Journal of Structural Engineering & Applied Mechanics

Vahid Falahi Hossein Mahbadi Mohammad Reza Eslami

In this study, ratcheting behavior of thick spherical vessels subjected to mechanical cyclic loads at elevated temperature, using the Chaboche unified viscoplastic model with combined kinematic and isotropic theory of plasticity, is investigated. Since this model is rate dependent, loading rate plays a crucial role on the ratcheting responses. A precise and general numerical procedure, using the modified successive approximation iterative method of solution to solve the non-linear equations, is developed to obtain the cyclic inelastic creep and plastic strains. Effects of loading and unloading rate, inside pressure, thickness of vessel, creep time and environmental temperature on ratcheting responses, and stress amplitude of the vessel due to the inside pressure cyclic loading at elevated temperature are obtained. The ratcheting response is observed for the load-controlled conditions, as investigated in this paper. It is shown that increasing the loading and unloading rates and the thickness of pressure vessels, result into decrease in the ratcheting rate while increasing the inside pressure, creep time, and temperature distribution increase the ratcheting rate. Also, stress amplitude decreases with increasing the creep time and thickness of vessel. On the other hand, increasing the loading and unloading rate, inside pressure, and temperature distribution result into increasing the stress amplitude. The results obtained using the applied method in this study is verified with the experimental data given in the literature. By simplifying the constitutive model, numerical results are compared with the finite elements results.

https://doi.org/10.31462/jseam.2020.03136152

Amr G. Abdellah Salah E. El-Metwally Ahmed M. Yousef

The behavior of masonry walls which consist of two different materials, brick and mortar, is quite complex. Therefore, the mechanical behavior of masonry walls can be simplified by adopting the homogenization technique, which considers the panel with average properties in the x- and y-directions. The wall is approximated as an orthotropic homogenized material with uniform properties in the bed direction, x-direction, and also in the direction perpendicular to the bed, y-direction. The nonlinear orthotropic mechanical behavior of masonry walls is developed by adopting an incremental finite element analysis approach for the prediction of the peak and post peak behavior. Based on continuum damage mechanics and a proposed failure criterion, the calculation of the damage evolution can be expressed by adopting the thermodynamics approach in the tension regime and a secant stiffness approach based on a proposed and modified constitutive law in the compression regime. Using the principles of continuum damage mechanics, the damage evolution can be then described and evaluated. The proposed model has been verified in compression and tension with very good correlation with tests. In addition, a lateral pushover analysis of a masonry panel has been performed and compared with experimental results, and the comparison show good correlation. The nonlinear orthotropic mechanical behavior of masonry walls is developed by adopting an incremental finite element analysis approach for the prediction of the peak and post peak behavior. Based on continuum damage mechanics and a proposed failure criterion, the calculation of the damage evolution can be expressed by adopting the thermodynamics approach in the tension regime and a secant stiffness approach based on a proposed and modified constitutive law in the compression regime. Using the principles of continuum damage mechanics, the damage evolution can be then described and evaluated. The proposed model has been verified in compression and tension with very good correlation with tests. In addition, a lateral pushover analysis of a masonry panel has been performed and compared with experimental results, and the comparison show good correlation.

https://doi.org/10.31462/jseam.2020.03153168

Mustafa Halûk Saraçoğlu Sefa Uzun

In civil engineering applications columns with variable cross-sections are commonly used for various reasons and buckling has a very important role in the design of these members. In this investigation square columns with variable cross-sections and circular columns with variable cross-sections is considered. These examples evaluated for four different strength classes of normal strength concrete and four different boundary conditions. ANSYS Parametric Design Language codes are developed to analyze the columns with variable cross-sections models systematically and obtained results are presented with tables and graphics. It has been revealed that boundary conditions and the shape of the cross-section effects the stability of the columns dependent to the critical buckling load values.

https://doi.org/10.31462/jseam.2020.03169179

İbrahim Özgür Dedeoğlu Yusuf Calayır

The outrigger systems, which is widely used with shear wall-framed systems at the tall buildings, increase the lateral stiffness of the structural bearing system and reduce the lateral drift of the structure under lateral loads. However, the traditional outrigger systems, besides these positive contributions, also create some limitations and problems affecting the modeling of the structure. Some of these; more interior space occupying as an architect, problems arising in the connection of outrigger and center core (especially when a concrete shear-wall core is used). On the other hand, the belt trusses known as “Virtual Outriggers” which have recently been used to build high-rise structures, have removed these problems. Unlike the traditional outrigger systems, belt trusses are formed between the outer columns. In this way belt trusses eliminate the problems arising from the direct connection of the outriggers to the center core and other problems associated with using outriggers. Extensive studies have been carried out on the examination of outrigger and belt truss systems used in high-rise buildings under static and dynamic loads. In this study, the linear earthquake responses of three structural models, which are shear wall-framed system, shear wall-framed system with traditional outriggers and shear wall-framed system with belt trusses, were performed by using modal time history analysis method. Lateral displacements and drifts of the structure, internal forces of the structural elements were obtained. These results of three structural models were compared with each other and the effectiveness of outrigger and belt truss systems were assessed. For earthquake input, three real earthquake records were selected. These records were scaled in accordance with the DD2 level earthquake design spectrum defined in Turkish Building Earthquake Standards (2018) and used in the analyses.

https://doi.org/10.31462/jseam.2020.03180203

Fethi Şermet Muhammet Ensar Yigit Sefa Ergun Emin Hökelekli

Wind energy is one of the most economical and clean energy sources in the world. Investments in wind energy are getting increase. Besides, the construction of huge-sized wind turbine towers can result in high costs. The safety in terms of stress and displacement values are also significant for a selected type of turbine towers along with cost. In the design of a wind turbine, the dynamic loads such as wind and earthquake which influence on the tower are also significant. In this regard, dynamic analyses performed for the selection of a wind turbine tower type enable a convenient optimization. In this research, three different towers which have 10 m high were designed. These towers with calculated wind forces and, the recorded acceleration data of earthquakes took place in Chi-Chi, Düzce and Kobe were analyzed using ABAQUS software calculating based on finite element method. The results show that the highest tensile and displacement values were obtained from steel tower type. In terms of stress and displacement values, the most suitable tower type was the hybrid tower.

https://doi.org/10.31462/jseam.2020.03204215