Variable mass loading effect on the long-term ambient response of a freeway bridge

Abstract

This study addresses the quantification and compensation of the so-called mass loading effect, a disturbance that typically occurs in structural health monitoring of bridges. Source of this effect is the time-variant traffic, which means that dynamic performance indicators such as identified resonance frequencies are also time-variant. Basis of this study is the ambient acceleration response of a freeway bridge in the Alps recorded in a long-term monitoring campaign. After statistical evaluation of the traffic over the bridge, stochastic finite element simulations are performed to quantify the effect of timevariant truck traffic on a resonance frequency identified from the recorded accelerations, which serves as performance indicator. The corresponding natural frequency of the numerical bridge-truck model is obtained both by modal analyses and response history analyses, whose results however show considerable differences. In an effort to reduce the temporal scatter of the performance indicator, the corresponding natural frequency of the numerical model is used to compensate for the mass loading effect. It it shown that the mass loading effect plays a significant role for the considered bridge, although temperature effects dominate as a disturbance for the identified resonance frequency.