Significance of non-stationary characteristics of ground-motion on structural damage: shaking table study

Mohammad M Kashani,Matthew S Dietz,Xiao Ge,Nicholas A Alexander,Adam J Crewe

doi:10.1007/s10518-019-00668-3

Mohammad M Kashani, Matthew S Dietz + Show 3 more

Open Access

https://doi.org/10.1007/s10518-019-00668-3

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Abstract

This paper reports the results of a set of benchmark medium-scale shaking table tests to investigate the significance of the non-stationary characteristics of ground-motion on nonlinear dynamic responses and the structural damage of reinforced concrete (RC) columns. To examine the influence of ground-motion characteristics, four RC columns are tested under (1) near-field without pulse, (2) near-field pulse-like, and (3) far-field ground-motions. These ground-motion records were spectrally matched by the reweighted Volterra series algorithm without changing non-ergodic characteristics. To explore the confinement effects, two sets of column specimens are designed to represent the modern well-confined and older lightly-confined RC columns. Each column is tested in slight, extensive and complete damage limit states. Then aftershock excitations are conducted to investigate the performance of severely damaged RC columns. Low amplitude white-noise tests are conducted on pristine columns and after each damage limit state experiment to detect natural frequency variant of damaged columns using transfer function estimate. Furthermore, using time–frequency analysis, the real-time variant frequency of test specimens is estimated. The significant duration of ground-motions accounting for the effect of non-stationary characteristics of ground-motion is also estimated by time-cumulative damage analysis of the test results. Finally, the time-variant stiffness degradation of RC columns is estimated.

Highlights

In performance-based design of reinforced concrete (RC) structures, ground columns in building structures, and piers in bridge structures are usually the most vulnerable components
A set of benchmark large-scale shaking table tests is conducted at the University of Bristol, to investigate the impact of the non-stationary content of ground-motion on the structural damage of RC columns and significant duration of ground-motion
The main conclusions of this study are as follows: 1. The transfer function estimate shows that concrete cover spalling is the main factor governing the natural frequency drop in RC columns

Summary

Introduction

In performance-based design of reinforced concrete (RC) structures, ground columns in building structures, and piers in bridge structures are usually the most vulnerable components. The seismic performance of the whole structure is governed by the performance of the piers when they are subjected to large earthquakes. This is because the current modern seismic design codes (CEN 2010; Caltrans 2013) rely on a proper detailing of the plastic hinge regions where most of the inelastic deformations are expected to occur. Several researchers have developed numerical analysis methods to study the behaviour of RC components with different detailing when subjected to different types of ground-motions (Domizio et al 2017; Kashani et al 2017a; Nojavan et al 2017; Su et al 2017). Other researchers (Kunnath et al 1997; Laplace et al 1999; Lehman 2000; Elwood 2004; Johnson et al 2006; Chen et al 2008; Phan et al 2007; Carrea 2010; Brown and Saiidi 2011) conducted several experimental studies on the impact of load history on structural damage of RC columns using quasi-static cyclic and dynamic shaking table tests

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