Structural dynamic testing for seismic response simulation and time variant reliability estimation

Abstract

The research work reported in this thesis addresses a few problems which arise in the context of experimental dynamic testing of engineering structures under earthquake loads. Firstly, we consider the problem of characterizing and controlling errors that occur during hybrid simulation based pseudo-dynamic testing with substructuring. The study notes the complex interaction between the errors, that originate due to the approximations involved in the numerical modelling, and the experimental errors associated with actuation and measurements. This interaction involves a nonlinear dynamic response simulation of the test structure, and the error of simulation is noted to be system state dependent. The study proposes an adaptive time stepping strategy which is based on the solution of an associated linearized variational equation of motion of the test structure. The proposed method is illustrated on systems displaying geometric nonlinearity and contact nonlinearity due to pounding. The test protocol is implemented on a reaction wall based multiple servo-hydraulic actuation-based test system. The study is followed by an investigation into experimental estimation of time variant reliability of engineering structures subjected to earthquake loads modelled as a set of random processes. Specifically, the study has developed an experimental protocol which employs a combination of Markov Chain splitting methods and surrogate modelling tools, to arrive at a sampling variance reduced estimator for the probability of failure. It is shown that the implementation of the experimental protocol does not require explicit knowledge of a valid mathematical model of the test structure. The procedure developed has been shown to be applicable to tackle the problems of time variant component and system reliability estimation, and the procedure can handle both linear and nonlinear vibrating systems. The proposed test protocol has been implemented not only on the reaction wall based multiple servo-hydraulic actuation-based test system, but also on a multi-actuator earthquake shaking table