Journal of Civil Engineering Researchers
Volume:4 Issue: 1, Winter 2022

The aftershocks may weaken or collapse structures that were previously damaged under the main earthquake and have not yet been repaired. In this paper, the seismic performance of an 8-story Steel moment frame structures designed in four types of soil is evaluated under the seismic sequence of earthquake and aftershock. The results showed that the seismic performance of the studied frame under the influence of severe aftershocks can be significantly different from the main earthquake mode alone. For example, in type 1 soil, aftershocks can increase the structure displacement by more than 50% compared to the main earthquake mode alone. It was also found that most aftershocks cause a significant increase in the durable displacement of the roof and in a small number of cases it also reduces it. In addition, the impact of aftershocks on the building damaged by the main earthquake will be much greater than in the case in which the structure under the main earthquake has not suffered much damage.

In recent years, the use of lightweight concrete in the world has grown exponentially. The reason is the lightening of the building and as a result the reduction of dead load and seismic force on the structures as well as better performance in terms of thermal insulation and energy saving. Therefore, it is necessary to study the potentials of using lightweight concrete in the construction industry. In this article, which is the result of analytical and experimental results about a special type of lightweight aggregate called Leica, the aim is to first achieve a lightweight concrete mixing design that has the necessary conditions as lightweight structural concrete. In this paper, during laboratory research, using Leica concrete grain style with an approximate compressive strength of 20 MPa and a specific gravity of approximately 1800 kg / m3 was obtained. Secondly, we investigated the structural behavior of concrete beams made with Leica lightweight aggregate experimentally and numerically. For this purpose, the first 5 concrete beams were made and examined in the laboratory, and finally, using ABAQUS finite element software, a suitable model was found to model such beams, which is in good coordination with the laboratory results. The compatibility of the results obtained from the modeling with the laboratory results is proof of the accuracy of the constructed model.

Reinforced concrete columns to steel beam connections are recently considered as structural system. This system takes the advantages of both through optimally combining metal and concrete structural elements. There are two connections through beam and through column connections. This study first reviewed the literature; then, it modeled a sample connection experimentally carried out in a laboratory by Cheng Chih and Cheng Tung Chen in 2005 through ABAQUS finite element software and investigated seismic performance of RCS connections under back/forward and monotonic loadings. Once the finite element model was validated, a parametric study (studying web steel panel thickness at the joint, studying coating thickness, etc.) was conducted; and finally, a modified model was proposed following connection results were compared showing a more stable and desired behavior in addition to increased capacity of the connections.

Helical piles have been extensively used as a deep foundation system for small to large load ranges and are thus suitable forvarious applications. Therefore, a concern over qualifying and quantifying their axial bearing capacities and performance characteristics seems to be warranted. This paper discusses design considerations, installation procedures, and results of full-scale field load tests. In this study, axial static loading tests on single, double, and triple helix helicalpiles under grouted and un-grouted conditions have been conducted. The field study has been performed on silty-clay soil, to investigate the behavior of helical piles. Also, the results of the piles load tests were interpreted using six methods presented in literature to predict the ultimate load capacity (Qu) for each pile. Results showed that in the silty-clay soil, grouted and un-grouted helical piles had a similar performance while grouted piles showed greater axial compressive strength. According to various limit load methods evaluation, it was concluded that the values for two methods of Chin, Decourt were close to the site values.

This paper presentsa new rectified square steel jacket for retrofitting of poorly confinedreinforced concrete columnsin flexural plastic hinge regions.All of the analyses was carried out based on finite elements procedure. Having verified the FE modeling, a deficient RC column designed according to pre-1971 codes was considered and eleven specimen with various detail of retrofitting were investigated. Effects of increasing at thickness of plate stiffeners, geometric shape of stiffeners and stiffened length of jacketed column have been studied.The results obtained from the parametric study indicated effectiveness of rectified jacket and allow a series of guidelines to be established.

In addition to the conventional lateral load resistance system such as different brace system, using of another kind of system that called Steel Plate Shear Wall (SPSW) is extending. Most of the SPSW that used in the constructionof the building structure are stiffened by other elements that perpendicular to the frame surface to prevent their buckling. Recent studies show that the performances of this kind of lateral load resistance systems will be improve if the infill plate buckled before the yielding of the surrounding frame. So using of too thick plate is developed that accrued some construction problem and decrease the economic advantage of them. Using of the perforated steel plate shear wall is an applied strategy to remove this problem and lead to the buckle of the infill plate. Using of the perforated steel plate incorporate some confusedness base onthe lacking of the code. In this paper 21 number of perforated steel plate shear walls analyzed under cyclic loading by usingof the ABAQUS. An appropriate perforated pattern is suggested by study on the hysteresis diagrams. The results show that using of bad pattern reduces the ability of energy absorption and suddenly remove the stability of the SPSW. Otherwise, using of the proper pattern improve the cyclic performance of the perforated steel plate shear wall camper to the other system