نشریه آنالیز سازه - زلزله
سال دوازدهم شماره 2 (تابستان 1394)

Thin wall shell structure has low weight and high resistance. The load capacity, buckling behavior and post buckling behavior of steel tanks thin wall, is very sensitive to geometric imperfections. Due to the small wall thickness of the shell structures enabling the creation of any deformation and there is a disturbance on the surface of the wall. Considering the types of errors occurred when build or assembled these structures, are not built these structure, ideally. This imperfections may be in the process of rolling, removable panels, installation or welding arise. Incomplete reports about the negative impact of the effect of welding on the axial bearing capacity.
Comprehensive research on the effects of imperfection of initial geometrical shape on the steel tank vibration modes, and its effect on the bearing capacity steel storage tanks that considerable research It's not done. In this research, the actual behavior of cylindrical shells with initial geometric imperfections on mode shapes steel tanks in the pre-buckling and post-buckling. And the effect of initial geometric imperfections on steel tanks slashing been paid. Using finite element software, ABAQUS, and verification of the results of the analysis and nonlinear analysis with experimental results. Been paid. Imperfect geometric shape has changed mods. The effect of these changes on slashing are very small

Todays applying concrete structures is more usual than other structures which are used in buildings as in most of the world’s countries the application ratio of concrete to steel has increased from 10 to 1. Sometimes these structures require strengthening vulnerable members because of deficiency in their loading system in usual and critical conditions. There are different methods for strengthening these members. One of them is developing dimension of section by fresh concrete. In this method, the cohesion extent of fresh concrete to hardened concrete has significant role in force transfer.In this experimental project, the bond stress created between hardened concrete (core) and fresh concrete (screen) in core samples was measured and the effect of changing three factors was investigated that they are the length of sample, screen thickness, and 28 days compressive strength of screen concrete on bond stress. The push-out method was applied in this experiment for cracking the samples.

In this study the seismic performance of hybrid braces composed of steel and shaped- memory alloys (SMA). is investigated Six types of hybrid braces were used, constituted by SMA content of 0, 20, 40, 60, 80, and 100%. A nonlinear dynamic analysis was performed under El Centro earthquake records, with the maximum acceleration of 0.6g and 0.9g. Our results showed that the seismic performance, i.e., the amount of energy absorption and residual strain, of steel–SMA hybrid braces depends on the SMA content. The optimal value of SMA content was 20%, as, at this concentration, a hybrid brace can be designed with good seismic performance at a justifiable fabrication cost.

The most modern control techniques to improve the structural behavior of structures against unconventional forces of wind and earthquake. In this regard, researchers using innovative tools such as tund mass damper (TMD) to reduce seismic vibrations. This paper examines the effect of the position and the percentage by mass damper TMD plan on seismic performance of concrete structures. For this purpose, a concrete structures eighteen floor, are selected. The TMD are uniformly distributed along the height of the structural models. Nonlinear dynamic time history analyses are used to determine the add TMD related response reduction. The results show an reduction in the dynamic response, by increasing damping ratios of structural systems caused by add TMD. Therefore, such systems can be used to retrofit buldings and improve their behavior under earthquake used.

In this study, to simulate the behavior gusset plate connection of bracing under cyclic loading is investigated. For this purpose to model and simulated the behavior of ABAQUS software is used gusset plate connection. In modeling the nonlinear static analysis, nonlinear materials and geometry, boundary conditions flexible and cyclic loading of used and finally the model is validated by the results of experimental models. This paper shows that cyclic behavior of the gusset plate connection can be well predicted by the finite element method. The simulation results and analysis as well as the ability to model the behavior of nonlinear seismic is capable connection plate. It can also gusset plate connection buckling in the pressure modeling and predict.

Near surface mounted (NSM) is a recent strengthening technique based on bonding carbon fiber reinforced polymer (CFRP) bars (rods or laminate strips) into pre-cut grooves on the concrete cover of the elements to strength. The corrosion or lack of steel bars in reinforced concrete members and the resulting deterioration of structures prompted research on fiber reinforced polymers (FRP) bars as potential reinforcement for concrete members, for use in new construction. These FRP bars can be used to increase flexural and shear capacity of existing concrete members at NSM (Near Surface Mounted) method.The paper presents the details and results of the experimental and numerical programs. Two large-scale reinforced concrete beams were designed, constructed, and tested under one point concentrated loading system. The specimens had two fixed-end support. They were in same size and reinforcement characteristic. A new type of CFRP bar was proposed in this study, the CFRP bars were manually made in laboratory and were hooked at end for anchoring in concrete. The test results has been used to calibrate the analytical models. Moreover extra analytical work has done.The results indicate that FRP bars can be used effectively in existing structures to increase their flexural capacity and change their crack pattern. Photographs taken at selected stages of loading illustrated the performance of each specimen. The force-displacement was presented and compared to find efficiency of FRP bars at NSM method.

These days, truss structures becomes more important due to their high performance. The benefits of frequent use of this particular type of structures include the participation of all members on dividing and distributing of loads, robustness (this means that the collapse of a limited number of members does not necessarily lead to the collapse of the main structures), covering large spans with minimum consumption, ease implementing, etc. Therefore, the optimization of truss structures can play a significant role on reducing costs. The particle swarm optimization algorithm has a number of advantages compared to other algorithms, which make it superior; some of these benefits is as: a small number of regulatory parameters, good use of required memory and high speed of convergence. The frequency resonances of the structures were selected as the constraints due to prevent large deformation and thereby prevent structural damage. The results of the new proposed algorithm is far better than the original PSO algorithm and other algorithms used in this research in both the rate of convergence and the quality of solutions for finding optimum design of truss structures considering dynamic constraints.

This paper seeks to design and shape a method for analyzing the functional reliability of the double-arch concrete dam. The quasi-stimulation was used to analyze the characteristics of possible concrete dam under seismic loading random stimulation is calculated. Meanwhile, response surface methodology based on the weighted regression method, combined with the reliability, performance calculated double-arch concrete. Finally, according to data from a random sample, was considered to be the convergence and stability of this method validation and analysis. Karun 4 earthquake-prone area of high seismic risk areas and the risks of earthquakes in this area is high.