Structural Health Monitoring of I-10 Twin Span Bridge - Part I: Analysis of Lateral Load Test.

摘要

The old I-10 Twin Span Bridge over Lake Pontchartrain was heavily damaged by the storm surges during Hurricane Katrina in 2005. A new 5.4-mile long replacement bridge was constructed with higher resistance to extreme events, such as storm surges and ship impacts. During the construction, a structural health monitoring system, including both superstructure and substructure, was implemented to study the lateral response of battered pile groups short-term and to monitor the “health” condition of the new bridge long-term. M19 pier on the main span of east bound, the second highest pier of the bridge, was selected to perform an in-situ large scale static lateral load test. The pier foundation consists of 24 square 3-ft. precast prestressed concrete (PPC) driven piles battered at 1:6 with an average embedment length of 87 ft. Among them, 8 piles were instrumented with micro electro mechanical systems (MEMS) In-Place Inclinometers (IPI) to monitor pile deflections. 12 piles were instrumented with sister bar type of strain gauges at two selected locations along the pile length to monitor moment and axial force. Other instruments also include triaxial accelerometers, tiltmeters, water pressure cells, and corrosion meters. A lateral load test was conducted by pulling two high strength steel strand tendons through the west bound and east bound M19 piers with hydraulic jacks; the lateral load was applied in 19 increments with a maximum load of 1870 kips. A high-order-polynomial curve fitting method was selected to best-fit the measured rotation profiles by IPI. From the fitted rotation profiles, bending moments, shear forces, and soil reactions were derived using the classic beam theory. P-y curves were obtained from the derived soil reaction profiles and deflection profiles. The back-calculation results were verified with the measurement data from IPI and strain gauges. FB-MultiPier was used for the analysis of pier behaviors in the design of the I-10 Bridge. Therefore, it was selected to simulate the pier response during the lateral load test and verify its performance with measured data and results from the back-calculation. A sensitivity analysis of the input parameters for FB-MultiPier was first conducted to help make decisions on selecting design parameters. Based on the analysis on the simulation results, a select set of inputs were presented as a reference for the design of similar battered pile group in the future