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1.
Main purpose of this study is to evaluate the dynamic behavior of fluid–rectangular tank–soil/foundation system with a simple and fast seismic analysis procedure. In this procedure, interaction effects are presented by Housner's two mass approximations for fluid and the cone model for soil/foundation system. This approach can determine; displacement at the height of the impulsive mass, the sloshing displacement and base forces for the soil/foundation system conditions including embedment and incompressible soil cases. Models and equations for proposed method were briefly explained for different tank–soil/foundation system combinations. By means of changing soil/foundation conditions, some comparisons are made on base forces and sloshing responses for the cases of embedment and no embedment. The results showed that the displacements and base shear forces generally decreased, with decreasing soil stiffness. However, embedment, wall flexibility, and soil–structure interaction (SSI) did not considerably affect the sloshing displacement. 相似文献
2.
In this research, a parametric study is carried out on the effect of soil–structure interaction on the ductility and strength demand of buildings with embedded foundation. Both kinematic interaction (KI) and inertial interaction effects are considered. The sub‐structure method is used in which the structure is modeled by a simplified single degree of freedom system with idealized bilinear behavior. Besides, the soil sub‐structure is considered as a homogeneous half‐space and is modeled by a discrete model based on the concept of cone models. The foundation is modeled as a rigid cylinder embedded in the soil with different embedment ratios. The soil–structure system is then analyzed subjected to a suit of 24 selected accelerograms recorded on alluvium deposits. An extensive parametric study is performed for a wide range of the introduced non‐dimensional key parameters, which control the problem. It is concluded that foundation embedment may increase the structural demands for slender buildings especially for the case of relatively soft soils. However, the increase in ductility demands may not be significant for shallow foundations with embedment depth to radius of foundation ratios up to one. Comparing the results with and without inclusion of KI reveals that the rocking input motion due to KI plays the main role in this phenomenon. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
3.
In-plane, dynamic soil–structure interaction (SSI) for incident-plane P and SV waves is analyzed for a two-dimensional (2D) model of a shear wall on a rigid foundation that is embedded in a soil layer over bedrock. The indirect-boundary-element method (IBEM) and non-singular Green's functions of distributed loads on inclined lines are used to solve the problem. Although this in-plane, dynamic SSI problem displays characteristics similar to those of 2D, out-of-plane, dynamic SSI, which was studied in our previous work, there exist some significant differences. In analyses of the SSI of the full-scale structures, which recorded strong earthquake shaking, our interpretations are often based on the peaks in the transfer functions of observed structural response. It is shown in this paper how the amplitudes and the frequencies of those peaks are affected by the relative rigidity and thichness of the soil layer below the foundation. 相似文献
4.
结构-地基动力相互作用体系振动台模型试验研究 总被引：81，自引：20，他引：61
本文设计实现了结构－地基动力相互作用体系的振动台试验,通过试验研究了动力相互作用体系的地震动反应的主要规律,由于动力相互作用的影响,软土地基中相互作用体系的频率远小于刚性地基上不考虑结构－地基相互作用的结构频率,而阻尼比例则远大于结构材料阻尼比,软上地基对地震动走滤波和隔震作用,由于上部结构的振动反馈,基底地震动与自由场地震动不相同,上部结构柱顶加速度反应主要由基础转动引起的摆动分量组成,平均分量次之,而弹性变形分量很小,桩身应变幅值呈桩顶大,桩尖小的倒三角形分布,桩上接触压力幅值呈桩顶小,桩尖大的三角形分布,试验表明,结构－地基动力相互作用对体系地震反应的影响是很是显著的,本试验为验证理论与计算分析的研究成果,改进或提出合理的计算模型和分析方法,提出了丰富的试验数据,为进一步研究奠定的基础。 相似文献
5.
