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1.
An evaluation of the wave passage effects on the relevant dynamic properties of structures with flexible foundation is presented. A simple soil–structure system similar to that used in practice to take into account the inertial interaction effects by the soil flexibility is studied. The kinematic interaction effects due to non‐vertically incident P, SV and Rayleigh waves are accounted for in this model. The effective period and damping of the system are obtained by establishing an equivalence between the interacting system excited by the foundation input motion and a replacement oscillator excited by the free‐field ground motion. In this way, the maximum structural response could be estimated from standard free‐field response spectra using the period and damping of the building modified by both the soil flexibility and the travelling wave effects. Also, an approximate solution for the travelling wave problem is examined over wide ranges of the main parameters involved. Numerical results are computed for a number of soil–structure systems to identify under which conditions the effects of wave passage are important. It comes out that these effects are generally negligible for the system period, but they may significantly change the system damping since the energy dissipation within the soil depends on both the wave radiation and the diffraction and scattering of the incident waves by the foundation. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
2.
The effects of soil–structure interaction in yielding systems are evaluated, including both kinematic and inertial interaction. The concepts developed previously for interacting elastic systems are extended to include the non‐linear behavior of the structure. A simple soil–structure system representative of code‐ designed buildings is investigated. The replacement oscillator approach used in practice to account for the elastic interaction effects is adjusted to consider the inelastic interaction effects. This is done by means of a non‐linear replacement oscillator defined by an effective ductility together with the known effective period and damping of the system for the elastic condition. To demonstrate the efficiency of this simplified approach, extensive numerical evaluations are conducted for elastoplastic structures with embedded foundation in a soil layer over elastic bedrock, excited by vertically propagating shear waves. Both strength and displacement demands are computed with and without regard to the effect of foundation flexibility, taking as control motion the great 1985 Michoacan earthquake recorded at a site representative of the soft zone in Mexico City. Results are properly interpreted to show the relative effects of interaction for elastic and yielding systems. Finally, it is demonstrated how to implement this information in the context of code design of buildings. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
3.
Parametric system identification is used to evaluate seismic soil–structure interaction effects in buildings. The input–output strong motion data pairs needed for evaluations of flexible- and fixed-base fundamental mode parameters are derived. Recordings of lateral free-field, foundation, and roof motions, as well as foundation rocking, are found to be necessary for direct evaluations of modal parameters for both cases of base fixity. For the common situation of missing free-field or base rocking motions, procedures are developed for estimating the modal parameters that cannot be directly evaluated. The accuracy of these estimation procedures for fundamental mode vibration period and damping is verified for eleven sites with complete instrumentation of the structure, foundation, and free-field. © 1998 John Wiley & Sons, Ltd. 相似文献
4.
The effects of soil‐structure interaction on the seismic response of multi‐span bridges are investigated by means of a modelling strategy based on the domain decomposition technique. First, the analysis methodology is presented: kinematic interaction analysis is performed in the frequency domain by means of a procedure accounting for radiation damping, soil–pile and pile‐to‐pile interaction; the seismic response of the superstructure is evaluated in the time domain by means of user‐friendly finite element programs introducing suitable lumped parameter models take into account the frequency‐dependent impedances of the soil–foundation system. Second, a real multi‐span railway bridge longitudinally restrained at one abutment is analyzed. The input motion is represented by two sets of real accelerograms: one consistent with the Italian seismic code and the other constituted by five records characterized by different frequency contents. The seismic response of the compliant‐base model is compared with that obtained from a fixed‐base model. Pile stress resultants due to kinematic and inertial interactions are also evaluated. The application demonstrates the importance of performing a comprehensive analysis of the soil–foundation–structure system in the design process, in order to capture the effects of soil‐structure interaction in each structural element that may be beneficial or detrimental. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
5.
A general procedure is presented to study the dynamic soil–structure interaction effects on the response of long-span suspension and cable-stayed bridges subjected to spatially varying ground motion at the supporting foundations. The foundation system is represented by multiple embedded cassion foundations and the frequency-dependent impedance matrix for the multiple foundations system takes into account also the cross-interaction among adjacent foundations through the soil. To illustrate the potential implementation of the analysis, a numerical example is presented in which the dynamic response of the Vincent–Thomas suspension bridge (Los Angeles, CA) subjected to the 1987 Whittier earthquake is investigated. Although both kinematic and inertial effects are included in the general procedure, only the kinematic effects of the soil–structure interaction are considered in the analysis of the test case. The results show the importance of the kinematic soil–foundation interaction on the structural response. These effects are related to the type, i.e. SH-, SV-, P- or Rayleigh waves and to the inclination of the seismic wave excitation. Moreover, rocking components of the foundation motion are emphasized by the embedment of the foundation system and greatly alter the structural response. 相似文献
6.
