نشریه آنالیز سازه - زلزله
سال پانزدهم شماره 4 (زمستان 1397)

The idea that a building can be uncoupled from the damaging effects of the ground movement produced by a strong earthquake has appealed to inventors and engineers for more than a century. Seismic isolation is effective in reducing seismic demand for buildings and decreasing seismic damage costs. Today the concept has matured into a practical reality and is taking its place as a viable alternate to conventional (fixed base) seismic resistant construction. This study, three bracing frame and three spacial moment frame were modeled and analyzed and the capacity curve wase plotted.The finaly, response modification Factors for steel frames equipped with base isolation were compiled as a table.Finally, based on the results of the analysis, it was observed that the structures equipped with the surface separator have a more obtuse curve than the non-separating state.

Country of Iran due to the existence of numerous faults and stresses by the borders of the shell,has been witnessing the occurrence of many earthquakes throughout the year. Thus providing resistant systems for structural stability against lateral forces of the main concerns of civil engineering in the country. The lateral resistant systems, Eccentrically Brace frame model, which relying on the rotation of link beam causes the absorption of structural earthquake force, while the excessive rotation of the link beam region can weaken the structural performance level, and makes some significant cracks in the concrete slab. In the present study, a new model of eccentrically brace system equipped with a steel plate in the lower link beam, and the beam out of the links provided. Numerical modeling in Abaqus software and protocol load is applied based on the ATC-24. The results show that the optimal positioning of steel plates and insert its plates in the lower link beam and the beam out of the links cause improve the shear performance of the bracing system in the development plastic hinges And increased shear strength and ductility of the bracing model. Finally, the energy absorption by the models has a significant performance in comparison with the current model.

Frames with a Khorjini connections is one of the most commonly used structural systems in Iran. In these frames, the beams are placed on the sides of the pillar and each beams are placed on a lower corridor. The columns are double-skinned and have a relatively long sheet at the Khorjini, so that the lower and upper corners are in place. What makes this type of connection a lot of use is the high speed and ease of execution of sophisticated frames. Several studies have shown that when exposed to the structure, the exposed fire will change its resistance. The purpose of this study is to investigate the behavior of steel beams with Khorjini connections at different temperatures and times. First, after the library studies, the laboratory test was verified by Abacus software. The results of the numerical investigation were compared with the results of the experimental study in the paper, and the results of this comparison showed that the matching of the experimental results and the results of the numerical study with a percentage difference of less than 10 Percentage. In order to develop a numerical model, 17 different models were investigated with temperature variations and exposure time of exposed beams. The results of this study showed that increasing the temperature of the heat in the Khorjini connection reduces the resistance, increases the amount of failure and deformation in the joint area. Other results of the study showed that as the Khorjini connections are exposed to more fire, the resistance will be reduced, the failure rate will increase and the structural deformation will be higher.

In recent years, the use of concrete-filled steel sections (CFST) has been widely used for many benefits, including excellent seismic performance, high strength, high flexibility and energy absorption capacity relative to concrete (RC) and steel sections in the construction industry. These columns are often more commonly used in the form of circles. The main reason for this is the point that circular sections create more enclosure than other sections in the core concrete. This makes the circular sections more widely used in columns (CFST) than in other sections. However, in some cases, the use of circular sections will be impossible, including architectural considerations, the implementation of more economical and easier connections in the quadratic sections than the circular sections, these causes certain shapes, including sections Square and flat sections and sections with L and T shape shapes are used in some parts of the building. considering the importance of this issue in this paper, we tried to introduce and investigate the mechanical behavior of short columns (CFST) with L-shaped geometric section and study the parametric effect of steel wall thickness and compressive stress of concrete on the capacity and mechanical behavior of these columns at the end and after analysis of the study samples, it was determined in the finite element analysis (FEM) that, in columns (CFST), the effect of the thickness of the steel structure was more effective on the capacity and mechanical behavior of the columns (CFST) with the geometric cross section L will be the shape.

Genetic algorithm (GA) is one of the meta-heuristic optimization algorithms. In this paper, the effects of spectral dynamic and equivalent static analysis methods on the calculated optimum weight of the frame are investigated by the means of GA. In the equivalent static analysis, the applied lateral load and design constraints are considered according to ASCE and LRFD-AISC specifications. The internal forces of the frame members are calculated using finite element method. Analysis and optimization of the frame are performed using a program written in MATLAB programming language. Three types of selection including stochastic selection, tournament selection, and ranking selection as well as three different types of crossover, single point, two-point, and continuous crossover are utilized in this study. Moreover, a comparison between equivalent static analysis and spectral dynamic analysis is presented. The results indicate that the difference between the optimum weight of the structure analyzed by spectral dynamic and equivalent static methods increases as the applied load is increased

Many of the common buildings in civil engineering are affected by lateral soil pressure. Basement walls, foundations of the bridges, tunnel walls, walls of underground tanks and etc. are such structures that the lateral pressure of soil has a significant effect on them. Therefore, in order to limit this pressure, using of gravity walls, cantilevers, buttressed cantilevers and other similar buildings are common. Such walls must have a satisfying safety factor to prevent sliding and overturning, and also in order to control bearing capacity of foundations and control general stability of the wall and the soil. In addition to endure static loads, Retaining walls must endure loading caused by dynamic forces such as cyclic loading and also the force that is caused by the earthquake, which is probable to occur during the using period of these wall. For the modeling of weight retaining walls in this research, Plaxis 8.6 software was used and retaining wall’s behavior under dynamic loading was evaluated. The results showed that the maximum displacement happens at the top of the wall and the maximum horizontal stress is created at the bottom one third of the retaining wall’s height. The analysis also showed a strong dependency between retaining wall’s behavior and changes of mechanical properties of the soil that is behind it. Analysis were done by changes in the mechanical properties of the soil and changes in height of the wall, and a sensible increase in the horizontal stress was observed.