فصلنامه رویکردهای نوین در مهندسی عمران
سال چهارم شماره 4 (زمستان 1399)

This study examines the type, thickness, and the way of gridding and placement of FRP sheets with concrete slabs. Shear and bending failures are two major failures in concrete members. One of the ways to reinforce structural members is to use polymer plates that are used due to their low thickness, good effect and balanced price. In this study, eight samples of reinforced concrete reinforced slab reinforced single, double and different location of modeling and results were investigated, of which 2 samples were single FRP, 3 samples were double FRP and 3 were grid mode of Reinforced concrete slab. Reinforced concrete slabs with dimensions of 3400 mm in length, 2500 mm in width and 160 mm in thickness. Longitudinal and transverse rebars with a score of 12 and at a distance of 20 mm from the surface of the slab. After reviewing, it was found that in general, slabs reinforced with CFRP fibers performed better in terms of loading and breaking, and by doubling these plates, a better effect is observed. In the discussion of FRP placement, whatever the regular grid mode and the placement of the force, has a great impact.

In this study, the effects of adding copper and plastic fibres and stone powder on flow parameters and hardening properties of self-compacting concrete have been investigated. The basic disadvantages of concrete include high specific gravity, low tensile strength compared to its compressive strength, low durability, and increasing tensile strength. By The use of fibres is expected to improve tensile strength, as well as reducing stiffness and, on the other hand, increasing the concrete plasticity. Today, self-compacting concrete solves one of the major problems in the implementation of concrete works in urban environments, which includes the noise pollution caused by the use of a vibrator to replacement concrete. Self-compacting concrete is a high-performance modern concrete that distinguishes its characteristics such as the lack need to internal or external density and the cross of dense reinforcement networks from conventional concrete. Another feature of self-compacting concrete is its high viscosity and stability as a result of the addition of fillers and the use of cement materials. But increasing the amount of cement materials and fillers in self-compacting concrete increases the brittleness of the concrete matrix, resulting in a decrease in deformability. Considering the successful experience of using fiber in concrete over the past years, in order to increase the deformability of ordinary, lightweight and high strength concrete, the use of fibres is an appropriate proposal to enhance of deformability of the self-compacting of concrete. Fiber concrete also has high energy absorption capacity and is not easily disassembled under impact loads.

Seismic performance is an important issue in the design of buildings located in seismic areas. One of the most important parameters in the design of structures is ductility (ductility; ductility plays the role of a fuse in the structure. Damage to a strong member (such as walls) that is expected to be able to maintain its stability in the structure in any case. The presence of a malleable member in the structure gives the occupants of the building the opportunity to leave the building during an earthquake. This is the same seismic expectation that comes from the structure, meaning that the structure does not act without warning and does not collapse once. In masonry buildings, the parameter of strength, especially shear strength, is very important. In this study, in order to know more engineers, to present the seismic weaknesses of masonry buildings during earthquakes and methods Fixing it during design and execution (before the structure is damaged and causes casualties and needs to be repaired) and also The wit of the damaged structure is addressed after the earthquake.

Optimization is one of the most important issues in civil engineering. In this research, artificial neural network (ANN) has been used to optimize the structure of steel structures. The multilayer neural network of perceptron, one of the most widely used neural networks, has been used. Different structures of artificial neural network with different number of hidden layers and number of different neurons have been modeled to achieve the best architecture of artificial neural network model. Neural network models have acceptable success in the optimization process. Dimensional properties of structures have been used in all these models. Models used for optimization have four input parameters, one output parameter is used. A large set of structural models has been used as a database. In the perceptron neural network, networks with different architecture with one and two hidden layers have been used to determine the most accurate network. Extracting and presenting the relationships governing a neural network model gives the user more confidence in using such models, thus facilitating the application of such models in engineering work.

In this research, it will be paid to evaluate the effects of the link beam length on seismic behavior of eccentric braced frames under near and far-fault earthquakes. For this purpose, four frame structures with different number of stories such as 3, 6, 9 and 12 have been used. For each of these frames, three different lengths of link beam are considered. After designing structures and preparation of non-linear models, these models are analyzed under a suite of 10 and 3 near and far-fault records, respectively. Nonlinear dynamic time history analyses are performed using scaled records for these structures, and the response values of the stories displacement, base shear and the rotation of link beam are evaluated for them. Based on the results of this study, it is specified that increasing the length of link beam and change the mode of the link beam from the shear to bending, the values of stories drift are considerably increased, but the values of base shear are decreased relatively. This result is similar for near and far-fault records. Therefore, it seems that the use of a short link beam would offer a better behavior to the braced frame if the architectural conditions allow. The results showed that in 0.8 m as an optimal length, the displacement response of frames under near-fault records up to 15 percent larger than the far-fault records. This difference is lower for base shear response.