Comparison of Two Beam Fatigue Tests

摘要

The objective of this study is to compare the fatigue behavior in two beam fatigue tests: the Four Point Bending Test (FPBT) and the Beam on Elastic Foundation (BOEF) test. It is believed that the BOEF test simulates the fatigue behavior of asphalt mixtures in a more realistic way. The beam specimens used for both the FPBT and BOEF tests are made of gravel asphalt concrete (GAC). Finite element simulations of the BOEF test are carried out to understand better the behavior of the GAC beam. The results show that in the BOEF tests, cracks will develop from the middle bottom of beam while the FPBTs at low temperature show no crack. This finding further supports the idea that improved fatigue tests are needed which better represent the cracking behavior of asphalt pavements. However, the BOEF test also shows the development of an accumulated strain along with the cyclic strain. This shows that further investigation is needed to determine the cause of fatigue cracks; are they due to the cyclic strain or due to the accumulated strain? Another important finding is that at a temperature of 5℃ and a frequency of 8 Hz, the fatigue life obtained with the BOEF test is 20 times higher (on average) than FPBT fatigue life.