Reliability Evaluation of the Impact of Pile Positioning Deviation on Pile Cap Punching Shear Resistance: A Case Study from Vietnam

Abstract

The deviations of the pile center coordinates (Δx, Δy) from the designed position during construction are a common issue affecting the structural safety. Although Vietnamese Standards (VNS) permit such deviations, their impact on the reliability of the pile caps is not quantitatively evaluated in the current design calculations. This study presents a quantitative reliability assessment of the punching shear resistance of a pile cap designed in accordance with VNS, based on a case study utilizing statistical data (mean μ, standard deviation σ) from 510 field measurements in a project in Vietnam. The reliability theory is employed to establish the limit state functions for punching shear cases (due to column and edge piles) and one-way shear (on inclined sections), with coordinate deviations (Δx, Δy) modeled as random variables. The reliability index (β) and probability of failure (Pf) for the load cases are determined using the First- Order Reliability Method (FORM) and verified by Monte Carlo Simulation (MCS). The analysis evaluates whether the pile cap design, when accounting for construction deviations, achieves the target reliability level referenced in Eurocode. The results clarify the actual safety level, providing a basis for recommendations to improve the design procedures and quality control for the pile foundation construction in Vietnam.