Complex site seismic oscillation input method
By constructing a three-dimensional finite element model of a complex site and calculating the equivalent nodal load, the problem of local topographic effects of irregular boundaries in seismic motion input of complex sites was solved, achieving more accurate seismic response analysis and providing a reference for seismic safety evaluation of complex sites.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-24
- Publication Date
- 2026-03-10
AI Technical Summary
In existing technologies, seismic motion input methods for complex sites fail to effectively consider the local topographic effects of irregular boundaries, resulting in inaccurate seismic response analysis results.
By constructing a three-dimensional complex site finite element model, modifying it to an infinite element artificial boundary, and combining the seismic wave acceleration time history curve and incident angle, the equivalent nodal load is calculated. The model is then expanded to form a large-size model, and the seismic response is mapped to the irregular boundary to realize the seismic motion input of the irregular boundary.
It accurately simulates the refraction, reflection, and scattering of seismic waves in complex sites, reflects the spatial inconsistency of seismic waves and the energy radiation damping effect, improves the accuracy of seismic response analysis, and provides a reference for seismic safety assessment of complex sites.
Smart Images
Figure CN121637880A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of geotechnical engineering anti-seismic analysis, and particularly relates to a complex site seismic input method. BACKGROUND
[0002] China's water energy resources ranks first in the world, with great development potential. The development of hydropower energy mainly depends on dam building, and the potential energy of water is used for power generation. In the western region with abundant water resources, the terrain is mainly mountainous valleys, and the terrain is complex and the traffic is inconvenient. The earth-rock dam has the advantages of local material, low engineering cost, environmental friendliness and short construction period, and becomes the first choice for dam construction in the region. The western region is in a strong earthquake zone, with high seismic intensity, shallow focus and wide influence. Due to the uncertain relative position between the potential seismic source area and the dam site, the incident direction of the seismic wave has multiple possibilities. Under different spatial incident angles, the dynamic characteristics of the site are significantly different, and three-dimensional seismic response analysis is needed to accurately evaluate the site. The rationality of the seismic input method is the key to the study of site seismic response.
[0003] The sedimentary valley site has a large size, and the influence of spatial non-uniform input of seismic waves cannot be ignored. It is a typical complex site. The wave input method of artificial boundary combined with equivalent node load can effectively simulate the spatial non-uniform input of seismic waves. For complex sites such as sedimentary valleys, due to the diversity of upstream and downstream artificial boundary materials and complex terrain, it is an irregular boundary, and the influence of local topographic effect needs to be considered when inputting the equivalent node load.
[0004] The commonly used artificial boundary at present is viscoelastic artificial boundary and infinite element artificial boundary. The infinite element artificial boundary uses the damper in the ABAQUS self-contained infinite element to absorb the reflection of the boundary seismic wave, and has better compatibility with the software. Therefore, when using the commercial software ABAQUS for finite element calculation, the infinite element artificial boundary is often considered as a truncated boundary to simulate the radiation damping effect of the semi-infinite foundation. The boundary node equivalent load is usually calculated by the following formula: ; In the formula, denotes the free-field stress tensor, denotes the boundary outer normal direction cosine vector, denotes the free-field velocity vector, denotes the node influence area. denotes the damping coefficient matrix of the infinite element artificial boundary, and the expression is as follows: ; ; In the above formula, , respectively represent tangential and normal damping coefficients, 、 respectively represent S-wave and P-wave velocities, represent material density.
[0005] At present, the method for seismic input on irregular boundary is less studied, in order to facilitate calculation, the irregular boundary of the site is often simplified as a homogeneous foundation, the same method as the regular boundary is used to calculate the equivalent node load on the irregular boundary, the site topography, soil fluctuation, refraction, reflection of seismic waves on the interface and the influence on the seismic response on the irregular boundary are not considered, and the method will affect the accuracy of the analysis results to some extent. SUMMARY
[0006] The technical problem to be solved by the present application is to provide a complex site seismic input method, which respectively deduces and calculates the seismic input on the regular boundary and the irregular boundary, thereby completing the seismic input of the complex site, and realizing the seismic response analysis of the complex site, thereby providing a reference for the seismic safety evaluation of the complex site.
