Method for determining interface blasting shock dynamics performance of Ming and Qing dynasty ancient building brick masonry structure

Abstract

The application provides a method for determining the blasting impact dynamics performance of a brick masonry structure interface of a Ming and Qing dynasty ancient building, and relates to the field of ancient building dynamics performance, and comprises the following steps: selecting bricks, and respectively preparing brick-mortar composite interface samples by using ordinary mortar, sticky rice mortar and tung oil mortar; establishing initial physical and mechanical state benchmark parameters; constructing a split Hopkinson pressure bar impact test system; performing impact loading tests on the interface samples in multiple impact speed modes according to each loading configuration, and synchronously collecting three-wave strain signals and high-speed photographic images of each working condition; calculating stress wave transmission coefficients, reflection coefficients, incident energy, reflected energy and transmitted energy, and determining the interface energy dissipation of each working condition; establishing a strain rate related dynamic strength model; and determining the interface damage critical strength threshold based on the dynamic peak stress. The application realizes systematic determination of the blasting impact dynamics performance of the brick masonry structure interface of the Ming and Qing dynasty ancient building.

Description

Technical Field

[0001] This invention relates to the field of ancient building dynamics performance technology, and in particular to a method for determining the interface blasting impact dynamics performance of brick masonry structures in Ming and Qing dynasty ancient buildings. Background Technology

[0002] The brick masonry structures of Ming and Qing dynasty buildings were generally constructed using blue bricks and traditional cementing materials such as glutinous rice mortar and tung oil mortar. The brick-mortar interface is the weakest link in the structural system in terms of mechanical properties, and its dynamic response characteristics directly affect the overall safety of the structure under impact loads. With the continuous advancement of urban underground engineering construction, the threat of blasting vibrations to nearby historical buildings is becoming increasingly serious. However, the current blasting vibration safety regulations are mainly formulated for modern concrete structures, and the material dynamic performance parameters used differ significantly from the actual conditions of Ming and Qing dynasty brick masonry structures. The regulations are seriously inadequate in their applicability to Ming and Qing dynasty buildings and cannot provide reliable parameter basis for the safety control of blasting construction of nearby historical buildings.

[0003] In addition, Ming and Qing dynasty buildings have been exposed to the natural environment for a long time. The brick-mortar interface is subjected to the combined effects of environmental factors such as acid rain erosion, salt corrosion and wet-dry cycles, and their mechanical properties degrade to varying degrees as their service life increases.

[0004] Chinese invention patent application number 202210727187.X discloses a method and system for foundation pit blasting excavation. This method establishes a numerical model for foundation pit blasting, combines a simplified model of the blast load with a vibration velocity attenuation fitting formula, analyzes vibration velocity attenuation data at multiple measuring points under different blasting methods, and selects between conventional blasting, shaped charge blasting, or static excavation schemes based on this. Furthermore, it optimizes blasting construction parameters using damage cloud maps. However, its analysis object is rock media, and the safety evaluation index used is based on macroscopic vibration velocity, without considering the dynamic performance parameters of adjacent building structural materials. Therefore, it cannot specifically characterize the impact damage mechanism and critical damage threshold of the brick masonry structure interface of Ming and Qing dynasty ancient buildings with special material compositions. Summary of the Invention

[0005] In view of this, the present invention provides a method for determining the dynamic performance of the interface of brick masonry structure in Ming and Qing dynasty ancient buildings under blasting impact, in order to solve the problem that there is no systematic characterization method for the dynamic performance of the brick-mortar interface of Ming and Qing dynasty ancient buildings under blasting impact in the existing technology, fill the data gap in the current specifications on the dynamic performance of traditional masonry interfaces, and realize the systematic determination of the dynamic performance of the interface of brick masonry structure in Ming and Qing dynasty ancient buildings under blasting impact.

[0006] The technical solution of this invention is implemented as follows: On one hand, this invention provides a method for determining the interface blasting impact dynamics properties of brick masonry structures in Ming and Qing dynasty ancient buildings, including: S1. Based on the typical specifications and mineral composition characteristics of Ming and Qing dynasty ancient building bricks, bricks were selected, and brick-mortar composite interface samples were prepared using ordinary mortar, glutinous rice mortar, and tung oil mortar, respectively. Among them, aging group samples were prepared for the brick-glutinous rice mortar interface, and the aging group samples were subjected to aging treatment. The wave velocity, density, elastic modulus, and Poisson's ratio of all interface samples were measured to establish the initial physical and mechanical state reference parameters. S2. Using a PMMA rod as the incident rod and the transmission rod, a spindle-shaped bullet is used to shape the incident wave waveform to construct a split Hopkinson bar impact test system. Based on the split Hopkinson bar impact test system, multiple impact velocities are used to carry out impact loading tests on the interface sample according to each loading configuration, and the three-wave strain signals and high-speed photographic images of each working condition are collected simultaneously. S3. Based on the three-wave strain signal, calculate the stress wave transmission coefficient and reflection coefficient of each working condition interface; calculate the incident energy, reflected energy and transmitted energy of each working condition, and determine the energy dissipation of each working condition interface. S4. Obtain the dynamic stress-strain relationship according to the dynamic stress-strain calculation method corresponding to each loading configuration, extract the dynamic peak stress, peak strain and dynamic elastic modulus, and establish a strain rate-related dynamic strength model; based on high-speed photography images and combined with the fracture morphology of the interface specimen after impact, identify the interface failure mode; using dynamic peak stress, peak strain, dynamic elastic modulus, dynamic strength model and interface energy dissipation as characterization indicators, and using the initial physical and mechanical state reference parameters as the benchmark, summarize the dynamic parameters under each loading configuration to form a set of interface dynamic performance parameters, and determine the critical strength threshold of interface damage based on the dynamic peak stress.

[0007] Based on the above technical solutions, preferably, the interface specimen includes four loading configurations: compression, tension, shear, and a combination of compression and shear. The compression configuration specimen has a cross-sectional diameter and height of 50mm, with bricks at both ends each having a thickness of 20mm and a mortar layer thickness of 10mm. The tension configuration specimen has a cross-sectional diameter of 50mm, a height of 20mm, and a mortar layer thickness of 10mm. The shear configuration specimen has a cross-sectional diameter and height of 50mm, a mortar layer thickness of 10mm, and a reserved gap of 5mm. The combination of compression and shear configuration specimen has a cross-sectional diameter and height of 50mm, with bricks at both ends having heights of 10mm and 20mm respectively, a mortar layer thickness of 10mm, and a brick surface inclination angle of 21.8°.

[0008] Based on the above technical solutions, the preferred aging treatment includes a combination of wet-dry cycle aging and salt corrosion aging treatment.

[0009] Based on the above technical solutions, preferably, step S2 specifically includes: PMMA was selected to make the incident rod and the transmission rod. Waveform-shaping bullets were used to shape the incident wave to construct a split Hopkinson pressure bar system. The split Hopkinson pressure bar system includes a pneumatic impact device, an incident rod, a transmission rod, an energy absorption device, and a high-speed data acquisition system. Based on the one-dimensional stress wave propagation theory, strain gauges are arranged on the incident rod and the transmission rod respectively to collect the incident wave strain, reflected wave strain and transmitted wave strain. Using multiple impact velocities as loading intensity variables and four loading configurations as loading mode variables, full-condition impact loading was sequentially applied to three types of mortar interface control groups and brick-glutinous rice mortar aging groups. Synchronous acquisition throughout the entire impact loading process yielded three-wave strain signals and high-speed photographic images. The three-wave strain signals included incident wave strain signal, reflected wave strain signal, and transmitted wave strain signal.

[0010] Based on the above technical solutions, preferably, the impact loading condition is as follows: Using three impact velocities of 3.0 m / s, 3.5 m / s, and 4.0 m / s as loading intensity variables, and compression, tension, shear, and a combination of compression and shear as loading configuration variables, the interface samples of three control groups (brick-ordinary mortar, brick-glutinous rice mortar, and brick-tung oil mortar) were subjected to full-condition combined impact loading at three impact velocities in sequence under four loading configurations. The aged brick-glutinous rice mortar samples were subjected to impact loading at a single impact velocity of 3.5 m / s under the four loading configurations in sequence.

