فصلنامه رویکردهای نوین در مهندسی عمران
سال ششم شماره 3 (پاییز 1401)

In this review article, we examine the behavior of earthen dams under earthquake movements. Earthen dams perform satisfactorily when exposed to strong earthquakes. Their performance is usually related to the nature of the soil used for the structure. Most well-constructed earthen dams can significantly vibrate the earthquake without damaging effects. Dams made of compacted clay materials on clay foundations or bedrock withstood strong ground movement. Compared to older embankments built on sandy materials or of sand or silt with inefficient density and tailings dams, all of them showed almost some instances of failure, which was initially due to the liquefaction capability of these materials. They are considered a type of hydraulic structure in this period, and tailings dams are the most dangerous types of earth dams. The more accurate and durable equipment and tools are used during the construction and operation of the dam, the minor deformation is created in the dam, and the more controllable it becomes. Utilizing up-to-date knowledge and benefiting from the construction and maintenance experiences of the dam can help the optimal management of the dam during construction and operation. Earth dams have better flexibility to accept the dynamic load due to earthquake force than concrete dams.

In this study, the optimization of prestressed cables in steel structures was evaluated. The type of optimization is considered as locating the position of the cables in the floors. Optimizing structures by considering the existing conditions and constraints or the same constraint functions has always been one of the goals of engineers and designers. So far, a lot of research has been done on optimization and various methods have been proposed to solve it. In general, optimization methods can be divided into three categories: mathematical methods, optimization criteria and meta-exploratory methods. In this research, genetic algorithm, which is one of the meta-heuristic methods, has been used. It is necessary to use the genetic algorithm method to have appropriate objective functions and constraints relative to the design variables. In this research, the weight or area of the structure as the objective function and the stress and deformation constraints at the same time are considered as constraints of the optimization problem. The optimal location, diameter and amount of prestressing force of the cables are considered as problem variables. OpenSees software and nonlinear static method were used to analyze the structures. To implement this issue, three- eight- and twelve-story structures with different span ratios in two modes of cross-bracing on top of each other as well as cross-bracing in different spans are examined and it is observed that in 60% of the models two The middle spans and only 40% of the two side spans are braced as the optimal spans, it is also observed that the coefficient of behavior for 3-story structures with one bracing span in the range of 4.61 to 5.88, in 8-story structures and 12-story with two bracing openings varied in the range of 3.51 to 4.9 and 4.04 to 5.34 respectively. It can also be said that the prestressing force for 3-story structures in the range of 0.12 to 0.18, for 8-storey structures in the range of 0.1 to 0.28 and in 12-storey structures in the range of 0.1 to 0.32 the final cable tension varied.

One of the common problems in the construction industry is the creation of cold joints between different layers of concrete during concreting, which occurs due to delays in the concreting process. Creating cold joints in concrete structures reduces the compressive and tensile strength of concrete. In this paper, we have tried to study the concrete strength of concrete samples by examining concrete samples from different angles and time delays in the concreting stages, which has received less attention from researchers. In this paper, concrete samples at zero, 30, 35, 40, 45 degree angles are used to obtain the optimal angle. Cubic samples were used to obtain the compressive strength of concrete and cylindrical specimens were used to obtain the Brazilian tensile strength of concrete. In concrete samples, in the first layer, ordinary concrete with a specific mixing design and in the second layer, calcium oxide additive in the amount of 15% cements were used. Using this method, we witnessed an increase in the adhesion of concrete between the first and second layers and also increased the compressive and tensile strength of concrete.

It is now known that the behavior of any structural system during an earthquake is largely determined by its energy dissipation capacity through ductile behavior. And shows the degree of nonlinear behavior of the structure.In this paper, in order to compare bending frames from the economic point of view and the effect of ductility on the amount of consumable materials, conventional reinforced concrete bending frames with different ductility and with different number of 6 and 12 floors are selected as representatives and observing all criteria. Aba are designed for each group. After proper typing and observing the executive points and preparing executive plans, the amount of consumable materials (concrete and steel) has been determined and all costs have been estimated according to the existing price list (2009). These costs only include the cost of materials used in the construction of beams, columns and foundations, and the cost of roof and other structural costs are not included because changing the type of ductility has no effect on other costs and only in the design of beams, columns and Foundations are effective.

Preloading is a well-known and classic way for soil treatment in engineering practice. For south part of Iran, this method is an economic and also effective way for soil treatment. In this method, the preloading is done using vertical drains to accelerate the consolidation and also a surcharge that is embankment. The preloading induces the required settlement to weak and compressible layers and hence the settlement would be reduced considerably after the compilation of the main structure and also the risk of differential settlement in the future would be decreased considerably. In this article the Mahshahr clarifying unit has been modeled and then the results were compared with instrumentation on site.