فهرست مطالب mohammadali barkhordari

Earthquake ground motions may vary significantly at multiple supports of long structures such as highway bridges and dams, due to the incoherence, wave-passage, and site-response effects. Therefore, it is expected that seismic behavior of this type of structures would be strongly affected by the changes caused by the motion of the earthquake along the length of the structure. To investigate the seismic vulnerability of these bridges, fragility analysis is performed using spatially variable ground motions. To achieve this aim, this study chooses a set of 70 box-girder bridges considering mechanical and geometrical uncertainties and creates a numerical model of the bridges in OpenSEES software, which can account for the inelastic response of its multiple components. These models are assessed using two scenario of applying the ground motion, uniform and multi-support excitation. The results show that the fragility of these bridges increases with decreasing deck radius by more than 50% (depending on damage level and deck radius) and also with non-flexibility considerations, component vulnerability and bridge system more than 10% is more than a uniform excitation.

In the present paper, the behavior of steel shear walls connected to frame beams only was investigated under various loading conditions (nonlinear static, cyclic and blast) using the finite element method and compared with that of the corresponding system with fully-connected infill walls (typical SPSW). The obtained results were discussed in terms of strength, initial stiffness, ductility, max of Von-Mises stress and max of in-plane and out-of-plane deformations. In the study, the effects of different system aspect ratios and various infill plate thicknesses were also considered. The adequacy of the finite element modeling approach for representing the responses of SPSWs under loading conditions was verified through comparison with experimental results. Results of pushover analyses showed that releasing of the infill wall connection to the columns limits the widespread yielding of the infill plate. This, in turn, affects the strength, initial stiffness and ductility of the system. Notably, the behavior of SPSW frames is not affected much by such configuration. Increasing the infill plate thickness in proportion to the decrease of its strength, not only offsets the effect of this configuration on the system strength, but also improves the system behavior in terms of initial stiffness and ductility (compared to the corresponding system with infill plate connected to boundary columns and beams). Results of cyclic analyses showed that the dissipated energy by the semi-connected SPSW is relatively decreased mainly due to the decrease of plate strength and energy absorption. Results of analyses under blast loading condition showed that both fully-connected and semi-connected SPSWs designed for seismic loading can partially resist against out-of-plane blast loading effects without failure.

By the growing interest in space structure using, the need for precise analysis and design of these structures is more than ever sensed. plane single-layer orthogonal grids are types of space structures which used in the bridge decks, ships and covering of the ceilings with short opening. In the aspect of the presence the different methods to analyze these structures and in the spite of the determined and simple relations are obtained to analyze and design single layer grids by plastic method, it is necessary to aware of the effect of theories and also the role of each theory in the result of the analysis in order to acquire a precise and accurate analysis of the structure. First, in this paper, analysis and design of plane grids has been stated by the means of upper bound and lower bound methods, which led to find closed from relationships Then, nonlinear analysis (elastoplastic) is carried out by considering different kinds of material modeling methods and geometric nonlinear behavior.The analysis is also carried out without considering each nonlinear effects in single layer grids by SAP and ABAQUS softwares. The results are compared to the each other and the plastic analysis. the effects of the simplifying hypothesises in the analysis results are investigated and the allowable applications of each analysis method described.