حامد قوهانی عرب

Today, construction of large structures is growing quickly. For this reason, it is necessary to find the material with a rather low weight and high strength. For this purpose, Steel-Concrete-Steel (SCS) sandwich structures were proposed. SCS structures are composed of two steel layers and one concrete layer. Due to their low weight and high strength and flexibility, they have become popular among engineers. In the present research, first, three specimens of push-out test of strip shear connector were modeled and validated using ABAQUS finite elements software. Then, since the present equations to predict the shear strength of the shear connectors are complicated and are not so precise, the authors proposed an equation taking the effects of different geometrical parameters and the concrete's compressive strength in to account. For this purpose, using the experimental design, 17 specimens were designed and modeled. Then, an equation was proposed using the Genetic Expression Programming Algorithm (GEP) to predict the system's shear strength. Finally, the performance of the proposed equation was evaluated using the error parameters.

In this paper, the damage detection of single tapered pole is studied. Structural damage has been identified using the vibration method. In this method, the APSO was used to detect the location and severity of the damage. The objective function for detecting damages, is a correlation coefficient based on natural frequencies. In order to accelerate the calculation of the natural frequencies of the structure, iterative method was used. In this paper, the damage is applied to the structure, by reduction of the stiffness matrix of the element in a finite element modeling and also in order to match the real situation, error in frequency is considered. To evaluate the efficiency and robustness of the proposed method in detecting damage of tapered poles, two numerical examples, including a police surveillance camera pole and a water storage pole under different damaged scenarios, are examined. In first and second example, structures are divided by 15 and 25 elements, respectively, with uniform moment of inertia. The results show that the proposed method is capable of detecting both location and severity of the damage properly, despite the complexity of some damage scenarios. Therefore, the algorithm can be used to detect the damage of other structures.

In this paper, a new meta-heuristic optimization method called the Jump of Circles Optimization Method is introduced. In any optimization problem, an answer zone is defined in which the optimization algorithms search the space to find the optimal answer. The method presented in this paper, uses two important pillars in searching the answer zone. The first pillar is to use the geometric principles. The Jump of Circles, uses the circle with decreasing radius. The second pillar is to use the meta-heuristic application. In meta-heuristic algorithms, the search points distribute randomly and jump in answer zone. In the proposed method, the center of the searching circle jumps and sits on the optimal point of each step. The proposed algorithm solves the optimization problem in two phases. The first phase is optimal area exploration and the second phase is exploiting the exploration. Finally, the most optimal point that will be obtained from the two phases, is the optimal answer of the problem. This paper focuses on engineering problems. So, to check the proposed method, three truss benchmark problems is solved. In addition, the Keane's bumpy function is solved using the Jump of Circles Optimization Method. The answer obtained from the proposed method are compared with some conventional methods and are presented in the paper. The superiority of the proposed method is observed clearly.

Concrete shear resistance is one of the most important parameters in concrete structures design. Suitable understanding of concrete behavior against shear forces has always been a problem for researchers. Many different methods have been developed for measuring and predicting shear strength. One of the most common method, is to find a relationship between compressive and shear strength. In this study, an attempt was made to provide a practical relationship between compressive and shear strength using an experimental design with compressive strength in the range of 20-30 MPa which resulted in 50 compressive and shear concrete specimens. Gene expression Programming (GEP) method has been used to estimate shear resistance and five relationships have been provided. In order to select the best relationship, in addition to considering error measurement parameters such as correlation coefficient,, Willmotts index, and etc ., the criterion of simplicity and easy use of the relation is also considered.

This study presents a new quadrilateral element for layered finite element analysis of laminated composite plates which is obtained through assemblage of membrane and plate bending elements. The membrane component is a new unsymmetric quadrilateral element with drilling degrees of freedom, in which two different types of displacement fields are used as the test and trial functions. The test function is a new kind of displacement field with drilling degrees of freedom obtained by using interpolation along the element edges. The trial function is a stress field computed through analytical solutions of Airy stress function. The bending component of lroposed element is a non-conforming plate element that its displacement is computed using third-order deformation modes and the rotational field of element is defined by using first-order Jacobean matrix. The results of numerical benchmark problems show that the the proposed element is capable for analysis of laminated composite plates with varius geometry and boundary. The maximum error of the proposed element among the considered numerical problems is only 1.5 percent.

In recent years, evaluation of reliability analysis of structures has become a straightforward and interesting topic among structural researchers. In the field of civil engineering, estimation of structural failure probability is highly investigated, considering probabilistic uncertainties of resistance and load parameters during modeling and designing of structures. To obtain an accurate failure probability, researchers often perform Monte Carlo simulation (MCS) that requires numerous modeling and cost. In the present study, based on MCS, an enhanced technique is developed that efficiently reduces number of structural modeling. The approach works by employing the concept of First Order Reliability Methods (FORMs) to determine closest point to the mean of random variables in failure region. Afterward, by presenting sub-intervals in various layers, to group generated samples in MCS, the possibility of reducing number of structural modeling with well-disciplined error and acceptable accuracy is achieved. In order to investigate the efficiency and robustness of the method, various numerical and engineering examples with complex limit state functions were attempted and the obtained results were compared with those based on the conventional reliability methods in the literature. Results show the high accuracy of proposed approach while the number of requires structural modeling were substantially reduced.