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Investigation of Endurance Time Method in Seismic Analysis of Vertically Irregular Elastic Steel Frames
, M.Sc. Thesis Sharif University of Technology ; Esmaeil Pourestekanchi, Homayun (Supervisor)
Abstract
Recent studies show that irregular structures have been damaged more than regular ones during earthquakes. This proves importance of seismic response determination of this type of structures. Today, Codes define irregularity in structures and restrict seismic analysis and design of these types of structures. The Endurance Time (ET) method is a time-history based dynamic pushover procedure for seismic analysis and design of structures that has been recently proposed in Sharif University. This thesis illustrates ET capability in analysis and design of vertically irregular frames. Irregular frames with three, seven and twelve story high were designed with two types of mass and stiffness...
Torsion Reduction of 3D In-Filled Frames Using Dampers Under Near Field Motions
, M.Sc. Thesis Sharif University of Technology ; Golafshani, Ali Akbar (Supervisor) ; Tabeshpour, Mohammad Reza (Supervisor)
Abstract
The pervious Iranian seismic code has not considered the ductility parameter in the seismic design of (steel) structures. , therefore; seismic vulnerability and retrofit of existing steel structures is becoming a vital engineering problem. Common ways of seismic retrofit such as adding a shear wall or bracing the structure cause huge forces in elements and foundations. Rehabilitation on the foundation has many constructional problems and leads to long down time. As far as known, the Infill Walls increase the lateral stiffness of frames and lead to reducing the period of the structure. Therefore, to have a reliable design, it is important to consider the effects of Infill Walls. It can be...
Seismic Performance Evaluation of Vertcial Irregular Structures through Nonlinear Time History Analysis
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
Incremental Dynamic Analysis (IDA) is a parametric analysis method that has recently emerged in several different forms to estimate more thoroughly structural performance under seismic loads. Using IDA , the objective is to study the effect of the irregular distribution of stiffness and strength along the height of a 9 story 3D steel structure model. The reference and each modified structure are hence forced to show the complete spectrum of behavior from elasticity to final global instability, allowing the estimation of capacities for the full range of limit-states and enabling a straightforward comparison without needing to “tune” the structures to the same fundamental period and/or the...
Investigating the Seismic Behaviour of Split-Level Building Structures
, M.Sc. Thesis Sharif University of Technology ; Khonsari, Vahid (Supervisor)
Abstract
Observations made after previous earthquakes have shown the crucial role of irregularities in initiating damage in buildings with irregularity, either in Plan or in Elevation. Since in existing Building Codes, there is no provision for the distribution of the Equivalent Static Loads for such buildings, designers have no option but to resort to Dynamic Analysis. In this work, the seismic behaviour of a group of two-dimensional steel building structures with irregularity in elevation, namely Split-Level buildings, was studied. The studied structures consist of a series of 5- and 15-storey frames having two parts with splitting distance of 150 cm. Both, moment-resisting and braced frames were...
Three Dimensional Analysis of Split-level Steel Moment-Resisting Frames
, M.Sc. Thesis Sharif University of Technology ; Khonsari, Vahid (Supervisor)
Abstract
Irregular buildings constitute a large portion of the modern urban structures. Based on experiences from past earthquakes, buildings with irregular configuration or asymmetrical distribution of structural properties trigger an increase in seismic demand, causing greater damages. Most of the building codes categorize the irregularities into two major types, ‘horizontal’ (in plan) and ‘vertical’ (in height). In this project the effects of splitting in levels, which could be classified as vertical irregularity, on the seismic behavior of some 3D steel structures are studied. The studied models consist of five-, ten- and fifteen-story 3D steel special moment-resisting frames (SMRF), each having...
Investigating the Behaviour Factor of Split-level Steel Braced Frames
, M.Sc. Thesis Sharif University of Technology ; Khansari, Vahid (Supervisor)
Abstract
In this work the response modification factor (RMF), behaviour factor, of two-dimensional regular and split-level steel braced frames was worked out and presented. A total number of 840 frames with various number of stories, spans, braced spans and span lengths were studied. Frames were loaded based on ASCE 7-10 and designed in accordance with AISC 360-10. Static nonlinear analysis and Uang method were used for obtaining the RMFs of the studied frames. The effect of split-level irregularity and parameters such as number of stories on the RMF were worked out and are presented in this thesis. Linear regression was used to develop formulae for RMFs of regular and split-level braced frames....
Investigating the Effect of Vertical Irregularity (Setback) on the Load Pattern in Nonlinear Static Analysis of Steel Structural Models
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofouei, Fayaz (Supervisor)
Abstract
Recent studies regarding the damage assessment of structures under severe earthquakes have shown that vertical irregularity of structures have considerable effects on the severity of the induced damages. In these cases, structure enters into its nonlinear behavior, and both structural and nonstructural elements sustain large forces and deformations. In general, nonlinear dynamic procedure (NDP) can provide more realistic results than nonlinear static procedures (NSPs). This is due to consideration of higher modes effects and the shifts in inertial load patterns as the structural system experiences nonlinear behavior. Nowadays, due to the complication of nonlinear dynamic analyses in...
Investigating an Appropriate lateral Load Pattern for Push-Over Analysis of Steel Moment Resisting Frame Structure with Vertical Irregularities (stiffness)
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayaz (Supervisor)
Abstract
The earthquake engineering is the meeting of knowledge and techniques in studying, designing, implementing, controlling and strengthening various structures against seismic loads. The assessment of the performance of structures through previous earthquakes has shown that one of the major causes of damage to the existing buildings is the excessive displacements caused by the asymmetric load distribution, stiffness or resistance. Such irregularities, lead to severe dynamic reactions, especially torsion ones. Today, many structures can be considered as irregularity in plan and height. For this reason, it is expected that these structures will be highly vulnerable to seismic loads as compared to...
Proposing an Appropriate Lateral Load Pattern for Push-over Analysis of Steel Moment Resisting Frame Structures with Mass Irregularity in Height
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofouei, Fayyaz (Supervisor)
Abstract
The irregularity in structures is divided into two categories of irregularity in vertical and irregularity in plan. The irregularity in vertical can be caused by ultra-change in dynamic properties of the structure such as mass, stiffness or strength. Research studies indicate that this irregularity leads to intensify the applied damages to structures in severe earthquakes. In general, nonlinear dynamic procedure (NDP) can provide more realistic results than nonlinear static procedures (NSPs). That is due to consideration of higher modes effects and the shifts in inertia load pattern as the structural system experiences nonlinear behavior. Nowadays, due to complexity of nonlinear dynamic...
Seismic Assessment of Steel Low-Rise Structures with Hat Knee Bracing System and Irregularities in Height
, M.Sc. Thesis Sharif University of Technology ; Mofid, Masoud (Supervisor)
Abstract
Seismic resistant structural systems or lateral load-bearing systems must enjoy adequate resistance and hardness against lateral forces and displacements in addition to resisting large deformations to absorb and dissipate energy. Since Iran is located in a seismic area and almost all metropolises of Iran are located in the vicinity of faults, it is critically important to pay close attention to development and application of efficient seismic systems in the constructional system of Iran. The HKB (Hat Knee Bracing) system is a lateral load-bearing system, the construction of which is inspired from divergent bracing systems. In other words, as in...