Stochastic analysis and design of vibrating barriers under simulated ground motion processes

Abstract

Vibration control techniques have developed remarkably over the past thirty years. These solutions are usually employed to protect new rather than existing structures, for which most of the available control devices may be costly and invasive to install. Recently, Vibrating Barriers (ViBas) have been proposed as a solution to protect both new and existing buildings. By exploiting the Structure-Soil-Structure-Interaction (SSSI) phenomenon, the ViBa is constructed away from the structures to be protected allowing the characteristics of the buildings to remain unaltered. The ViBa is envisaged as a vibrating mass placed into the soil, through which the control device interacts with the structure in its proximity and is therefore able to control vibrations for cluster of buildings. Up until now the efficiency of the ViBa has only been demonstrated for simple cases of seismic deterministic input and stationary Gaussian stochastic processes. This research explores the multiple interactions between a building and a ViBa device in order to assess its performance in realistic earthquake scenarios. By means of Direct Stochastic methods, this research presents a methodology to design the ViBa validated through pertinent Monte Carlo Simulation. The effects of the input selection on the ViBa performance are investigated by analysis of the building-soil-ViBa system response under advanced stochastic Ground Motion Models (GMMs). In regard to this, a technique is proposed to simulate earthquake ground motions in agreement with seismic codes and reproducing the non-stationarity and natural variability typical of recorded earthquakes. Initial investigations on the response of linear and non-linear structures, under the proposed ground motion and a traditional quasi-stationary and non-stationary model, have demonstrated that the choice of the ground motion has considerable influence over the study of the reliability of structures also for the simple case of linear behaving structures. From the analyses, the sensitivity of the distribution of the relevant response parameters (e.g. the peak displacement) to the GMMs is shown. All spectrum compatible models adopted fulfil the code provisions, however noticeable differences in the distribution of response parameters are observed. Moreover, studies on the sensitivity of structural responses to damping variation have been performed to address the significance of the GMM selection in relation to the assumptions on the structural damping. Finally, some drawbacks in the current seismic codes have also been identified. In order to establish the methodology for the design of the ViBa under stochastic excitation, the discrete formulation for buildings-soil-ViBa-systems available in the frequency domain has been extended to the time domain. The methodology proposed in this work enables a simplified reliability assessment by defining the mean value of the maxima response displacements under stationary Gaussian stochastic seismic action firstly and successively verified for non-stationary input. From the investigations, the effectiveness of the ViBa is exhibited as having reductions of up to 37.80 % of the mean and up to 41.49% of the fractile 95% of the peak displacements.

Date of Award	2017
Original language	English
Awarding Institution	University of Brighton