[0011] Based on the above technical solutions, preferably, step S3 specifically includes: Based on the strain of the incident wave, reflected wave, and transmitted wave, the stress wave transmission coefficient at the interface is calculated under various working conditions. With reflection coefficient The results were obtained under different mortar types, aging states, and impact velocities. and The variation law of stress wave attenuation under the condition of impedance mismatch at the brick-mortar interface; Based on three-wave strain data, the incident energy, reflected energy, and transmitted energy under each working condition were calculated to determine the interface energy dissipation and obtain comparative characteristics of interface energy dissipation under different mortar types and aging states.

[0012] Based on the above technical solutions, the preferred formula for calculating the interface energy dissipation is:

[0013]

[0014]

[0015]

[0016] in, This represents the amount of energy dissipated at the interface. Indicates incident energy, Indicates reflected energy. Indicates transmission energy. Indicates the elastic modulus of the rod. Indicates the cross-sectional area of ​​the rod. This indicates the propagation speed of stress waves in the rod. Indicates the duration of stress wave action. Indicates the strain of the incident wave. Indicates the strain of the reflected wave. Indicates the strain of the transmitted wave. Represents the incident wave stress time history. Represents the stress time history of the reflected wave. This represents the stress time history of the transmitted wave.

[0017] Based on the above technical solutions, preferably, step S4 specifically includes: Dynamic stress-strain curves were calculated for each loading condition using the dynamic stress-strain calculation method corresponding to each loading configuration, and the dynamic peak stress for each loading condition was extracted. Peak strain and dynamic elastic modulus ; Power function fitting was performed with the strain rate corresponding to the three impact velocities as the abscissa and the dynamic strength value corresponding to each working condition under each loading configuration as the ordinate to establish dynamic enhancement factor models for various interfaces; among them, the compression and tension configurations exhibit positive strain rate effects, while the shear and compression-shear composite configurations exhibit negative strain rate effects. Based on the dynamic stress-strain curves of the brick-glutinous rice mortar control group and the aging group, and combined with the initial physical and mechanical state reference parameters, the stress-strain curves before and after aging under various loading configurations were compared. and The change in aging dynamic strength degradation coefficient Quantitatively characterize the degree of dynamic strength degradation of the interface caused by aging; By analyzing high-speed photographic images frame by frame, the crack initiation location and propagation path are determined. Combined with macroscopic observation of the fracture morphology of the interface sample after impact, the interface failure mode is determined, and the correspondence between the interface failure mode and mortar type, aging state and impact velocity is established. by , , Using the dynamic enhancement factor model as the strength-deformation dimension, the interface energy dissipation as the energy dimension, and the comparison parameters before and after aging as the aging state dimension, a set of dynamic performance parameters for the interface of brick masonry structure of Ming and Qing ancient buildings is constructed. Under various loading configurations of different mortar types As the critical damage intensity threshold for the corresponding interface, a differentiated damage criterion considering aging state is established.

[0018] Based on the above technical solutions, the preferred interface failure modes include mortar cohesive failure, interface bonding failure, brick cracking failure, and mixed failure.

[0019] More preferably, the establishment of the differentiated interface dynamic intensity damage criterion specifically includes: Obtain the starting stress of the nonlinear segment of the dynamic stress-strain curve for each working condition. Define the strength damage initiation coefficient ;in, Represents the stress in the nonlinear stage. Indicates dynamic peak stress; Summary of various mortar types and loading configurations As the critical damage strength threshold for the corresponding interface, the brick-glutinous rice mortar control group under each loading configuration was used. As a benchmark for the critical strength threshold in the unaged state, the corresponding working conditions of the aging group are used. The critical threshold for aging state correction is used as the difference between the non-aging critical threshold and the aging correction critical threshold as the amount of reduction in resistance to interfacial damage caused by aging. Set the dynamic stress requirement value for the interface, compare the critical threshold of the control group with that of the unaged component and the critical threshold of the aging group with that of the aged component, and determine that there is a risk of damage to the interface when the dynamic stress requirement value exceeds the corresponding threshold.

[0020] The present invention has the following advantages over the prior art: (1) By constructing a complete interface dynamic performance parameter system and dynamic strength damage criterion through interface sample preparation and initial state characterization, split Hopkinson bar impact test, interface stress wave propagation and energy dissipation analysis, interface dynamic response parameter extraction and damage criterion, the dynamic performance of interface blasting impact dynamics of brick masonry structure of Ming and Qing ancient buildings was systematically determined.

[0021] (2) For the first time, impact tests were conducted on the interface systems of traditional cementitious materials such as glutinous rice mortar and tung oil mortar under four loading modes: compression, tension, shear and combined compression and shear. A complete set of interface dynamic performance parameters covering dynamic peak stress, peak strain, dynamic elastic modulus and strain rate-related dynamic strength models was established, filling the data gap in the current specifications on the dynamic performance parameters of traditional masonry interfaces, and providing a direct and usable experimental basis for the establishment of dynamic analysis models for ancient building structures. (3) An aging control group was specially set up for the brick-glutinous rice mortar interface. The long-term service deterioration state of the brick masonry structure of Ming and Qing ancient buildings was simulated by dry and wet cycle and salt corrosion composite aging treatment. The differential deterioration law of interface dynamic strength and deformation capacity under four loading modes was quantitatively revealed. The degree of interface dynamic performance degradation caused by aging was quantitatively characterized by the aging dynamic strength deterioration coefficient. This solved the technical problem that existing studies could not distinguish the difference in dynamic performance between newly made components and aged components. (4) By introducing the strength damage initiation coefficient, the inherent mechanical characteristics of the Ming and Qing ancient masonry interface with extremely short elastic response segment and nonlinear deformation throughout the entire bearing process are revealed. The dynamic peak stress is used as the critical strength threshold for the initiation of interface damage and its rational basis is given. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a flowchart illustrating a method for determining the interface blasting impact dynamics of brick masonry structures in Ming and Qing dynasty ancient buildings, according to the present invention. Figure 2 This is a schematic diagram of the interface sample structure for a method of determining the interface blasting impact dynamics of brick masonry structures in Ming and Qing dynasty ancient buildings according to the present invention. Figure 3 The SHPB test system and stress wave propagation principle diagram are for the method of determining the interface blasting impact dynamics of brick masonry structure in Ming and Qing dynasty ancient buildings according to the present invention. Figure 4 This is a schematic diagram of the stress wave time history curve and energy distribution of a method for determining the interface blasting impact dynamics of brick masonry structures in Ming and Qing dynasty ancient buildings, according to the present invention. Figure 5 This is a schematic diagram illustrating the damage evolution and safety threshold determination of a method for determining the interface blasting impact dynamics of brick masonry structures in Ming and Qing dynasty ancient buildings, as described in this invention. Figure 6This is a schematic diagram of the brick-mortar interface strain rate versus dynamic strength fitting curve, which is part of the method for determining the interface blasting impact dynamics of brick masonry structures in Ming and Qing dynasty buildings according to the present invention. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] like Figure 1 As shown, this invention provides a method for determining the blasting impact dynamics properties of the interface of brick masonry structures in Ming and Qing dynasty ancient buildings, comprising: S1. Based on the typical specifications and mineral composition characteristics of Ming and Qing dynasty ancient building bricks, bricks were selected, and brick-mortar composite interface samples were prepared using ordinary mortar, glutinous rice mortar, and tung oil mortar, respectively. Among them, aging group samples were prepared for the brick-glutinous rice mortar interface, and the aging group samples were subjected to aging treatment. The wave velocity, density, elastic modulus, and Poisson's ratio of all interface samples were measured to establish the initial physical and mechanical state reference parameters. like Figure 2 As shown, Figure 2 (a) in the diagram is a schematic of the compression loading configuration. Figure 2 (b) in the diagram is a schematic diagram of the tensile loading configuration. Figure 2 (c) in the diagram is a schematic diagram of the shear loading configuration. Figure 2 (d) in the figure is a schematic diagram of the compression-shear loading configuration. The interface specimens include four loading configurations: compression, tension, shear, and compression-shear combined. The compression configuration specimen has a cross-sectional diameter and height of 50 mm, a brick thickness of 20 mm at each end, and a mortar layer thickness of 10 mm in the middle. The tension configuration specimen has a cross-sectional diameter of 50 mm, a height of 20 mm, and a mortar layer thickness of 10 mm in the middle. The shear configuration specimen has a cross-sectional diameter and height of 50 mm, a mortar layer thickness of 10 mm in the middle, and a reserved gap of 5 mm. The compression-shear combined configuration specimen has a cross-sectional diameter and height of 50 mm, a brick height of 10 mm and 20 mm at each end, a mortar layer thickness of 10 mm in the middle, and a brick surface inclination angle of 21.8°.

