Insights from Reliability-Based Design to Complement Load and Resistance Factor Design Approach

Abstract

Reliability analysis and reliability-based design (RBD) via the first-order reliability method (FORM) can overcome some limitations and ambiguities in the load and resistance factor design (LRFD) approach, for example in situations where loads contribute not only destabilizing but also stabilizing effects, situations where load and resistance sensitivities vary due to different geometric and other details, situations with spatial variability and parametric correlations, and situations with different targets of probability of failure. Examples of RBD are presented to show that under these circumstances RBD can offer interesting insights apart from providing valuable guidance on what load and resistance factor values to use in LRFD. Specifically, this study investigates RBD of a shallow footing subjected to both vertical and horizontal loads in different proportions, laterally loaded piles with depth-dependent nonlinear p-y curves and different cantilever lengths, and an anchored sheet pile wall in which the load effects and resistance are nonlinear functions of soil shear strength, unit weight, geometry, and parametric correlations. This study demonstrates that RBD can automatically reveal critical design scenarios and obtain design values of loads and resistance which reflect different parametric sensitivities across different scenarios.