《地震工程与结构动力学》2018,47(5):1229-1249
This paper deals with the effect of the foundation mass on the filtering action exerted by embedded foundations. The system under examination comprises a rigid rectangular foundation embedded in a homogeneous isotropic viscoelastic half‐space under harmonic shear waves propagating vertically. The problem is addressed both theoretically and numerically by means of a hybrid approach, where the foundation mass is explicitly included in the kinematic interaction between the foundation and the surrounding soil, thus referring to a “quasi‐kinematic” interaction problem. Based on the results of an extensive parametric study, it is shown that the filtering problem depends essentially on three dimensionless parameters, i.e.: the dimensionless frequency of the input motion, the foundation width‐to‐embedment depth ratio, and the foundation‐to‐soil mass density ratio. In complements to the translational and rotational kinematic interaction factors that are commonly adopted to quantify the filtering effect of rigid massless foundations on the free‐field motion, an additional kinematic interaction factor is introduced, referring to the horizontal motion at the top of a rigid massive foundation. New analytical expressions for the above kinematic interaction factors are proposed and compared with foundation‐to‐free‐field transfer functions computed from available earthquake recordings on two instrumented buildings in LA (California) and Thessaloniki (Greece). Results indicate that the foundation mass can have a strong beneficial effect on the filtering action with increasing foundation‐to‐soil mass density and foundation width‐to‐embedment depth ratios. 相似文献
6.
Evaluation of interaction effects on the system period and the system damping due to foundation embedment and layer depth 总被引：1，自引：0，他引：1
On the basis of some simplifying assumptions, a parametric analysis is made of the interaction effects on the effective period and damping of structures with embedded foundation in a soil layer. A simplified three-dimensional interaction model is used, in which the depth of a cylindrical foundation, the degree of contact between the ground and the footing walls and the depth of a homogeneous stratum over rigid rock are considered variable. The soil is replaced with impedance functions that are taken from a data base obtained with an appropriate numerical technique, so that suitable springs and -pots dependent on the excitation frequency are used. The system period and system damping are determined from the steady-state response of an equivalent single oscillator with flexible base subjected to a harmonic motion with constant amplitude, by equating its resonant response with that of a replacement oscillator with rigid base excited with the same motion. The influence of the foundation embedment and soil layer is investigated for several depths of both the footing and the stratum.It is confirmed that the system period decreases and the system damping increases with the foundation embedment only for sidewalls extending along the entire foundation depth. For embedded footings without sidewall or with sidewall in null contact with the surrounding soil, the effective system parameters behave opposite to those corresponding to the interface condition of total contact. Also, the system damping increases significantly with the layer depth, while the system period is practically insensitive to variations of this characteristic parameter. Finally, introducing additional permissible simplifications, an improved approximate solution for the effective period and damping of coupled systems is presented, which differs from previous analogous approximations in that damping factors of second order are not neglected and the foundation depth is explicitly considered. 相似文献
7.
8.
Centrifuge modeling of seismic response of layered soft clay 总被引：1，自引：0，他引：1
Centrifuge modeling is a valuable tool used to study the response of geotechnical structures to infrequent or extreme events
such as earthquakes. A series of centrifuge model tests was conducted at 80g using an electro-hydraulic earthquake simulator mounted on the C-CORE geotechnical centrifuge to study the dynamic response
of soft soils and seismic soil–structure interaction (SSI). The acceleration records at different locations within the soil
bed and at its surface along with the settlement records at the surface were used to analyze the soft soil seismic response.
In addition, the records of acceleration at the surface of a foundation model partially embedded in the soil were used to
investigate the seismic SSI. Centrifuge data was used to evaluate the variation of shear modulus and damping ratio with shear
strain amplitude and confining pressure, and to assess their effects on site response. Site response analysis using the measured
shear wave velocity, estimated modulus reduction and damping ratio as input parameters produced good agreement with the measured
site response. A spectral analysis of the results showed that the stiffness of the soil deposits had a significant effect
on the characteristics of the input motions and the overall behavior of the structure. The peak surface acceleration measured
in the centrifuge was significantly amplified, especially for low amplitude base acceleration. The amplification of the earthquake
shaking as well as the frequency of the response spectra decreased with increasing earthquake intensity. The results clearly
demonstrate that the layering system has to be considered, and not just the average shear wave velocity, when evaluating the
local site effects. 相似文献
9.
