Sharif Digital Repository

Continuous improvement of the existing seismic design codes and regulations clearly shows the need for evaluation and probable retrofitting of the existing building structures. A large amount of literature has been produced on different topics related to retrofitting including FEMA 273, ATC 40, FEMA356 and most recently the draft of FEMA 440. On the other hand, it has been long recognized that the response of buildings to strong ground shaking caused by earthquakes results in inelastic behavior. Until recently, most structural analysis techniques devised for practical application relied on linear procedures to predict the seismic response of the building structures. But due to various... 

In recent years there has been a huge amount of attention in the application of the base isolation system as a passive procedure to limit seismic response of structures. A number of international codes including UBC97, ASCE07-2005, and ASCE-2010 have devoted a special part for the Seismic analysis and design of base-isolated structures. The present work investigates the vertical distribution of the lateral seismic force, for base-isolated structures suggested by the ASCE07_05 code under near field earthquakes. Near field earthquakes have attracted so much interest among the researchers and engineers due to their disastrous effects on structures. According to the recorded data, it is... 

In existing societies, transportation of water, oil, gas and other liquids in great amounts between distant locations is economically feasible only through pipelines. Design of buried pipelines against static loads is an established and straight forward process. On the other hand, because of difficulties in predicting the behavior of buried pipelines under seismic loads and also lack of sufficient studies in this field, there is no specific code oriented approach for performance analysis of buried pipelines under seismic loads. Due to insufficient three dimensional numerical analyses on the behavior of buried pipelines crossing active normal and normal-oblique faults for different dip angles... 

Buried pipelines are among the most important elements of lifelines that are used for distribution of water, gas, petroleum, etc. Previous studies indicate that the severe damages that resulted in complete disruption of pipelines, is mainly due to permanent ground displacement caused by faulting. Previous studies on this subject have mostly focused on strike-slip and normal faulting. Since it is reported that damages due to reverse faulting can be more severe than damages caused by normal faulting, a comprehensive study on the behavior of buried pipelines subjected to reverse faulting is needed. In this thesis, the effect of various parameters including burial depth, pipe diameter, pipe wall... 

Recent studies in the area of damage assessment of structures under severe earthquakes have shown that plan asymmetry of structures have considerable effects on the severity of the induced damages. In these cases, structure enters into its nonlinear behaviour, and both structural and nonstructural elements sustain large forces and deformations. Nowadays, due to the complication of nonlinear dynamic analyses in estimating these forces and deformations in case of seismic ground motion, the use of nonlinear static analysis methods has increased. These procedures expose the structures to monotonically increasing lateral forces with an invariant height-wise distribution until a predetermined... 

Damage and collapse in structural systems due to unexpected structural loading that seems to be inevitable sometimes leads to financial and human losses, despite of all safety measures considered for the system. Therefore, using structural health monitoring methods in order to estimate structural damages and preventing structural collapse, have drawn a lot of attention. In this study, the performance of different system identification methods such as mode shape curvature method, energy method, etc., to extract the dynamic properties of a cable-stayed bridge is examined. One of the main features of this study is to consider the seismic response of the bridge under multiple support excitations... 

Shape memory alloys (SMAs) are metallic materials that have unique properties, including shape memory effects, superelastic effects, and high damping characteristics. Recovery of large deformation and capability of energy dissipation during mechanical loading-unloading cycles are special properties of superelastic effect of shape memory alloys. Due to these distinctive macroscopic behaviors, not present in most traditional materials, SMAs are the basis for innovative applications like devices for protecting buildings from structural vibrations. This paper presents a numerical investigation aimed at evaluating the improvements achievable through devices for passive seismic protection of... 

Various types of passive energy dissipating systems have been introduced for controlling the seismic response of structures during the last few decades. A number of these control devices have been practically implemented in different structures all over the world. Shape Memory Alloy (SMA) is among those passive control systems that have attracted a large attention due to its innate features, i.e., recovering the induced residual strains upon unloading (superelastic effect) or by heating (shape memory effect).This study investigates the seismic behavior of a set of steel structural models with different number of stories and eccentricities equipped with a type of fixed SMA connections. In the... 

In this research, the performance of a new friction damper with two different slip loads to improve the seismic response of steel structural models is investigated. Also, different slip loads are considered in different floors to reduce the response parameters such as story drifts, permanent story drifts, absolute floor accelerations, and base shear forces. In this regard and as the first step, three steel moment resisting frame models with 4, 8 and 12 number of stories are designed using the AISC-LRFD and ASCE 7-10 codes. Then, the effects of slip load changes of the two level friction dampers on the seismic response of the structural models were investigated and the domain of the slip... 

One of existing passive control procedures for reducing the seismic response of structures is using tuned mass dampers. This damper consists of three main elements, including mass, damping and stiffness. A conventional tuned mass damper consists of a relatively small auxiliary mass attached to a main structure to be protected. The principle of operation consists in inducing a vibration energy transfer from the main structure to the auxiliary mass, which dissipates the input energy while vibrating out of phase with the structural motion. In this study, the usage of non-conventional tuned mass dampers (TMD) with large mass ratios, in reducing the seismic response of structures and the way to... 

