Experimental and analytical approaches for load rating reinforced concrete slab bridge

Load testing of bridges is often used as a reliable method for assessing the capacity of in-service bridges with low analytical load rating factors. This paper presents a detailed load rating study of an 82-year-old concrete slab bridge with an unusually large aspect ratio of 3.73 by performing non-destructive diagnostic and proof load tests. The test-based modified rating factor is evaluated based on the American Association of State Highway and Transportation Officials (AASHTO) approach and the structural effective strip width approach which is then compared with the analytical rating factor from a simplified 1-D beam-line model. Field data is also used to evaluate the impact of the rotational stiffness of the bridge on its global response and load rating factor. The field test results based on the AASHTO approach reveal that the rating factor improves by up to 53% compared to the analytical rating factor. Monitoring the rotational residual response at the bridge supports is proven to be an effective method for assessing the global response of the bridge during field testing. The study shows that adding a rotational spring with a field-calibrated rotational stiffness to the 1-D analytical model of the bridge can significantly increase the load rating factor.