Abstract
Displacement-based seismic design (DBSD) is an iterative process because the strength and stiffness of a structure are needed to be adjusted in order to achieve a specific performance level, which is extremely inconvenient for designers in practice. Yield point spectra-based seismic design is treated as an alternative design method in which yield displacement as a basic parameter will not lead to an iterative process even though the lateral strength or stiffness of a structure changes during the whole design process. Along this line, this study focuses on investigating the yield point spectra (YPS) for structures located at different soil sites. YPS are computed for EPP systems under 601 earthquake ground motions. YPS for four soil sites are quantitatively analyzed by considering the influence of the vibration period, ductility factor, damping ratio, postyield stiffness ratio, and P-delta effect. The results indicate that compared with the effects of the damping ratio, the effects of the postyield stiffness ratio and P-delta effect on YPS are more profound. Finally, a prediction equation is proposed accounting for four soil sites and six ductility factors.
Highlights
In force-based seismic design, the deformation and energy dissipation capacity of structures are insufficient when subjected to large earthquake excitations, which is confirmed by postearthquake field reconnaissance [1, 2]. us, structures need to satisfy multiple performance objectives when subjected to different intensities of earthquake ground motions; that is, there is a need for performance-based seismic design (PBSD) that aims to mitigate the impact of earthquake disasters in terms of structural damage, economic losses, and casualties [3]
A prediction equation was proposed based on the statistical results in which the effects of damping ratios and P-delta effects were considered. e main conclusions can be drawn as follows: (1) yield point spectra (YPS) are highly dependent on vibration periods
The yield displacement, Δy, increases with the increase of vibration periods. e same tendency can be observed for the yield strength coefficient, Cy, in the short-period range, while the reverse phenomenon is presented in the medium- to long-period range
Summary
In force-based seismic design, the deformation and energy dissipation capacity of structures are insufficient when subjected to large earthquake excitations, which is confirmed by postearthquake field reconnaissance [1, 2]. us, structures need to satisfy multiple performance objectives when subjected to different intensities of earthquake ground motions; that is, there is a need for performance-based seismic design (PBSD) that aims to mitigate the impact of earthquake disasters in terms of structural damage, economic losses, and casualties [3]. DBSD is an iterative process that is extremely inconvenient for designers in practice [14, 15] Along this line, Aschheim and Black [16] propose an alternative design method, yield point spectra (YPS), which treats yield displacement as a basic parameter. E authors illustrated the seismic design of a single bridge column with explicit consideration of P-delta effects and pointed out that the YPS’s design results satisfy the performance limits of the system ductility and drift with no iterations, while five iterations were needed to obtain an acceptable design for the structural first-order demand by inelastic response spectra. No specific yield strength coefficient-yield displacement, Cy-Δy, relationship can be found in the literature and seismic codes except the ones [17, 22] that only consider one selected ground motion, i.e., the 1940 El Centro earthquake record. The yield point is defined by the yield displacement, Δy, and the yield force, Fy, as shown in Figure 1. e ratio of the yield force, Fy, to the weight of the structure, W, is the yield strength coefficient, Cy. e analytical expression for Cy is provided as follows: Cy
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