An Intensity Measure for the Rocking Fragility Analysis of Rigid Blocks Subjected to Floor Motions

Abstract

A novel intensity measure (IM), dimensionless floor displacement, is presented for evaluating the seismic fragility of freestanding rigid blocks subjected to one-sine acceleration pulses in this paper. The rocking responses of rigid blocks are simulated using an equivalent single-degree-of-freedom (SDOF) model with a bespoke discrete damper to account for energy dissipation. The performance of various IMs is compared using simulation results for four different block models under different excitation conditions. In comparison to some well-known IMs, the proposed IM, determined by excitation magnitude and frequency as well as block geometry parameters, displays a considerably stronger correlation with the peak rotation of the rocking block. The comparative results show that effective IMs should consider not only the excitation characteristics but also the block geometric parameters. Finally, the fragility curve generated by the proposed IM performs best by significantly reducing the dispersion.

Seismic Overturning Fragility Analysis for Rigid Blocks Subjected to Floor Motions

“…Figure 4 displays six selected runs of rotation-time history derived from the experiment and the simulation. The comparison shows that this numerical model with discrete damping can correctly approximate the maximum rocking angle and predict overturning [59,60].…”

“…Correspondingly, for a rocking-overturning fragility analysis, various IMs, including univariate IMs [57,58] and bivariate ones [56], have been proposed. A novel dimensionless IM, determined by the excitation magnitude, frequency, and block geometry parameters, was presented by Liu et al [59] for evaluating the seismic rocking fragility, which demonstrates a closer correlation with the maximum rocking angle, thus achieve less dispersion of the fragility functions.…”

“…In addition, the least squares method is used to obtain the parameters of the fragility functions. A novel IM [59], used for the first time in an overturning fragility analysis, receives the smallest hybrid ratio and the smallest coefficient of variation compared with some well-known IMs. Finally, the effect of different analysis strip widths is also examined, and the results show that the overturning fragility curves have good robustness against the change of the analysis strip width.…”

A multi‐level approach to predict the seismic response of rigid rocking structures using artificial neural networks

“…Later, Petrone et al 21 and Lachanas et al 22 verified the importance of PGV and PGA to the overturning of slender and stocky rocking structures, respectively. Liu et al 23 showed the influence of the combined consideration of peak and frequency characteristics of the ground excitation on rocking response. Further accreditation of velocity and frequency characteristics as optimal intensity measures (IMs) (i.e., exhibiting a strong correlation with the response) came from Pappas et al 24 and Kavvadias et al 25 Recently, Giouvanidis and Dimitrakopoulos 26 revealed the remarkable contribution of duration-based characteristics, such as the uniform duration t uni and cumulative absolute velocity of exceedance CAV exc , to rocking amplification (i.e., rocking without overturning).…”

“…verified the importance of PGV and PGA to the overturning of slender and stocky rocking structures, respectively. Liu et al 23 . showed the influence of the combined consideration of peak and frequency characteristics of the ground excitation on rocking response.…”