Seismic PBD of Piles from Monte Carlo Simulation Using EQWEAP Analysis with Weighted Intensities

Abstract

This paper discusses the seismic performance based design (PBD) analysis on piles using one-dimensional stress wave equation and Monte Carlo Simulation. Seismic responses of the piles were monitored at a wider spectrum of earthquake intensities rather than the target ones. To obtain appropriate estimations, weights of the intensities were calculated from the probability density function solvable from the seismic hazard curve. Probabilities of failure of the piles were evaluated for uncertainties of soil parameters and seismic records, and then calibrated with the weights. The result of the numerical study indicates that the seismic force is the most dominant factor. Large diameter pile will exert cracks around pile head under moderate earthquakes. Therefore assessment based on only the pile head would become very critical. For design and maximum consideration (MCE) earthquakes, the piles were found satisfied because of performance required on ductility resistance and ultimate moment capacity. Probabilities of failure of the piles were also found sensitive to horizontal load from the superstructure. Comparing the correspondent reliability indexes with those required for acceptable foundations, the seismic performance of the piles can be assessed. With the suggested factor of safety, the seismic performance of the piles was found to be 1.1~2.2 for design and MCE quakes in this study.