Cable stayed bridge are characterized by a long fundamental period, large flexibility, lightweight and low structural damping, which is vulnerable to large amplitude oscillations when excited by earthquake. So, it is important to study the seismic behavior of cable-stayed bridges. Spatial variation of seismic ground motions denotes the differences in amplitude and phase of seismic motions recorded over extended areas. The result of past analyzes indicate that the effect of the spatial variation on the response of bridges can be detrimental. On the other hand, tuned mass dampers (TMDs) or vibration absorbers are small mass-spring-dashpot units calibrated to be in resonance with a particular... 

The utilized structural systems in high-rise buildings are under develop in terms of quantity and quality to increase their resistance under gravity and lateral loads. In addition, widespread researches are conducted to introduce and employ modern structural systems for high-rise buildings to improve there behavior in response to the applied forces, and to reduced the levels of hazards imposed by lateral forces. In this regard in recent years, use of diagrid structural systems has gained most of engineers and architects attention. Architectural limitations and improper site conditions may commonly result in construction of buildings with torsional irregularities. However, presence of... 

Use of high-rise structures has become very common in recent decades for different purposes. Since, these structures are vulnerable to the wind and earthquake loads, many ways have been proposed to reduce or dissipate the input wind or seismic energy to the building structures. In this study, the effect of the tuned mass damper (TMD) with high mass ratio for high-rise structures is investigated. The proper functioning of the TMD to limit the vibrations of a structure is depended on the appropriate adjustment of its mass, stiffness and damping characteristics according to the load and structural specifications. The vibrational characteristics of the structures could change during sever... 

Tuned Mass Dampers(TMD) are among the most studied passive or active control devices that have been used around the world to control the lateral vibration of different building structures. On the other hand, since 2-D structural models are not appropriate for estimating the true response of the eccentric structures, application of 3-D models have been considered for determining their seismic-induced coupled lateral-torsional behavior. In this research, the performance of the Active Tuned Mass Dampers (ATMD) in controlling the seismic response of 3-D structural models was investigated. Three structural models with 4, 8 and 15 number of stories and 3 different eccentricities (0, 10% and 15%)... 

The objective of this study is to evaluate the seismic vulnerability of the existing buildings subjected to the near field earthquakes. The main applications of this research are loss estimation and performance evaluation of the existing buildings. That could provide a better solution and particularly more useful information to the owners, investors, and insurers about the expected performance of buildings under earthquake excitations. A number of 2, 5 and 8 story reinforced concrete buildings, designed according to the old Iranian seismic provisions of ISIRI-519 and ACI 318-83 codes for the ordinary moment resisting frames, are considered. By the use of a number of near field earthquake... 

In the present study, the performance of Viscoelastic Dampers in reducing the seismic response of the structures was investigated. For this purpose, first the effect of added damping to the system was studied. Number of 3-D steel structural models, with and without eccentricity which are designed with the 2800 code (first edition) and 519 code provisions that is not satisfied the provisions of the code-2800(third edition) is considered. It is assume that this system is located on a relatively stiff soil (soil type II based on Iranian Seismic Standard Code - 2800), a number of compatible earthquake records also considered to be used in the parametric studies. The results indicate that in... 

Up to now, many seismic design methods and construction technologies have been investigated to reduce the seismic responses of bridges, buildings and potentially vulnerable structures. [1] Introducing a new effective systems aim to control of vibration caused by earthquake on the structures will be useful. This system is based on repelling of imposed force to the structures with tuned mass dampers (TMDs), to gain minimum damage. The detuning of the structures by equipped with TMDs resulted from nonlinear behavior due to dynamic loads such as strong ground motions are real concern in the practical applications. The application of TMDs, as expected, can reduce the deformation of the... 

A large number of bridges in Iran are deteriorating under long and heavy traffic loadings, while getting closer to the end of their design life time. Therefore, many of them have been exhibiting various problems such as excessive vibration or large deflection under the normal service loadings. So, mitigating traffic-induced bridge vibration and damages is necessary to extend their efficient period of serviceability. On the other hand, application of active and passive control devices in structural retrofitting have absorbed the attention of many engineers and researchers. In this work, the performance of an active control system made of piezoelectric actuators is investigated in reducing the... 

Nowadays, buried pipelines are being widely used to transport water, oil andother liquids in large quantities and far distances because of their efficiency and security. Soit is necessary to investigate the seismic behavior of these important facilities due to severeground motions. In this study, the seismic behavior of buried pipelines subjected to multiple support excitations isinvestigated. The approach adopted here, is based on a 3-D modeling of a portion ofpipeline by using the theory of beams on elastic foundation. In the model used, interactionand possible slippage between soil and pipeline has been considered by modeling the soilwith elastoplastic springs in three orthogonal... 

In this study, seismic performance of steel diagrid structures is investigated using far-field earthquake records and their seismic performance factors, such as overstrength factor (Ω_0), ductility ratio (µ_T) and response modification coefficient (R) are evaluated according to the FEMA P695. To meet this objective, 12 archetype 3-D models of diagrid structure with two different height of 8 and 12 stories and three different diagonal angles of 45, 63.4 and 71.5 degrees are designed according to the ASCE 7-10 and using response modification factor R=3.6. With regard to the main horizontal beam connections with the diagrid system, equal number of models with pin and rigid type of connections...