Vibrations of a Bridge with Random Structural Irregularities Under Random Traffic Load and a Probabilistic Structural Degradation Assessment Approach

Abstract

PurposeDynamic loads like traffic make bridges vibrate. Especially for bridges with a large span, vibrations have a significant impact on their structural stability and durability. Due to material defects, fatigue and other influences, a bridge typically has random structural irregularities, which affect its dynamic response. In this work, an effective mathematical approach is presented to study the dynamic response of a model single span slender beam bridge, in the presence of random structural irregularities. In addition, an approach to assess the structural degradation of a bridge is presented.MethodsThe slender beam bridge is modelled as an Euler-Bernoulli beam and the random structural irregularities are considered by random fields in the bending stiffness and the mass per unit length. As an illustrative example, the vibrations of a model road bridge are investigated for randomly crossing vehicles. After Monte Carlo experiments with and without random structural irregularities the vibrations and mechanical stresses of the bridge are determined and analysed.ResultsThe study shows statistically significant variations in the most dominant frequencies with and without random structural irregularities.ConclusionThe influence of the random irregularities on the structural stability status of a bridge may not be negligible. The probability of a serious structural degradation in the bridge can be assessed by means of a binomial logistic model. The developed approach enables a better understanding of the vibrations and structural status of bridges, taking into account random structural irregularities and random traffic.