Stop criteria for proof load testing using a traffic light system

During a proof load test on a bridge, high magnitude loads are applied. To avoid causing irreversible damage, thresholds to the structural responses, the so-called stop criteria, need to be defined. This paper proposes to categorize stop criteria into three levels: green light (related to the serviceability limit state), yellow light (related to potential irreversible damage) and red light (related to potential local collapse). For the Ultimate Limit State, stop criteria for shear and flexure are defined. Shear stop criteria are derived from mechanical models, using traditional strain measurements and acoustic emission measurements. These stop criteria are validated with experiments on reinforced concrete slab strips, straight slabs, and skewed slabs. The resulting traffic light system gives the bridge engineer a tool to make decisions during a proof load test. This approach is a step forward in the interpretation of structural responses during proof load testing.