Abstract
This study uses a generalized and parametrized reduced-order model in the frequency-domain to evaluate the effects of asynchronous excitation on the lateral response of bridge structures. Bridge geometry parametric regions, corresponding conceptually to valley profile shapes, are explored. Both modal and bounding analyses, that are dependent on bridge geometry alone, are employed to highlight regions where the first mode is anti-symmetrical and the likely error between identical support excitation (ISE) and multi-support excitation (MSE) analyses is large. Numerical time history analyses, using a heuristic bridge case and spatiotemporal ground motion from the SMART-1 array, are employed. These analyses confirm that in parametric configurations where the first mode is anti-symmetrical the error between MSE and ISE is often larger. This confirms the utility of geometry only modal and bounding analyses in identifying critical regions. These critical parametric cases of a first mode that is anti-symmetrical correspond to shallow valleys with a central rise. In these cases it is recommended that both ISE and MSE analyses should be employed to be conservative.
Highlights
Many attempts have been made (Leger and Ide et al 1990; Monti and Nuti et al 1996; Lin and Zhang et al 2004; Soyluk 2004), among others, to examine the effect of spatially varying earthquake ground motion (SVEGM) on the response of long, extended, structures
We assume that there exists a singleton station who’s power is greater or equal to the power of any of the stations used for multi-support excitation (MSE), that is
A large-scale parametric study was presented to explore the sensitivity of the responses to asynchronous excitation of a heuristic bridge where geometry parameters of the bridge differed conceptually due to valley profile
Summary
Many attempts have been made (Leger and Ide et al 1990; Monti and Nuti et al 1996; Lin and Zhang et al 2004; Soyluk 2004), among others, to examine the effect of spatially varying earthquake ground motion (SVEGM) on the response of long, extended, structures. Recent studies primarily examined the response of symmetrical and unsymmetrical structures (Zerva 1990; Hao 1991; Hahn and Liu 1994); investigated the spatial variability effect on suspension and cable bridges (Nazmy and Abdel‐Ghaffar 1992; Camara and Astiz 2012); evaluated the effect of the anti-symmetrical mode on the bridge responses (Price and Eberhard 1998; Lee and Poon et al 2006; Papadopoulos and Sextos 2018); exploring the effect of valley profile on the accuracy of ISE analyses for linear and nonlinear cases (Meibodi Alexander et al 2020) and developed the nonlinear dynamic analysis to incorporate SVEGM effects (Wen 1976; Guyader and Iwan 2006; Sextos and Kappos 2009; Mitseas and Kougioumtzoglou et al 2018) In this context, the objective of this paper is first to understand and explore the mathematical features on a generalized reduced-order model to calculate the dynamic response of the multi-support bridge when spatial variability of the ground motion is taken into account. To assess the relative importance of proposed geometrical parameters, the Auto Modal Participation factor (AMP) and Cross Modal Participation factor (CMP) and investigate its correlation with bridge responses from large-scale parametric studies conducted in the companion papers
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