Energy based seismic assessment and design

Alıcı, Fırat Soner
The need to improve the reliability of current earthquake resistant design procedures has promoted energy-based concepts that employ seismic input energy and energy dissipation capacity of structures as the main design tools. Energy based approaches provide effective tools at both design and assessment stages for a comprehensive interpretation of the seismic behavior of structural systems during an earthquake excitation. Energy based assessment and design procedure includes two crucial aspects. The first one is the prediction of input energy spectra, considering both the structural and ground motion related parameters. The second concern is the evaluation of the actual energy absorption and dissipation capacity of structural systems during seismic response. In this regard, the aim of this study is first to introduce a procedure for the prediction of earthquake input energy spectra considering the effects of structural properties (damping ratio ξ and lateral strength ratio Rµ) and ground motion characteristics (moment magnitude Mw, soil type S, fault type F, distance to fault R). Furthermore, the effects of inelastic behavior and near-fault ground motions on input energy are also considered, and presented in this study. Then the energy dissipation characteristics of SDOF and MDOF systems are studied, respectively. In this sense, the relation between input energy and dissipated energy is obtained, and sensitivity of energy dissipation efficiency of SDOF systems is assessed. In this scope, two different Rµ–ξ–T spectra, as an improvement to equal displacement rule, are derived for estimating the maximum displacement of inelastic SDOF systems from the maximum displacement of equivalent linear SDOF systems. In the application stage, the predicted input energy and displacement spectra are integrated to attain the energy dissipation mechanisms of MDOF systems. Accordingly, it is aimed that a sufficient number of plastic hinges required to dissipate the imparted energy are detected from response spectrum analysis, by using the modal energy formulation of MDOF systems and estimated modal inelastic displacements. Thus, it is ensured that unlike the capacity design in which all beam-column connections are designated and designed as potential plastic hinge locations, a limited number of plastic hinges at the predefined locations can dissipate the imparted energy during seismic response efficiently. Based on the obtained results in this study, the suggested method improves the capacity based seismic design procedures in improving the seismic performance of structural systems.
Citation Formats
F. S. Alıcı, “Energy based seismic assessment and design,” Ph.D. - Doctoral Program, Middle East Technical University, 2019.