Evaluation of Model Factors for Barrette Piles Based on CYCU/Barrette/64

Model factors for barrette piles at the ultimate limit state under compression loading were evaluated in this study. A total of 64 rectangular pile load test results from different locations around the world were compiled as CYCU/Barrette/64. The database was divided into a drained group and an undrained group corresponding to the dominant soil conditions along the shaft length. The measured capacity was interpreted from a load-displacement curve using nine common methods. The model factors for barrette pile under compression loading were determined to provide engineers with the statistics to implement reliability-based design (RBD). It was found that the drained model factors (Qm/Qp), where Qm = interpreted capacity and Qp = predicted capacity, range from 0.57 to 1.09 and the undrained model factors range from 0.64 to 1.31. A model factor less than 1 is unconservative (predicted capacity is larger than the interpreted capacity). These model factors can be used to calibrate resistance factors for RBD at the ultimate limit state (ULS). Hyperbolic model factors were also determined to calibrate deformation factors for RBD at the serviceability limit state (SLS) at any tolerable displacement value. The mean hyperbolic model factors were determined as (1) mean a=15.65 mm and mean b=1.07 under drained conditions; and (2) mean a=15.86 mm and mean b=0.81 under undrained conditions. The load-displacement curves are fitted to these hyperbolic model factors (a and b) using Q/Qp=rho/(a+b rho), where Q = applied load and rho = pile head displacement. It was found that the model factors might depend on some input parameters, although there are insufficient load tests to establish this preliminary finding conclusively.