Sharif Digital Repository

The method of nonlinear time history analysis is well known as one of the most accurate techniques in seismic analysis of structures. However, this method needs much effort in terms of required data and computational cost. Within the time constrains of design consulting firms, more simple analysis tools are also desirable. One of the simple methods which have been gaining ground, as an alternative to time history analysis, is nonlinear static pushover analysis. In this method, the capacity curve of the structure with respect to the roof displacement is established. In nonlinear static pushover analysis, disproportionate increases in the roof displacement and even outright reversals the... 

The aim of the work presented in this thesis is deal with some of the aspects in the FEM analysis of sandwich panels containing holes which comprised with foam core. It is a new topic in this field; so the activities that have been done about this case are poor with respect to its performances in engineering. The main emphasis is placed on the treatment of the foam core since the core often is the weakest part of the sandwich and therefore in many ways governs the capacity and lifetime of the whole sandwich structure. Because of increasing application including construction, aircraft and transportation, marine and etc., different load conditions are considered for the analysis and... 

In steel structured buildings the connection of columns to foundations is of practical significance. This connection customarily is performed by a base plate, which is connected to the foundation with bolts. The columns and base plates are usually prepared separately, and later are welded together by contractors. Due to the errors in the process of fabrication, these plates are proposed with larger dimensions than those suggested by the designers. However, it is believed that the utilization of stiffeners, which are welded to the columns in a perpendicular state, reduces the stress field inside the base plates significantly. Therefore, by use of stiffeners the thickness of base plates can be... 

Dynamic behavior of space structures are of great complexities. On the event of severe earthquake these structures exhibit high resistance and on the other hand, their high rigidity and small deformation makes it necessary to pay attention to their dynamic behavior, especially when combined with other types of structural systems. Also due to lack of sufficient codes and references, their dynamic behavior is still unknown to a great extend. Among these kinds of structures, reinforced concrete double curvature shells, and especially funicular shells, are much more important than others. In this thesis, dynamic response of these kind of structures, especially reinforced concrete domes, in... 

The Overstrength, Ductility and the Response Modification Factor (R) for 70 steel X-braced , Inverted-V-Braced and Offcenter Bracing System frames were evaluated by performing pushover analysis of model structure with various stories (3,6,9,12&15 story) and span length (4,6&8 meter). Some result were compared with those from nonlinear dynamic analysis. According to the analysis result the R factors obtained from nonlinear dynamic analysis are 15% more than obtained from pushover analysis and R factors computed from pushover analysis were generally smaller than the values given in the design codes. R factors in Irregular structure in height are about 90% of R values in regular structure in... 

The widespread usage of corrugated steel plates as girders and steel shear walls necessitates the need for further investigation of theseefficient structural members. Having significant initial stiffness, high capability of energy dissipation and special geometry are the fundamental reasons for this study. The nonlinear behavior of trapezoidal corrugated steel shear walls with rectangular opening has been studied in this thesis. A series of corrugated and simple shear walls with and without opening regarding different angles of corrugation and different infill plat thicknesses have been investigated. This analytical study was conducted to compare the initial stiffness, ultimate strength,... 

Today, with the replacement of the old method of force-based design by the new method of performance-based design in structural and earthquake engineering, many structural and earthquake researchers have focused in their studies on this area. The performance-based design aims at enabling engineers to design structures with predictable performance. Designing space structures has particular complexities. In space structures, the failure of a structural member does not necessarily mean the failure of the entire structure, because the redistribution of power will occur between the adjacent members after the failure of a member and the structure can thus have further support capacity. Similarly,... 

Dynamic response of structures, against ground motion, is one of the most important issues in earthquake engineering. A variety of approaches and apparatus have been developed for this purpose. One of these equipments is metallic dampers. Such apparatuses provide damping, accompanied with reasonably strong lateral stiffness; hence, they are named as “Added Damping And Stiffness” (ADAS). The present study aims to evaluate the performance of a common metal damper consisted of triangular metal plates known as “Triangular Added Damping And Stiffness” (TADAS). In this investigation, the performance of TADAS, in an eight story irregular in plan steel structure, is extensively considered. A 3-D... 

