Pile Load Test and Implementation of Specifications of Load and Resistance Factor Design

An instrumented pile load test was performed as part of the foundation design for the Caminada Bay Bridge project in south Louisiana. Both static and dynamic load tests were performed. The load-transfer curve of the test pile was obtained from strain measurements by using sister bar strain gauges at six locations along the pile shaft. The test pile resistance was determined by the Tomlinson method for cohesive soils and by the Nordlund method for cohesionless soils. The dynamic and the static load testing results indicated the test pile did not achieve the desired design resistance. The static analysis model was calibrated on the basis of observations of the pile load testing program. The design pile length was revised to benefit from the shallower scour depths for the revised pile design. The low resistance of the test pile resulted in the engineer's decision to use dynamic testing on the production piles to ensure adequate resistances. Taking advantage of the static load test of the instrumented test pile instead of simply using the smaller resistance factor from dynamic tests, the engineer combined the results of the two test methods and used a combination of resistance factors from both the static and dynamic load tests. This paper presents the evaluation of load test results and the rationale used for the selection of the resistance factor.