Abstract
Vehicle overload is detrimental to bridges and traffic safety. This paper presents a study on the fatigue performance of typical reinforced concrete (RC) beams of highway bridges under vehicle overload. A definition method of vehicle overload and a construction method of overload ladder spectrum were first proposed based on traffic data acquisition, statistical analysis and structural calculation of the highway bridges in Guangzhou. A fatigue experimental method was also proposed with the three-ladder vehicle overload spectrum, and the fatigue tests of 15 RC beams strengthened with carbon fiber reinforced polymer (CFRP) under three loading levels were then carried out. The fatigue performance and the failure mechanism of the strengthened beams were presented and discussed, and two fatigue life prediction methods were proposed with the established modified Palmgren-Miner rule and the loading level equivalent method respectively. The results showed that the fatigue performance of the strengthened RC beams was severely degraded under overload ladder spectrum compared with that under constant amplitude cyclic load, and the life prediction methods were proved effective.
Highlights
The vehicle over-limit cases are unavoidable in China, though measures have been taken to limit the quantity of cargo transport [1]
Corresponding to the stiffness degradation process of the strengthened beam, the fatigue failure process of the reinforced concrete (RC) beam strengthened with carbon fiber laminate (CFL) under overload ladder spectrum was mainly accompanied by the following phenomena: main crack initiation and propagation on concrete, interfacial crack initiation and propagation in CFL-concrete interface (CFL debonding), fatigue damage accumulation and yielding of main steel bars, and crushing of concrete in compression area
Based on the traffic data of a highway in Guangzhou collected by this research group in the earlier period, a definition method of vehicle overload was proposed
Summary
The vehicle over-limit cases are unavoidable in China, though measures have been taken to limit the quantity of cargo transport [1]. The proposed spectrum construction method provides a good foundation for experimental study on fatigue performance of bridge structures under vehicle random loads. Found a relatively larger estimation error (36.8–56.5%) of life prediction using Palmgren-Miner rule with the fatigue testing data of FRP strengthened RC beams under three-ladder load spectrum (three-stage variable amplitude cyclic loading). The results of Found et al [20] show that the Palmgren-Miner linear damage rule may no longer be valid for woven carbon fiber reinforced laminates under two-stage fatigue loading. These fatigue experiments did not consider the influence of vehicle overload, and the testing data is not enough. The fatigue failure mechanism of RC beams strengthened with CFRP under overload spectrum was presented and discussed, and two life prediction methods were proposed
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