The paper presents a numerical model for the dynamic analysis of pile groups with inclined piles in horizontally layered soil deposits. Piles are modelled with Euler–Bernoulli beams, while the soil is supposed to be constituted by independent infinite viscoelastic horizontal layers. The pile–soil–pile interaction as well as the hysteretic and geometric damping is taken into account by means of two‐dimensional elastodynamic Green's functions. Piles cap is considered by introducing a rigid constraint; the condensation of the problem permits a consistent derivation of both the dynamic impedance matrix of the soil–foundation system and the foundation input motion. These quantities are those used to perform inertial soil–structure interaction analyses in the framework of the substructure approach. Furthermore, the model allows evaluating the kinematic stress resultants in piles resulting from waves propagating in the soil deposit, taking into account the pile–soil–pile interactions. The model validation is carried out by performing accuracy analyses and comparing results in terms of dynamic impedance functions, kinematic response parameters and pile stress resultants, with those furnished by 3D refined finite element models. To this purpose, classical elastodynamic solutions are adopted to define the soil–pile interaction problem. The model results in low computational demands without significant loss of precision, compared with more rigorous approaches or refined finite element models. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
7.
Masoud Moghaddasi Gregory A. MacRae J. G. Chase Misko Cubrinovski Stefano Pampanin 《地震工程与结构动力学》2015,44(11):1805-1821
This paper introduces a simple method to consider the effects of inertial soil–structure interaction (SSI) on the seismic demands of a yielding single‐degree‐of‐freedom structure. This involves idealizing the yielding soil–structure system as an effective substitute oscillator having a modified period, damping ratio, and ductility. A parametric study is conducted to obtain the ratio between the displacement ductility demand of a flexible‐base system and that of the corresponding fixed‐base system. It is shown that while additional foundation damping can reduce the overall response, the effects of SSI may also increase the ductility demand of some structures, mostly being ductile and having large structural aspect ratio, up to 15%. Finally, a design procedure is provided for incorporation of the SSI effects on structural response. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
8.
The paper presents a numerical model for the analysis of the soil–structure kinematic interaction of single piles and pile groups embedded in layered soil deposits during seismic actions. A finite element model is considered for the pile group and the soil is assumed to be a Winkler‐type medium. The pile–soil–pile interaction and the radiation problem are accounted for by means of elastodynamic Green's functions. Condensation of the problem permits a consistent and straightforward derivation of both the impedance functions and the foundation input motion, which are necessary to perform the inertial soil–structure interaction analyses. The model proposed allows calculating the internal forces induced by soil–pile and pile‐to‐pile interactions. Comparisons with data available in literature are made to study the convergence and validate the model. An application to a realistic pile foundation is given to demonstrate the potential of the model to catch the dynamic behaviour of the soil–foundation system and the stress resultants in each pile. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
9.
J.X. Zhao 《Soil Dynamics and Earthquake Engineering》1998,17(2):73-88
A practical method for estimating kinematic interaction from earthquake records is presented. The kinematic interaction is characterized by a two-parameter model and these parameters can be estimated by using a frequency-domain systems identification method. The simple model can be used to model both wave passage effects and the effects of incoherent wave fields. Numerical simulation tests show that kinematic interaction parameters can be estimated to their best accuracy by using building base responses and the free-field excitation and can also be estimated by using building responses, base responses and the free-field excitation. The method was applied to two buildings with raft foundations and it was found that kinematic interaction was significant during earthquakes. Published theoretical models (wave passage effect) for vertically incident SH waves can be used to estimate the transfer functions up to 4–5 Hz and the models for horizontally propagating waves under-predict the estimated transfer functions by a significant amount at frequencies beyond about 1–2 Hz. Theoretical models for a massless rigid foundation under the excitation of an incoherent wave field predict the general trend of the estimated transfer function reasonably well over a large frequency range. The results of numerical examples show that the recorded response spectral attenuation of basement records at high frequencies with respect to the free-field is mainly caused by kinematic interaction, while the changes in storey shear and overturning moment in a structure due to soil flexibility are mainly the results of inertial interaction. 相似文献
10.
