Lifetime Deflections of Long-Span Bridges under Dynamic and Growing Traffic Loads

Steady traffic growth may pose a safety hazard to in-service bridges, especially long-span bridges subjected to the simultaneous presence of multiple heavy-duty trucks. This study presents a methodology for evaluating the statistical extrapolation of traffic-load effects on long-span bridges. As part of the contributions advancing the state of the art, this study addresses several challenging issues, including traffic growth, and the resulting dynamic impact, and actual traffic patterns. The nonstationarity of the traffic-load effects due to traffic growth is considered in a series system compounded by several interval traffic models. The dynamic impacts of traffic loads were simulated by a traffic-bridge-coupled vibration system, and the statistical characteristics were captured using a level-crossing model. The actual traffic pattern was simulated by stochastic traffic flows on the basis of the statistics of the weigh-in-motion measurements of a highway bridge. Two numerical examples show the ability of the interval-traffic-growth model to capture the nonstationarity of the growing traffic loads. In addition, a case study of a long-span suspension bridge shows the effectiveness of implementing the proposed methodology for the statistical extrapolation of the maximum deflection. The numerical results of the case study also reveal that the degradation of road-roughness conditions leads to more level crossings but also results in a slight increase in the extrapolation of the deflection. However, traffic growth results in rapid increases in both the extrapolated deflection and the probability of exceedance of the deflection limit. (C) 2017 American Society of Civil Engineers.