[0026] Understandably, the sample preparation process, through the systematic preparation of three types of interface samples—ordinary mortar, glutinous rice mortar (including an aging control group), and tung oil mortar—ensures that the test system effectively simulates the actual service condition of the brick masonry structure of ancient Ming and Qing dynasty buildings.

[0027] In one embodiment of the invention, sintered clay bricks with properties similar to those of Ming and Qing dynasty brick masonry were selected as model blocks, with overall dimensions of 245mm × 110mm × 50mm. Before construction, the bricks underwent basic mechanical property testing, with measured compressive strength of approximately 4.5MPa and elastic modulus of approximately 3.9GPa. Before construction, the brick raw materials were screened based on the typical specifications and mineral composition characteristics of Ming and Qing dynasty blue bricks, and cut and polished to uniform dimensions to ensure consistent geometric dimensions and flat end faces for each sample, meeting the precision requirements of the split Hopkinson compression bar test.

[0028] In one embodiment of the present invention, according to the construction specifications for masonry structures, the mortar thickness of the prepared interface sample is selected to be 10 mm. The processed bricks are combined with three different types of mortar, including ordinary mortar, glutinous rice mortar, and tung oil mortar. The preparation scheme is shown in Table 1. Table 1 Mortar Preparation Scheme

[0029] In one embodiment of the present invention, the aging treatment includes a combined dry-wet cycle and salt corrosion aging treatment, specifically including: The prepared aging group samples were immersed in a 5% sodium sulfate solution for 14 hours, and then dried at 105℃ for 10 hours. Immersion-drying was recorded as one cycle, and the cycle was repeated 15 times to complete the salt corrosion-wet-dry cycle pretreatment and obtain the pretreated samples. An artificial acid rain solution with a pH of 3.5 was prepared by mixing sulfuric acid and nitric acid in a volume ratio of 9:1. The pretreated sample was sprayed with the solution for 15 minutes every 8 hours, and this was recorded as one cycle. The acid rain spray corrosion treatment was completed after 45 cycles.

[0030] Understandably, the criteria for determining the termination of aging are: the efflorescence on the wall surface tends to stabilize, the mortar layer shows slight powdering, and there are no through cracks at the interface, meaning that performance degradation has been achieved while retaining the initial load-bearing capacity. The entire aging process is recorded, including the number of cycles and solution concentration, to ensure the controllability and repeatability of the aging process.

[0031] This invention specifically sets up an aging control group for the brick-glutinous rice mortar interface. Through dry-wet cycle and salt corrosion composite aging treatment, it simulates the long-term service deterioration state of brick masonry structures in ancient Ming and Qing dynasty buildings. It quantitatively reveals the differentiated deterioration law of interface dynamic strength and deformation capacity under four loading modes caused by aging. The aging dynamic strength deterioration coefficient is used to quantitatively characterize the degree of interface dynamic performance degradation caused by aging. This solves the technical problem that existing studies cannot distinguish the difference in dynamic performance between newly made components and aged components.

[0032] In one embodiment of the present invention, the acoustic wave test is performed using an acoustic wave detector. Before the test, a coupling agent is uniformly applied to the surface of the sample to ensure signal stability. The longitudinal wave velocity is measured separately. With transverse wave velocity The average value of the test results at each measuring point was taken as the wave velocity value of the sample. The longitudinal wave velocity of the control group brick-glutinous rice mortar sample was 1432 m / s and the transverse wave velocity was 941 m / s, which were used as the initial wave velocity reference. The mass was weighed using an electronic balance, and the dimensions were measured with vernier calipers. The density of the sample was calculated, and the density of the glutinous rice mortar was 983 kg / m³. 3 The highest value was observed for Class III mortar. The defects in brick edges and corners, interface bonding state, and crack development were recorded to differentiate the appearance between the control group and the aging group. During the acoustic velocity test, cylindrical samples were directly measured using an acoustic wave meter. The acoustic wave test results at the brick interface are shown in Table 2. Table 2 Wave velocity statistics of interface samples

[0033] As shown in Table 2, the wave velocity of the brick-glutinous rice mortar combination is the highest among the three combinations, indicating that the interface between the glutinous rice mortar and the brick is more compact and the acoustic impedance matching is better.

[0034] In one embodiment of the present invention, the elastic modulus shear modulus and Poisson's ratio Calculate according to the elastic wave propagation theory using the following formula: (1) In the formula, The longitudinal wave velocity of the medium; The transverse wave velocity of the medium; The density of the medium; The elastic modulus of the medium; The shear modulus of the medium; The material's Poisson's ratio.

[0035] The test results of elastic modulus and Poisson's ratio of various interface specimens are shown in Table 3. Table 3. Test results of elastic modulus and Poisson's ratio for various interface specimens.

[0036] Table 3 shows that the elastic modulus of the brick-mortar composite with glutinous rice mortar interfacial bonding is still the highest among the three groups, indicating that the interfacial bonding of glutinous rice mortar plays an important role in the overall stiffness of the composite. Analysis of Poisson's ratio reveals that the Poisson's ratio of the composite is lower than that of its corresponding material, a phenomenon related to the effect of the brick-mortar interface on lateral deformation constraint. In summary, glutinous rice mortar exhibits outstanding advantages in both stiffness and interfacial bonding, and also demonstrates good resistance to deformation.

[0037] S2. Using a PMMA rod as the incident rod and the transmission rod, a spindle-shaped bullet is used to shape the incident wave waveform to construct a split Hopkinson bar impact test system. Based on the split Hopkinson bar impact test system, multiple impact velocities are used to sequentially perform impact loading tests on the interface sample according to each loading configuration, and the three-wave strain signals and high-speed photographic images of each working condition are collected simultaneously.

[0038] Understandably, the Split Hopkinson Pressure Bar (SHPB) is a dynamic mechanical performance testing device based on one-dimensional stress wave theory. Its main components include a pneumatic impact device, an incident bar, a transmission bar, an energy absorption device, and a high-speed data acquisition system. A physical image is shown below. Figure 3 As shown. The air gun releases high-pressure gas, propelling a spindle-shaped bullet (impact rod) within the launch tube to axially impact the left end of the incident rod at a preset velocity. The stress wave generated by the impact propagates to the right within the incident rod. Upon reaching the interface sample, due to the impedance mismatch between the rod and the sample, the stress wave splits: one part reflects back to the incident rod, forming a reflected wave; the other part passes through the sample and continues into the transmission rod, forming a transmitted wave. The absorbing rod, located at the right end of the transmission rod, absorbs the remaining energy of the transmitted wave, preventing secondary reflections that could interfere with the signal. Strain gauges 1 and 2 are respectively positioned on the incident and transmission rods. The strain signal is converted into a voltage signal via a Wheatstone bridge, amplified by a dynamic strain gauge, acquired by an oscilloscope, and finally transmitted to a computer for storage and processing to obtain the incident wave strain. Strain of reflected waves With transmitted wave strain This refers to a three-wave signal. During the test, the impact rod, driven by pneumatics, axially impacts the incident rod at a certain speed, generating a one-dimensional stress wave in the rod. When the stress wave propagates to the sample interface, it splits into a transmitted wave and a reflected wave. By collecting and processing the above signals through strain gauges pre-arranged on the rod, the dynamic response characteristics of the sample under impact load can be obtained by inversion.

