush ≤p≤p lock time (p) lock (The pressure at which all pores completely collapse), the material is in a transitional phase, the pores gradually collapse, and finally compressed to complete compaction. The relationship between hydrostatic pressure and volumetric strain is:

[0091]

[0092] Among them, K tran p is the bulk modulus of the transition section. max μ is the maximum pressure reached before unloading. max The maximum volumetric strain reached before unloading is given by F, the compressibility coefficient, and K1, the bulk modulus constant.

[0093] When p > p lock At this time, the material is in a fully compacted state, and its pressure-volume relationship is set as a cubic polynomial, which can be expressed as:

[0094]

[0095] Where K1, K2, and K3 are bulk modulus constants. This is the equivalent volumetric strain.

[0096] A normal spring and a tangential spring are introduced at the bonding interface, and a fracture energy model is applied to the springs to simulate the fracture process at the contact surface. (Refer to...) Figure 4 As shown.

[0097] First, the incremental method is used to calculate the normal and tangential contact forces at the next time step of the virtual interface.

[0098]

[0099] Among them, F n F s For the normal and tangential contact forces, k n k s A represents the normal and tangential contact stiffness over a single surface area (unit: Pa / m). c Let Δdu be the area of ​​the virtual interface. n Δdu s This represents the relative displacement increments in the normal and tangential directions.

[0100] Equation (2-9) is used to determine tensile failure, correct the normal contact force and tensile strength, and provide...

[0101]

[0102] Where, σ t0 σ t (t0) and σ t (t1) represents the tensile strength on the virtual interface at the initial time, the current time, and the next time, Δu n G represents the relative displacement in the normal direction on the virtual interface at the current moment. ft Tensile fracture energy (unit: Pa·m).

[0103] Equation (2-10) is used to determine shear failure and correct tangential contact force and cohesion.

[0104]

[0105] Where φ is the internal friction angle of the virtual interface, c0, c(t0), and c(t1) are the cohesive forces on the virtual interface at the initial moment, the current moment, and the next moment, respectively, and Δu s G represents the tangential relative displacement on the virtual interface at the current moment. fs Shear fracture energy (unit: Pa·m).

[0106] When the tensile strength or cohesion on the bonding surface drops to 0 at a certain moment, the bonding surface will then break.

[0107] Example 3

[0108] refer to Figure 5 As shown, the masonry wall breakage and scattering assessment system based on the masonry wall breakage and scattering assessment model according to a specific embodiment of the present invention includes: a data acquisition unit 10, which is used to acquire the current state parameters of the masonry wall; an assessment unit 20, which is used to input the acquired state parameters into a pre-established masonry wall breakage and scattering assessment model to generate an assessment result, wherein the masonry wall breakage and scattering assessment model is established using any one of the methods described above; and an early warning unit 30, which is used to determine the early warning level based on the assessment result and issue an early warning message corresponding to the early warning level.

[0109] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. Any simple modifications, equivalent changes, and alterations made to the foregoing exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. A method for establishing an assessment model for broken and scattered masonry walls, characterized in that, Includes the following steps: Construct masonry specimens and real masonry walls composed of typical masonry blocks; SHPB experiments were conducted on masonry specimens to obtain dynamic constitutive curves and fragmentation distribution characteristics under different strain rates. Full-scale explosive impact tests were conducted on real masonry walls to obtain the basic laws governing the impact fracture and fragmentation of masonry walls. Based on data obtained from SHPB experiments and full-scale explosive impact tests, a binary structural mechanical model of block-joint structure was constructed, including a block-masonry impact crushing mechanical model and a crushed block group dispersion and accumulation mechanical model. The block-joint binary structural mechanical model was introduced into the continuous-discontinuous element method to conduct numerical simulation of the fracture and scattering law of masonry wall under different parameters. as well as Numerical simulation results and full-scale explosion impact test results are input into a BP neural network for machine learning to construct an assessment model for masonry wall breakage and scattering. The numerical simulation was conducted by combining numerical methods for the propagation process of gas cloud combustion and explosion with a three-dimensional full-size masonry wall model. The dynamic constitutive curves under different strain rates include the block damage and breakage constitutive curve and the fracture friction constitutive curve of the joint. The construction of the mechanical model for the dispersion and accumulation of the broken block group includes: collecting high-speed photography data of the actual process of masonry wall dispersion; analyzing the high-speed photography data to obtain the spatiotemporal motion law of masonry fragments under airflow; and conducting CFD numerical simulation of a single complex-shaped block under different flow velocities to establish the correspondence between gas velocity, broken block shape, and broken block resistance, and to form calculation formulas for the force and torque of the broken block. Introducing a mechanical model into the continuous-discontinuous element method, numerical simulations of the fragmentation and scattering behavior of masonry walls under different parameters are conducted. This includes: using blocks to represent the continuous medium properties of the material, and using interfaces between blocks to represent the discontinuous medium properties; employing nodal fracture mode and adaptive fracture mode to describe the process of internal crack interconnection within the blocks; using a half-plane algorithm for rapid identification of three-dimensional block contact states; describing the contact and collision process between fragments using a rigid inelastic collision model with momentum conservation and energy loss; using a rebound coefficient to represent energy loss during the fragment collision process; and using a complex block air resistance model considering shape and velocity to describe the process of fragment scattering and accumulating under high-speed airflow.