[0007] The technical scheme of the present application is: A complex site seismic input method, specifically comprising the following steps: (1) constructing a three-dimensional complex site finite element model; (2) modifying the finite element boundary of the three-dimensional complex site finite element model into an infinite element artificial boundary to form a three-dimensional complex site finite element-infinite element coupling model, and performing ground stress balance on the three-dimensional complex site finite element-infinite element coupling model; (3) determining the seismic input parameters on the bottom boundary surface of the complex site according to the seismic evaluation data, synthesizing the seismic wave acceleration time history curve according to the complex site bottom acceleration response spectrum, and determining the seismic wave incidence angle according to the potential source position distribution around the complex site; (4) combining the seismic wave acceleration time history curve and the seismic wave incidence angle to calculate the equivalent node load of any node on the regular boundary surface of the infinite element artificial boundary of the finite element-infinite element coupling model, as the seismic input of the regular boundary of the complex site; (5) extending and expanding the three-dimensional complex site finite element model along the irregular boundary direction to form a large-size model, and calculating the equivalent node load of any node on the regular boundary surface of the large-size model to perform seismic input on the regular boundary surface of the large-size model, and no seismic input on the irregular boundary surface of the large-size model, then obtaining the seismic response of the complex site by using the large-size model, and extracting the stress and velocity time histories of each node on any irregular section in the stable region of the seismic response of the large-size model, since any irregular section of the large-size model is parallel to the irregular boundary surface thereof, the stress and velocity time histories of each node on any irregular section are taken as the stress and velocity time histories of each node on the irregular boundary surface, and finally the equivalent node load of any node on the irregular boundary surface of the complex site is calculated according to the stress and velocity time histories of each node on the irregular boundary surface, as the seismic input on the irregular boundary of the complex site.
[0008] The specific steps of constructing the three-dimensional complex site finite element model are: S11, extracting position coordinate data of the complex site based on the geological exploration results of the complex site to be simulated; S12, assigning values to soil parameters in the complex site based on in-situ test results of the complex site; S13, constructing a three-dimensional complex site finite element model by using a finite element analysis software in combination with the position coordinate data of the complex site and the soil parameters.
[0009] The steps of constructing the three-dimensional complex site finite element model by using the finite element analysis software are: defining a complex site geometric model based on the position coordinate data of the complex site, defining material properties based on the soil parameters of the complex site, defining static and dynamic analysis steps, element types and element grid sizes of the three-dimensional complex site finite element model, and then defining jobs, wherein the defined jobs include geostress balance, infinite element artificial boundary parameter setting and seismic dynamic response analysis.
[0010] The boundary of the three-dimensional complex site finite element model is modified into an infinite element artificial boundary by modifying the corresponding keywords of the boundary in the finite element analysis software, so that the parameters of the infinite element artificial boundary are automatically calculated by the finite element analysis software, thereby modifying the boundary of the three-dimensional complex site finite element model into the infinite element artificial boundary.
[0011] The specific steps of geostress balance of the three-dimensional complex site finite element-infinite element coupling model are: re-modifying the infinite element artificial boundary of the three-dimensional complex site finite element-infinite element coupling model into a finite element boundary to form the original three-dimensional complex site finite element model, setting displacement boundary conditions, applying gravity to the three-dimensional complex site finite element model to obtain initial soil geostress, and the vertical displacement of the initial soil geostress is 10 -5The initial soil stress is guaranteed to be unchanged, and the initial soil stress is introduced into the finite element-infinite element coupling model as a prestress by using a finite element analysis software to balance the ground stress.