[0039] This invention uses a PMMA rod instead of a metal rod, matching the wave impedance to that of the ancient brick, resulting in a reflection coefficient of only 0.15 and improving stress wave transmission efficiency. This is achieved through the wave impedance formula... Calculation: PMMA rod (ρe≈1190 kg / m) 3 Ce≈2650 m / s and ancient bricks (ρb≈1800 kg / m 3With Cb≈1800 m / s, after impedance matching, R≈0.15 is obtained. At this reflection coefficient, the transmitted energy is about 85%, ensuring sufficient signal-to-noise ratio of the transmitted wave and avoiding secondary damage, thus meeting the testing requirements of the ancient brick-mortar brittle system. Here, ρe represents the density of the incident rod (PMMA rod), Ce represents the stress wave propagation velocity in the incident rod (PMMA rod), ρb represents the density of the ancient brick sample, Cb represents the stress wave propagation velocity in the ancient brick sample, and R represents the wave impedance.

[0040] This invention uses a spindle-shaped bullet with a gentle rising edge of the incident wave, suppressing high-frequency oscillations and making it suitable for brittle interface samples. The rising edge duration of the incident wave is t. r Based on bullet length L b Together with the cone angle θ, t is determined: r With L b Positively correlated with θ, and negatively correlated with θ.

[0041] In one specific embodiment, L is selected. b =200 mm, cone angle θ is 10°, corresponding to t r The time is approximately 80~120 μs, which is sufficient to achieve stress homogenization inside the specimen and suppress high-frequency oscillations, thus meeting the requirements for constant strain rate loading.

[0042] In one embodiment of the present invention, the SHPB system controls the impact velocity by adjusting the impact stroke to achieve stable loading of the interface impact load, as shown in Table 4: Table 4. Material Parameters of Medium and Rod

[0043] The test procedure is as follows Figure 3 As shown, in order to reduce the frictional effect between the rod and the sample contact surface and to ensure the continuity of the loading process, petroleum jelly is uniformly applied as a lubricating medium at the rod-sample contact interface.

[0044] Understandably, the implementation of the SHPB experiment requires two basic assumptions to be met: (1) The one-dimensional stress wave assumption requires that the members keep their axes aligned and that the axial stress in the cross section is uniformly distributed. (2) Stress uniformity assumption requires that the stress and deformation of the rod and specimen along the axial direction meet the basic requirement of uniform distribution during the propagation of stress wave.

[0045] The interface displacement at both ends of the specimen can be expressed by equation (2):

[0046] When the specimen length is L, the strain calculation formula in the specimen is: (3) In the formula, Let L be the initial average strain along the axial direction of the specimen; L is the length of the specimen. Differentiating the strain expression in equation (3) with respect to time, we can obtain the formula for calculating the average strain rate of the specimen cross-section: (4) In the formula, Let be the initial average strain rate of the specimen. Based on the homogeneity assumption and the basic theory of elasticity, the axial forces acting on the two ends of the specimen are as follows: (5) In the formula, and This is the resultant axial force on the compression sections at both ends of the specimen; Let be the effective bearing area of ​​the cross-section of the rod; E is the elastic modulus of the rod material. Based on this, the average stress inside the specimen can be further expressed as: (6) In the formula, Let be the average stress across the specimen cross section; A be the cross-sectional area of ​​the specimen. When both the assumptions of uniform stress distribution and one-dimensional stress wave are true: (7) Substituting equation (7) into equations (3), (4), and (6), we get: (8) In the formula, D is the diameter of the rod, and D is the diameter of the sample. The average strain represents the strain under the resultant axial force on the compression sections at both ends of the specimen. The average strain rate represents the resultant axial force acting on the compression sections at both ends of the specimen. The formula for calculating the average stress when the axial resultant force on the compression sections at both ends of the specimen is expressed.

[0047] When the Brazilian disc specimen is much smaller than the length of the rod, its dynamic tensile stress can be expressed as: (9) In the formula, The average tensile stress of the disk; This is the area of ​​the cross-section; Let D be the diameter of the rod, and B be the diameter of the specimen. The specimen reaches stress equilibrium at both ends, and the formulas for calculating the average strain, average strain rate, and average stress are as follows: (10) in, This represents the average strain when the stresses at both ends of the specimen are in equilibrium. This represents the average strain rate when the stresses at both ends of the specimen are in equilibrium. This is the formula for calculating the average stress when the stresses at both ends of the specimen are in equilibrium.

[0048] For composite medium specimens, based on the SHPB testing system, four different stress state tests were designed and improved, namely interface compression, tension, shear and oblique shear tests, which correspond to four action mechanisms: normal compression, normal tension, pure shear and combined shear, respectively, so as to realize the testing of interface strength and deformation characteristics under dynamic loading conditions.

[0049] The compressive stress and strain at the interface are calculated using equation (8), and the tensile stress and strain are calculated using equation (10). When the specimen is subjected to a shear load, the shear stress at the shear surface is calculated as follows: (11) In the formula, This represents the shear stress on the shear surface of the sample. Let be the effective area of ​​the shear plane. When the stress state between the two ends of the specimen reaches stress equilibrium, the expressions for the average strain, average strain rate, and average stress of the specimen can be derived as follows: (12) in, This represents the average strain of the specimen under shear load. This represents the average strain rate of the specimen under shear load. This represents the average stress when the specimen is subjected to shear load.

[0050] When the specimen is subjected to an oblique shear load, the force on the oblique shear surface is decomposed into normal force and tangential shear stress, and its calculation expression is: (13) In the formula, , These are the normal stress and tangential stress borne on the oblique shear surface of the specimen, respectively. The shear area is the oblique shear area. Let be the angle formed between the oblique shear plane and the horizontal plane. When the stress equilibrium condition at both ends is satisfied, the expressions for calculating the normal mean strain, mean strain rate, and mean stress of the oblique shear plane are: (14) in, This represents the average strain in the normal direction of the oblique shear plane. This represents the normal mean strain rate of the oblique shear plane. This represents the average stress in the normal direction of the oblique shear plane.

[0051] Similarly, the expressions for calculating the tangential average strain, average strain rate, and average stress of the oblique shear plane are as follows: (15) in, This represents the average tangential strain on the oblique shear plane. This represents the tangential average strain rate of the oblique shear plane. This represents the average tangential stress on the oblique shear surface.

[0052] This invention is the first to conduct impact tests on the interface systems of traditional cementitious materials such as glutinous rice mortar and tung oil mortar under four loading modes: compression, tension, shear, and combined compression and shear. It establishes a complete set of interface dynamic performance parameters covering dynamic peak stress, peak strain, dynamic elastic modulus, and strain rate-related dynamic strength models, filling the data gap in the current specifications for dynamic performance parameters of traditional masonry interfaces, and providing direct and usable experimental basis for the establishment of dynamic analysis models for ancient building structures.

[0053] In one embodiment of the present invention, step S2 specifically includes: PMMA was selected to make the incident rod and the transmission rod. Waveform-shaping bullets were used to shape the incident wave to construct a split Hopkinson pressure bar system. The split Hopkinson pressure bar system includes a pneumatic impact device, an incident rod, a transmission rod, an energy absorption device, and a high-speed data acquisition system. Based on the one-dimensional stress wave propagation theory, strain gauges are arranged on the incident rod and the transmission rod respectively to collect the incident wave strain, reflected wave strain and transmitted wave strain, with a data acquisition frequency of not less than 1MHz. Using multiple impact velocities as loading intensity variables and four loading configurations as loading mode variables, full-condition impact loading was carried out sequentially on the three types of mortar interface control groups and the brick-glutinous rice mortar aging group, with no less than 3 effective repeated tests set for each condition. Synchronous acquisition throughout the entire impact loading process yielded three-wave strain signals and high-speed photographic images. The three-wave strain signals include incident wave strain signal, reflected wave strain signal, and transmitted wave strain signal.

