Use of Ricker motions as an alternative to pushover testing

Abstract

Use of Ricker motions as an alternative to pushover testingLoli, Marianna; Knappett, Jonathan; Anastasopoulos, Ioannis; Brown, Michael General rightsCopyright and moral rights for the publications made accessible in Discovery Research Portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from Discovery Research Portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain.• You may freely distribute the URL identifying the publication in the public portal. Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. When undertaking centrifuge studies on seismic soil-structure interaction, it is useful to be able to define the pseudo-static 'pushover' response of the structure. Normally, this requires separate centrifuge experiments with horizontal actuators. This paper describes an alternative procedure, using Ricker ground motions to obtain the pushover response, thereby allowing both this and the response to seismic shaking to be determined using a centrifuge-mounted shaker. The paper presents an application of this technique to a 1:50 scale model bridge pier with two different shallow foundations, as part of a study on seismic protection using rocking isolation. The moment-rotation ('backbone') behaviour of the footings was accurately determined in the centrifuge to large rotations, as verified through independent three-dimensional dynamic non-linear finite-element modelling. Ricker wavelet ground motions are therefore shown to be a useful tool for the identification of pushover response without requiring additional actuators. Furthermore, a simplified analytical methodology is developed, which allows one to predict the maximum foundation rotation induced by a specific Ricker pulse. This methodology may be useful in predicting the characteristics (frequency and acceleration magnitude) of the Ricker pulse required to describe the pushover response of any (practically) rigid oscillator supported on shallow foundations.

Centrifuge modeling of rocking‐isolated inelastic RC bridge piers

“…Close approximation of the monotonic Μ-θ backbone curve was achieved, and the results were in good agreement with FE predictions. These characterization tests are reported in [44]. The third element of testing, which is the main scope of this paper, involved four centrifuge model tests, two for each of the alternative designs, wherein the RC model piers were subjected to different earthquake scenarios using real records of varying intensities.…”

“…where t h , t m , and C are parameters taken equal to 0.52, 0.35, and 0.22, respectively (determined through curve fitting of experimental results), and N u is the ultimate capacity in pure vertical loading. In addition to theoretical predictions, the foundation capacities were also calculated using numerical simulations with finite elements (FE)-details are reported in [44].…”

Wavelet analysis for relating soil amplification and liquefaction effects with seismic performance of precast structures

“…Wavelet transform has gained ground in the analysis of signals with abrupt changes [17] such as earthquake ground motions [18][19][20][21][22][23][24]. Haigh et al [25], for instance, show that the harmonic wavelet analysis is a versatile tool that can give information especially for occurrence of liquefaction, even if traditional time or frequency domain analysis is not available.…”

Editorial

“…The third paper, by Loli et al (2015), presents the use of Ricker ground motions, generated by a centrifuge shaker, to model the pseudo-static pushover of a bridge pier resting on a shallow foundation. This enables investigation of the response of a model structure under both static and seismic conditions, without the need of an additional actuator system.…”