[0012] The specific steps of calculating the equivalent node load of any node on the regular boundary surface of the finite element-infinite element coupling model by combining the acceleration time-history curve of the seismic wave and the incident angle of the seismic wave are as follows: S41, calculating the velocity time-history of any node on the regular boundary surface in three directions, specifically as follows: (1); In formula (1), are the velocities of any node on the regular boundary surface of the infinite element artificial boundary in X, Y and Z directions, that is, the free field velocity vector; represents the incident time of the incident SV wave, which is obtained by the forward propagation of ; , , represent the delay time of the incident SV wave, the reflected SV wave and the reflected P wave to the any node; , , represent the velocities of the incident SV wave, the reflected SV wave and the reflected P wave to the any node; the included angle between the incident direction of the incident SV wave and the vertical direction is , which is the oblique incidence angle; the included angle between the incident direction of the incident SV wave and the horizontal direction is , that is, the incident azimuth angle; the included angle between the reflected SV wave and the vertical direction is ; and the included angle between the reflected P wave and the vertical direction is ; is the ratio of the amplitude of the reflected SV wave to the amplitude of the incident SV wave; represents the ratio of the amplitude of the reflected P wave to the amplitude of the incident SV wave; S42, calculating the free field stress tensor of any node on the regular boundary surface, including the free field stress tensor of any node on the regular boundary surface caused by the incident SV wave, the free field stress tensor of any node on the regular boundary surface caused by the reflected SV wave, and the free field stress tensor of any node on the regular boundary surface caused by the reflected P wave; The calculation of the free field stress tensor of any node on the regular boundary surface caused by the incident SV wave is specifically as follows: (2); The calculation of the free field stress tensor of any node on the regular boundary surface caused by the reflected SV wave is specifically as follows: (3); The calculation of the free field stress tensor of an arbitrary node on the regular boundary surface caused by the reflected P wave is specifically shown in the following formula (4): (4) ; In the formula (2) - formula (4), , , , , , Six components of the free field stress tensor of an arbitrary node on the regular boundary surface caused by the incident SV wave; , , , , , Six components of the free field stress tensor of an arbitrary node on the regular boundary surface caused by the reflected SV wave; , , , , , Six components of the free field stress tensor of an arbitrary node on the regular boundary surface caused by the reflected P wave; The material density of the three-dimensional complex site finite element model is represented by The wave speed of the incident SV wave or the reflected SV wave is represented by The wave speed of the reflected P wave is represented by The first order Lame constant, which is the ratio of the transverse tensile stress of the material of the three-dimensional complex site finite element model to the longitudinal strain generated under the action of the longitudinal tensile stress, is represented by The second order Lame constant, which is the shear modulus of the material of the three-dimensional complex site finite element model, is represented by The six components of the free field stress tensor of an arbitrary node on the regular boundary surface caused by the incident SV wave, the reflected SV wave and the reflected P wave are added up in correspondence to obtain the six components of the free field stress tensor of an arbitrary node on the regular boundary surface; S43, the free field velocity vector and the free field stress tensor of an arbitrary node on the regular boundary surface calculated are brought into the following formula (5) to calculate the equivalent node load of an arbitrary node on the regular boundary surface ; (5) ; In the formula (5), The free field stress tensor of an arbitrary node on the regular boundary surface reached by the incident SV wave emitted at time t is represented by The cosine vector of the normal direction outside the infinite element artificial boundary is represented by The damping coefficient matrix is represented by The free field velocity vector of an arbitrary node on the regular boundary surface reached by the incident SV wave emitted at time t is represented by This represents the area of influence at any node.
[0013] The time delay of the incident SV wave, reflected SV wave, and reflected P wave reaching any node. , , The calculation formula is shown in the following formula (6): (6); In equation (6), Represents the height of the finite element-infinite element coupled model. Represents the three-dimensional coordinates of any node in the finite element-infinite element coupled model.
[0014] The ratio of the reflected SV wave amplitude to the incident SV wave amplitude. The ratio of the amplitude of the reflected P-wave to the amplitude of the incident SV-wave It is calculated by the following formula (7): (7).
[0015] After forming the large-size model, the unit mesh is re-divided, and the size ratio of the unit mesh of the large-size model to the size of the unit mesh of the three-dimensional complex site finite element model is 3-5:1. Then, the equivalent nodal load of any node on the regular boundary surface of the large-size model is calculated according to Equations (2)-(5).
