Monitoring the Foundations of a Bridge during Construction and While in Service

This paper presents the results of the monitoring of the performance of the foundations of the Sagamore Parkway Bridge over the Wabash River in West Lafayette, Indiana, during construction and while in service. One of the interior bridge piers (Pier 7) and its supporting 3×5 pipe pile group were instrumented with vibrating-wire strain gauges to study the bridge response to dead and live loads, the load transfer mechanism from the bridge pier to the pile cap and group piles, and the distribution of loads among the individual piles in the pile group. The measured loads and the estimated design loads were compared to verify the assumptions made in the design of the bridge foundations. The load–settlement response of Pier 7 was almost linear during bridge construction, and no significant changes were observed in its load–settlement response when the bridge was in service. Analysis of the loads carried by different components of the foundation elements showed that, at the end of bridge construction, the piles carried about 77% and the pile cap carried the remaining 23% of the total superstructure load from Pier 7. The contribution of the pile cap to the total foundation capacity, which is not usually considered in bridge foundation design, was considerable in this case. Consideration of the additional load carrying capacity coming of the pile cap may lead to more-economical design when scour is not a concern and the additional capacity is not negligible.