Sharif Digital Repository

A probabilistic method is presented for identifying the dynamic soil-foundation stiffnesses of building structures. It is based on model updating of a Timoshenko beam resting on sway and rocking springs, which respectively represent the superstructure and the soil-foundation system. Unlike those previously employed for this particular problem, the proposed method is a Bayesian one, which accounts for the prevailing uncertainties due to modeling and measurement errors. As such, it yields the probability distribution of the system parameters as opposed to average/deterministic values. In this approach, the joint probability density function of the parameters that control the flexible-base... 

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... 

The simultaneous effect of uplift phenomenon and vertical vibration of soil-structure system is investigated in this study. The super-structure is modeled as an equivalent single-degree of freedom with bilinear behavior mounted on a rigid foundation resting on distributed tensionless Winkler springs and dampers. The effect of vertical excitation on the response of soil-structure systems allowed to uplift is investigated parametrically through time history analysis for a wide range of systems subjected to sine pulse and a group of ground motions recorded on the soil type of C. The results consist of maximum displacement of the uplifting system and ductility demand of the super-structure as a... 

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... 

It is well-known that the behavior of soil-structure systems can be well described using a limited number of non-dimensional parameters. This is the outcome of researches based on the premise that the foundation is bonded to the ground. Here, it is shown the concept can be extended to systems with foundation uplift. A set of non-dimensional parameters are introduced which controls the main features of uplifting systems. The super-structure is modeled as an equivalent single-degree of freedom system with elastic behavior mounted on a rigid foundation resting on distributed tensionless Winkler springs and dampers. The effect of foundation uplift on response of soil-structure systems are... 

This thesis studies the effect of soil-structure interaction on the seismic performance of structures with due account of uncertainties. The motivation for this study stems from the significant uncertainty in the earthquake ground motion and in the properties of the soil and the nonlinear behavior of the structure. The soil-structure system is modeled by the sub-structure method. The uncertainty in the properties of the system is described by random variables that are input to this model. Monte Carlo sampling is employed to compute the probability distribution of responses that describe the seismic performance of the structure, such as the ductility demand. In each sample, a randomly... 

In recent decades, the soil-structure effect has been considered in seismic studies. Most of these researches are based on the premise that the foundation is bonded to the ground. However, several examples of structures that experienced uplift have been reported. Uplift affects the soil-structure contribution and nonlinear behavior of the structure. It seems that a parametric study should be done for the simultaneous effects of the soil-structure interaction, foundation uplift and inelastic behavior of the superstructure. Although the most accurate methods to estimate the behavior of structures is the nonlinear time history analysis, this analysis is very time consuming. The endurance time... 

Regarding to the value and the modeling, damping has remarkable effect on the response of the systems. More over the structural damping the soil damping also exist in the soil-structure systems. Damping resources in soil include material damping and radiation damping. The high amount of radiation damping in some cases have been led to paying less attention to material damping in some studeis. Although in many cases this is not true and in systems with little radiation damping the material damping could be really important. Generally the role of soil damping depends on the properties of the structure. On the other hand in structures with multi-degree of freedom, soil existence affects the... 

Since the early 1980s, it is well-known that the dynamic properties of structures are effected by flexibility of the underlying soil due to Soil-Structure Interaction (SSI). As a result, the soil-structure systems usually has a longer natural period and higher damping ratio that structure would have in the fixed-base state. The importance of SSI effect as well as the complexity of the phenomenon have made it the subject of several researches for the last four decades. It also has found its way into some seismic codes and provisions as simplified guidelines.In the present paper, a simplified 3DOF model is suggested as the soil-structure system by replacing the structure by a SDOF model using... 

Estimating the nonlinear behavior of sturctures, always have been one of the main concerns of civil engineers. One of the most recent methods for estimating behavior of structures is MIDA technique. It is a procedure that in some levels, substituted for IDA. Although this method presents the approximate results, high accuracy, fastness and inexpensive procedure made this manner to an efficient method. Indeed, this method has been presented to be exerted instead of exact IDA method which is too complicated and prolix. Up to now, no one has used this method for structures incorporating soil-structure interaction. In theMIDA manner, there is no dynamic analysis of ... 

Usually the structures are designed based on the fixed-base assumption; however thisassumption is not always correct and the bed flexibility should be considered. This effectwhich is called soil-structure interaction, change the response of structure on both elasticand inelastic behavior. In the regulations for the design of structures on flexible base,generally soil-structure system is replaced with an equivalent fixed base structure; in theway that the design force of soil-structure system with reasonable accuracy can beestimated by equivalent fixed-base structure. In some regulations, dynamic characteristicsof equivalent structure have been determined on elastic state and the results have... 

The importance of the liquid storage tanks in this era is as much as their contained liquid that we use in our daily lives. Many studies have been carried out on these influential structures considering various aspects. The major damages inflicted to the liquid storage tanks in Loma Prieta, Lozan, Hokaido, Arzinkan, Northridge, Kobe, Izmit & Haiti Earthquakes, has led the researchers to perform various experimental and analytical studies on this regard in the last few decades. The most important part of a safe design of a storage tank is the accurate estimation of the seismically induced lateral forces that should be transferred to its base through the tank shell and its support. Moreover,... 

This study focuses on the risk assessment of reinforced concrete tall buildings subjected to ground motion excitation. In order to assess the vulnerability of tall buildings, twelve-, and twenty-four-story four-bay reinforced concrete moment resisting frames are studied. This evaluation is done through developing fragility curves. These fragility curves provide the probability of exceeding the multiple damage states for a given intensity (e.g. CAV) of ground motion excitation. To develop the fragility curves, a great number of nonlinear dynamic analyses were conducted in the open-source platform OpenSees. Since the PEER Guidelines for Performance-Based Seismic Design of tall buildings (PEER,... 

In the last few decades Seismic Regulations attitude’s has been undergone significant changes from various aspects. One of these aspects is entering new topics based on the latest scientific achievements. Soil-Structure Interaction terms was from such issues which had found their ways into Seismic codes as an optional effective factor. In recent years, Based on this new attitude and Scientific achievements, Soil-Structure Interaction terms entrance into Iranian seismic code (2800 Standard), is also has been studied. Naturally, applying these criteria will impact on the design and performance of structures, because of reducing effect of soil structure interaction on decreasing base shear... 

Masonry buildings are one of the most vulnerable structures against earthquakes, and therefore their seismic response should be evaluated in order to mitigate casualties in the future. Although there are numerous experimental and analytical studies on these buildings, few have aimed on Confined Masonry (CM) buildings to simulate and predict their seismic performance. To estimate damage, assess vulnerability and choose the best retrofitting method, fragility curves can be utilized as a powerful tool. In this paper, the hysteretic behavior of two typical CM walls with and without opening is calibrated in both In-plane (IP) and Out-of-Plane (OOP) loading directions making use of OPENSEES... 

In conventional method of modeling and design of structures it is assumed that structures are fixedly supported, however, this assumption is generally far from reality; because, not only the majority of buildings’ bases are not stiff enough to suppose them rigid, but also if their foundations are shallow there exist no piles underneath them, they may separate from their bases – the event which is called foundation uplift. Although according to past studies permission of foundation uplift as well as incorporation of base flexibility may markedly affect any structure’s dynamic response, is spite of about half a century which has elapsed since the beginning of these studies, it seems that still...