This paper is concerned with the dynamic response of rigid strip foundations of arbitrary geometry embedded in a homogeneous elastic half-space. The embedded rigid foundation is modelled by an equivalent domain in a uniform half-space which is subjected to an appropriate body force field. The components of the impedance matrix are determined through the solution of a linear simultaneous equation system which is established by invoking rigid body displacements of discrete locations within the equivalent domain and appropriate equilibrium consideration. It is found that high numerical efficiency and flexibility can be achieved using the body force model when compared to boundary integral formulations through the selection of appropriate displacement influence functions and a ‘parent domain’ in the analysis. Numerical results are presented to illustrate the influence of the embedment ratio, frequency of excitation, foundation geometry and Poisson's ratio on the vertical, horizontal, rocking and coupled impedances of a single embedded foundation. The effect on the impedance due to the presence of an adjacent embedment is investigated for various distances between foundations and embedment ratios. 相似文献
10.
均匀土-桩基-结构相互作用体系的计算分析 总被引：14，自引：4，他引：14
本文以结构－地基动力相互作用振动台模型试验为基础，结合通用有限元软件ANSYS，对均匀土－桩基－结构动力相互作用体系进行了三维有限元分析。计算中土体采用等效线性模型，利用面－面接触单元考虑土体与结构交界面的状态非线性，计算与试验得出的规律基本一致。桩基与土体间发生了脱开再闭合和滑移现象。桩身应变幅值分布呈桩顶大、桩尖小的倒三角分布，角桩的应变幅值较大，边排中桩和中桩的应变幅值较小。桩土接触压力幅值呈桩顶小、桩尖大的三角形分布。在沿振动方向的三排桩中，边排桩的滑移比中排桩的滑移量大。通过计算分析与试验的对照研究，验证了采用的计算模型与分析方法的合理性，为结构－地基相互作用的进一步研究奠定了基础。 相似文献
11.
设计并完成了野外大比例(1:2)土-箱形基础-框架结构相互作用系统顶部小幅激振试验.通过改变上部结构质量和基础侧限埋深,激振试验得到了同一基础不同上部结构质量与同一上部结构不同基础侧限埋深等5种工况下相互作用对系统自振频率及箱形基础阻抗函数的影响.由试验结果分析可知,当上部结构质量增加时,上部结构与土体间的相对刚度降低,相互作用对系统自振频率的影响减弱;同时由于上部结构和基础间惯性相互作用的影响,基础阻抗函数随上部结构质量的增加而增加.随着基础侧限埋深的减小,基础刚度降低,相互作用体现得更加明显.与理论结果相比,无侧限埋深基础的平动和转动基础阻抗值和理论值吻合较好.由于基础侧边回填土剪切模量小于基础底部土体剪切模量,所以同理论值相比试验得到的基础侧限埋深对基础阻抗影响系数相对较小. 相似文献
12.
设计并完成了野外大比例(1∶2)土-箱形基础-框架结构相互作用系统顶部小幅激振试验。通过改变上部结构质量和基础侧限埋深,激振试验得到了同一基础不同上部结构质量与同一上部结构不同基础侧限埋深等5种工况下相互作用对系统自振频率及箱形基础阻抗函数的影响。由试验结果分析可知,当上部结构质量增加时,上部结构与土体间的相对刚度降低,相互作用对系统自振频率的影响减弱;同时由于上部结构和基础间惯性相互作用的影响,基础阻抗函数随上部结构质量的增加而增加。随着基础侧限埋深的减小,基础刚度降低,相互作用体现得更加明显。与理论结果相比,无侧限埋深基础的平动和转动基础阻抗值和理论值吻合较好。由于基础侧边回填土剪切模量小于基础底部土体剪切模量,所以同理论值相比试验得到的基础侧限埋深对基础阻抗影响系数相对较小。 相似文献
13.
Foundation soil interaction is studied using an analytical two-dimensional model, for circular foundations embedded in a homogeneous elastic half-space and for incident plane P- and SV- and for surface Rayleigh waves. The scattered waves are expanded in complete series of cyclindrical wave functions. A detailed analysis is presented of the foundation response to unit amplitude incident waves as a function of the type of incident waves and angle of incidence, the depth of the embedment and the foundation mass per unit length.It is shown that free-field translations and point rotation approximate well the foundation input motion only for very long incident waves. For shorter incident waves, those in general overestimate the foundation input motion. Neglecting the rotation of the foundation input motion (which is usually done in practice) may eliminate a major contribution to the base excitation of buildings and may cause nonconservative estimates of the forces in these buildings. Incident waves appear as ‘longer’ to a shallow foundation than to a deeper foundation. Therefore, deeper foundations are more effective in reflecting and scattering the short incident waves. 相似文献
14.
