Ground motion intensity measures (IMs) possess a significant role in earthquake engineering, especially during ground motion selection for nonlinear response history analyses and dynamic shake table tests as well as for probabilistic seismic engineering. Conventional IMs are not capable of accounting for the duration-related cumulative plastic damage, the frequency content of the ground motions, and the hysteretic behavior of the structural members which can be considered inherently by seismic energy-based IMs. However, many efforts have been paid for conventional IMs to relate them to the structural response. To benefit from these efforts, an empirical correlation study between energy-based and conventional IMs is required. To this end, constant ductility seismic input energy and hysteretic energy imparted to diverse single-degree-of-freedom (SDoF) systems were calculated for near-field earthquake records. The empirical correlations of the energy-based IMs with conventional spectrum-based, peak amplitude-based and cumulative-based IMs have been investigated based on the response history analyses. Further, predictive models between energy parameters and spectral acceleration were suggested considering different constant ductility levels. Hence, ground motion characteristics reflected by the input and hysteretic energy can be explicitly considered in performance-based earthquake engineering applications.
Determination of site fundamental periods is remarkably important to classify soil deposits and to identify the resonant probability of any structures during an earthquake. Recent developments in the literature exposed that the fundamental period is a better proxy than time-averaged velocity to 30 m (VS30) or the best complementary parameter to VS30 to evaluate the soil characteristics. Because great efforts have been paid to achieve VS30 maps of many regions and countries, an approximate methodology based on this parameter and engineering bedrock depth (Zbr), in which the shear-wave velocity reaches 760 m/s (Z0.76) or 1000 m/s (Z1.0), is presented here to find out the site fundamental periods. The methodology is developed and verified using the Kiban Kyoshin network database. Outcomes of the proposed methodology are also compared with some of the literature equations and methods. The comparative studies resulted in a great correlation with a relatively low standard deviation. Therefore, it is conceivable to apply the proposed methodology easily to the regions where VS30 and engineering bedrock depth are already known.
Energy based seismic design Layered soil profile Fundamental period ResonanceEnergy based seismic design getting attraction since it accounts for all structural (hysteretic behavior of structural members), earthquake (amplitude, duration and frequency content) and soil (bearing capacity, frequency content) characteristics. To develop an efficient energy based seismic design procedure, accurate determination of the fundamental periods of the soil deposits is crucial. Hence, several analytical, numerical and approximate methods were suggested in the literature to find out fundamental periods of layered soil profiles. However, practitioners tend to use the simplest and the roughest methods, generally. In this particular research, a statistical study was performed to find out the best fit coefficient for the total travel time having minimum standard deviation. In the analyses, the calculated fundamental periods of 459 different soil profiles are compared with the results of almost exact analytical equations. Resultantly, the equation generally preferred by the practitioners is improved. It is proved that the improved equation has higher accuracy with lowest standard deviation and higher correlation. Therefore, using the improved equation to determine fundamental period of the layered soil profiles is highly suggested.
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