A new energetic based ground motion selection and modification algorithm

This paper presents a new ground motion modification and selection procedure to be used for performing the response history analysis of structures. The proposed selection and scaling procedure is based on an energetic comparison in a frequency band. The Conditional Mean Spectrum is used as target spectrum while only the records providing a relevant contribution to the hazard at the site are considered. The set of ground motion with the same hysteretic energy demand is obtained matching the acceleration of the target spectrum at the period of interest T_ref and selecting only the scaled spectra having a similar Housner intensity in the period range 0.2T_ref – 2T_ref. A set of records which are spectrum compatible and have a similar hysteretic energy demand are obtained. This aspect can be reflected in terms of expected equal level of damage on the structure, since the damage parameters coming from the response history analyses have a very low dispersion. As a result, the new energetic approach allows selecting a set of ground motion according to the spectrum-compatibility criterion, to the frequency content representativeness and to the consistency of the expected structural damage for the given hazard scenario. Different intensity-based Ground Motion Selection and Modification (GMSM) methods are based on the common statement consisting in modifying the real records to have the same intensity measure (IM) obtained from Probabilistic Seismic Hazard Analysis (PSHA) (Allin & Cornell, 1968). The scaling of ground motions are performed to match a target design response spectrum (Katsanos et al. 2010). Since the main goal of the response history analyses is to predict the dynamic behavior of structures, the most critical issue is the selection of a set of ground motions that determines a low variability in the structural response. The new proposed GMSM procedure based on the energy content of the records leads to control the main parameters that affect the dynamic response of a structure. The selection procedure has been carried out by using the “Ground Motion Selection And Modification” tool of the software OPENSIGNAL 4.1 (Cimellaro & Marasco, 2015).) that it is showed in Figure 1. Figure 1 “Ground Motion Selection And Modification” component of OPENSIGNAL 4.1 software. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig296_1.tif"/>

Thus, this procedure is capable to minimize the dispersion of the structural dynamic response parameters (EDP) with respect to the mean value.

Low variability of EDP allows to increase the accuracy on the estimation of the consequence functions (casualties, repair time, repair costs, etc.).