Structural evaluation through load testing, coupled with advanced Finite Element Analysis (FEA) is a powerful tool to load rate posted bridges with the aim of removing current posting. Based on SDR’s vast experience in structural evaluation and load testing, bridges can carry much higher loads than those predicted by design codes. Load testing captures actual behavior of the structure (load distribution) and accounts for strength enhancing factors not included in design.

The LA-1 bridge over Lockport Canal was built in 1959. The bridge load rating is controlled by the reinforced concrete slab spans. SDR was tasked with performing the structural evaluation though load testing of the slab spans with the aim of removing the current posting.

Test results, along with the FEA, reveal that due to the support conditions of the slab, partial fixed end moments are developed, causing significant reduction in mid-span moment as compared to moment calculated assuming simple-beam action. The slab behaved in two-way bending action rather than the one-way bending action used in conventional design and load rating. Load rating of the bridge was carried out in consideration of the test findings and FEA results, which resulted in a load rating factor increase from 0.75 to 1.22.