Sharif Digital Repository

The primary goal of seismic design requirements of building codes is to protect life safety of occupants during severe earthquakes. Thus it is required that collapse probability of designed buildings to be acceptably low. However current design codes are strength based and intrinsically experimental. Thus collapse safety of buildings designed by these codes is not known quantitatively. The history of formation and update of seismic building codes is marked by big earthquakes; often serving as landmarks for the evolution of seismic codes and detecting its deficiencies. As time passes, the design criteria become more and more articulate and ambitious, just as the design objectives evolve from... 

In this thesis, the semi-hinged connections such as double-angle connections, which are welded to the beam web and bolted to the column flange, are investigated. In this study it's tried to establish the effect of clearance setback between beam end and column flange and/or web. When the beam rotates, it is desirable to avoid the bottom flange of the beam bearing against the column as this can induce large forces in the connection. The usual way of achieving this is to ensure that the connection extends at least a few millimeters beyond the end of the beam. For this purpose, several connections are designed and considered, based on two different shear capacities for the beam. For each... 

Steel bracing systems can be used effectively for seismic retrofitting of existing RC buildings as well as for seismic design of new building. Steel bracing system has been used to increase the lateral load resistance of steel structures. In recent years the concept of steel bracing has also been applied to the retrofitting of reinforced concrete frames, especially to improve seismic performance of non-ductile reinforced concrete buildings. The use of steel bracing systems for seismic rehabilitation of RC frames offers some advantages such as (a) minimal added weight to the structure; (b) ease and speed of construction;(c) increased architectural flexibility; in comparison with RC shear... 

Determining nonlinear dynamic behavior of structures is always one of the main goals of structure and earthquake engineers. The Modal Incremental Dynamic Analysis (MIDA) is one of the newest methods for analyzing the seismic behavior of structures. Indeed, this method has superseded the exact IDA method which is too complicated and prolix. Although, this method represents approximate results, high accuracy, fastness and low cost procedure made it an efficient and useful technique. Many researchers have used this method and investigated the accuracy of that and achieved proper results. Up to now no one has applied this method on structures which are equipped with dampers. In the procedure of... 

One of the most efficient methods in stiffening tall buildings to withstand lateral loads such as wind loading is to link the shear resisting core to the exterior columns using outrigger trusses. Many tall buildings such as Taipei 101 have benefited from outriggers. In this system, the outriggers force the perimeter frame to take part in resisting the bending moment of the lateral load acting on the structure by developing axial restraining forces in the windward and the leeward columns of the perimeter frame and forming a resisting moment.Most of the present analytical methods have studied the performance of outrigger braced structures neglecting shear deformation of the shear wall core and... 

Steel plate shear walls (SPSWs) are popular lateral force resisting systems whose practical applications range from high seismic regions to medium and low seismic areas and wind load applications. The factors which make SPSW attractive include its energy dissipation capacity, excellent ductility, constructability, speed of construction compared to concrete shear walls, reduced architectural footprint compared to concrete shear walls, and increased inelastic deformation capacity as compared to braced frames and concrete shear walls.
In this research, characteristics and behavior of un-stiffened perforated SPSWs using non-linear finite elements software has been investigated. In order to... 

Existing design methods for steel frames has been improved over the last three decades in order to incorporate the behavior of semi-rigid steel connections in furtherance of frame design and since the analysis and design of structures is often done based on the assumption of completely rigid or pinned behavior,therefore, the actual behavior of connections and their modeling can help to understand the actual behavior of structures.Knowledge of the initial rotational stiffness of the connection is important for elastic analysis of structures. Investigations show that structures with semi-rigid connections have many features which are the causes to prefer these kinds of connections to the... 

To investigate the accurate performance of a structure, the knowledge of the way its connections function, is of great importance. Moreover, cognition of the actual behavior of connections which is often semi-rigid can lead to better apprehension of the actual and more accurate behavior of structures, whilst it is often considered to be pinned or fully-rigid.Therefore, in this study a new semi-rigid steel connection of beam to column will be introduced, and its behavior will be investigated using commercial finite element packages along with mathematical approximate modeling methods. One of the features of this connection is that its behavior mainly depends uponfolding of top and bottom... 

Despite all the developments of construction industry, there are some limitations in this important industry. For example, one of the common limitations of buildings is restrictions of architectural designs that often rise due to location of lateral load-resisting systems of buildings and usually rise disagreement between structure and architecture engineers. The lateral load-resisting systems and location of them are very important, therefore, in this study we attempt to investigate the changes of their location in structure’s stories. Due to architectural restrictions, the removal and movement of lateral load-resisting systems have been done only in some stories or from a story to the... 

OBS Bracing System is a kind of concentric bracing frame that consists of three members and with y-shape layout can provide a necessary opening in the building. In this investigation will evalouate OBS Bracing System with Knee element. Buildings equipped with OBS-Knee bracing system considered SCBF. To design these buildings according to regulations, it is needed to have Seismic performance coefficients such as response modification factor (R), over strength factor (Ω0) and deflection amplification factor (Cd). The purpose of the present investigation is quantifying these parameters and evaluation of accuracy based on the proposed method in FEMA P695. In the mentioned method, at first by... 

