Sharif Digital Repository

Based on the code specifications, in moment-resisting frames the span-to-depth ratio has to be larger than a minimum value to make sure of adequate plastic hinging at beam-ends. This provision poses a restriction on the use of deep beams with short spans, especially for the framed-tube system in tall buildings. In this thesis, a new energy dissipation method is introduced for moment-resisting frames by modifying the mid-span of the beam by two different methods, resulting in: (i) Perforated Shear Links (PSLs) and (ii) Slit Shear Links (SSLs). The links dissipate energy through shear yielding of the web, weakened by perforation or slitting, respectively. A thorough study is conducted on the... 

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... 

This thesis presents the results of three tests to evaluate cyclic behavior of special moment resisting frames (SMRFs) with slitted web section. Typically, in SMRFs energy is dissipated by formation of plastic hinges at the beam ends. Nevertheless, based on the codes, the span-to-depth ratio of beams in SMRFs should be larger than a minimum value to assure the development of plastic hinges with sufficient length at beam ends, reducing application of short span beams. Reduced beam section (RBS) was developed to improve the performance of steel moment frame connections by weakening the flanges at a short distance from the columns. In this thesis, an alternative approach is proposed for short... 

In this research, a structural lateral bracing system called ‘Chevron Knee Bracing’ (CKB) on reinforced frames is investigated. This new form of framing system is constructed through the knee and the diagonal brace elements. The diagonal brace component provides the required level of lateral stiffness and stays in the elastic range without buckling at any time. However, the knee part is a fuse-like component that dissipates energy by the formation of plastic flexural and/or shear hinges at its ends and mid-span, when the building is subjected to severe lateral loads. For this purpose, first, by elastic studying of the system, three new and practical parameters are established. Then, the best... 

In this paper the predictive equations for collapse assessment of shear links used in eccentric braced frames are developed. An extensive database including results of over 70 cyclic tests on steel wide flange shear links is collected and the structural parameters governing the hysteresis behavior are calibrated using a simplified numerical model. The methodology of calibration is to minimize the discrepancy between the experimental hysteresis loops and the corresponding numerical results using Particle Swarm Optimization (PSO) algorithm. The objective function of PSO algorithm is minimized by iterating parameters that govern the hysteresis behavior of the numerical model. Stepwise...