[0054] In one embodiment of the present invention, the multi-condition impact loading path is as follows: Using three impact velocities of 3.0 m / s, 3.5 m / s, and 4.0 m / s as loading intensity variables, and compression, tension, shear, and a combination of compression and shear as loading configuration variables, the interface samples of three control groups (brick-ordinary mortar, brick-glutinous rice mortar, and brick-tung oil mortar) were subjected to full-condition combined impact loading at three impact velocities in sequence under four loading configurations. The aged brick-glutinous rice mortar samples were subjected to impact loading at a single impact velocity of 3.5 m / s under the four loading configurations in sequence.

[0055] Specifically, based on the above-mentioned experimental system and principles, and considering the material properties of the brick-mortar interface and the requirements for controllable loading, the interface impact dynamics test scheme is designed as shown in Table 5. The test objects include three types of interfaces: brick-ordinary mortar, brick-glutinous rice mortar, and brick-tung oil mortar. Compression, tensile, shear, and compression-shear tests are carried out respectively. Table 5. SHPB Test Scheme for Brick-Mortar Interface

[0056] As shown in Table 5, glutinous rice mortar has the best mechanical properties among the three types of mortar and is the most representative in the restoration of ancient Ming and Qing buildings. The kinetic test after aging focuses on the brick-glutinous rice mortar interface as a typical object.

[0057] S3. Based on the three-wave strain signal, calculate the stress wave transmission coefficient and reflection coefficient of each working condition interface; calculate the incident energy, reflected energy and transmitted energy of each working condition, and determine the energy dissipation of each working condition interface. In one embodiment of the present invention, according to the SHPB test scheme set in Table 5, four dynamic loading tests—compression, splitting, shear, and compression-shear—were carried out on three types of interface specimens. Strain data of incident, reflected, and transmitted waves under each working condition were obtained and converted into corresponding stress waveforms. Taking a brick-glutinous rice mortar interface specimen as an example... Figure 4 As shown, the stress waveforms of the specimen under the above four stress states and the corresponding equilibrium verification results are presented. Figure 4 (a) in the figure represents the compression test. Figure 4 (b) in the figure represents a tensile test. Figure 4 (c) in the figure represents the shear test. Figure 4 (d) in the figure represents the compression-shear test.

[0058] In one embodiment of the present invention, step S3 specifically includes: Based on the strain of the incident wave, reflected wave, and transmitted wave, the stress wave transmission coefficient at the interface is calculated under various working conditions. With reflection coefficient The results were obtained under different mortar types, aging states, and impact velocities. and The variation law, and the characteristic parameters of stress wave attenuation under the condition of wave impedance mismatch at the brick-mortar interface: (16) In the formula, The stress wave transmission coefficient; The stress wave reflection coefficient; For the incident wave strain; For the strain of the reflected wave; For the strain of the transmitted wave; Based on three-wave strain data, the incident energy, reflected energy, and transmitted energy under each working condition were calculated to determine the interface energy dissipation and obtain comparative characteristics of interface energy dissipation under different mortar types and aging states.

[0059] Understandably, by substituting the measured data into equation (16) for calculation, the variation of transmission coefficient and reflection coefficient with loading speed and mortar medium type can be obtained, revealing the controlling effect of wave impedance mismatch on stress wave propagation. When the compressive stress wave interacts with the brick-mortar interface, the reflection effect of the interface on the stress wave is stronger than the transmission effect, that is, the overall transmission coefficient is lower than the reflection coefficient; the transmission and reflection coefficients show a monotonically decreasing trend with the increase of impact velocity. The transmission capabilities of the three mortars, from strongest to weakest, are glutinous rice mortar, tung oil mortar, and ordinary mortar.

[0060] In one embodiment of the present invention, the formula for calculating the interface energy dissipation is as follows: (17) in, This represents the amount of energy dissipated at the interface. Indicates incident energy, Indicates reflected energy. Indicates transmission energy. Indicates the elastic modulus of the rod. Indicates the cross-sectional area of ​​the rod. This indicates the propagation speed of stress waves in the rod. Indicates the duration of stress wave action. Indicates the strain of the incident wave. Indicates the strain of the reflected wave. Indicates the strain of the transmitted wave. Represents the incident wave stress time history. Represents the stress time history of the reflected wave. This represents the stress time history of the transmitted wave.

[0061] Understandably, by substituting the measured waveform data under various working conditions into equation (17), the energy time history evolution characteristics of the interface sample under different test conditions can be obtained. Taking the glutinous rice mortar interface sample as an example, such as... Figure 5 As shown, the energy evolution of the sample under four stress states—compression, tension, shear, and compressive-shear—over time is presented. Figure 5 (a) in the figure represents the compression test. Figure 5 (b) in the figure represents a tensile test. Figure 5 (c) in the figure represents the shear test. Figure 5 (d) in the figure represents the compression-shear test.

[0062] Figure 4This indicates that incident energy, reflected energy, and transmitted energy all undergo an evolutionary process from continuous growth to a tendency to plateau. Under the same incident energy conditions, the reflected energy ranking is tensile > shear > compression > compressive-shear, while the ranking of transmitted energy and dissipated energy is the opposite. In the compression and compressive-shear states, interface closure and friction effects cause dissipated energy to remain dominant; in the tensile and shear states, the energy distribution changes in stages as damage develops, gradually evolving from transmission-dominated in the early stage to dissipation-dominated in the later stage.

[0063] S4. Obtain the dynamic stress-strain relationship according to the dynamic stress-strain calculation method corresponding to each loading configuration, extract the dynamic peak stress, peak strain and dynamic elastic modulus, and establish a strain rate-related dynamic strength model; based on high-speed photography images and combined with the fracture morphology of the interface specimen after impact, identify the interface failure mode; using dynamic peak stress, peak strain, dynamic elastic modulus, dynamic strength model and interface energy dissipation as characterization indicators, and using the initial physical and mechanical state reference parameters as the benchmark, summarize the dynamic parameters under each loading configuration to form a set of interface dynamic performance parameters, and determine the critical strength threshold of interface damage based on the dynamic peak stress.

[0064] Specifically, step S4 includes: Dynamic stress-strain curves were calculated for each loading condition using the dynamic stress-strain calculation method corresponding to each loading configuration, and the dynamic peak stress for each loading condition was extracted. Peak strain and dynamic elastic modulus ; The dynamic enhancement factor model of various interfaces was established by fitting the strain rate corresponding to the three impact velocities on the x-axis and the dynamic strength value corresponding to each working condition under each loading configuration on the y-axis; among them, the compression and tension configurations showed a positive strain rate effect, while the shear and compression-shear composite configurations showed a negative strain rate effect. Based on the dynamic stress-strain curves of the brick-glutinous rice mortar control group and the aging group, and combined with the initial physical and mechanical state reference parameters, the stress-strain curves before and after aging under various loading configurations were compared. and The change in aging dynamic strength degradation coefficient Quantitatively characterize the degree of dynamic strength degradation of the interface caused by aging; By analyzing high-speed photographic images frame by frame, the crack initiation location and propagation path were determined. Combined with macroscopic observation of the fracture morphology of the interface sample after impact, the interface failure modes were classified into four categories: mortar cohesive failure, interface bond failure, brick cracking failure, and mixed failure. The correspondence between failure modes and mortar type, aging state, and impact velocity was established. Among them, mixed failure refers to the inclusion of at least two of the following: mortar cohesive failure, interface bond failure, and brick cracking failure. by , , Using the dynamic enhancement factor model as the strength-deformation dimension, the interface energy dissipation as the energy dimension, and the comparison parameters before and after aging as the aging state dimension, a set of dynamic performance parameters for the interface of brick masonry structure of Ming and Qing ancient buildings is constructed. Under various loading configurations of different mortar types As the critical damage intensity threshold for the corresponding interface, a differentiated damage criterion considering aging state is established.

