Sharif Digital Repository

Nowadays, the design of new structures and the renovation of existing buildings against earthquakes using energy absorption systems are very common. On the other hand, the near-field earthquake are characterized by directivity related velocity pulses with large accelerations. Recent studies have shown that the performance of the passive energy dissipation mechanisms are significantly depended on the characteristics of the near field velocity pulses. The efficiency of various passive dampers in damage mitigation of different building structures have been carefully evaluated under near field and far field earthquake records. In this study, the ability of viscoelastic dampers in controlling the... 

Abstract
In this research, the effect of irregularity in the plan floor of structures, including geometric and torsional irregularity on the seismic behavior of steel moment frames braced with chevron knee braces (CKBs) has been investigated. To achieve this, three–dimensional 5-, 8-, 12-story steel buildings models with regular and irregular plan floors were built in OpenSees software and subjected to nonlinear static (pushover) and nonlinear incremental dynamic analysis (IDA) under 22 ground motion records. The performance of each model was then examined by calculation of three seismic design parameters: response modification (R), structural over strength (Ω), and structural ductility... 

As you know, the behavior factor is one of the important parameters and values for calculating earthquake force and base cutting in the building. In this research, the effect of coefficient of behavior (R) on metal structures has been investigated. For this purpose, we selected a metal structure with an average bending frame and dual system with shear wall and examined it. To determining the effect of this coefficient on different structures, we modeled the structures with regular and irregular plans. Considering the structure height effect and also the type of soil on the site of the proposed structure to the factor and refractive coefficient (B) and its direct impact on the magnitude of... 

A new structural system of diagonally arranged elements, the so called "diagrid", has been introduced in recent years in which the frames that are made up of intersected members surrounding the main structure. This type of system provides excellent shear rigidity and stiffness, in contrast to the similar tubular structures. The triangular configuration offers structural stability for gravity and lateral loads, and the removal of external columns gives the building a unique architectural beauty. The seismic performance factors (SPFs) for diagrid systems are not yet explicitly introduced in the existing building codes and few studies have been conducted on the assessment of this parameter. In... 

The system considered on this structure is for the design on mid-high Buildings from 15 and 20 floors above the base level and n floors below the base level and the limitation of the number of floors is due to the computer facility and restrictions. There is going to be an irregularity in some chosen floor at lower-floor, mid-floor, or upper-floor which is assuming one floor from the structure to have a different height with respect to the others. The height of the considered floor is going to increase up to 25% with respect to the other floors and the design of outriggers with these three assumptions is going to be assessed separately. In this system, a central core of steel is constructed... 

Since the main weight of structures comes from the weight of floor systems, it is desirable to use tin and light floor system in order to reduce gravity and seismic force induced in the structure. However architectural aspects limit the application of short spans in the structural system. The objective of this work was to analyze the adequacy of a design method widely used in the modeling of waffle slabs interaction with steel columns as its supports in steel frames, and to verify if it represents the slab behavior satisfactorily. A real scale waffle slab was laid on a steel column and submitted to service loads. Subsequently it was analyzed with FE method for measuring specific stress,... 

Previously, numerous studies were carried out on the shear walls and important information are available in various fields, including wall design with various sections, wall design in areas with high seismicity risk, issues related to the reinforcement of boundary element and etc. In the design codes of reinforced concrete structures in the field of seismic design, some criteria for reinforcement of boundary element in the walls were conducted, but these codes do not answer to designers to arrange the wall with or without eccentricity with respect to column or the effect of separation of wall from the column. Due to the fact that we have a powerful software such as ETABS, design of shear... 

Shear walls are constructed to counter the effects of lateral load acting on a structure. In residential construction, shear walls are straight walls that typically form a box which provides all of the lateral support for the building. When shear walls are designed and constructed properly, and they will have the strength and stiffness to resist the horizontal forces. Thus shear walls are one of the most effective building elements in resisting lateral forces during earthquake. By constructing shear walls damages due to effect of lateral forces due to earthquake and high winds can be minimized. Shear walls construction will provide larger stiffness to the buildings there by reducing the... 

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... 

This study proposes an efficient risk-targeted framework for integrated optimal seismic design and quantifying target safety of steel Special Moment-Resisting Frames (steel SMRFs) with and without various passive damping devices such as Buckling-Restrained Braces (BRBs), Friction Dampers (FDs), and Fluid Viscous Dampers (FVDs). This framework provides an automated design procedure formulated as a constrained single-objective optimization problem to achieve the minimum Life Cycle Cost (LCC) within the Particle Swarm Optimization (PSO) algorithm and can be the basis of current seismic codes for target safety calibration. LCC includes initial construction cost and lifetime seismic losses such... 

