Reliability of Plastic Rotation Calculations for Damage Assessment of Moment-Resisting Framed Structures

Abstract eng:
Performance-based standards use plastic rotation as an important measure to determine whether the response meets the acceptance criteria for moment-resisting frames. Since plastic rotation is the key parameter in performance-based seismic engineering, the method used to calculate this quantity must be robust and accurate. Although engineers often rely on the plastic rotation output from structural analysis software packages to determine acceptable performance, the actual calculation methods usually depend on the analytical formulations utilized in the particular software. Difficulties in verifying the accuracy of the output results exist because material nonlinearity is often coupled with geometric nonlinearity in the analysis of moment-resisting frames, yet a robust analytical framework for the verification process is currently unavailable because of the lack of analytical theory. To address this problem, an analytical method to calculate the plastic rotations of plastic hinges in moment-resisting frames is presented in this research. The element stiffness matrices are rigorously derived using a member formulation, which includes the coupling of geometric and material nonlinearity effects from the beginning of the derivation. Numerical simulation is performed to calculate the nonlinear responses of structural models subjected to static and dynamic loads. Plastic rotations and other response measures are compared with those obtained using other methods of handling geometric nonlinearity to demonstrate the feasibility of the proposed analytical method.

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