The elastodynamic response of coupled soil-pile-structure systems to seismic loading is studied using rigorous three-dimentional (3D) finite element models. The system under investigation comprises of a single pile supporting a single degree of freedom (SDOF) structure founded on a homogeneous viscoelastic soil layer over rigid rock. Parametric analyses are carried out in the frequency domain, focusing on the dynamic characteristics of the structure, as affected by typical foundation properties such as pile slenderness and soil-pile relative stiffness. Numerical results demonstrate the strong influence on effective natural SSI period of the foundation properties and the crucial importance of cross swaying-rocking stiffness of the pile. Furthermore, the notion of a pseudo-natural SSI frequency is introduced, as the frequency where pile-head motion is minimized with respect to free field surface motion. Dynamic pile bending is examined and the relative contributions of kinematic and inertial interaction, as affected by the frequency content of input motion, are elucidated. 相似文献
11.
This paper presents a simple and stable procedure for the estimation of periods and dampings of piled shear buildings taking soil–structure interaction into account. A substructuring methodology that includes the three-dimensional character of the foundations is used. The structure is analyzed as founded on an elastic homogeneous half-space and excited by vertically incident S waves. The strategies proposed in the literature to estimate the period and damping are revised, and a modified strategy is proposed including crossed impedances and all damping terms. Ready-to-use graphs are presented for the estimation of flexible-base period and damping in terms of their fixed-base values and the system configuration. Maximum shear forces together with base displacement and rocking peak response are also provided. It is shown that cross-coupled impedances and kinematic interaction factors need to be taken into account to obtain accurate results for piled buildings. 相似文献
12.
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
13.
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
14.
The kinematic soil–foundation interaction changes the free field ground motion to a different motion at the foundation of a structure. This interaction effect may be expressed by the ratio of the peak horizontal acceleration of a rigid and relatively lightweight foundation to the peak horizontal acceleration at the ground surface in the free field. It is found that the interaction effect can be defined by a simple function of the ratio of the peak horizontal ground velocity and ground acceleration in the free field, the length of the foundation and the shear wave velocity in the soil. Predictive equations for the kinematic soil foundation effect are derived using 350 strong motion records generated by 114 earthquakes world-wide. At the same time, an attenuation relationship is derived for the ratio of the peak horizontal ground velocity and acceleration from the same set of data. Ten case histories are studied; the interaction effects are calculated by using the predictive equations and then compared with measured field values. The results of the comparison illustrate the degree of predictive capability of the method when the foundation mass and the inertial soil–foundation interaction are not considered. 相似文献
15.
A substructuring method has been implemented for the seismic analysis of bridge piers founded on vertical piles and pile groups in multi-layered soil. The method reproduces semi-analytically both the kinematic and inertial soil–structure interaction, in a simple realistic way. Vertical S-wave propagation and the pile-to-pile interplay are treated with sufficient rigor, within the realm of equivalent-linear soil behaviour, while a variety of support conditions of the bridge deck on the pier can be studied with the method. Analyses are performed in both frequency and time domains, with the excitation specified at the surface of the outcropping (‘elastic’) rock. A parameter study explores the role of soil–structure interaction by elucidating, for typical bridge piers founded on soft soil, the key phenomena and parameters associated with the interplay between seismic excitation, soil profile, pile–foundation, and superstructure. Results illustrate the potential errors from ignoring: (i) the radiation damping generated from the oscillating piles, and (ii) the rotational component of motion at the head of the single pile or the pile-group cap. Results are obtained for accelerations of bridge deck and foundation points, as well as for bending moments along the piles. © 1997 by John Wiley & Sons, Ltd. 相似文献
16.
This paper presents a statistical study of the kinematic soil-foundation-structure interaction effects on the maximum inelastic
deformation demands of structures. Discussed here is the inelastic displacement ratio defined as the maximum inelastic displacement
demands of structures subjected to foundation input motions divide by those of structures subjected to free-field ground motions.