[0016] The stress and velocity time histories of each node on the irregular boundary surface of the complex site are then derived to the nodes of each element mesh in the three-dimensional complex site finite element model through the mapping relationship between the element meshes. The velocity mapping is performed by interpolation based on the element shape function, and the stress mapping is performed by the stress recovery method. Finally, the stress and velocity time histories of each node on the irregular boundary surface of the three-dimensional complex site finite element model are substituted into equations (2)-(5) to calculate the equivalent node load of any node on the irregular boundary surface of the complex site, which is used as the seismic input of the irregular boundary of the complex site.
[0017] Advantages of this invention: (1), the present application is obtained by extending the three-dimensional complex site finite element model along the irregular boundary direction, forming a large size model, then inputting the seismic wave to obtain the stress and velocity time history of each node on the irregular boundary surface of the complex site, finally, the equivalent node load on the irregular boundary surface of the complex site is calculated as the seismic input of the irregular boundary of the complex site according to the calculation formula of the equivalent node load, so as to simulate the refraction, reflection and scattering of the seismic wave in the complex site topography, consider the amplification or inhibition effect of the complex site space topography effect on the seismic load in the seismic load calculation, and the calculation result is more consistent with the actual site dynamic response compared with the irregular surface seismic input method commonly used in the past engineering.
[0018] (2), the present application is based on finite element analysis software, adopts the artificial boundary of infinite element to simulate the radiation damping of semi-infinite foundation, the equivalent node load on the regular boundary surface is derived by using the calculation formula of the equivalent node load, and the equivalent node load on the irregular boundary surface is obtained by using the large size model to obtain the seismic response of the complex site, so as to realize the seismic input of the complex site in the form of equivalent node load, which can well simulate the seismic wave propagation characteristics in long and large structure which cannot be ignored, compared with the seismic wave vibration input method, the spatial non-uniformity of seismic wave propagation and the spatial radiation damping effect of seismic wave energy can be more truly reflected.
[0019] (3), the calculation of the equivalent node load of the present application fully reveals the influence of the incidence angle of the seismic wave on the seismic response of the complex site, reflects the influence of the spatial incidence of the seismic wave on the dynamic response of the site, through the method of mapping the coarse grid of the large size model to the fine grid of the three-dimensional complex site finite element model, so as to reduce the calculation scale of stress and velocity, and then accurately obtain the seismic input of the irregular boundary of the complex site, realize the seismic response analysis of the complex site, and provide reference for the seismic safety evaluation of the complex site. BRIEF DESCRIPTION OF DRAWINGS
[0020] Figure 1 is the flow chart of the present application.
[0021] Figure 2 is the three-dimensional schematic diagram of the three-dimensional complex site finite element model of the present application.
[0022] Figure 3 is the grid division diagram of the three-dimensional complex site finite element model of the present application.
[0023] Figure 4 is the three-dimensional schematic diagram of the large size model of the present application.
[0024] Figure 5 is the grid division diagram of the large size model of the present application. DETAILED DESCRIPTION
[0025] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.