2. The method for establishing a masonry wall breakage and scattering assessment model according to claim 1, characterized in that, The typical blocks include sintered brick blocks, ordinary concrete blocks, and aerated concrete blocks.

3. The method for establishing a masonry wall breakage and scattering assessment model according to claim 1, characterized in that, When performing numerical simulation of the propagation process of gas cloud combustion and explosion, the second-order finite volume method is used for gas flow calculation and analysis; the chemical reaction source term is handled by combining the splitting operator and the relaxation time step to simulate the rigidity problem of the chemical reaction; the Kurganov algorithm, the MUSCL method, and the second-order and third-order Runge-Kutta methods are used to ensure that the spatiotemporal calculation accuracy is at least second-order; the submerged boundary method is used to calculate the gas-solid coupling effect; and a multi-core CPU parallel strategy is adopted.

4. The method for establishing a masonry wall breakage and scattering assessment model according to claim 1, characterized in that, The parameters include gas source type, gas source location, gas source volume, gas source concentration, block type, block arrangement, joint thickness, joint strength, and wall thickness; the masonry wall breakage and scattering pattern includes the degree of damage and breakage of the masonry wall, the scattering distance of the broken pieces, and the accumulation range.

5. The method for establishing a masonry wall breakage and scattering assessment model according to claim 1, characterized in that, It also includes the following steps: verifying the constructed masonry wall breakage and scattering assessment model through relevant accidents.

6. A method for assessing the fragmentation and scattering of masonry walls based on a masonry wall fragmentation and scattering assessment model, characterized in that, Includes the following steps: Obtain the current state parameters of the masonry wall; and The acquired state parameters are input into a pre-established masonry wall breakage and scattering assessment model to generate assessment results. The masonry wall breakage and scattering assessment model is established using the method described in any one of claims 1 to 5.

7. The method for assessing the breakage and scattering of masonry walls according to claim 6, characterized in that, The current state parameters of the masonry wall include the location of the gas source, the volume of the gas source, the type of masonry block, the strength of the mortar joint, and the wall thickness.

8. The method for assessing the breakage and scattering of masonry walls according to claim 6, characterized in that, The assessment results include the degree of damage and breakage of the masonry wall, the distance the broken pieces scattered, and the accumulation range.

9. The method for assessing the breakage and scattering of masonry walls according to claim 6, characterized in that, Also includes: The warning level is determined based on the assessment results, and a warning message corresponding to the warning level is issued.

10. A masonry wall breakage and scattering assessment system based on a masonry wall breakage and scattering assessment model, characterized in that, include: The data acquisition unit is used to acquire the current state parameters of the masonry wall. as well as The evaluation unit is used to input the acquired state parameters into a pre-established masonry wall breakage and scattering evaluation model to generate evaluation results. The masonry wall breakage and scattering assessment model is established using the method described in any one of claims 1 to 5.

11. The masonry wall breakage and scattering assessment system according to claim 10, characterized in that, Also includes: An early warning unit is used to determine the early warning level based on the assessment results and issue early warning information corresponding to the early warning level.

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