The displacement ratio is computed for a wide period range of elasto-plastic single-degree-of-freedom (SDOF) systems with
various levels of lateral strength ratios and with different sizes of foundations. Seventy-two earthquake ground motions recorded
on firm soil with average shear wave velocities between 180 m/s and 360 m/s are adopted. The effects of period of vibration,
level of lateral yielding strength and dimension of foundations are investigated. The results show that kinematic interaction
will reduce the maximum inelastic displacement demands of structures, especially for systems with short periods of vibration,
and the larger the foundation size the smaller the maximum inelastic displacement becomes. In addition, the inelastic displacement
ratio is nearly not affected by the strength ratio of structures for systems with periods of vibration greater than about
0.3 s and with strength ratios smaller than about 3.0. Expressions obtained from nonlinear regression analyses are also proposed
for estimating the effects of kinematic soil-foundation-structure interaction from the maximum deformation demand of the inelastic
system subjected to free-field ground motions. 相似文献
17.
Antiplane response of a dike with flexible soil-structure interface to incident SH waves 总被引：2，自引：0，他引：2
Abdul Hayir Maria I. Todorovska Mihailo D. Trifunac 《Soil Dynamics and Earthquake Engineering》2001,21(7)
Studies of the effects of differential ground motions on structural response generally do not consider the effects of the soil-structure interaction. On the other end, studies of soil-structure interaction commonly assume that the foundation of the structure (surface or embedded) is rigid. The former ignore the scattering of waves from the foundation and radiation of energy from the structure back to the soil, while the latter ignore quasi-static forces in the foundations and lower part of the structure deforming due to the wave passage. This paper studies a simple model of a dike but considers both the soil-structure interaction and the flexibility of the foundation. The structure is represented by a wedge resting on a half-space and excited by incident plane SH-waves. The structural ‘foundation’ is a flexible surface that can deform during the passage of seismic waves. The wave function expansion method is used to solve for the motions in the half-pace and in the structure. The displacements and stresses in the structure are compared with those for a fixed-base model shaken by the free-field motion. The results show large displacements near the base of the structure due to the differential motion of the base caused by the wave passage. 相似文献
18.
The inertial interaction analysis of a structure founded on piles is conventionally performed by imposing that the Foundation Input Motion is merely that of the free field, thus neglecting the kinematic interaction between piles and soil generated by the passage of seismic waves. This would lead to unnecessary overconservatism in the design, as there is evidence that the free-field motion may be thoroughly filtered out by piles (generally reduced), especially in the case of soft soils, where piles are recurrently required to carry out the total load transmitted by the superstructure and/or to reduce foundation settlements. Results provided from analytical and numerical tools elucidate the crucial aspects controlling the mechanism of filtering effect. Reduced design spectra are also suggested to account for the beneficial effect coming from the piles when the inertial interaction analysis of the superstructure is being performed. 相似文献
19.
A closed-form analytical solution is presented for the dynamic response of a SDOF oscillator, supported by a flexible foundation embedded in an elastic half-space, and excited by plane SH waves. The solution is obtained by the wave function expansion method. The solution is verified for the special case of a rigid foundation by comparison with published results. The model is used to investigate the effect of the foundation flexibility on the system response. The results show that the effect is significant for both foundation response and structural relative response. For a system with more flexible foundation, the radiation damping is smaller, the foundation response is larger, especially for obliquely incident waves, while the structural relative response is smaller, and the system frequency shifts towards lower frequencies. This simple model may be helpful to obtain insight into the effects of soil–structure interaction for a slim structure on an extended flexible foundation. 相似文献
20.
Soil‐structure system frequency and damping: Estimation from eigenvalues and results for a 2D model in layered half‐space 
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下载免费PDF全文 This paper presents a formulation for estimation of the frequency and damping of a soil‐structure interaction system based on the classical modal analysis and solving the system eigenvalue problem. Without loss of generality, the structure is represented by a single degree of freedom oscillator, while the soil effects are included through impedance functions for in‐plane motion of a 2D rigid foundation. For the results presented in this paper, the impedance functions were computed by the indirect boundary element method for a rectangular foundation embedded in a soil layer over elastic bedrock. The study shows that the classical modal‐analysis approach works well, with the exception of squat, stiff structures, even though the impedance functions are frequency‐dependent and the soil‐structure interaction system does not possess normal modes. The study also shows that system frequency and damping are independent of the wave passage effects, contrary to findings of some previous studies, and that the site conditions, represented by the soil‐layer thickness and stiffness contrast between bedrock and soil layer, have significant influences on both system frequency and system damping. Finally, the paper examines the accuracy of some of the simple methods for estimation of these two system parameters and comments on some conflicting conclusions of previous studies about the effects of foundation embedment. 相似文献