Assessment of vibration intensity as a condition and safety indicator for short-span bridges

Abstract

Over the years, there have been numerous efforts by researchers in quantifying structural performance and damage from vibration measurements. Curves proposed by several authors try to relate acceleration spectrums to damage level, which were determined based on experimental surveys conducted on buildings. The present work investigates a vibration based criteria for bridge structures as a basis of damage and performance evaluation in existing bridges and also as a way to predict long-term performance during the initial design stage. To achieve this, a database of Brazilian bridges was analysed, whose structural design and dynamic parameters are known. For damage evaluation, a damage index based on dynamic property variation and the general structural condition, observed during detailed inspections, were taken into account. Measured vibration was subsequently assessed against the damage index and an additional reliability index to fatigue, which resulted in a clear correlation between bridge vibration and the indices. As a final result, from the observed correlations, limits of acceleration are proposed to be considered in existing and newly designed bridges to certify an acceptable long-term condition and safety against fatigue effects. A critical assessment of current Brazilian Standard (NBR-15307 2005), which estimates damage as a function of bridge vibration, was also conducted.