A Comparative Study of Drilled Shaft Design Using LRFD and Expanded RBD

A comparative study of drilled shaft design is presented using a Load and Resistance Factor Design (LRFD) method and an expanded reliability-based design (RBD E ) method recently developed by the authors. A design example that has been used in the literature to illustrate LRFD is re-analyzed using Monte Carlo Simulation (MCS) and is re-designed using RBD E . The MCS results show that the feasible design obtained from LRFD might have a failure probability different from the target failure probability (pT) adopted in the LRFD calibration. The RBD E method gives a design that corresponds to the pT or a design that is consistent with the LRFD feasible design at its real level of failure probability. RBD E allows design engineers to adjust pT without additional calculations, and they have the flexibility to make assumptions and/or simplifications deemed appropriate. Such flexibility is illustrated by exploring the effect of the dead to live load ratio on design.