Displacement-based Performance Design of Structures Equipped with Viscous Damper

نوروزوند, مهسا and محبی, دکتر محتشم and شاکری, دکتر کاظم (2019) Displacement-based Performance Design of Structures Equipped with Viscous Damper. Masters thesis, University of Mohaghegh Ardabili.

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Abstract

Research Aim: An effective design approach should be capable to achieve a predictable and desirable performance level under design earthquakes. To this end, direct displacement-based design (DDBD) as one of performance-based design approaches has been proposed. This method has been developed for designing different structural systems and control systems such as fluid viscous damper (FVD). The seismic performance assessment of frames equipped with linear FVD, which have been designed using the DDBD method shows that the designed frame can achieve the desirable performance level. However, this design method leads an over-design because the average value of drift ratios under different earthquake records is significantly less than the target limit. Hence, this design method can not be considered as an effective design approach for structures equipped with FVD. In this study to solve the drawback of over-design, a modified version of DDBD has been proposed for designing steel moment-resisting frames equipped with FVD that in this method, the effect of higher modes and difference between spectral velocity and pseudo-spectral velocity have been implemented. This proposed design method has been also extended for the structures equipped with nonlinear FVD. Research method: for evaluating the proposed DDBD method, different steel moment-resisting frames with heights of 4, 8 and 12 stories equipped with linear and nonlinear FVDs have been designed using the proposed method. The designed frames have been then subjected to different earthquake records that have been scaled such that the average of their spectral accelerations is matched to the design spectrum. Findings: The results show that in the steel moment-resisting frames equipped with linear FVD designed using the DDBD method, the average value of drift ratios under test earthquake records is significantly less than the target limit. Hence, this design method can not be considered as an effective design approach for structures equipped with FVD while evaluating the seismic performance of steel moment-resisting frames designed using the proposed modified DDBD shows that the average value of drift ratios under test earthquake records is close to the target limit. The similar results have been also found in the frames equipped with nonlinear FVD which have been designed using the proposed DDBD method. Therefore it can be concluded that the drawback of over-design has been solved and the proposed modified DDBD method can be considered as an effective approach for designing the steel moment-resisting frames equipped with linear and nonlinear FVDs. Conclusion: the results of this research show that for effectively designing the steel moment-resisting frames equipped with FVD using DDBD method, considering the effect of higher modes and difference between spectral velocity and pseudo-spectral velocity in the design process is essential.

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