Vehicle Weight Limit Analysis Method for Reinforced Concrete Bridges Based on Bridge Fatigue Life
【Abstract】To determine the reasonable weight limit for reinforced concrete bridges, a vehicle weight limit analysis method based on fatigue life was conducted with the consideration of the effects of the random traffic flow parameters and overload violation rate, in view of fatigue performance of reinforced concrete bridges based on the S-N curve and Palmgren-Miner linear cumulative damage rule was proposed. The random traffic flow was firstly simulated according to the collected traffic data and Monte Carlo method, and then calibrated using the initial value of weight limit and overload violation rates to exclude overweight trucks. The traffic-induced stress spectrum of the bridge was obtained by rain-flow counting algorithm and fatigue life was calculated based on the S-N curve and Palmgren-Miner rule. The procedure was iterated until the value of weight limit was able to achieve the desired fatigue life of the bridge and thus deemed as the final reasonable value. Taking the traffic data of a specific area and a typical simply-supported T-beam bridge as an example, the expected working life was determined for different average daily traffic volumes (ADTVs) and different violation rates. The results show that both the ADTV and the overload violation rate can significantly affect the fatigue life of the bridge components and the vehicle weight limit on bridge. The higher the ADTV is, the shorter the bridge fatigue life can be. Specifically, the desired bridge fatigue life is much longer than expected working life under different weight limits when the ADTV is less than 6,000. However, the expected working life can only be achieved under certain weight limits when the ADTV is larger than 8,000. The higher the violation rate is, the less effective the method of setting vehicle weight limit is to prolong the bridge fatigue life. With small violation rate, the bridge fatigue life increases rapidly with the decrease of the initial weight limit value. However, with large violation rate, limited increment of bridge fatigue life can be achieved with the decrease of the initial weight limit value.
【Keywords】 bridge engineering; vehicle weight limit on bridge; linear cumulative damage rule; fatigue life; S-N curve; overload violation rate;
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