Sharif Digital Repository

The seismic behavior of the non-structural components and their effect on the overall performance of the building structures is among the important issue that should be thoroughly investigated from different aspects such as the resiliency, and the replacing cost. On the other hand, in analysis and design of structures, assuming a rigid under-laying soil is not always right and the effect of soil-structure interaction should be taken into account in certain cases. A flexible support could affect the dynamic characteristics of the structures through elongating their natural vibrating periods as well as increasing their damping ratios, thus should not be ignored. If the period of a... 

During the last few decades, the seismic codes have allowed the building structures to behave nonlinearly under the strong ground motions to dissipate the input seismic energy. That usually takes place by formation of plastic hinges in the structural elements which in turn leads to some permanent deformation, such as residual drifts, in these structural members. Repairing these damages are both time and cost consuming. Rocking frames are among the newly introduced re-centering lateral resistance systems which in combination with some dissipating devices (fuse) prevents the formation of plastic hinge in the main frame by concentrating the plastic deformation in these energy dissipating fuse,... 

The main purpose of this study is to estimate the natural frequency and damping ratio for soil-structure systems with embedded foundation with sufficient accuracy. The results are then compared to guidelines in current seismic codes. This is done through an extensive parametric study using a set of non-dimensional parameters, which define the soil-structure systems. For this purpose a simplified soil-structure model is used. Although more rigorous models and numerical solutions are available, they are time consuming and not suitable for parametric study. Existing formula for seismic provisions for the equivalent period and damping ratio of soil-structure systems are based on studies on... 

This paper puts forward a probabilistic approach for simultaneous identification of the dynamic stiffnesses of the soil-foundation and the foundation input motion of soil-structure systems from sparsely-measured structural responses. The soil-structure system in this approach is represented by a shear building resting on sway- and rocking-representative springs and dashpots. The proposed approach employs unknown-input extended Kalman filtering in time domain. This method is built upon Bayesian updating and accounts for two major sources of uncertainty in the problem: the process noise that account for the modeling errors and the measurement noise. In the proposed method, the state vector of... 

The primary objective of this thesis is twofold: First, the effect of soil-structure interaction (SSI) on the collapse probability of structures are studied. Second, the consequences of practicing the SSI provisions of two prominent seismic design guidelines, i.e., ASCE 7-10 and ASCE 7-16, on the performance of building structures are evaluated and compared. The analyses are conducted for a wide range of dimensionless parameters, which represent different structures on a variety of soil types. To compute the probability of collapse, incremental dynamic analyses are conducted in which In addition to ground motion variability, the uncertainties in the properties of the soil-structure systems... 

Investigating the behavior of piled-raft foundations is a three-dimensional problem. The shape and location of the piles in the raft as well as the complex interaction of the soil-structure in these foundations should be analyzed in a three-dimensional fashion to indicate the real behavior of this type of foundations. The soil must also be analyzed in a nonlinear state to achieve the correct bearing capacity of these foundations. In this research, a nonlinear 3D analysis was performed using FLAC3D to investigate the behavior of piled-raft foundations, and the effect of various factors such as the length, arrangement and number of the piles, the loading level and the thickness of the raft, on... 

Up till now, various contributions of research to soil-structure-interaction context have been primarily focused on structural systems exhibiting elastic-perfectly plastic material behavior. In this paper, combined effects of material degradation, p-delta, and soil-structure-interaction considering foundation uplift have been deemed to determine seismic response of a single degree of freedom system. The system is composed of a column with a lumped mass on top that is placed on a rigid foundation. The foundation is mounted on Winkler springs and dashpots to account for soil-foundation compliance and material/radiational damping. The springs are tensionless to guarantee that uplift phenomenon... 

In this research the flexibility of subterranean levels on foundation input motion (FIM), especially rocking component is investigated through parameter analyses. The so-called motion is induced as a result of kinematic soil-structure interaction (SSI). The foregoing interaction reduces the translational component of foundation input motion in rigid embedded foundations when compared to the free-field motion (FFM), as well as yielding rocking component in the foundation. On the other hand, increasing the embedment depth which is equivalent to the presence of subterranean levels in a building decreases the commonly-held “rigid” assumption’s accuracy for the embedded part. Given this effect,... 

