Structural Identification and Evaluation of the Oceanic S-31 Bridge
The Oceanic S-31Bridge was constructed in 1939 and rehabilitated in 1970. It consists of 57 spans with a 98-feet bascule span over the navigable channel. The bridge serves as a critical link for emergency vehicles and school buses. The bridge in its current condition is highly deteriorated and is scheduled for replacement in the next five to 10 years. Due to its deterioration and damage to one of the stringers noted during a routine inspection, Monmouth County hired Intelligent Infrastructure Systems to evaluate the safety of the bridge and identify the required interventions and operational conditions under which the bridge may continue to serve safely until its replacement can be commissioned.
To fully conceptualize the extent of deterioration, Intelligent Infrastructure Systems performed a detail visual inspection of the structure and mapped all areas of deterioration (together with estimates of percent section loss) directly onto a 3D CAD model of the bridge. This geometric model was then used as the basis for a refined finite element (FE) model that explicitly represented areas of observed section loss through reduction in element thickness or complete removal of elements. This model was then used to design a load test to capture the most critical live load actions and quantitatively measure how the most significant areas of deterioration were influenced when forces were transferred through the structure. This test was carried out by Intelligent Infrastructure Systems and the results were used to calibrate the refined FE model, which was then used to perform a series of scenario analyses. Based on the results of these analyses, a series of emergency repairs were identified and implemented. In addition, a more cost-effective retrofit than the one originally planned that employed a novel “trussing” of some of the most deteriorated areas was developed that proved lighter, easier to fabricate, and less labor intensive to install than the conventional alternative. Even with the retrofit, further deterioration of the bridge remained a concern for the county and so Intelligent Infrastructure Systems designed and will implement a long-term monitoring system to allow for a continuous assessment of performance and on-going deterioration until the bridge can be removed from service. As a result of our services, the bridge posting was raised from 3 tons to 15 tons.