A Simple and Efficient Intensity Measure to Account for Nonlinear Structural Behavior

Abstract

A fundamental issue that arises in the framework of probabilistic seismic risk analysis is the choice of ground motion intensity measures (IMs). A new structure-specific IM, namely, relative average spectral acceleration (ASA R ), is being proposed herein, and a comparison with current IMs is performed based on (1) a large data set of recorded earthquake signals;(2) numerical analyses conducted with state-of-the-art finite element (FE) models, representing actual load-bearing walls and frame structures, and validated against experimental test; and (3) systematic statistical analyses of the results. According to a comparative study of the case of nonlinear structural behavior, the ASA R proves to be the most efficient IM with respect to demand parameters, such as maximum interstory drift, frequency drop and maximum ductility demand. Beyond the sufficiency and simplicity of its formulation, which allow for the use of existing ground motion prediction models, the ASA R offers a promising IM for performance-based seismic design and/or assessment.

Strategy for the selection of input ground motion for inelastic structural response analysis based on naïve Bayesian classifier

“…In conclusion, taking into account multiple IM leads to a better description of the complexity of the seismic signals; furthermore, since the structural response evolves as a function of plastic hinge formation, a single IM is not always able to follow this evolution describing all the complexity of the structural demand. That is why the results presented in this paper can be improved using more specific IM defined to better relate the input ground motion and the structural response (De Biasio et al 2014;Lestuzzi et al 2004). In this sense, the naïve Bayesian classifier is conceived as a tool able to collect and fully exploit the published results on the best IMs as a function of the structural response.…”

“…This is not surprising, since these parameters describe the spectral velocity or acceleration content averaged over two frequencies, taking into account the fundamental frequency degradation related to the appearance of plastic hinges or cracks in the structures. Furthermore, several authors investigated the best way of defining the frequency integration range for pseudo-displacement/velocity and acceleration spectra, in order to customize the IM parameter as a function of the investigated structure properties (De Biasio et al 2014;Lestuzzi et al 2004).…”

Empirical ground-motion models adapted to the intensity measure ASA 40

“…The relative average-spectral-acceleration (ASA r ) is a new intensity measure presented by De Biasio et al (2014). Its main advantage over SA is its efficiency as an intensity measure appropriate for the structures that behave non-linearly.…”

“…It takes into account the lengthening of the fundamental period due to progressive loss of stiffness caused by irreversible damage processes. The optimum value of frequency drop, R, of the structure was chosen as 40 % by De Biasio et al (2014). The prediction of the new intensity measure ASA 40 using probabilistic seismic hazard analysis (PSHA) would enforce its sufficiency as a robust intensity measure for the analysis of non-linearly behaving structures.…”

“…However, in the case of inelastic structural behaviour, SA does not take into account the contribution of higher modes to the overall dynamic response or the lengthening of the fundamental period due to progressive loss of stiffness caused by irreversible damage processes. A structure-specific intensity measure has been developed by De Biasio et al (2014) in order to consider the lengthening of the fundamental period of the structure. The new intensity measure is named relative average spectral pseudo-acceleration (ASA r ).…”