Sharif Digital Repository

Energy production from fossil fuels such as oil and gas is one of the non-renewable energies, which causes many environmental problems such as global warming and environmental pollution. The existence of these problems has led to agreements such as the Glasgow Environmental Agreement, which obligates governments to apply methods to reduce the production of greenhouse gases, which include reducing the consumption of fossil fuels and increasing the use of renewable energy. Sea wave energy is one of the renewable energies that can be used to generate electricity. In the seas of Iran, including the Caspian Sea, Persian Gulf and Oman, there are sources of wave energy that can be used and are... 

There is an increasing interest and use of energy foundations worldwide. Heat transfer from/to energy piles may cause plastic contraction of soft clay with a low overconsolidation ratio (OCR) during heating and cooling. This can influence pile-soil interaction due to thermally induced excess pore water pressure and changes of lateral stress acting on the pile.These thermally induced phenomena cause additional plastic settlement of the soil and pile. The irreversible settlement may cause serviceability or even ultimate limit state problems for floating energy piles whose capacity is mainly derived from shaft resistance. Due to intended operational needs or by accident, cyclic non-symmetrical... 

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... 

The use of shape memory alloys (SMAs) has been seriously considered in earthquake engineering due to their unique capabilities, such as the ability to tolerate cyclic deformations, recentering, and dissipating energy. Consequently, the effect of hybrid connections (SMA and steel based beam-column connection) in asymmetric structures is investigated in this research.A 4 story steel special moment resisting frame with 0%, 10%, and 20% eccentricities have been considered to find out the performance of a novel beam-column connection in reducing the seismic response of structures such as maximum drift ratio and residual displacement. In order to find out this issue first, the symmetric model has... 

This paper proposes a novel probabilistic approach to account for soil-structure interaction (SSI) in the seismic design of building structures. In this approach, an SSI response modification factor, RSSI, is introduced to capture SSI effects on the seismic performance of structures. The proposed procedure quantifies RSSI such that the probability distribution of the collapse capacity of the structure designed to account for SSI concurs with that of the structure designed using the default fixed-base provisions. The proposed approach is employed for special steel moment frame buildings with surface foundation. A surrogate single degree of freedom (SDOF) system is developed in this study and... 

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... 

This paper proposes a novel probabilistic framework for output-only identification of a soil-structure system. The system is modeled by a vertical shear beam resting on the soil representative springs. The proposed framework estimates the unknown parameters of the system and the foundation input motion time history simultaneously, using sparsely measured responses of the structure. The unknown parameters of the system include stiffness of the sway and rocking springs, shear modulus of the beam, and the modal damping ratios of the system. These parameters are modeled as random variables whose joint probability distribution is updated in a Bayesian scheme using the observations of structural... 

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,... 

Foundation which is lowest load-bearing part of structure, transfers load of superstructure to substructure. Because structures are usually placed on soils, the response of the soils influences the motion of the structures and the motion of structures affects the response of the soils. This phenomenon is termed Soil Structure Interaction (SSI). One of these mutual effects is the rocking of shallow foundations in which the base of the foundation under dynamic loading may separate from the underlying ground, by rotating about the longitudinal axis. This rotational mode elongates natural period of the soil-structure system and decreases the base shear demands of the superstructure. Indeed... 

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... 

Damage detection of civil structures and infrastructures using partial modal information has been an interesting field of research. So far, three main algorithms are introduced for health monitoring of structures. The first method relies on identifying stiffness and mass properties, as physical parameters, of structures using inverse eigenvalue problem considering mass modifications in 2D and 3D shear-frame models of structures. Comparing the identified matrices with the primary values, one can detect the damage occurrence, its level and severity in the structure. Applicability of this method in health monitoring of offshore jacket platforms as one of noteworthy civil infrastructures has... 

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 objective of this research is to investigate the use of passive control system to reduce the seismic response of fixed-roof, above-ground, cylindrical steel tanks as well as to decrease the damage caused to these structures in the event of an earthquake. The most crucial step for a safe design in this case is determining the lateral forces due to earthquake with sufficient accuracy; These forces are eventually resisted by the storage tank walls and the supports. Determining analiytical solution to the problem is not possible due to the interaction of the liquid with the structure. Therefore, numerical approach was adopted to determine the response of the tank using ANSYS program. Two... 

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... 

This thesis reveals the influence of soil-structure interaction (SSI) on the collapse potential of structures and also investigates the change in collapse margin ratio (CMR) of structures for which the design base shear has been reduced based on the soil-structure interaction provisions. According to the properties of structures and seismic excitations, SSI can increase, decrease or make no change in the response of structures. Based on seismic design codes for fixed-base structures, SSI causes reduction in design base shear of buildings. These provisions are based on linear behavior of structures. But under strong ground motions, specially at collapse level, structures can experience strong... 

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... 

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... 

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,... 

This thesis revisits the effect of dynamic soil-structure interaction (SSI) on multistory buildings with a probabilistic approach. For this purpose, the relationship between the strength demands of fixed- and flexible-base multi-degree-of-freedom (MDOF) systems, or strength reduction factor thereof, with that of fixed- and flexible-base equivalent single-degree-of-freedom (eSDOF) systems is investigated considering prevailing uncertainties. To this end, Monte Carlo sampling analysis is employed in which a suite of nearly 2000 records are utilized to properly quantify the ground motion uncertainty. The soil-structure system is modeled by the sub-structure method. The uncertainty in the...