Estimated and Measured Settlements of Shallow Foundation Supporting Bridge Substructure

Abstract

Shallow foundations have numerous advantages when compared to deep foundations; primarily: low cost, fast construction and being environment friendly. Shallow foundations on soils are underutilized to support highway bridge substructures. This is due to a limited performance data and overestimation of settlements. Despite the success of previous shallow foundation studies, more research is needed to evaluate the performance of shallow foundations as a highway bridge foundation. To study the field performance of shallow foundations on soil, the central pier footing was instrumented and monitored during the construction of a two-span highway bridge in Columbus, Ohio. A-2-4 and A-3a soil types were encountered in a borehole. The field instrumentations consisted of multiple sensors and stations for recording contact pressure under the footing, settlement of the footing and tilting of pier columns tied to the footing. A USGS quality benchmark was incorporated to establish a solid permanent benchmark at the site. The field performance data collected in the study provided further insight into how contact pressure, footing settlement and column/wall tilting were correlated with each other throughout various construction stages. The study also produced outcome on general reliability of the settlement prediction methods outlined in the AASHTO LRFD design specifications and provided enhancement to the elastic half-space method.