[0065] Understandably, the reduction in peak stress of the aging group compared to the control group under each loading mode reflects the degree of dynamic strength degradation caused by aging. The direction and magnitude of the change in peak strain of the aging group compared to the control group under each loading mode reflect the degree of interface embrittlement caused by aging.

[0066] In one embodiment of the present invention, the dynamic stress-strain relationship of the interface specimen is calculated using the three-wave method based on the strain signal acquired by the SHPB test, with the compression loading mode as an example for illustration: The dynamic compressive stress-strain curves of the brick-mortar interface under different working conditions were calculated using Equation (8). The interface compressive mechanical response exhibits typical elastoplastic characteristics, with a clear nonlinear hardening stage before the peak stress and softening behavior after the peak.

[0067] After verifying the stress uniformity, dynamic stress-strain curves were plotted for each working condition based on equations (10), (12), and (14) to obtain the following key characteristic quantities: For tensile, shear, and combined compression-shear loading modes, dynamic mechanical characteristic quantities and dynamic peak stresses under each mode are extracted using the same data processing workflow. Peak strain Slope of the elastic segment (dynamic elastic modulus) ).

[0068] In one embodiment of the present invention, using the different strain rate conditions corresponding to three impact velocities of 3.0 m / s, 3.5 m / s, and 4.0 m / s, and taking the tung oil mortar interface as an example, the variation law of the dynamic strength of the interface with strain rate under each loading mode is analyzed, and a dynamic enhancement factor model suitable for the interface of ancient masonry in the Ming and Qing dynasties is established: Under both compression and tension modes, the peak stress at the interface of tung oil mortar showed a monotonically increasing trend with increasing impact velocity: under compression mode, the peak stress increased from 1.75 MPa at 3.0 m / s to 2.26 MPa at 3.5 m / s and 3.70 MPa at 4.0 m / s; under tension mode, the peak stress increased from 0.26 MPa to 0.33 MPa and 0.40 MPa. Both showed a significant positive strain rate effect, that is, the higher the impact velocity, the stronger the dynamic bearing capacity of the interface.

[0069] Under both shear and compression-shear modes, the peak interfacial stress monotonically decreases with increasing impact velocity: under shear mode, the peak stress decreases from 0.95 MPa at 3.0 m / s to 0.81 MPa at 3.5 m / s and 0.62 MPa at 4.0 m / s; under compression-shear mode, the peak stress decreases from 2.40 MPa to 1.90 MPa and 1.40 MPa, exhibiting a negative strain rate effect. These phenomena indicate that the interface of ancient masonry is more prone to interfacial slip failure under shear stress with increasing impact intensity, which is fundamentally different from the dynamic strengthening mechanism under compression mode. Therefore, different stress states need to be considered separately in the safety assessment of blasting vibration.

[0070] Using the strain rate corresponding to each impact velocity as the abscissa and the normalized dynamic strength (DIF) as the ordinate, fitting curves were established for dynamic tensile strength and dynamic shear strength, respectively. The fitting curves are shown in the figure below. Figure 6 As shown, the fitting parameters are as follows: the fitting parameter for dynamic tensile strength is 0.935, and the fitting parameter for dynamic shear strength is 0.916. The fitting parameters are close, indicating that the dynamic strengthening characteristics of the glutinous rice mortar interface in terms of tensile and shear strength have similar strain rate sensitivity. Figure 6 (a) in the figure is the dynamic tensile strength fitting curve. Figure 6 (b) in the figure is the dynamic shear strength fitting curve.

[0071] In one embodiment of the present invention, the peak stresses of the control group and the aging group are extracted from the dynamic stress-strain curves of each loading mode. Define an aging dynamic strength degradation coefficient λσ to quantitatively characterize the degree of interface dynamic strength degradation caused by aging: The peak stress variations under four loading modes—compression, tension, shear, and compression-shear—were compared one by one to analyze the differentiated degradation patterns of the interface dynamic strength under different stress states caused by aging. Furthermore, the trends of peak stress variations under various impact velocities (3.0, 3.5, and 4.0 m / s) were compared to analyze whether the degree of aging degradation further intensifies with increasing impact intensity.

[0072] The peak stresses of the glutinous rice mortar control group and the aging group were extracted from the dynamic stress-strain curves of the four loading modes, and the aging dynamic strength degradation coefficient λσ of each mode was calculated. The results are as follows: Under the compression mode, the peak stress decreased from 2.76 MPa to 2.25 MPa, λσ=0.848, a decrease of 14.2%; under the tensile mode, it decreased from 0.41 MPa to 0.38 MPa, λσ=0.927, a decrease of 7.3%; under the shear mode, it decreased from 0.86 MPa to 0.74 MPa, λσ=0.860, a decrease of 14.0%; under the compression-shear mode, it decreased from 2.06 MPa to 1.81 MPa, λσ=0.879, a decrease of 12.1%.

[0073] The above results indicate that aging has a different effect on the degradation of the dynamic strength of the interface under the four loading modes: compression and shear modes are most significantly affected by aging, with degradation exceeding 14%; compression-shear mode is the second most affected; and tension mode has the smallest strength degradation, only 7.3%, but its deformation capacity degradation is far greater than its strength degradation.

[0074] In one embodiment of the present invention, dynamic peak strain variation analysis The direction of analysis is as follows: The influence of aging on the interface deformation capacity. Comparing the peak strains of the control group and the aging group under the four loading modes, all modes showed a trend of decreasing peak strain after aging, indicating that the interface tends to become brittle overall after aging. Among them, the peak strain of the tensile mode decreased from 0.0008 to 0.00045, a decrease of 43.7%, with the most prominent embrittlement effect; the peak strain of the compression-shear mode decreased from 0.00146 to 0.00102, a decrease of 30.1%, which is also not negligible; the peak strain decreases of the compression and shear modes were relatively smaller, at 14.3% and 15.0%, respectively.

[0075] Based on the degradation patterns of peak stress and peak strain, it can be seen that aging weakens the interface's deformation capacity significantly more than it weakens its strength. Especially under tensile and compressive-shear modes, the interface will reach peak failure with a smaller amount of deformation after aging, and its adaptability to explosive impact loads will decrease significantly.

[0076] In one embodiment of this invention, the comparison of aging effects between different mortar types includes: Taking the impact velocity of 3.5 m / s as a representative condition, the peak stress of the glutinous rice mortar control group, the aging group, the tung oil mortar and the ordinary mortar were compared laterally. The strength ranking of the four loading modes was highly consistent, showing the following pattern: glutinous rice mortar (control group) > tung oil mortar ≥ glutinous rice mortar (aging group) > ordinary mortar.

[0077] Specifically, under compression mode, the peak stress of the glutinous rice mortar control group was 2.75 MPa, which decreased to 2.21 MPa after aging, basically on par with the tung oil mortar's 2.26 MPa, indicating that its dynamic strength advantage was disappearing. Under tensile mode, the peak stress of the aged group was 0.375 MPa, still higher than the tung oil mortar's 0.32 MPa, retaining a certain strength advantage. Under shear mode, the gap between the aged group (0.72 MPa) and the tung oil mortar (0.81 MPa) widened, and the weakening of shear strength by aging significantly reduced the relative advantage of the glutinous rice mortar. Under compression-shear mode, the difference between the aged group (1.80 MPa) and the tung oil mortar (1.90 MPa) was small, and the two were close.

