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Dynamic characteristics of structures—viz., natural frequencies, damping ratios, and mode shapes—are central to earthquake resistant design (model validation) and health monitoring. For civil structures like buildings and bridges, these characteristics can be highly influenced by surrounding soil in addition to the super-structure’s properties and cannot be correctly estimated using numerical modeling. For example, soil’s flexibility decreases the natural frequencies of the system; and in most cases, soil provides additional damping due to material hysteresis and radiation. On account of this fact, system identification techniques must be applied to extract such information from field data,... 

The circular flexible cylindrical liquid tanks are usually made of steel or aluminum and in majority of cases are built on grade due to its economic advantages. The most important part of a safe design of storage tanks is the accurate estimation of the seismically induced lateral forces that should be transformed to its base through the tank shell and its support . seismic behavior of the liquid storage tank is quite different from regular buildings industrial structures due to its nonlinear behavior caused by complex distribution of hydrodynamic pressure, buckling of its wall, etc.. moreover, the effect of rocking motion caused by under laying soft soil, on its response parameter could be... 

Tall building development has been rapidly increasing world wide introducing new challenges that need to be met through engineering judgment. In modern tall buildings, lateral loads induced by wind or earthquake are often resisted by a system of coupled shear walls. But when the building increases in height, the stiffness of the structure becomes more important and introduction of outrigger beams between the shear walls and external columns is often used to provide sufficient lateral stiffness to the structure.In general, earthquake ground motion can occur anywhere in the world and the risk associated with tall buildings, especially under severe earthquakes,... 

Observed performance of nonstructural components and building contents during recent earthquakes demonstrated their significance to control economic seismic losses and downtime. Since a large portion of nonstructural equipments installed in buildings are acceleration sensitive devices, reasonable estimation of the acceleration they undergo during an earthquake has an important role in rational design of secondary systems and subsequently in reducing the earthquake damages. Although a comprehensive amount of research studies have been conducted to date to approximate the floor acceleration demands of a multistory building subjected to the earthquake ground motion, in most work, the soil... 

In the current design Codes, the estimation of maximum inelastic Single Degree Of Freedom (SDOF) displacements is done through simplified procedures by either applying modification factors on maximum SDOF elastic displacement demands or by considering equivalent SDOF systems with elongated fundamental period and increased damping ratio. Thus, the inherent uncertainty caused by approximating maximum inelastic displacements with maximum elastic displacements is neglected. On the other hand, in time history dynamic analysis of structures, the free field recorded ground motions are applied to the base of structures. Obviously, this procedure would be correct when the structure is built on firm... 

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

The circular flexible cylindrical liquid tanks usually are made of steel or aluminum and in majority of cases are built on grade due to its economic advantages. The most important part of a safe design of a storage tanks is the accurate estimation of the seismically induced lateral forces that should be transferred to its base through the tank shell and its support. Seismic behavior of liquid storage tanks is quite different from regular buildings and industrial structures due to its nonlinear behavior caused by complex distribution of hydrodynamic pressure, buckling of its walls, etc.. Moreover, the effect of rocking motion caused by the under laying soft soil, on its response parameters... 

Performance-based seismic design method, with a new look and a totally different philosophy, as an alternative design method instead of strength-based design method has been suggested in the new generation of seismic codes. Massive problems such as the need for complex dynamic analysis and consequently, spending high cost and time in researches forced researchers to seek more effective methods to evaluate seismic performance of structures. This idea in the optimal design of structures that require repeated analysis seems to be more effective. In the Endurance Time (ET) method, structures are subjected to specially designed intensifying acceleration functions and their response at various... 

Rubble-mound breakwaters are one of the most customary breakwaters, which make a calm and safe area for ships to berth. To protect these structures from sea wave attacks, armour layers consisting of rocks or concrete blocks are put on their outer surface. Providing the stability of the armour layer is an important procedure in the design of breakwaters. Until now, design of the armour layer is based on the empirical formulae and physical modeling tests. The current research aims to study the stability of the armour layer by the numerical method and employing the commercial code FLOW-3D. In the present research, the effect of geometrical parameters such as breakwater slope and armour diameter... 

The feasibility of passive energy dissipation devices such as viscous fluid dampers in controlling the torsional response of structures against seismic loadings has been explored by different researchers in recent years. In the majority of these studies, it is assumed that the structures are located on rigid bases. On the other hand, the effect of Soil-Structure Interaction (SSI) for the structures located on soft soil, on their dynamic parameters and structural responses can be prominent. In this study, the application of viscous fluid dampers in improving the torsional behavior of asymmetric concrete moment resisting frame buildings is investigated, taking into account the soil-structure... 

Numerous structures which are involved in seismic soil-pile-structure interaction have been damaged، failure in piles or even collapsed that can’t predict. Because of difficult modeling in soil، pile، structure interaction prediction the response of structure is impossible. In this study with using the finite element Abaqus software tries to understand the effect of soil pile structure interaction in structure response. By using the time history of Elcentro، structure with different boundary conditions were analyzed and the response of them were compared. Models have different boundary condition such as fixed base، pile groups and pile raft. Also in this study the effect of mat in... 