Recent studies on inelastic behavior of soil-structure systems indicate that seismic design codes provisions, which use the same response modification factor for fixed base structures and soil-structure systems, are not appropriate and could lead to an increase in ductility demand of structures (as a part of soil-structure system). As a result, to reduce design base shear and design forces with regards to collaboration of soil-structure interaction could be in non-conservative manner. In all of these studies, the ductility component of the response modification factor (i.e. Rµ ) has been the major concern and the overstrength component has been ignored. However, the existence of... 

Shape memory alloys (SMA) are materials with shape memory effect and high recentering capacity. Recently, application of SMAs in building structures and for the purpose of structure control during earthquake has been considered by many researchers. Researchers have tried to reduce the residual displacement of the structure after earthquake and also increase the dissipated energy by using this material in different forms such as wire, spring, bolt, etc.. In this research the seismic performance of steel structures equipped with SMA connection has been studied, considering the soil and structure interaction. The purpose of this research is to investigate the amount of required SMA bolts in... 

In this research, the effect of nonlinear behavior of soil on the nonlinear responses of super-structure has been investigated. During the design process of practical buildings, engineers usually disregard the effect of soil-structure interaction. In some cases in which the effect of soil-structure interaction is considered, nonlinear behavior of soil usually is modeled through an equivalent linear method which is proposed by the most existing design codes. Past studies show that considering the effect of soil-structure interaction, could change the responses of super-structure in comparison with those whose base are fixed. In many of these studies, nonlinear behavior of beneath soil is... 

The primary objective of this thesis is twofold: First, the effect of soil-structure interaction (SSI) and SSI seismic design provisions on the seismic risk estimates of buildings are studied. Risk, in this context, denotes the probability distribution of seismic monetary loss due to structural and non-structural damage. The risk analysis here uncovers the probability that SSI is beneficial, detrimental, or ineffective on seismic losses. Moreover, the consequence of practicing SSI provisions of current seismic codes on the seismic risk of structures is investigated. Second, the consequences of practicing the SSI provisions of two prominent seismic design guidelines, i.e., ASCE 7-10 and the... 

The main objective of this study is to identify the contribution of different damping mechanisms in equivalent damping of inelastic soil- structure systems which can be used to reach a better estimation of inelastic soil- structure systems response using some simplified methods. This mechanisms include the material damping of soil and structure, radiation damping of soil and also the structure’s nonlinear behavior. Despite the studies have been done, even in the fixed base systems, there is not an exact prediction for the contribution rate of inherent damping and energy absorption related to nonlinear behavior in equivalent damping of system. Considering the flexibility of soil under the... 

The behavior of soil-structure interface plays an important role in the static and dynamic analysis of soil-structure systems. Development of new materials such as polymer concrete requires an understanding of the behavior and their interaction with other materials. In this investigation, the interface behavior between polymer concrete and ordinary concrete with sand was studied using interface direct shear tests. In order to find optimum content of epoxy resin for polymer concrete, a series of tensile and compressive tests were conducted. To study the mechanical properties of concretes-sand interfaces behavior two series of interface direct shear tests were conducted at three different... 

Different structural systems have been declared and used in recent decades. To identify more about their performance, it's crucial that while evaluating their characteristic, the effect of miscellaneous natural phenomena would be evaluated. One of these phenomena is SSI or Soil effect actively on the structure performance. As modeling has serious effect on the results precision related with SSI effect, usage of 3D Models those that are more compatible with the real ones is important. So, in this research two 2 and 5 story building possessing real dimension in the format of 3D-Modeling with all effective details were modeled by finite element method. For seismic analysis, 7 couple records... 

The direct technique in which response of the soil and the structure is obtained using numerical methods like finite element is not an appropriate method for seismic analysis of soil-structure interaction of buildings. For this reason, the effects of the foundation and retaining walls are considered for a building with underground floors. Interaction models include a concrete moment frame with ten stories and zero to five underground floors in which constructed on a specific soil and analyzed in FLAC software. Three types of accelerograph Tabas, El-Centro, and Luma are used for time history analysis. Indeed, for a model with a rigid foundation, a ten stories moment frame without an... 

The main purpose of this study is stochastic analysis of base-isolated structures considering soil-structure interaction. Due to stochastic nature of earthquake and existence of uncertainties in non-linear behavior of and properties of soil, it is better to calculate the responses of the structure via random vibrations approach. In this approach first of all, the differential equations of structure are obtained in deterministic vibration mode and then by the available theories, differential equations of covariance of the responses are obtained. Solving these equations leads to the finding of the standard deviations of the responses of the structure in each moment. In backward differential...