[0078] The above comparison shows that aging treatment weakens the dynamic strength advantage of glutinous rice mortar interface under various loading modes to varying degrees. The deterioration effect is most obvious under compression mode. After aging, the dynamic load-bearing capacity of glutinous rice mortar interface is comparable to that of tung oil mortar and far exceeds that of ordinary mortar, which confirms the substantial impact of aging on the dynamic performance of traditional process materials.

[0079] In one embodiment of the present invention, a systematic method for interface failure mode recognition and classification is established by combining high-speed photographic images during the SHPB test with the fracture morphology of the specimen after impact, specifically including: In the SHPB test, a high-speed photography system was simultaneously activated to record the initiation time, propagation path, and penetration time of the interface cracks during the impact process. The crack initiation location (inside the mortar / at the brick-mortar interface / inside the brick) and the final propagation path were determined by analyzing the frame-by-frame images, which served as the primary basis for classifying the failure mode. After the impact test, macroscopic photography was performed on the fracture surface of the specimens, and a preliminary judgment was made based on the cross-sectional characteristics: those with smooth cross-sections and no mortar residue tended to be interface debonding failure; those with rough cross-sections and mortar residue on the brick surface tended to be mortar cohesive failure; and those with visible brick fragments on the cross-section tended to be brick cracking failure.

[0080] In one embodiment of the present invention, a dynamic intensity damage criterion for differentiated interfaces is established, specifically including: Obtain the starting stress of the nonlinear segment of the dynamic stress-strain curve for each working condition. Define the strength damage initiation coefficient ;in, Represents the stress in the nonlinear stage. Indicates dynamic peak stress; Summary of various mortar types and loading configurations As the critical damage strength threshold for the corresponding interface, the brick-glutinous rice mortar control group under each loading configuration was used. As a benchmark for the critical strength threshold in the unaged state, the corresponding working conditions of the aging group are used. The critical threshold for aging state correction is used as the difference between the non-aging critical threshold and the aging correction critical threshold as the amount of reduction in interfacial damage resistance caused by aging: 0.51 MPa in compression mode, 0.03 MPa in tensile mode, 0.12 MPa in shear mode, and 0.25 MPa in compression-shear mode. Set the dynamic stress requirement value for the interface, compare the critical threshold of the control group with that of the unaged component and the critical threshold of the aging group with that of the aged component, and determine that there is a risk of damage to the interface when the dynamic stress requirement value exceeds the corresponding threshold.

[0081] Understandably, based on the readings of the nonlinear segment starting point of the stress-strain curves for each working condition, the ξ values ​​for each condition are concentrated in the range of 0.97 to 1.00. This result indicates that the interface of the Ming and Qing dynasty masonry is almost entirely in a nonlinear deformation stage before reaching the dynamic peak stress, with an extremely short elastic response segment, and the occurrence of interface damage is almost synchronous with the peak load. Therefore, using the dynamic peak stress... The critical strength criterion for the initiation of interface damage is reasonable; that is, when the dynamic stress on the interface reaches... When the interface is deemed to have entered a damaged state, under the framework of strength damage criterion, the dynamic peak stress of the glutinous rice mortar control group under each loading mode is used as the critical strength threshold benchmark for the unaged state, and the dynamic peak stress of the corresponding working condition of the aged group is used as the modified critical threshold for the aged state. The difference between the two is the amount of reduction in interface damage resistance caused by aging.

[0082] In the parameter set of glutinous rice mortar, the comparison results of peak stress and peak strain between the control group and the aging group were systematically compiled to form a parameter set for comparing the dynamic performance before and after aging, which reflects the following two aspects: The reduction in peak stress of the aging group compared to the control group under each loading mode reflects the degree of dynamic strength degradation caused by aging. The direction and magnitude of the change in peak strain of the aging group compared to the control group under each loading mode reflect the degree of interface embrittlement caused by aging.

[0083] The comparison parameter set does not require the introduction of new calculation formulas. It is directly based on the analysis results of experimental data and can be summarized and organized to serve as a qualitative and quantitative reference for performance reduction in actual dynamic safety assessment of cultural relics and buildings.

[0084] This invention introduces a strength damage initiation coefficient to reveal the inherent mechanical characteristics of Ming and Qing dynasty masonry interfaces, which have extremely short elastic response segments and nonlinear deformation throughout the entire bearing process. It uses dynamic peak stress as the critical strength threshold for the initiation of interface damage and provides the rationale for this.

[0085] In one embodiment of the present invention, taking an impact velocity of 3.5 m / s as a representative condition, the critical strength thresholds of the aged group under the four modes of compression, tension, shear, and compression-shear were reduced by 14.2%, 7.3%, 14.0%, and 12.1%, respectively, compared with the control group. The above results indicate that the interface subjected to aging and degradation will enter a damaged state at a lower dynamic stress level, and its ability to resist impact damage is systematically weaker than that of the unaged state.

[0086] Combined with the peak strain degradation analysis, the aging interface exhibits a dual adverse characteristic: on the one hand, the critical strength threshold decreases, and damage initiation occurs earlier; on the other hand, the peak strain decreases, and the interface enters the softening stage more quickly after reaching the peak, accelerating the damage development rate. These two factors combined significantly reduce the overall damage resistance of the aging interface under blast impact loads, particularly in tensile and compression-shear modes. Although the strength degradation is smallest in the tensile mode (7.3%), its peak strain reduction is as high as 43.7%, indicating that aging weakens the interface's deformation capacity far more than its strength effect under this mode, and the risk of interface embrittlement cannot be ignored.

[0087] This invention summarizes the dynamic peak stresses determined for each mortar type and loading mode into a table of critical thresholds for interface dynamic strength damage. This table serves as the final quantitative evaluation index output of this method. In practical engineering applications, the interface dynamic stress requirement value can be calculated based on blasting vibration monitoring data and compared with the aforementioned critical threshold. When the dynamic stress requirement value exceeds the corresponding threshold, it is determined that there is a risk of interface damage. For components that have already undergone aging and deterioration, the critical threshold corresponding to the aging group should be used for evaluation to reflect the actual weakening of the interface's impact resistance due to aging. This provides a direct and usable quantitative basis for the safety control of blasting construction of adjacent cultural relics and buildings.

[0088] This invention establishes a complete system of interface dynamic performance parameters and dynamic strength damage criteria by constructing a complete interface dynamic performance parameter system and a system of dynamic strength damage criteria through interface sample preparation and initial state characterization, split Hopkinson bar impact test, interface stress wave propagation and energy dissipation analysis, interface dynamic response parameter extraction and damage criteria. This enables the systematic determination of the interface blasting impact dynamic performance of brick masonry structures in Ming and Qing dynasty ancient buildings.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining the interface blasting impact dynamics of brick masonry structures in Ming and Qing dynasty ancient buildings, characterized in that, include: S1. Based on the typical specifications and mineral composition characteristics of Ming and Qing dynasty ancient building bricks, bricks were selected, and brick-mortar composite interface samples were prepared using ordinary mortar, glutinous rice mortar and tung oil mortar respectively. Among them, brick-glutinous rice mortar interface samples were additionally prepared for aging, and the aging samples were subjected to aging treatment. Wave velocity, density, elastic modulus and Poisson's ratio were measured for all interface samples to establish the initial physical and mechanical state reference parameters; S2. Using a PMMA rod as the incident rod and the transmission rod, a spindle-shaped bullet is used to shape the incident wave waveform to construct a split Hopkinson bar impact test system. Based on the split Hopkinson bar impact test system, multiple impact velocities are used to carry out impact loading tests on the interface sample according to each loading configuration, and the three-wave strain signals and high-speed photographic images of each working condition are collected simultaneously. S3. Based on the three-wave strain signal, calculate the stress wave transmission coefficient and reflection coefficient of each working condition interface; calculate the incident energy, reflected energy and transmitted energy of each working condition, and determine the energy dissipation of each working condition interface. S4. Obtain the dynamic stress-strain relationship according to the dynamic stress-strain calculation method corresponding to each loading configuration, extract the dynamic peak stress, peak strain and dynamic elastic modulus, and establish a strain rate-related dynamic strength model; based on high-speed photography images and combined with the fracture morphology of the interface sample after impact, identify the interface failure mode. Using dynamic peak stress, peak strain, dynamic elastic modulus, dynamic strength model, and interface energy dissipation as characterization indicators, and taking the initial physical and mechanical state reference parameters as the benchmark, the dynamic parameters under each loading configuration are summarized to form a set of interface dynamic performance parameters, and the critical strength threshold for interface damage is determined based on the dynamic peak stress.

