Pile Setup and Restrike Procedures

The primary objective of this research is to provide MoDOT with rational procedures and guidelines to incorporate pile setup in MoDOT pile design. Pile setup refers to the time-dependent increase in the capacity of driven piles that occurs after the end of pile driving. High-strain dynamic load test data from end of driving (EOD) and beginning of restrike (BOR) were compiled from sites in Northern Missouri and Southeast Missouri to develop models of pile setup in these regions where the use of friction piles is common. Reliability analysis was performed using the model developed from Northern Missouri data to probabilistically calibrate resistance factors that can be applied to the expected pile setup without the need for restrikes. The application of these resistance factors is shown to produce significant cost benefits over the current common practice of ignoring pile setup. In addition, pile setup factors within the first 24 hrs. of the EOD were examined to provide information on the likelihood of successful restrikes for various levels of required capacity. Data from sites in Southeast Missouri were insufficient to develop a meaningful model of pile setup and associated resistance factors. The limited data that were used showed moderate levels of pile setup, indicating the use of restrike analysis in Southeast Missouri may be cost effective. Additional data collection at sites in Southeast Missouri is recommended.

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Report number: cmr 23-014
Published: August 2023

Project number: TR202207
Authors: Brent L. Rosenblad and Andrew Z. Boeckmann

Performing organization: University of Missouri-Columbia

Impacts of Hydraulic Modeling Methods on Bridge Scour Analysis

This study has three primary purposes: 1) to investigate the impacts of hydraulic modeling methods on bridge scour analysis, 2) to develop recommendations for sediment/soil sampling methods, and 3) to conduct bridge scour risk assessments. Field data were collected at five study sites to obtain the required terrain and soil/sediment input data for hydraulic modeling and scour analyses. The recommended methods developed for soil/sediment sampling in the overbank areas are soil augers or test pits, and for overwater locations, a FISP or clamshell sampler is recommended. Contraction, abutment, and pier scour depths were computed using the HEC-18 guidelines with hydraulic conditions determined from a 1-D model (HEC-RAS) and a 2-D model (SRH-2D).Determining the required input parameters for scour calculations from HEC-RAS results was found to be difficult with many potential sources of human error. In contrast, the Hydraulic Toolbox program for scour calculations can auto-populate the required input parameters directly from SRH-2D output data. For all bridge sites evaluated, estimates for at least one of the main scour categories (i.e., channel contraction scour, pier scour, or abutment scour) were more than 50% different between the HEC-RAS 1-D and SRH-2D results. The key findings from comparing model results were: 1) the angle of attack was the dominant pier scour input parameter and 2) flow conveyance over inundated roadway embankments was significantly greater for SRH-2D relative to the HEC-RAS model. The 2-D modeling methods are recommended for future use given the significant differences observed between the 1-D and 2-D scour results, increased availability of terrain data, current computing resources, and ease of use. Finally, due to differences in the HEC-RAS and SRH-2D estimated scour depths, reanalyzing high-risk and/or visually vulnerable bridges is recommended.

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Report number: cmr 23-013
Published: August 2023

Project number: TR202017
Authors: Amanda L. Cox, Ronaldo Luna, Peter Kickham, and Harrison Wooters

Performing organization: Water Access Technology, Environment, and Resources (WATER) Institute