Investigation on dynamic behaviour of a full-scale reinforced concrete bridge subjected to strong earthquakes using an automated analysis platform

Abstract

In this paper, the condition of a full-scale concrete bridge subjected to strong earthquakes is evaluated using vibration-based analyses. A new computational toolkit is developed in MATLAB environment for damage identification and long-term monitoring. Two types of parametric and non-parametric analysis methods are carried out on monitoring data. Moreover, a dynamic performance index is proposed based on an AutoRegressive Moving Average with eXogenous excitation (ARMAX) model. This index utilises the response predicted from an ARMAX model to evaluate bridge behaviour during strong earthquakes. Based on the results, a minor but permanent drop of 0.05 Hz in natural frequency of the first transverse and vertical modes is observed after the first strong earthquake. Also, a significant drop in frequency of the first transverse mode is observed during the two strong earthquakes. The results of the index show that the bridge did not follow linear behaviour during the two strong earthquakes as expected from a linear system. A close to flag-shaped force-displacement relationship is also observed during the first strong earthquake that can be an indication of nonlinearity in bridge behaviour. The analysis results illustrate the efficiency of the new monitoring platform for long-term monitoring and management of large datasets.

Keywords:

• Automated structural health monitoring
• time-series analysis
• ARMAX model
• nonlinear behaviour
• MATLAB
• full-scale bridge

Acknowledgements

The financial supports of the New Zealand Earthquake Commission (EQC) is gratefully acknowledged. The acceleration data was recorded using instruments installed on the bridge as part of the GeoNet Structures Instrumentation Programme. S. R. Uma, John Young, Mostafa Nayyerloo and Kevin Fenaughty of GNS Science provided acceleration records and details of the instrument installation on the bridge. Their assistance is greatly acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.