Generalized VHM Failure Envelopes for Pseudo-Static design of RC Pile Groups

Abstract

The paper presents generalized failure envelopes for an indicative reinforced concrete (RC) pile group layout in the combined VHM loading space. The limit equilibrium method is employed, reproducing certain failure modes in function of the applied load path of interest. Emphasis is placed on the role of the axial load-dependent bending strength and stiffness of the RC piles, and the coupling between their lateral load- and moment-capacity. The importance of setting a conventional limit on the axial bearing capacity of the piles and its effect on the predicted failure modes is also critically evaluated. The advantages of the proposed methodology are illustrated through a worked example on pseudo-static seismic design of a bridge pile group. The code-compliant estimation of capacity (Lateral Load and Overturning Moment) is compared to the ultimate resistance, estimated using the proposed method. The study illustrates that conventional approaches, widely applied in practice, not only violate the physics of the problem but in some cases can also yield un-conservative estimates.