Comprehensive Recalibration of Pile Resistance with WEAP Software in Initial and Restrike Conditions for Load and Resistance Factor Design

Abstract

The Oregon Department of Transportation (DOT) uses the DRIVEN pile capacity software and wave equation analysis of piles (WEAP) software to control driving stresses and establish field resistance from the bearing graph. Typically, the Oregon DOT's piles exhibit setup after the end of initial driving, and the DOT may restrike. In this study to recalibrate the pile resistance with WEAP for load resistance factor design, a new database was formed by culling existing databases, including the PDLT2000 database from NCHRP Report 507 and the Deep Foundation Load Test Database. The resulting information was merged with 166 other cases to create a new comprehensive database. Neither the Deep Foundation Load Test Database nor the PDLT2000 database was proved correct after they were cross-checked with other sources. The largest source of anomalies and missing data was the blow count, especially at the beginning of restrike. Input tiers and output ranks were designed to assist with data qualifying, the ranking of data quality, and statistical profiling for calibration at the end of initial driving and the beginning of restrike. Of 322 piles, a total of 175 supplied quality data for WEAP resistance prediction, which generated Davisson's mean bias and coefficient of variation statistics for recalibration. Bias was compared with that reported in NCHRP Report 507. A study of variables, including blow count ranges, the artificial removal of outliers, and soil type differences, is presented. First-order, second-moment resistance factors are given at the end of initial driving and the beginning of restrike for 10 scenarios. Advanced Monte Carlo procedures, with random number generation and lognormal tail fits, provide end-of-initial-driving and beginning-of-restrike resistance factors to form a basis for the future implementation of five Oregon DOT scenarios.