Strong‐motion duration and response scaling of yielding and degrading eccentric structures

Abstract

Plan irregular structures, whose complex response represents a generalisation of the simpler de-coupled motion ascribed to symmetric buildings, make up a large proportion of the failures during major earthquakes. This paper examines the seismic response scaling of degrading and no-degrading eccentric structures subjected to bidirectional earthquake action and its relationship with the duration of the ground motion by means of dimensional and orientational analyses. Structures with reflectionally symmetric stiffness distribution and mass eccentricity subjected to orthogonal pairs of ideal pulses are considered as the fundamental case. The application of Vaschy-Buckingham's Π-theorem reduces the number of variables governing the peak orthogonal displacements leading to the emergence of remarkable order in the structural response. If orientationally consistent dimensionless parameters are selected, the response becomes self-similar. By contrast, when degradation is introduced, peak inelastic displacements are dramatically affected and the self-similarity in the response is lost immediately after the onset of inelastic deformations. Conversely, if the uniform duration, instead of the period, of the strong motion is adopted as a timescale, a practically self-similar response is observed. This offers unequivocal proof of the fundamental role played by the ground-motion duration in defining the peak displacement response of degrading structures even at small inelastic demands, although its importance increases with increasing deformation levels. Finally, the existence of complete similarities, or similarities of the first kind, are explored and the practical implications of these findings are briefly outlined in the context of real pulse-like ground motions with varying degrees of coherency.

Hybrid data‐driven hazard‐consistent drift models for SMRF

“…However, there is a 70 and 53% variation in the inter‐storey drift demands for life safety and collapse prevention level, respectively, at the Oakland site. This increased variation at higher hazard levels, where the responses are generally inelastic, indicates that the inelastic drifts could be controlled by specific characteristics of ground motions beyond spectral content that are not well incorporated in the elastic spectral shape used in this study 21,42 . Besides, the drift plots presented above illustrate in a striking manner the inability of Eurocode 8 to ensure a consistent exceedance level for a given EDP, especially at a lower hazard.…”

“…This increased variation at higher hazard levels, where the responses are generally inelastic, indicates that the inelastic drifts could be controlled by specific characteristics of ground motions beyond spectral content that are not well incorporated in the elastic spectral shape used in this study. 21,42 Besides, the drift plots presented above illustrate in a striking manner the inability of Eurocode 8 to ensure a consistent exceedance level for a given EDP, especially at a lower hazard. Arguably, the better the code, the more it will result in well-controlled structural designs, where similar risk levels are expected on all structures depending on their function.…”

“…Interestingly, most structural parameters (Figure 12A) and duration‐related metrics (Figure 12B) have very low collinearity with θ mod . Although ground motion duration is not expected to be used independently to predict seismic responses, it has been recently argued that duration may play a role in the seismic response of yielding systems, even at low levels of demand 42 . On the other hand, the velocity‐, acceleration‐, (Figure 12B) and spectral acceleration‐related parameters (Figure 12C) have prominent collinearity with θ mod .…”

“…Although simplified non-deteriorating models have been shown to predict reasonably well mean global structural responses, for example, 40,41 a deterioration model that captures the strength and stiffness degradation of the structural component is generally expected to be more reliable even at lower levels of earthquake demand, 42 and there have been recent calls to use the higher levels of model sophistication even for design level demand assessments. 43 To examine the accuracy of these claims, alternative models without deterioration were assessed, and their outputs were compared with the deteriorating ones.…”

A probabilistic strong floor motion duration model for seismic performance assessment of non‐structural building elements

“…A further insight on the importance of shaking duration was also obtain by reconnaissance reports that documented considerable non-structural damage after seismic events that exhibited moderate intensities and long durations, such as the Nisqually earthquake in 2011, 1 suggesting a direct influence of the earthquake duration in the non-structural damage. Although several recent studies have investigated the influence of strong ground motion duration (SGMD) on the seismic response of structural systems, [21][22][23][24] no specific information could be found by the authors in the public literature on the characterisation of strong floor motion duration (SFMD). This is despite that floor motion duration is a key parameter when selecting historical or generating synthetic floor motions for the seismic response assessment of NSEs or when generating input shake-table test records for the seismic qualification of NSEs.…”