Sharif Digital Repository

Concentric and eccentric chevron braces are among the more economical lateral force resisting systems for structures. However, chevron braced systems are prone to concentration of damage in a single story and formation of soft stories when buckling occurs in the bracing elements. This leads to a gradual loss in the structural performance, particularly as the height of the structure increases. One of the most notable methods to alleviate this problem and improve the structural performance is the addition of zipper struts to concentrically chevron braced frames that are known to improve the distribution of plastic energy dissipation along the height of the structure. While this usually... 

Study of former earthquakes damages reveals that irregular structures are more susceptive to failure than regular ones. Irregular structures are classified into two categories, namely those with irregularity in elevation and the ones with irregularity in plan. Besides, one of the crucial parameters in working out the earthquake’s equivalent static load is response modification coefficient (R). Based on the type of seismic lateral force-resisting system, this parameter can have various values. In this research, using nonlinear static analysis, the response modification coefficient of a great number of 3-D steel frames of 5, 7 and 9 m spans and having 1 to 10 stories with various... 

With increasing population and lack of habitable spaces, the building heights increased in cities around the world. Placing components of a structure in tandem may cause a permanent failure of the members due to strength reduction. During recent years, this kind of failure occurred in different places of the world, and is called progressive collapse. There are some various samples of the progressive collapse which all are good samples of failures such as building failure in Ronan Point in the UK, Twin Towers or the world trade center in NY, and Pentagon building. According to these issues, different institutions codified guidelines and codes in this field such as Department of Defense as DoD... 

Bracing Systems are usually a set of inclined members that are embedded in structures to resist lateral forces and control lateral displacements. There are different types and behaviors for Bracing Systems depending on the way of assembling and locating them in the structure. Braced Frames, such as Concentrically Braced Frames (CBFs), generally have high stiffness and low ductility. Another Type of Braced Frames is Eccentrically Braced Frames (EBFs) which improves CBFs by establishing suitable ductility as well as stiffness. Inelastic behavior of Links involved with EBFs caused this in EBFs. Nevertheless, these systems have no efficiency in next earthquake, because links are parts of beams... 

A new eccentrically braced system is discussed. In this system which Named “eccentrically braced frame with vertical link”, the braces is connected to vertical link, instead of floor beam. The vertical link acts as a ductile energy-dissipating element, allowing the rest of the construction such as floor beams, braces and columns remain in the elastic range. In this paper, a parametric study is performed on sample frames with push-over analysis. In these analysis, the efficacy of the variation of link length, link area and the position of the link beam, is studied. The results showed that, the most important effective parameters in improvement of inelastic behavior of frame is decreasing of... 

Studying the performance of irregular structures in past earthquakes reveals that due to their severe vulnerability, we need to accurately assess the behavioral characteristics of such structures. On the other hand, all existing seismic codes recommend the use of response modification factor to determine the base shear, design forces of the members, and the design drift ratios, which seem to have limited comprehensiveness. Moreover, the response modification factor for a structural system is discussed in a general manner and the effect of factors such as number of bays, number of stories, span length, story height and irregularities are not considered. In this research, the effects of... 

Although the moment frame can show deformable behavior against seismic loads, but its flexibility and low stiffness, especially in tall structures, cause the governance criterion to be designed. The use of eccentrically braced frames was able to solve the displacement problem to some extent, because it has the characteristics of both flexural frame systems and conccentric bracing. Different methods have been proposed to eliminate residual displacements in this type of system, one of which is the use of post tensioned cables. The aim of this study was to investigate the seismic behavior of a steel structure with a eccentrically braced frame system with post tension cable.The cables are anchor... 

Conventional eccentric braced frames often sustain large residual deformations and significant damages after strong earthquakes which may lead to heavy damages or even destruction of the structure. Here, a self-centering, Y-inverted, eccentrically braced frame (SC-YEBF) is proposed which combines the lateral load resisting benefits of YEBF including strength, stiffness and energy dissipation capacity with the re-centering capacity of post-tensioned (PT) high strength steel strands used at beam-to-column connections. A design procedure is presented assuming that all the seismic input energy is dissipated through inherent damping and plastic deformations of the link-beams. Thus, in the... 

This study investigates the seismic behavior of eccentrically braced frames (EBFs) taking into account the influence of masonry infill walls. The primary objectives of the study are to predict the seismic global response and develop associated fragility curves using a nonmodel scenario-based machine learning framework. To model the infill walls, equivalent diagonal struts are employed, and a nonlinear pushover analysis is conducted to assess the overall impact of infills on 4- and 8-story EBF structures. An extensive database of 4 bare and 48 infilled EBFs with various infill properties is assembled to predict story-based engineering demand parameters (EDPs) containing peak and residual... 

In the present study it was intended to evaluate the seismic performance of multi-story EBF structures for designing. When adopting this method, parametric studies are carried out based on the nonlinear performance of such systems whiting the framework of nonlinear static and dynamic analyses. In lines with seismic strengthening of such structures, this study tries to reassess the performance of these systems through increasing ductility and replacing bracing frames with energy damper and special seismic systems. As a result, a fuse type performance is created to protect the other elements of the structure. This study describes the seismic strengthening of this type of dampers using simple... 

This thesis illustrates the typical seismic retrofitting of bridges using a model governing transverse seismic response of retrofitted bridges by simplified analytical models of the end diaphragms based on the fundamental dynamic concept as well as previous research works. For three types of ductile diaphragm devices such as Eccentrically Braced Frames (EBF), Triangular-plate Added Damping and Stiffness Devices (TADAS) and Chevron Knee Bracing (CKB)and Shear Panel System(SPS), finite element nonlinear analytical models are developed in separate flexural and shear yielding modes, and the capability of the proposed finite element models is ascertained.The IDA (Incremental Dynamic Analyses) are...