The interaction of perpendicularly tunneling beneath existing metro station is investigated. In this paper E4R7 station, in line 7 of Tehran Metro (Tehran Urban and Suburban Railway co., TUSRC); Iran has been studied. This existing station has some special specifications such as a new pre-supporting system that is called Concrete Arch Pre-supporting System (CAPS). Construction of CAPS is mainly based on an Old Iranian small water tunnels excavation method, Quanat, which is faster and more economical than other common methods. CAPS is a rib like structure consisting of concrete piles and arch beams constructed around underground space before its construction. This method has been utilized in... 

Considering the role of fluid storage tanks within or after an earthquake and the irreparable damages of such structures that arise from the flammable or toxic nature of the fluids stored in them, it is very important to ensure stability and durability of the tanks under seismic loading. One of the most important damages to storage tanks within the past earthquakes has been lack of stability of their shells taking place in the form of a local bulge of wall, known as “elephant foot buckling’. This phenomenon is a subsequent of high levels of hoop tension, which is a result of containing liquid pressure, along with axial load of surrounding walls. Recent studies reveal that there is no... 

It is several decades that the effect of soil-structure interaction (SSI) has been known to engineers. Many methods have been developed to estimate this effect, but modal analysis of soil-structure systems is one of the most popular techniques due to its simplicity and better insight. Due to this reasons, modal analysis found its place in codes and provisions such as NEHRP. Presence of soil beneath the structure not only would alter the natural periods and damping ratio of structure but also would impose some new vibration modes to the system due to soil’s degrees of freedom. Consequently, response of structure is a combination of the effects of all these modes. But, in practice,... 

Base flexibility of structures, cause changes in seismic input motions to the structure, and hence, result in variations in structural seismic responses. This phenomenon is commonly referred to as soil-structure interaction (SSI). The effect of base flexibility on seismic responses is usually investigated from two main aspects: 1) Kinematic interaction (KI) , 2) Inertial Interaction (II). KI effects are induced, first, because of the stiffness contrast between the foundation and the flexible base, and second, because of phase difference of the receiving waves in the contact boundary between the foundation and the flexible base. These effects may results in variations in frequency content of... 

Liquid storage tanks as part of the lifeline facilities play an important role in the rescuer work and drinking water supply after earthquakes. Importance of these structures demonstrates the need for investigating their dynamic behavior under dynamic loading. To assure the safety of liquid storage tanks, the dynamic response of liquid storage tanks has been studied intensively in the past. Housner proposed a widely used analytical model in which the hydrodynamic pressures are separated into impulsive and convective components. This model is mostly used for the horizontal groud motion. In this study, considering soil-structure interaction (SSI), nonlinear dynamic behavior of concrete... 

In the past few decades, shaking tables are widely used to evaluate system response of structures under seismic excitations. These devices are used without any fundamental research performed on a shaking table system as an entity model. In most of these studies for simplicity, it is assumed that there exist no considerable vibration and displacement around the shaking tables, and no attention is paid to the peripheral substances such as soil settled under the foundation.
In this thesis, result of ambient vibration test on shaking table system (solid deck, concrete foundation and soil layer) has been presented. Precise sensors known as low frequency and high accuracy accelerometers have... 

Considering the role of fluid storage tanks within or after an earthquake and the irreparable damages from their destruction that arise from the nature of the fluids of flammable or toxic nature stored in those tanks, it is very important to ensure stability and durability of the tanks when an earthquake is occurring. One of the most important damages to storage tanks within the past earthquakes has been lack of stability of their walls taking place in the form of elephant buckling. A certain storage tank was subject to a case study in this research and the tank's body, foundation, anchorages, the tread between the fluid and tank's body and between the bottom sheet and foundation were... 

Reducing the seismic response of structures under dynamic loads has been highly considered by many researchers in the past few decades. Among them, Tuned Mass Dampers (TMD) have been studied extensively and used as a mean to control the response of structures under earthquake and wind loadings. In the majority of these studies, it is assumed that the structural models are located on rigid base and only their linear response has been considered. Soil-Structure Interaction (SSI) and nonlinear response of structures could have significant effect on the dynamic characteristics of structures that could results in detuning of TMDs. In this study, a number of 3-D nonlinear steel structural models... 

In order to simplify the dynamic analysis of soil-structure systems, the structural element of the foundation is usually assumed to be rigid. While the rigid foundation assumption is acceptable for block-type machine foundations, it may influence the dynamic response of other structures such as structures with a central rigid core. Previous research has shown that the flexibility of the foundation structural elements affect dynamic stiffness of underlying soil so it can change the structural response. The aim of this thesis is to study the influence of foundation flexibility on the global response of soil-structure systems including structures with a rigid core. Since the response of the...