Correction factors for SSI effects predicted by simplified models: 2D versus 3D rectangular embedded foundations 
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下载免费PDF全文 The effects of soil‐structure interaction (SSI) are often studied using two‐dimensional (2D) or axisymmetric three‐dimensional (3D) models to avoid the high cost of the more realistic, fully 3D models, which require 2 to 3 orders of magnitude more computer time and storage. This paper analyzes the error and presents correction factors for system frequency, system damping, and peak amplitude of structural response computed using impedances for linear in‐plane 2D models with rectangular foundations, embedded in uniform or layered half‐space. They are computed by comparison with results for 3D rectangular foundations with the same vertical cross‐section and different aspect ratios. The structure is represented by a single degree‐of‐freedom oscillator. Correction factors are presented for a range of the model parameters. The results show that in‐plane 2D approximations overestimate the SSI effects, exaggerating the frequency shift, the radiation damping, and the reduction of the peak amplitude. The errors are larger for stiffer, taller, and heavier structures, deeper foundations, and deeper soil layer. For example, for a stiff structure like Millikan library (NS response; length‐to‐width ratio ≈ 1), the error is 6.5% in system frequency, 44% in system damping, and 140% in peak amplitude. The antiplane 2D approximation has an opposite effect on system frequency and the same effect on system damping and peak relative response. Linear response analysis of a case study shows that the NEHRP‐2015 provisions for reduction of base shear force due to SSI may be unsafe for some structures. The presented correction factor diagrams can be used in practical design and other applications. 相似文献
15.
In this study, simplified numerical models are developed to analyze the soil-structure interaction (SSI) effect on frame structures equipped with viscoelastic dampers (VEDs) based on pile group foundation. First, a single degree-of-freedom (SDOF) oscillator is successfully utilized to replace the SDOF energy dissipated structure considering the SSI effect. The equivalent period and damping ratio of the system are obtained through analogical analysis using the frequency transfer function with adoption of the modal strain energy (MSE) technique. A parametric analysis is carried out to study the SSI effect on the performance of VEDs. Then the equilibrium equations of the multi degree-of-freedom (MDOF) structure with VEDs considering SSI effect are established in the frequency domain. Based on the assumption that the superstructure of the coupled system possesses the classical normal mode, the MDOF superstructure is decoupled to a set of individual SDOF systems resting on a rigid foundation with adoption of the MSE technique through formula derivation. Numerical results demonstrate that the proposed methods have the advantage of reducing computational cost, however, retaining the satisfactory accuracy. The numerical method proposed herein can provide a fast evaluation of the efficiency of VEDs considering the SSI effect. 相似文献
16.
A study on the seismic response of massive flexible strip-foundations embedded in layered soils and subjected to seismic excitation is presented. Emphasis is placed on the investigation of the system response with the aid of a boundary element–finite element formulation proper for the treatment of such soil–structure interaction problems. In the formulation, the boundary element method (BEM) is employed to overcome the difficulties that arise from modeling the infinite soil domain, and the finite element method (FEM) is applied to model the embedded massive flexible strip-foundation. The numerical solution for the soil–foundation system is obtained by coupling the FEM with the BEM through compatibility and equilibrium conditions at the soil–foundation and soil layer interfaces. A parametric study is conducted to investigate the effects of foundation stiffness and embedment on the seismic response. 相似文献
17.
The investigation reported in this paper studies the effects of soil–structure interaction (SSI) on the seismic response and damage of building–foundation systems. A simple structural model is used for conducting a parametric study using a typical record obtained in the soft soil area of Mexico City during the 1985 earthquake. Peak response parameters chosen for this study were the roof displacement relative to the base and the hysteretic energy dissipated by the simple structural model. A damage parameter is also evaluated for investigating the SSI effects on the seismic damage of buildings. The results indicate that in most cases of inelastic response, SSI effects can be evaluated considering the rigid‐base case and the SSI period. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
18.