This paper aims at producing surrogate models which can predict building structural response under ground motion loads. Rapid response prediction has a great influence on post-event decision-making. The current study follows mentioned purpose in two main sections. The first section proposed deep models, able at estimating displacement time-series response by using only ground motion and roof acceleration. By this point, different preprocessing methods and their effects are studied. Also, a novel loss function is introduced and a hybrid model consists of different deep layers utilized to gain accurate models. These models train and evaluate on two case-study buildings; a special moment frame... 

The response modification factor (coefficient of behavior) of structures (R) is a parameter that is used during their design using the linear static analysis method to account for the effects of the non-linear response of the structure considered. Therefore, the existing seismic codes consider it necessary to use the R factor during the design process. In addition, for each family of structural systems, the Codes propose a specific R factor in a very general manner. In this project, an effort has been made to obtain and propose a correct, relatively accurate, and logical coefficient of behavior for two-dimensional steel frames equipped with a special type of bracing. In this regard, the... 

In this study, several novel cable-pipe damper brace (CPDB) systems are introduced. The CPDBs consist of steel cables wrapped around supporting pipes and arranged as cross-bracing in steel frames. The arrangements are such that the cables are always in tension when a lateral load is applied to the steel frames. The wrapping of cables around pipes makes the systems act like a friction damper in a seismic event. In addition, the possibility of energy dissipation by plastic pipe deformation and yielding of cables is investigated. Each system is analyzed by nonlinear finite element method to investigate its lateral strength and cyclic behavior. The primary results of this study showed that some... 

This study aims to parametric study and model steel joints with side plates. steel joints with continuum plates have been seismically acceptable for years, assuming they are designed to be stronger than beams. After the Northridge earthquake, the belief that the adequacy conditions of flexural frame joints were limited to stiffness and strength factors was challenged for two main reasons. First, at the junction of the beam with the column, high tension is created by the seismic force, and as a result, it buckles and loses its strength before reaching the projected force. The second problem is due to the problem of making such connections that it is difficult to weld. Therefore, the problem... 

In this thesis, the strain rise phenomenon and its adverse effect on the deformation capacity of steel elements, members, and connectors were investigated. The high-rate increase in plastic strains was termed strain rise. In this study, the sharp increase in plastic strains and its causes were investigated through conducting experiments and extensive numerical analyses. The causes of strain rise were fallen into two categories as primary and secondary. To limit the adverse effect of strain rise two methods of decreasing the initial stress concentration and expanding the plastic volume were proposed. The strain rise in the saddle and pre-Northridge connections as a result of primary effects... 

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... 

The purpose of this research is to study the behavior of some kind of conventional and retrofitted Khorjini connections, such as stress and strain concentration and eventually strain-jumping phenomenon. Thus the software ABAQUS 2019 was used to fabricate the FEM models of the connections with experimental prototypes. In analytical studies, 21 specimens with different sizes of the connection components were analyzed. True stress-strain curves for steel and weld materials were used and damage initiation and revolution were considered in the weld material. Also cracking of the welds was considered by a micromechanical method. The main defects of the connection are severe initial stiffness... 

The purpose of this study was to find the optimal position and slip force of friction dampers, for improving the seismic performance of regular and irregular steel structures and comparison of dampers final pattern of these buildings.In this regard, one to six floor regular and irregular buildings were designed. These buildings were modeled three-dimensionally in the OpenSees Software, and were subjected to horizontal components of seven far field accelerogram in order to investigate the need for their rehabilitation. The results of the time history analysis of these buildings showed that inter-story drifts exceeds the acceptance criteria which has been assumed 2.5% according to the Life... 

The objective of this thesis is to evaluate and calibrate design load combinations of steel building structures of Iran based on the reliability theory. The importance of this research stems from recognition that the design load combinations for steel structures in Section 6 of the National Building Code of Iran have been completely adopted from the ASCE/SEI 7-10 standard, whereas the factors that affect these load combinations differ in Iran from those of the United States. Examples are the difference in the construction industry economy, lower quality of here and the differences in probability distributions for the specifications of steel. Hence, the load combinations need to be calibrated... 

In this research, probability distribution of structural demand is estimated using a simplified dynamic analysis which is named Endurance Time method. In this method, the structure is subjected to nonlinear dynamic time history analysis, which its acceleration increases in time. It can be extracted the median of structural demand for earthquakes with different return periods. In customary researches, this estimation is performed using Incremental Dynamic Analysis knowns as IDA. The significant computational effort of IDA is the dominant obstacle that researchers and engineers encounter with. The main advantage of Endurance Time method is the fast estimation of structural demands by reducing...