Macroscopic effect of distance from seacoast on bridge deterioration – Statistical data assessment of structural condition recordings

Abstract

Airborne sea chlorides that are transported inland by wind and deposited on structures’ surfaces are a principal deterioration factor for coastal bridges. In this paper, a dataset for almost 20,000 coastal bridges, which was extracted from the National Bridge Inventory (NBI) of the US Federal Highway Administration, is exploited to conduct a macroscopic statistical study on the deterioration effect of airborne chlorides. The study focuses directly at the very final stage of the overall physical phenomenon, in which deterioration due to seacoast effect is evident. To distinguish this effect, the extracted coastal bridge sample was segmented to produce consistent subsamples in terms of other coexisting factors influencing deterioration, including use of deicing salt and earthquake hazard. Year of bridge construction/reconstruction, structural materials (reinforced/prestressed concrete, structural steel) and structural types (simple/continuous spans) were also taken into account. Moreover, bridge groups based on the bridges’ distances from the seacoast were formed using high accuracy coastline and bridge coordinates. Hence, structural condition ratings for bridge components recorded in the NBI database were statistically assessed with respect to corresponding coastal distances. It was statistically deduced that, under certain conditions, bridges can be noticeably affected by sea chlorides at coastal distances up to 2–3 km inland.