Evaluation of Pile Load Tests for Use in Missouri LRFD Guidelines

US Transportation Collection2014PDFResearch PaperLuna, RonaldoMissouri University of Science and Technology. Department of Civil, Architectural and Environmental EngineeringMissouri. Department of Transportation. Research, Development and TechnologyUnited States. Department of Transportation. Federal Highway AdministrationMissouri. Department of Transportation. Research, Development and TechnologyMissouriBridge constructionEvaluation and assessmentLoad and resistance factor designLoad testsPiles (Supports)Resistance testsBridge engineeringBridge foundationsPile drivingResistance (Mechanics)LRFDReport cmr14-015Project TRyy1226This research studied the use of pile load tests for the development of resistance factors in the LRFD design specifications currently adopted by the Missouri DOT. To this end, three (3) bridge sites were identified to conduct a pile load test in conjunction with the normal bridge contracting activities. This allowed a side by side comparisons with production piles and the impact to the design. Since most of the issues with pile driving and pile capacities are for friction piles that require dynamic testing, the pile load tests locations were selected in geologic regions with relatively deep firm ground or bedrock. In this way, an end bearing condition was avoided. Two sites were selected in the Southeastern Lowlands region and one in the Northern Glaciated Plains region. The pile load tests yielded high resolution data for both the load capacity and load transfer distributions. The different pile and soil types produced different degrees of pile setup and these conditions were examined with a series of restrikes, as necessary. Full displacement piles in overconsolidated clays had unexpected results and the highest restrike capacities compared to the other sites. All the static and dynamic pile load tests produced capacities higher than the ones estimated by the design engineers. The resistance factors back calculated based on the pile load test data generated higher resistance factors than the 0.65 suggested by AASHTO LRFD specifications. Additionally, pile load tests data from other sources in Missouri and the neighboring states were collected and compiled for future use by the Missouri DOT.133