Calculation Method and Influence Factor Analysis for the Normal Working Life of Reinforced Concrete Highway Bridges

Abstract

Aimed at the working life of bridges under the reiteration function of vehicle load, which is not mentioned in the current bridge design codes, this paper introduced the concept of normal working life. The authors regarded reinforced concrete bridges as the research object and proposed a fast method to calculate the working life to judge whether the working life can fit the requirement of design working life. On the basis of the equivalent constant amplitude stress amplitude method of Miner’s criterion, the cumulative damages of the bridges were calculated, the average annual damage degrees were obtained by determining the relationship between cumulative damages and times, and the working life of the bridges was estimated. This method was applied to the calculations of T-beam bridges, and the influences of spans, transverse diaphragms, reinforcement ratios, vehicle loads, and S–N curve equations were analyzed. The calculation results showed that vehicle loads and S–N curve equations determine the accuracy of working life. The calculated life in accordance with the fatigue vehicle model in the specification is much longer than the design life. The load varies greatly from region to region. Compared with Guizhou Province, Jiangsu and Liaoning provinces have a higher traffic flow of heavy vehicles over 35 t, which results in years unfilled with the design life. With the increase in spans, the working life increases accordingly because the reinforcement ratios increase with the spans. The diaphragm plates and reinforcement ratios have a great influence on the working life. The working life of bridges with diaphragm plates is 18%–63% lower than that of bridges without diaphragm plates. The reinforcement ratios are lower, and the reduction rates of the working life are greater.