2. The method for determining the interface blasting impact dynamics of brick masonry structures in Ming and Qing dynasty ancient buildings as described in claim 1, characterized in that: The interface specimens include four loading configurations: compression, tension, shear, and a combination of compression and shear. The compression configuration specimen has a cross-sectional diameter and height of 50 mm, with 20 mm thick bricks at each end and a 10 mm thick mortar layer in the middle. The tension configuration specimen has a cross-sectional diameter of 50 mm, a height of 20 mm, and a 10 mm thick mortar layer in the middle. The shear configuration specimen has a cross-sectional diameter and height of 50 mm, with a 10 mm thick mortar layer in the middle and a 5 mm pre-reserved gap. The combination of compression and shear configuration specimen has a cross-sectional diameter and height of 50 mm, with bricks at both ends of 10 mm and 20 mm heights respectively, a 10 mm thick mortar layer in the middle, and a brick surface inclination angle of 21.8°.

3. The method for determining the interface blasting impact dynamics of brick masonry structures in Ming and Qing dynasty ancient buildings as described in claim 2, characterized in that: The aging treatment includes a combination of wet-dry cycle aging and salt corrosion aging treatment.

4. The method for determining the interface blasting impact dynamics of brick masonry structures in Ming and Qing dynasty ancient buildings as described in claim 1, characterized in that: Step S2 specifically includes: PMMA was selected to make the incident rod and the transmission rod. Waveform-shaping bullets were used to shape the incident wave to construct a split Hopkinson pressure bar system. The split Hopkinson pressure bar system includes a pneumatic impact device, an incident rod, a transmission rod, an energy absorption device, and a high-speed data acquisition system. Based on the one-dimensional stress wave propagation theory, strain gauges are arranged on the incident rod and the transmission rod respectively to collect the incident wave strain, reflected wave strain and transmitted wave strain. Using multiple impact velocities as loading intensity variables and four loading configurations as loading mode variables, full-condition impact loading was sequentially applied to three types of mortar interface control groups and brick-glutinous rice mortar aging groups. Synchronous acquisition throughout the entire impact loading process yielded three-wave strain signals and high-speed photographic images. The three-wave strain signals included incident wave strain signal, reflected wave strain signal, and transmitted wave strain signal.

5. The method for determining the interface blasting impact dynamics of brick masonry structures in Ming and Qing dynasty ancient buildings as described in claim 4, characterized in that: The impact loading condition is as follows: Using three impact velocities of 3.0 m / s, 3.5 m / s, and 4.0 m / s as loading intensity variables, and compression, tension, shear, and a combination of compression and shear as loading configuration variables, the interface samples of three control groups (brick-ordinary mortar, brick-glutinous rice mortar, and brick-tung oil mortar) were subjected to full-condition combined impact loading at three impact velocities in sequence under four loading configurations. The aged brick-glutinous rice mortar samples were subjected to impact loading at a single impact velocity of 3.5 m / s under the four loading configurations in sequence.

6. The method for determining the interface blasting impact dynamics of brick masonry structures in Ming and Qing dynasty ancient buildings as described in claim 1, characterized in that: Step S3 specifically includes: Based on the strain of the incident wave, reflected wave, and transmitted wave, the stress wave transmission coefficient at the interface is calculated under various working conditions. With reflection coefficient The results were obtained under different mortar types, aging states, and impact velocities. and The variation law of stress wave attenuation under the condition of impedance mismatch at the brick-mortar interface; Based on three-wave strain data, the incident energy, reflected energy, and transmitted energy under each working condition were calculated to determine the interface energy dissipation and obtain comparative characteristics of interface energy dissipation under different mortar types and aging states.

7. The method for determining the interface blasting impact dynamics of brick masonry structures in Ming and Qing dynasty ancient buildings as described in claim 6, characterized in that: The formula for calculating the interface energy dissipation is: in, This represents the amount of energy dissipated at the interface. Indicates incident energy, Indicates reflected energy. Indicates transmission energy. Indicates the elastic modulus of the rod. Indicates the cross-sectional area of ​​the rod. This indicates the propagation speed of stress waves in the rod. Indicates the duration of stress wave action. Indicates the strain of the incident wave. Indicates the strain of the reflected wave. Indicates the strain of the transmitted wave. Represents the incident wave stress time history. Represents the stress time history of the reflected wave. This represents the stress time history of the transmitted wave.

8. The method for determining the interface blasting impact dynamics of brick masonry structures in Ming and Qing dynasty ancient buildings as described in claim 1, characterized in that: Step S4 specifically includes: Dynamic stress-strain curves were calculated for each loading condition using the dynamic stress-strain calculation method corresponding to each loading configuration, and the dynamic peak stress for each loading condition was extracted. Peak strain and dynamic elastic modulus ; Power function fitting was performed with the strain rate corresponding to the three impact velocities as the abscissa and the dynamic strength value corresponding to each working condition under each loading configuration as the ordinate to establish dynamic enhancement factor models for various interfaces; among them, the compression and tension configurations exhibit positive strain rate effects, while the shear and compression-shear composite configurations exhibit negative strain rate effects. Based on the dynamic stress-strain curves of the brick-glutinous rice mortar control group and the aging group, and combined with the initial physical and mechanical state reference parameters, the stress-strain curves before and after aging under various loading configurations were compared. and The change in aging dynamic strength degradation coefficient Quantitatively characterize the degree of dynamic strength degradation of the interface caused by aging; By analyzing high-speed photographic images frame by frame, the crack initiation location and propagation path are determined. Combined with macroscopic observation of the fracture morphology of the interface sample after impact, the interface failure mode is determined, and the correspondence between the interface failure mode and mortar type, aging state and impact velocity is established. by , , Using the dynamic enhancement factor model as the strength-deformation dimension, the interface energy dissipation as the energy dimension, and the comparison parameters before and after aging as the aging state dimension, a set of dynamic performance parameters for the interface of brick masonry structure of Ming and Qing ancient buildings is constructed. Under various loading configurations of different mortar types As the critical damage intensity threshold for the corresponding interface, a differentiated damage criterion considering aging state is established.

9. The method for determining the interface blasting impact dynamics of brick masonry structures in Ming and Qing dynasty ancient buildings as described in claim 8, characterized in that: The interface failure modes include mortar cohesive failure, interface bonding failure, brick cracking failure, and mixed failure.

10. The method for determining the interface blasting impact dynamics of brick masonry structures in Ming and Qing dynasty ancient buildings as described in claim 9, characterized in that: The establishment of the differential interface dynamic intensity damage criterion specifically includes: Obtain the starting stress of the nonlinear segment of the dynamic stress-strain curve for each working condition. Define the strength damage initiation coefficient ;in, Represents the stress in the nonlinear stage. Indicates dynamic peak stress; Summary of various mortar types and loading configurations As the critical damage strength threshold for the corresponding interface, the brick-glutinous rice mortar control group under each loading configuration was used. As a benchmark for the critical strength threshold in the unaged state, the corresponding working conditions of the aging group are used. The critical threshold for aging state correction is used as the difference between the non-aging critical threshold and the aging correction critical threshold as the amount of reduction in resistance to interfacial damage caused by aging. Set the dynamic stress requirement value for the interface, compare the critical threshold of the control group with that of the unaged component and the critical threshold of the aging group with that of the aged component, and determine that there is a risk of damage to the interface when the dynamic stress requirement value exceeds the corresponding threshold.

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