Abstract
To disclose the impacts of hysteretic energy (HE) demand on energy-based seismic design, this paper introduces the dimensionless parameter βEH to express the cumulative HE indirectly and establishes the βEH spectrum for energy-based seismic design. After analyzing numerous seismic responses of a single degree-of-freedom (SDOF) system, the author set up a simplified βEH spectral formula based on the genetic algorithm. Then, 750 ground motion records were selected according to Chinese site classification, and used to examine the effects of soil type and damping ratio on the βEH spectra. The results show that the soil type, site group and damping ratio have significant effects on the βEH spectra; the ductility ratio has an impact on the spectral value but not the spectral shape.
Highlights
Proposed by Housner [1], the energy-based seismic design involves more ground motion features than force- and displacement-based seismic designs
Sun et al [17] defined the ratio of the equivalent velocity of hysteretic energy (HE) to the peak ground velocity (PGV) as a dimensionless parameter βEh for indirect expression of the HE, developed the βEh spectra against the regression results on various seismic responses of the single degree-of-freedom (SDOF) system, and set up the relationship between the PGV and the peak ground acceleration (PGA)
This section explores the impacts of soil type, site group, structural damping ratio and ductility ratio on the HE demand of the SDOF system, which is represented by the dimensionless parameter E EH
Summary
Proposed by Housner [1], the energy-based seismic design involves more ground motion features (e.g. acceleration amplitude, spectral features and seismic duration) than force- and displacement-based seismic designs. On 89 pairs of bidirectional seismic motion records, Wang et al [15, 16] established the mean normalized input energy spectra and HE spectra, and created a normalized HE spectrum of constant ductility ratios to estimate the story HE demand, where the normalized HE is defined as the ratio of the HE to the square of the peak ground acceleration (PGA). Dogru et al [18] assessed the energy parameters against the total energy input and HE for special steel concentrically braced frames (CBFs) with different heights, conducted nonlinear dynamic time history analysis on the HE variation along the frame height, and eventually derived the seismic energy demand spectrum and HE distributions of the CBFs. In general, none of the existing HE spectra refers to Chinese site classifications. This paper selected 750 ground motion records by Chinese site classification, and derived the simplified βEH spectra of cumulative HE demand using the energy-balance equation of SDOF system. The author examined the effects of soil type, structural damping ratio and ductility ratio over the HE spectra, and presented the mathematical expression of simplified βEH spectrum
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