Structures having buckling restrained braces (BRB) as earthquake resisting system, have the qualities of high lateral stiffness and the ability to damp the energy coming from earthquake, at the same time.In addition to new structures, these braces can also be used in rehabilitating old steel or concrete buildings. By using this kind of resisting system, smaller sections are needed in design of buildings and also the cost of repair after earthquake can be highly reduced.The most important advantage of buckling restrained braces is their equal behavior and capacity in both tention and compression, that causes high energy absorption as a result of symmetric and stable cyclic behavior. All these... 

One of the advantages of Steel Plate Shear Walls (SPSWs) is the possibility of using openings with varying sizes in the infill plates depending on a need basis. Openings are used for various reasons, such as the possibility of installing utilities and for architectural reasons. However, the latest research studies suggest that the use of large-sized openings in infill plates calls for the use of heavy stiffeners or special measures for ensuring system stability. The seismic behavior of two SPSWs with large unstiffened opening (one with a rectangular opening in the middle of the plate and the other with two oval openings on the sides of the infill plate) was studied experimentally and... 

OBS1 frame is a concentric bracing system that consists of three elements, and it provides openings for building using a y-form structure. In the present thesis, the OBS system has been accompanied by a smart damping system.The buildings in which this lateral bearing system is employed are considered as SCBF frames. According to design guidelines, seismic performance parameters are required to design these buildings, including response modification coefficient (R), over-strength factor (Ω) and displacement amplification factor (Cd). This thesis aims to quantify these parameters and evaluate their accuracy based on the method proposed by FEMA-P695. In this method, first, the required initial... 

All buildings should be designed to bear both gravity loads and lateral loads such as earthquake. Resisting system for earthquake can be moment resisting frame, shear wall, brace or combination of them. Normally for strengthening of reinforce concrete buildings, shear wall should be added, but in some cases after constructing RC buildings, engineers find out that building does not have enough strength against seismic loads. In this case, adding shear wall is difficult because of architectural restrictions and assembling braces on the original frame is easier.
Structural engineers always looking to find a structural element to absorb earthquake energy to prevent potential damages of other... 

This study is devoted to the analysis and design of a recently proposed steel-FRP deck system. A methodology is being proposed to analysis the elastic behavior of the proposed deck. In this method the deck is modeled as an equivalent orthotropic plate which is constrained by rotational springs along its edges. An analytical model of the proposed deck is derived by using Rayleigh-Ritz method where the primary Rayleigh-Ritz shape functions are generated from orthonormal polynomials by using Gram-Schmidt procedure. The results of the proposed methodology show good agreement with finite element analysis results. In order to test the applicability of the proposed deck as buildings flooring... 

The study of bolted moment end-plate connections, both beam to column and beam to beam connections, is quite general and standard nowadays. Buildings which utilize such connections are widely being used and the reorganization of their significant benefits is growing. The research work reported in this thesis presents the results of several parametric analyses to determine the moment–rotation curve of bolted moment end-plate connections utilizing Rectangular Hollow Sections (RHS) and two rows of bolts using Finite Element Modeling (FEM). Previous experimental studies have focused on the moment-rotation relationship under pure bending. This project particularly involves further numerical... 

In the recent decades, outrigger systems have come into widespread use in tall buildings. This structural form has good capability to reduce the response of the high-rise structures subjected to lateral loads. Despite extensive recent use, outrigger is not listed as seismic load resistance system in current building codes and specific design guidelines is not available. In the other hands, inherent damping of structure influence on the analysis and design of the tall buildings. Measurements in actual buildings indicate that the damping in tall buildings is lower than damping in low to mid-rise buildings. Recently, a novel structural system, which is defined as damped outrigger, has been... 

Performance based design becomes an effective method for estimating seismic demands of buildings. Incremental dynamic analysis (IDA) based on a nonlinear response time history analysis (NL-RHA) is considered to be the most accurate method in seismic demand calculations. However, modal incremental dynamic analysis (MIDA), based on the equivalent single degree-of-freedom (SDF) oscillator, is also often used in studying structural engineering performances. The MIDA procedure for estimating seismic demands is extended to unsymmetric-plan buildings. In the MIDA procedure, the seismic demand due to individual terms in the modal expansion of the effective earthquake forces is determined by... 

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... 

In today’s world, the use of lateral load-bearing systems, such as bracings, has become a pretty common practice. Often showing axial deformation behavior, these members exhibit proper performance under tensile loads but tend to become unstable under compressive loads. In contrast to common bracing systems, the buckling-restrained bracing (BRB) systems perform well under not only tensile loads but also compressive loads. Recent studies have paid greater deals of attention to the application of short-core BRB systems in different structures. The bracing core has been shortened to increase the core deformation and hence the energy dissipation capacity of the bracing system. In this condition,...