Sharif Digital Repository

Semi-analytical solutions for the nonlinear, one dimensional wave equation have been investigated. The aim of this procedure is to deliver fast and yet accurate approaches for solving the abovementioned equasions. These solutions make a good alternative for full-numerical methods, which are usually time consuming and combersome. Therefore the proposed methods may find complete priority, considering design goals. Lack of a fast numerical method for solving the nonlinear, steady state cases, make the proposed approaches relevant, dealing theses problems. By employing the presented methods, It is possible to effieciently simulate the behavior of the space-wave packet, incident on the nonlinear... 

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... 

The structure performances during past earthquakes indicate the importance of predicting behaviors of irregular structures under earthquakes. If the irregularity exceeds an expected limit, a seismic analysis should be carried out by a dynamic analysis method. The Endurance Time (ET) is a time-history method, base on dynamic analysis for seismic analyzing and designing the structures, in which structures are subjected to intensifying accelerogram functions and their Endurance Time is measured. One of the most applicable methods for RCF analysis is the Concentrated Hinge Model which is used in this research too. The needed parameters for modeling plasticity in concentrated hinge are achieved... 

One of the main issues concerning the irregular building structures is the determination of the critical directions of earthquake input to them that leads to maximum structural response parameters. In applying the seismic excitations to the structures, there is always a critical direction in which the application of seismic loads in those directions, would cause the structural system to experience its maximum responses. Therefore, considering the probability of positioning of the structure’s principal axes in that critical direction, the structure needs to be designed based on the critical seismic induced demands. In this project, the CQC3 method has been used to determine the critical... 

Existing structural irregularities (in plan and elevation) has always been among the important causes of structural failures under strong earthquakes. The torsional related damages have especially been very important in multi-story buildings as the torsional behavior of structures changes their uniform translational vibration and causes concentration of demands in the elements at the perimeter of the buildings. On the other hand, the Tuned Mass Dampers (TMD) have in general been accepted as an effective passive structural control device to suppress the structural vibration. In this study, Three 3-D, irregular (in plan) steel structural models with 4, 8 and 15 number of floors are considered... 

Past earthquakes show that irregular structures have been more vulnerable than their regular counterparts. One of the common types of irregular buildings in urban areas is split-level ones. On the other hand, beam-to-column connections in steel structures are mostly of "semi-rigid" type. In this work, effects of different levels of rigidity of connections, 100%, 75%, 50% and 25%, on the behavior of a number of two-dimensional split-level steel structures, with 1.5 m difference in levels of floors, 2, 3, 5 and 6 bays, and 5, 10 and 15 stories, were studied. All frames were analyzed “with” and “without” considering the P-∆ phenomenon, with two methods, ‘equivalent static load,’ and ‘modal... 

This research has been performed with the aim of gaining familiarity with various types of seismic isolation systems, their unique features and numerous advantages, factors affecting their performance and finally their modelling and design. Despite the advantages of seismic isolation systems as control instruments, but where there is not enough information on the involved parameters in the performance of these systems, there is possibility of unpredictable behavior of the structures. Hence, considering the extent and influence of each parameter involved in the performance of the isolators, a parametric study is performed utilizing the 3D models under multi-directional excitations, using the... 

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...