Stiffness Evaluation and Current Status of a Degraded Road Bridge Slab Located in a Mountainous Area

In the mountainous area of the Hokuriku region, bridges are experiencing early deterioration caused by salt damage, alkali-silica reaction (ASR), and frost damage. Survival time analysis was carried out using the inspection data to study the relationship between the degradation tendency of bridges and the regional characteristics. In addition, the causes of the degradation of the reinforced concrete (RC) slab of a road bridge, which deteriorated early, were investigated using cylindrical core extraction. Polarizing microscopic observation of the specimens collected from the slab confirmed that ASR was the cause of the deterioration. The reduction in the mechanical properties of concrete due to ASR was also studied and reported. Moreover, vehicle running tests using a test truck were carried out. Then, long-term monitoring of the responses of the test bridge due to live load based on the bridge weigh-in-motion method was also performed for ordinary vehicles. The stiffness of the RC slab was evaluated by comparing the results obtained from the tests and the numerical analyses. It was found that the current stiffness of the slab remarkably decreased as compared with the results when the slab was sound. Finally, this study proposes an approach for the soundness evaluation of RC slabs.