Inelastic displacement ratios (IDRs) of nonlinear soil–structure interaction (SSI) systems located at sites with cohesive soils are investigated in this study. To capture the effects of inelastic cyclic behavior of the supporting soil, the Beam on Nonlinear Winkler Foundation (BNWF) model is used. The superstructure is modeled using an inelastic single-degree-of-freedom (SDOF) system model. Nonlinear SSI systems representing various combinations of unconfined compressive strengths and shear wave velocities are considered in the analysis. A set of strong ground motions recorded at sites with soft to stiff soils is used for considering the record-to-record variability of IDRs. It is observed that IDRs for nonlinear SSI systems are sensitive to the strength and the stiffness properties of both the soil and the structure. For the case of SSI systems on the top of cohesive soils, the compressive strength of the soil has a significant impact on the IDRs, which cannot be captured by considering only the shear wave velocity of the soil. Based on the results of nonlinear time-history analysis, a new equation is proposed for estimating the mean and the dispersion of IDRs of SSI systems depending on the characteristic properties of the supporting soil, dimensions of the foundation, and properties of the superstructure. A probabilistic framework is presented for the performance-based seismic design of SSI systems located at sites with cohesive soils. 相似文献
19.
This paper evaluates the inertial soil–structure interaction (SSI) effects on linear and bilinear structures supported on foundation that is able to translate and rock when subject to near-fault ground motions. Through rigorous dimensional analysis, the peak structural responses (e.g. structural drift and total acceleration) of the soil–foundation–structure interacting (SFSI) systems are characterized by a set of dimensionless Π-parameters, which can decisively describe the interactive behavior of SFSI systems. By comparing the normalized structural responses of various structure–foundation systems with their fixed-base counterparts, the study reveals that SSI effects highly depend on the structure-to-pulse frequency ratio, Πω, the foundation-to-structure stiffness ratio, Πk, damping coefficient of foundation impedance, Πc, the foundation rocking, and the development of nonlinearity in structures. For linear structures, the SSI effects are insignificant when the structure-to-pulse frequency ratio (Πω) is smaller than 1.5 and can amplify the structural responses when Πω is higher than 1.5. Foundation rocking can shift and enlarge the response amplification zone of SSI. For nonlinear structures, SSI tends to reduce the structural responses for Πω<3 while can increase the ductility demands for Πω≥3. The bilinear structures may experience more significant SSI effects than linear structures in certain frequency ranges. The numerical simulations on ten real building cases exhibiting significant rocking and a detailed case study on a nine-story frame structure demonstrate the applicability of dimensional analysis results to predict the SSI effects on realistic building structures. The study demonstrates that the dimensional analysis provides a concise and systematic way of evaluating SSI effects. 相似文献
20.
Different levels of model sophistication have recently emerged to support seismic risk assessment of bridges, but mostly at the expense of neglecting the influence of vertical ground motions (VGMs). In this paper, the influence of VGMs on bridge seismic response is presented and the results are compared with the case of horizontal‐only excitations. An advanced finite element model that accounts for VGMs is first developed. Then, to investigate the effect of soil–structure interaction (SSI) including liquefaction potential, the same bridge with soil‐foundation and fixed boundary conditions is also analyzed. Results show that the inclusion of the VGMs has a significant influence on the seismic response, especially for the axial force in columns, normal force of bearings, and the vertical deck bending moments. However, VGMs do not have as much influence on the seismic demand of the pile cap displacements or pile maximum axial forces. Also, the significant fluctuation of the column axial force can reduce its shear and flexural capacity, and a heightened reversal of flexural effects may induce damage in the deck. In addition, relative to the fixed base case, SSI effects tend to reduce response quantities for certain ground motions while increasing demands for others. This phenomenon is explained as a function of the frequency content of the ground motions, the shift in natural vertical periods, and the VGM spectral accelerations at higher modes. Moreover, the mechanisms of liquefaction are isolated relative to SSI effects in nonliquefiable soils, revealing the influence of liquefaction on bridge response under VGMs. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献