[0026] A complex site seismic input method, specifically comprising the following steps: (1) constructing a three-dimensional complex site finite element model, specifically comprising the following steps: S11, extracting position coordinate data of the complex site based on the geological exploration results of the complex site to be simulated; S12, assigning values to the soil parameters in the complex site based on the in-situ test results of the complex site; S13, constructing a three-dimensional complex site finite element model by using a finite element analysis software in combination with the position coordinate data and the soil parameters of the complex site, specifically comprising the following steps: defining a complex site geometric model based on the position coordinate data of the complex site, defining material properties based on the soil parameters of the complex site, defining a static-dynamic analysis step, an element type and an element grid size of the three-dimensional complex site finite element model, and then defining a job, wherein the defined job comprises a geostress balance, an infinite element artificial boundary parameter setting and a seismic dynamic response analysis; (2) constructing a three-dimensional complex site finite element-infinite element coupling model and performing geostress balance, specifically comprising the following steps: S21, modifying the keywords corresponding to the boundary in the finite element analysis software ABAQUS, so that the ABAQUS automatically calculates the parameters of the infinite element artificial boundary, thereby modifying the boundary of the three-dimensional complex site finite element model into the infinite element artificial boundary to form the three-dimensional complex site finite element-infinite element coupling model; S22, modifying the infinite element artificial boundary of the three-dimensional complex site finite element-infinite element coupling model into the finite element boundary again to form the original three-dimensional complex site finite element model, setting a displacement boundary condition, applying gravity to the three-dimensional complex site finite element model to obtain an initial soil geostress, and the vertical displacement of the initial soil geostress is less than 10 meters; then ensuring that the node number of the three-dimensional complex site finite element model remains unchanged, and importing the initial soil geostress as a prestress into the finite element-infinite element coupling model by using the ODB import method of the finite element analysis software ABAQUS to perform geostress balance; -5 (3) determining the seismic motion parameters on the bottom boundary surface of the complex site according to seismic safety evaluation data; synthesizing a seismic wave acceleration time history curve according to the complex site bottom acceleration response spectrum; and determining a seismic wave incidence angle according to the potential source location distribution around the complex site; (4) The equivalent node load of any node on the regular boundary of the artificial boundary of the finite-infinite element coupling model is calculated according to the acceleration time-history curve of the seismic wave and the incident angle of the seismic wave, and is taken as the seismic motion input of the regular boundary of the complex site, and the specific steps are as follows: S41, the velocity time-history of any node on the regular boundary in three directions is calculated, and the specific formula (1) is as follows: (1); In formula (1), are the velocities of any node on the regular boundary of the artificial boundary in X, Y and Z directions, i.e. the free field velocity vector; represents the incident time of the incident SV wave, which is obtained by the forward propagation of ; , , represent the delay time of the incident SV wave, the reflected SV wave and the reflected P wave to any node; , , represent the velocity of the incident SV wave, the reflected SV wave and the reflected P wave to any node; the included angle between the incident direction of the incident SV wave and the vertical direction is , which is the oblique incidence angle; the included angle between the incident direction of the incident SV wave and the horizontal direction is , which is the incident azimuth angle; the included angle between the reflected SV wave and the vertical direction is ; and the included angle between the reflected P wave and the vertical direction is ; is the ratio of the amplitude of the reflected SV wave to the amplitude of the incident SV wave; represents the ratio of the amplitude of the reflected P wave to the amplitude of the incident SV wave; Wherein, the delay time of the incident SV wave, the reflected SV wave and the reflected P wave to any node , , is calculated according to formula (6) as follows: (6); In formula (6), represents the height of the finite-infinite element coupling model, represents the three-dimensional coordinates of any node in the finite-infinite element coupling model; the ratio of the amplitude of the reflected SV wave to the amplitude of the incident SV wave , and the ratio of the amplitude of the reflected P wave to the amplitude of the incident SV wave are calculated according to formula (7) as follows: (7); S42. Calculate the free field stress tensor of any node on the regular boundary surface, including the free field stress tensor of any node on the regular boundary surface caused by the incident SV wave, the free field stress tensor of any node on the regular boundary