A framework for load rating in-service reinforced concrete bridges without construction plans

The load rating assessment of in-service reinforced concrete bridges faces a significant challenge due to the absence of original construction plans. This lack of information makes it difficult to ensure the structural safety of aging bridges under current traffic loads. A framework is proposed to address this issue, presenting a four-level system that requires sequential increments of information to approximate the analysis and the actual structure’s behavior. The proposed workflow should be used before load testing the structure, and the sequential adoption of increasing levels of information may prevent the use of expensive and time-consuming tools; thus, this methodology aims to simplify the structural evaluation process. Ultimately, this workflow enables the structural safety assessment for a specific live load, illustrated by evaluating six bridges under the live loads of ten vehicles. As the level of information increases, so does the bridge’s safety, and reducing the level of information does not lead to unsafe analysis since lower levels are inherently conservative. Bridges designed according to dated standards have an extra hidden load-bearing capacity due to conservative assumptions embedded in their design. Finally, the illustrative application of the workflow proved to be easily adjustable, efficient, and reliable for assessing existing bridges.