The Response modification factor R represents the behavior of the structure such as ductility, overstrength and the inherent redundancy. This factor shall be defined according to the type of lateral force resisting system. However, there are some complexities and/or uncertainties in codes related to the R factor according to the height, form of irregularities and structural systems. Therefore, from the scientific point of view as well as reliability, it is very clear that the R factor cannot be similar for all kinds of structures, categorized as a specific group. In this investigation, assuming a low-rise, vertically irregular structure with a heliport which has a dual structural system... 

Plan irregularities of structures due to the governing regional and environmental conditions are a pretty important issue from the architectural as well as structural design point of view. Most of the time, especially in mid-rise and/or high-rise buildings with plan irregularities, dual system of Moment Resisting Frames (MRF), accompanied with shear walls are strongly suggested. Considering the previous works and investigations of researchers, reveals not too many studies and researches in this regards; specially, when it comes into new area and application of the Steel Shear Walls (SSW). In the present work, at first it is proposed to model and analyze a MRF steel structure with plan... 

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... 

The construction industry is one of the most important economic sectors, which shares a major part of Gross Domestic Product (GDP) and employment. In Iran many development projects are designed and implemented annually which billions of Rials are due as a result of construction and operation for executive bodies. The Organization for Development, Renovation and Equipping Schools (ODRES) as the executive branch of the Ministry of Education, is one of the largest construction bodies which undertakes construction of hundreds of educational, cultural and athletic projects annually. Given that the project delivery methods and the need to choose the correct method of contract payments exerts great... 

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... 

This paper investigates the behavior of the Y-shaped bracing system. Because of the special type of eccentricity in this system, the behavior of the frame is strongly dependent on the geometrical changes of the braces. So that even in the elastic region, it shows the geometrically nonlinear behavior. The amount of eccentricity is very effective on the nonlinear behavior of the frame. Also the ratio of cross sections of the bracing members has a very important impact on the expected performance of the frame. The results show that this system tolerates large displacements, and can act like a base isolation system. Firstly, using a two-dimensional accurate modeling related to the geometrical... 

In this article a new structural bracing system is discussed. In this framing system, a special form of diagonal braces, that connected to the knee elements instead of beam-column joints, is investigated. The diagonal elements provide lateral stiffness during moderate earthquakes. However the knee elements is designed to have one plastic joints in yielding of knee elements for dissipation of the energy caused by strong earthquake. First by elastic studying of the system and establishment of new and practical parameters, a suitable shape for brace and knee elements is proposed. Then by development of applicable and very well accuracy models in Drain-2DX , the inelastic behavior of the... 

Base plate is one of the important and sensitive elements of a structure which roles as a connector of force and moment in column to foundation joint and prevents from stress concentration in the joint area. As until now there has been several numerical and experimental researches conducted about base plate connections, but in practice for design, base plate is considered as a cantilever beam which undertakes compressive force and bending moment. In this method of design many important factors such as separation and deflection of base plate, interaction of base plate with bolts and foundation aren’t taken into consideration. Therefore there is an urgent need to design base plates considering... 

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... 

Implementation and development of large infrastructure projects are considered as the most important tools for governments to achieve sustainable development. Need of enormous finance, high level of technology and massive workload are the main feature of these projects. These projects cause significant effects on economic, technological and even political and social status in nations. So the appropriate project delivery method selection is very important for the preparation and implementation of this kind of projects. Also, mistake in this field will bring irreversible costs and losses.
Thus, the appropriate policy in decision making process about the project delivery method... 

It is well known that the most rigorous method to assess the performance and to predict the seismic demands of a structure subjected to earthquake is nonlinear time history analysis. However, this technique is accompanied by complexities and difficulties in evaluating the seismic demands of structures and requires superior knowledge and skill. As a result, in recent years, nonlinear static analysis has been proposed in performance based design procedures. One of the primary assumptions of nonlinear static procedures is that the behavior of a structure with multiple degrees of freedom (MDOF) subjected to seismic ground motion can be estimated from the response of an oscillator with a single... 

Off-Center 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 . Buildings have a concentric lateral bracing system equipped with Off-Center bracing system in lower floors are 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 ...