surface caused by the reflected SV wave, and the free field stress tensor of any node on the regular boundary surface caused by the reflected P wave. The calculation of the free field stress tensor at any node on a regular boundary surface caused by the incident SV wave is shown in the following equation (2): (2); The calculation of the free field stress tensor at any node on a regular boundary surface caused by the reflected SV wave is shown in the following equation (3): (3); The calculation of the free field stress tensor at any node on a regular boundary surface caused by the reflected P-wave is shown in the following equation (4): (4); In equations (2)-(4), , , , , , These are the six components of the free field stress tensor at any node on a regular boundary surface caused by the incident SV wave; , , , , , These are the six components of the free field stress tensor at any node on a regular boundary surface caused by the reflection of SV waves; , , , , , These are the six components of the free field stress tensor at any node on a regular boundary surface caused by the reflection of a P-wave. Material density representing a finite element model of a complex three-dimensional site. Represents the wave velocity of the incident SV wave or the reflected SV wave. Represents the wave velocity of the reflected P-wave; Representing the first-order Lamé constant, it is the ratio of the transverse tensile stress to the longitudinal strain generated under longitudinal tensile stress in the material of a three-dimensional complex site finite element model. represents the second-order Lamé constant, which is the shear modulus of the material in the finite element model of a three-dimensional complex site. The six components of the free field stress tensor caused by the incident SV wave, the reflected SV wave, and the reflected P wave are summed to obtain the six components of the free field stress tensor of any node on the regular boundary surface. S43. Substitute the calculated free field velocity vector and free field stress tensor of any node on the regular boundary surface into the following equation (5) to calculate the equivalent nodal load of any node on the regular boundary surface. ; (5); In equation (5), The free field stress tensor represents the stress of the incident SV wave emitted at time t reaching any node. The cosine vector representing the direction of the outward normal to the infinite element artificial boundary; Represents the damping coefficient matrix; The vector represents the free field velocity of the incident SV wave emitted at time t reaching any node; Represents the area of influence at any node; (5) Calculate the equivalent nodal load of any node on the irregular boundary surface of the complex site as the seismic motion input of the irregular boundary surface of the complex site. This includes the following steps: S51. Extend and expand the three-dimensional complex site finite element model along the irregular boundary direction to form a large-size model and divide it into unit meshes. The size ratio of the unit mesh of the large-size model to the size of the unit mesh of the three-dimensional complex site finite element model is 3-5:1. Then, calculate the equivalent nodal load of any node on the regular boundary surface of the large-size model according to Equations (2)-(5) as the seismic input on the regular boundary surface of the large-size model. Then, perform the seismic input on the regular boundary surface of the large-size model. There is no seismic input on the irregular boundary surface of the large-size model. Then, use the large-size model to obtain the seismic response of the complex site. Extract the stress and velocity time history of each node on any irregular cut surface of the seismic response stable region of the large-size model, i.e., the dynamic response. Since any irregular cut surface of the large-size model is parallel to its irregular boundary surface, the stress and velocity time history of each node on any irregular cut surface is used as the stress and velocity time history (dynamic response) of each node on the irregular boundary surface. S52. The stress and velocity time histories of each node on the irregular boundary surface of the large-size model are then derived to the nodes of each element mesh of the three-dimensional complex site finite element model through the mapping relationship between element meshes. The velocity mapping is performed by interpolation based on the element shape function, and the stress mapping is performed by the stress recovery method. S53. Substitute the stress and velocity time history of each node on the irregular boundary surface of the three-dimensional complex site finite element model into equation (2)-(5) to calculate the equivalent nodal load of any node on the irregular boundary surface of the complex site, and use it as the seismic input of the irregular boundary of the complex site.
[0027] To verify the correctness of this invention, the seismic response of a river valley site was simulated and compared with the boundary element numerical solution results in Sun Weiyu's literature. Using the same geometric and material parameters and the same seismic waves as the aforementioned literature, the analysis was performed. =0°、 = 0° and 𝛿 = 15° The calculation results of the two sets of seismic wave incident angles at 0° show that the calculated horizontal and vertical acceleration amplification factors at different locations are consistent with the results in the literature, demonstrating the correctness of the present invention.
