A new Interstate 10 (I-10) Twin Span Bridge over Lake Pontchartrain was recently constructed to replace the old bridge that was heavily damaged by Hurricane Katrina in 2005. A large portion of the bridge is supported by batter pile group foundations. To evaluate the performance of batter pile foundations under lateral loading, a selected pier (M19 eastbound) of the new bridge was instrumented and used to monitor the pier during a unique full-scale lateral load testing. The M19 pier foundation consists of 24 precast prestressed concrete (PPC) 33.53m (110ft) long batter piles, among which 8 piles were instrumented with microelectromechanical sensor (MEMS) in-place inclinometers (IPI), and 12 piles were instrumented with strain gauges. The test was conducted by pulling the M19 eastbound and westbound piers toward each other by using high-strength steel tendons. A maximum of 8320kN (1870 kips) lateral load was applied in increments. A high-order polynomial curve fitting method was applied to fit the measured rotation profiles from the IPIs. The fitted rotation curves were then used to deduce the bending moment, shear force and soil reaction profiles. The calculated moments from curve fitting were compared with the moments calculated from strain gauges, and the results showed good agreements. The p-y curves of the soils at different depths were back-calculated, and the results showed little evidence of group effect.

1. Introduction

Pile foundations are usually designed to support highway bridges and other structures, primarily to safely carry superstructure axial loads deep into the ground. However, in many cases structures (such as bridges, quays and harbours) are subjected to lateral loads caused by high winds, wave action, water pressure, earthquakes and ship impacts. Therefore, it becomes essential to understand the resistance behaviour of piles and pile groups to lateral loads.

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