| Summary: | In design stage, the conventional steel buildings are commonly using the methods of pinned design which means that the behavior of the connection is fully on the basis of pin and rigid design which means that the behavior of the connection is completely rigid. In contrast, the real behavior of joints are not fully rigid or fully pinned, therefore the discrepancy between these manners is called semi-rigid connection. Therefore, this study is lead to evaluate the semi-rigid connected frame under the dynamic loading by applying damper. The numerical method on the basis of stiffness matrix method, which is developed using in Matlab Program, is used to assess this condition that can be divided in the main five steps. Firstly, mass and stiffness matrixes of semi-rigid connection frame are obtained. Secondly, formulation of damping matrix is developed. Thirdly, solving the dynamic equation by central method. Fourthly, the changes of spring coefficient, natural frequency, damper frequency and damper ratio are considered. Finally, numerical method is verified by SAP 2000 modeling. In conclusion, by increasing the spring stiffness coefficient the lateral rigidity of frame increases. In the case of the constant section area of frame member, as the spring coefficient of semi-rigid increases while it reaches to rigid connection, the text increment of spring coefficient cannot improve rigidity of the frame. It means that there is no absolute rigid connection, and vice versa it is true for pinned connection. Other noticeable results are that, applying of damper and addition of damper ratio can dissipate vibration caused by dynamic loading in the shorter time and modify the amount of frame displacement at resonance frequency.
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