[0028] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for complex site ground motion input, characterized by: Specifically comprising the following steps: (1) constructing a three-dimensional complex site finite element model; (2) modifying the finite element boundary of the three-dimensional complex site finite element model into an infinite element artificial boundary to form a three-dimensional complex site finite element-infinite element coupling model, and balancing the ground stress of the three-dimensional complex site finite element-infinite element coupling model; (3) determining the ground motion parameters on the bottom boundary surface of the complex site according to the seismic evaluation data; synthesizing the ground motion wave acceleration time history curve according to the complex site bottom acceleration response spectrum; determining the ground motion wave incidence angle according to the potential source location distribution around the complex site; (4) combining the ground motion wave acceleration time history curve and the ground motion wave incidence angle to calculate the equivalent node load of any node on the regular boundary surface of the infinite element artificial boundary of the finite element-infinite element coupling model as the ground motion input of the regular boundary of the complex site; (5) extending and expanding the three-dimensional complex site finite element model along the irregular boundary direction to form a large-size model, and calculating the equivalent node load of any node on the regular boundary surface of the large-size model to perform ground motion input on the regular boundary surface of the large-size model, and the irregular boundary surface of the large-size model has no ground motion input, then obtaining the seismic response of the complex site by using the large-size model, and extracting the stress and velocity time history of each node on any irregular section in the stable region of the seismic response of the large-size model, since any irregular section of the large-size model is parallel to the irregular boundary surface, so the stress and velocity time history of each node on any irregular section are taken as the stress and velocity time history of each node on the irregular boundary surface, and finally the equivalent node load of any node on the irregular boundary surface of the complex site is calculated according to the stress and velocity time history of each node on the irregular boundary surface as the ground motion input of the irregular boundary of the complex site.
2. The method of claim 1, wherein: The specific steps of constructing the three-dimensional complex site finite element model are: S11, extracting the position coordinate data of the complex site based on the geological exploration results of the complex site to be simulated; S12, assigning values to the soil parameters in the complex site based on the in-situ test results of the complex site; S13, constructing a three-dimensional complex site finite element model by using a finite element analysis software in combination with the position coordinate data and soil parameters of the complex site.
3. The method of claim 2, wherein: The steps of the finite element analysis software for constructing the three-dimensional complex site finite element model are: defining the complex site geometric model based on the position coordinate data of the complex site, defining the material properties based on the soil parameters of the complex site, defining the static and dynamic analysis steps, element types and element grid sizes of the three-dimensional complex site finite element model, and then defining the tasks, the defined tasks including ground stress balancing, infinite element artificial boundary parameter setting and seismic dynamic response analysis.
4. The method of claim 1, wherein: The boundary of the three-dimensional complex site finite element model is modified into an infinite element artificial boundary by modifying the corresponding keywords of the boundary in the finite element analysis software, so that the finite element analysis software automatically calculates the parameters of the infinite element artificial boundary, thereby modifying the boundary of the three-dimensional complex site finite element model into an infinite element artificial boundary.
5. The method of claim 1, wherein: The specific steps of the three-dimensional complex site finite element-infinite element coupling model for stress balance are as follows: the artificial boundary of the three-dimensional complex site finite element-infinite element coupling model is modified into a finite element boundary to form the original three-dimensional complex site finite element model, displacement boundary conditions are set, gravity is applied to the three-dimensional complex site finite element model to obtain initial soil stress, and the vertical displacement of the initial soil stress is less than 10 -5 meters; then the node number of the three-dimensional complex site finite element model is kept unchanged, the initial soil stress is introduced into the finite element-infinite element coupling model as prestress by using a finite element analysis software, and stress balance is performed.
