Comparative Assessment of Multiple Deterioration Mechanisms Affecting the Seismic Fragility of Aging Highway Bridges

At present, a significant percentage of bridges within the United States (US) are nearing the end of their service life and are also located in regions characterized by moderate to high seismicity. Being in direct contact with the external atmosphere these infrastructure elements are often subjected to harsh environmental conditions with the degree of deterioration depending on the type, frequency, and severity of the environmental stressors as well as the age of the highway bridge. In view of such deteriorating infrastructure scenario, this paper focuses on the structural strength degradation of critical bridge components due to five distinct chemical processes, such as: a) freeze-thaw cycles, b) sulfate attack, c) carbonation, d) deicing salt exposure, and e) marine splash conditions. A three span steel girder bridge located in Central and Southeastern United States is used as a case study example to assess the influence of these degrading mechanisms on seismic vulnerability.