Study on the vibration feature of concrete deck slabs under fatigue wheel loading

Abstract

The concrete deck slab is an important part in the concrete bridge, which supports the traffic load directly. However, the damages due to the fatigue, corrosion, etc. in the concrete slabs have not been restrained fully at all. It can be usually observed in the aging bridges all around the world, significantly influencing the structure safety and durability. Particularly, the fatigue induced concrete cracks can be viewed as a very serious problem that needs to be dealt with in both of the structure maintenance and health monitoring stages. But precisely detecting such cracks is still not an easy work currently since the slab is usually underneath the traffic pavement. One thing for sure is that the cracks may lead to the stiffness variations, and in this sense a study on the vibration feature variation due to the fatigue concrete cracks was carried out for the purpose of trying to relate the vibration characteristics to the fatigue damage concrete cracks. In detail, a fatigue wheel load test were carried out to initiate and develop concrete cracks, in which two full scale concrete deck slab test specimens were designed and manufactured. During the wheel loading test, the impact vibration tests were carried out on these specimens at certain wheel load cycles, in which a newly developed lightweight impact vibration equipment was introduced for the vibration excitation. Based on the test results, it can be found the vibration frequencies and modes appeared observable variations due to the concrete cracks. Moreover, a discussion of using the vibration feature to assess the fatigue damage levels of the concrete deck slab was made through Modal Assurance Criterion (MAC) evaluation.