Abstract
To enhance regional design and construction practices for driven piles, FHWA permitted the development of regional resistance factors for the design of foundation piles. By fitting allowable stress design safety factors to the load and resistance factor design (LRFD) framework, several state departments of transportation (DOTs), including the Iowa DOT, have adopted interim procedures. Subsequently, an LRFD procedure that incorporates setup was developed for piles in cohesive soils through comprehensive research in Iowa. The proposed LRFD procedure used an Iowa DOT in-house static analysis method and the wave equation analysis program for construction control. To verify the adequacy of the proposed procedure and investigate its economic implications, differences in pile design between the interim and the proposed LRFD procedures were evaluated on the basis of independent data collected from more than 600 production steel H-piles driven in cohesive soils. This study concluded that the proposed LRFD procedure would not significantly increase the design and construction costs. The incorporation of pile setup into the LRFD procedure was found to provide additional economic benefits. Although the current Iowa DOT policy is to drive piles to the contract length, if a suitable pile termination procedure were used once the desired resistance was achieved, a general saving of 20% in pile length would be anticipated for both procedures. Although the research and findings presented in this paper are specific to a local area, these methods could be adopted nationally to increase the efficiency of bridge foundations for all states.
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