فصلنامه رویکردهای نوین در مهندسی عمران
سال ششم شماره 4 (زمستان 1401)

Along with earthquakes and floods, landslides can be considered one of the most important natural disasters in the world, in which several factors can play a role. Researchers prepared a zoning map using different methods to manage the risk of landslides. The purpose of this article is to review the studies conducted. In the field of landslide risk zoning, the results obtained from this research show that there is no specific method to prepare a landslide risk zoning map. To obtain a map with minimum error, different methods, including random forest, should be used to produce a landslide risk potential model. Various methods have also been developed in the GIS environment to produce landslide potential models. These methods are generally divided into data-oriented and knowledge-oriented methods. Data-oriented methods are based on existing landslide points, and knowledge-oriented methods are based on expert judgment. Random forest algorithms can be mentioned among the data-oriented methods. Available data depends on the scale of the study and the type of method used.

The ductility coefficient is used to calculate the ductility strength coefficient and then the response modulation coefficient R. The modulus of response R is used in seismic loading standards to reduce the amount of forces due to the nonlinear behavior of structures in earthquakes. They have become inseparable in seismic design, because they have good use and performance due to earthquake force. In recent decades, in order to reduce the problems caused by conventional methods, studies on energy dissipation systems have been conducted in valid world regulations, including FEMA and ASCE regulations, one of which is attenuator systems, dampers. Visco is elastic, which is inactive in the control systems. In this study, while getting acquainted with viscoelastic dampers, in order to investigate the effect of viscoelastic dampers on seismic vibration response and ductility reduction coefficient, a 6-story structural model in two modes without dampers and with 2D damping with soft concrete bending frame in soft SeismoStruct software has been modeled that the results of this study show that the incorporation of visco-elastic dampers leads to a reduction in roof floor displacement and base shear. The studied structures showed that the proper efficiency of these systems in reducing the vibration response of the structures.

In this research, there are 19 different mixtures, each of them consists of a combination of gray and 325-1, 425-1, and 525-1 cement. The samples are made by replacing 10, 20, 30, 40, and 50 percent of white cement instead of gray cement. They have been prepared in the relevant molds as described below and subjected to compressive and tensile tests, water absorption and finally carbonation, the results of which are given in the relevant tables in the fourth chapter. In general, 228 concrete samples were concreted in 7 combinations in 4 different molds, and the samples were measured after 28 days under the mentioned tests. The general results show the high compressive strength of the samples containing a high percentage of white cement, which showed completely opposite results in carbonation, but the water absorption was also lower in concrete containing white cement than gray cement.

Composite members consisting of steel beam and CFT concrete column have been of great interest in the last few decades. Tubular columns are highly desirable in bending frames due to their high bending and twisting resistance and stiffness. Composite columns have considerable capabilities and efficiency due to the simultaneous benefit of the beneficial properties of steel and concrete materials. Also, the presence of concrete core in the CFT column causes the local buckling in the steel wall of these columns to be delayed. Therefore, proposing a suitable connection between the steel beam and the composite column makes it possible to take advantage of the potential benefits of these sections. Concrete in steel columns was initially used as a protective layer against impact and especially fire. This is because steel sections in extreme heat, very vulnerable and exposed to fire quickly lose their mechanical properties, as an example of the destruction of the two famous World Trade Towers 11 (WTC), September in America, which is one of the reasons The main effect of fire was to reduce and lower the mechanical properties of the steel used.

In the past years, special attention has been drawn to the explosion and its effect on various structures, especially thin-walled structures. One of the most effective factors for changing the behavior of such structures is thermal and shock loads caused by explosions. In the meantime, considering the geometric nature of the shells, which have a wide surface and thinness, as well as their wide application in various industries such as missile industries, nuclear industries, shipbuilding and silo construction, it is necessary to investigate the effect of these loads on the nonlinear dynamic behavior of the shells.  However, knowing the large deformation of such structures under these loads, practical and cost-effective solutions such as strengthening the shells using hardeners are recommended. On the other hand, implementation problems and the possibility of creating an opening in the shells lead to a change in their behavior. In this thesis, using the ABAQUS finite element software, the elastoplastic response of single-curvature steel shells with and without opening and stiffener against blast loads is investigated. For this purpose, the effect of the supporting conditions, the thickness of the single curved shell, the mass of the TNT material, the distance from the place of explosion to the centre of the shell, the curvature of the shell, and the effect of opening and stiffener have been investigated. The results indicated better performance of the shell with the bearing support condition compared to other support conditions. Increasing the curvature of the shell initially led to an increase in displacement and then a decreasing trend. Results of the research indicate that the creation of circular and square openings has reduced the stiffness of the shell, followed by an increase in displacement, and the increase in displacement for square openings is more than circular openings.