6. The method of claim 1, wherein: The specific steps of calculating the equivalent node load of any node on the regular boundary surface of the artificial boundary of the finite-infinite element coupling model by combining the acceleration time-history curve of the seismic wave and the incident angle of the seismic wave are as follows: S41, calculating the velocity time-history of any node on the regular boundary surface in three directions, and the specific formula (1) is as follows: （1）； In formula (1), respectively represent the velocity of the arbitrary node in the X, Y, Z direction on the regular boundary surface of the unbounded artificial boundary, i.e. the free field velocity vector; represents the incidence time of the incident SV wave, and is obtained according to the forward propagation of ; , , respectively represent the delay time of the incident SV wave, the reflected SV wave and the reflected P wave to the arbitrary node; , , respectively represent the velocity of the incident SV wave, the reflected SV wave and the reflected P wave to the arbitrary node; the angle between the incidence direction of the incident SV wave and the vertical direction is , which is the oblique incidence angle; the angle between the incidence direction of the incident SV wave and the horizontal direction is , i.e. the incidence azimuth angle; the angle between the reflected SV wave and the vertical direction is , and the angle between the reflected P wave and the vertical direction is ; is the ratio of the amplitude of the reflected SV wave to the amplitude of the incident SV wave; represents the ratio of the amplitude of the reflected P wave to the amplitude of the incident SV wave; S42, calculating the free field stress tensor of any node on the regular boundary surface, including the free field stress tensor of any node on the regular boundary surface caused by the incident SV wave, the free field stress tensor of any node on the regular boundary surface caused by the reflected SV wave, and the free field stress tensor of any node on the regular boundary surface caused by the reflected P wave; The calculation of the free field stress tensor of any node on the regular boundary surface caused by the incident SV wave is specifically shown in formula (2) as follows: （2）； The calculation of the free field stress tensor of any node on the regular boundary surface caused by the reflected SV wave is specifically shown in formula (3) as follows: （3）； The calculation of the free field stress tensor of any node on the regular boundary surface caused by the reflected P wave is specifically shown in formula (4) as follows: （4）； in formula (2) - formula (4), 、 、 、 、 、 Six components of the free-field stress tensor of an arbitrary node on the regular boundary surface caused by the incident SV wave; 、 、 、 、 、 Six components of the free-field stress tensor of an arbitrary node on the regular boundary surface caused by the reflected SV wave; 、 、 、 、 、 Six components of the free-field stress tensor of an arbitrary node on the regular boundary surface caused by the reflected P wave; represents the material density of the three-dimensional complex site finite element model, represents the wave velocity of the incident SV wave or the reflected SV wave, represents the wave velocity of the reflected P wave; represents the first-order Lame constant, which is the ratio of the transverse tensile stress of the material of the three-dimensional complex site finite element model to the longitudinal strain generated under the action of the longitudinal tensile stress; represents the second-order Lame constant, which is the shear modulus of the material of the three-dimensional complex site finite element model; The six components of the free field stress tensors caused by the incident SV wave, the reflected SV wave and the reflected P wave are added correspondingly to obtain the six components of the free field stress tensor of any node on the regular boundary surface. S43, the calculated free field velocity vector and free field stress tensor of any node on the regular boundary surface are brought into the following formula (5) to calculate the equivalent node load of any node on the regular boundary surface ; （5）； In formula (5), represents the free-field stress tensor of the incident SV wave emitted at time t reaching any node; represents the cosine vector of the normal direction outside the artificial boundary of the infinite element; represents the damping coefficient matrix; represents the free-field velocity vector of the incident SV wave emitted at time t reaching any node; represents the influence area at any node.
7. The method of claim 6, wherein: The delay time of the incident SV wave, the reflected SV wave, and the reflected P wave to reach any node , , The calculation formula of the delay time of the incident SV wave, the reflected SV wave, and the reflected P wave to reach any node is shown in the following formula (6): （6）； In formula (6), represents the height of the finite element-infinite element coupling model, represents the three-dimensional coordinates of any node in the finite element-infinite element coupling model.
8. The method of claim 6, wherein: The ratio of the reflected SV wave amplitude value to the incident SV wave amplitude value The ratio of the reflected P wave amplitude value to the incident SV wave amplitude value Is calculated from the following equation (7): （7）。 9. The method of claim 6, wherein: After the large-size model is formed, the unit grid is re-divided, the size ratio of the unit grid of the large-size model to the unit grid of the three-dimensional complex site finite element model is 3-5:1, and then the equivalent node load of any node on the regular boundary surface of the large-size model is calculated according to formula (2)-formula (5).
10. The method of claim 9, wherein: The stress and velocity time-history of each node on the irregular boundary surface of the complex site are mapped to the nodes of each unit grid of the three-dimensional complex site finite element model through the mapping relationship between the unit grids, the velocity mapping is performed by interpolation based on the element shape function, the stress mapping is performed by the stress recovery method, finally, the stress and velocity time-history of each node on the irregular boundary surface of the three-dimensional complex site finite element model are brought into formula (2)-formula (5) to calculate the equivalent node load of any node on the irregular boundary surface of the complex site as the seismic input of the irregular boundary of the complex site.