SummaryThis paper assesses the seismic fragility of single degree of freedom rocking structures within a probabilistic framework. The focus is on slender rigid structures that exhibit negative stiffness during rocking. The analysis considers ground motions with near‐fault characteristics, either solely coherent pulses or synthetic ground motions that include, in addition, a stochastic high‐frequency component. The study offers normalized fragility curves that estimate the overturning tendency, as well as the peak response rotation of a rocking structure. It shows that the use of bivariate intensity measures (IMs) can lead to superior fragility curves compared with conventional univariate IMs. Regardless, the study advocates the use of dimensionless–orientationless IMs that offer an approximately ‘universal’ description of rocking behavior/fragility, a normalized description almost indifferent to the amplitude and the predominant frequency of the excitation or the size and the slenderness of the rocking structure. Importantly, the analysis unveils hidden order in rocking response. There exists a critical peak ground acceleration, below and above which, peak rocking response scales differently. In particular, when the structure does not overturn, the peak rotation follows approximately a biplanar pattern with respect to the intensity and the predominant frequency of the excitation. Finally, the analysis verifies that rocking overturning depends primarily on the velocity characteristics of the ground motion. Copyright © 2015 John Wiley & Sons, Ltd.

SUMMARYNonlinear static (pushover) analysis has become a popular tool during the last decade for the seismic assessment of buildings. Nevertheless, its main advantage of lower computational cost compared to nonlinear dynamic time-history analysis (THA) is counter-balanced by its inherent restriction to structures wherein the fundamental mode dominates the response. Extension of the pushover approach to consider higher modes e ects has attracted attention, but such work has hitherto focused mainly on buildings, while corresponding work on bridges has been very limited. Hence, the aim of this study is to adapt the modal pushover analysis procedure for the assessment of bridges, and investigate its applicability in the case of an existing, long and curved, bridge, designed according to current seismic codes; this bridge is assessed using three nonlinear static analysis methods, as well as THA. Comparative evaluation of the calculated response of the bridge illustrates the applicability and potential of the modal pushover method for bridges, and quantiÿes its relative accuracy compared to that obtained through other inelastic methods.

Citation: Paraskeva, T. S. & Kappos, A. J. (2010). Further development of a multimodal pushover analysis procedure for seismic assessment of bridges. Earthquake Engineering and Structural Dynamics, 39(2), pp. 211-222. doi: 10.1002/eqe.947 This is the accepted version of the paper.This version of the publication may differ from the final published version. SUMMARY An improvement is first suggested to the modal pushover analysis (MPA) procedure for bridges initially proposed by the writers [1], the key idea being that the deformed shape of the structure responding inelastically to the considered earthquake level is used in lieu of the elastic mode shape. The proposed MPA procedure is then verified by applying it to two actual bridges. The first structure is the Krystallopigi bridge, a 638m-long multi-span bridge, with significant curvature in plan, unequal pier heights, and different types of pier-to-deck connections. The second structure is a 100m-long three-span overpass bridge, typical in modern motorway construction in Europe, which, although ostensibly a regular structure, is found to exhibit a rather unsymmetric response in the transverse direction, mainly due to torsional irregularity. The bridges are assessed using response spectrum, 'standard' pushover (SPA), and modal pushover analysis, and finally using non-linear response history analysis (NL-RHA) for a number of spectrum-compatible motions. The MPA provided a good estimate of the maximum inelastic deck displacement for several earthquake intensities. The SPA on the other hand could not predict well the inelastic deck displacements along the bridge, because of the low contribution of the first mode to the total response of the bridge. PermanentKEYWORDS: bridges, seismic assessment, pushover analysis, inelastic response, reinforced concrete, higher mode effects INTRODUCTION Extension of the 'standard', fundamental mode based, pushover analysis (SPA), to consider higher mode effects has attracted attention over the last decade. Several efforts made in this direction are briefly reviewed in a previous paper by Paraskeva et al. [1] wherein the Modal Pushover Analysis (MPA) proposed by Chopra and Goel [2] was extended to the case of bridges; the procedure was applied to a rather complex actual bridge, and results were compared with those from single-mode pushover and responsehistory analysis.

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