A method for devising omnidirectional inelastic response models from uniaxial behavior

There is a wide variety of nonlinear hysteretic numerical models for simulating the mechanical responses of structural and geotechnical components or subsystems. A large subset of these models is constructed to offer only uniaxial responses and is typically packaged as zero-length macroelements. When multi-axial responses are required, these uniaxial elements are attached orthogonally to the host structural model and offer uncoupled reactions. In nonlinear loading regimes, this approach yields inaccurate estimates of both the directions and magnitudes of the reaction forces, with the latter occasionally exceeding the intrinsic capacity/strength of the modeled medium or component. A framework based on multi-surface plasticity is offered herein to address the problem. Specifically, omnidirectional macroelement models are proposed, and examples implemented in ABAQUS for “ p - y ” models used in pile-soil interaction analyses, and triple friction pendulum (TFP) bearings. The developed p - y model is verified against three-dimensional continuum finite element simulations of a laterally loaded pile embedded in sand, and the omnidirectional TFP model is validated against laboratory test data. The proposed approach can be applied to other similar problems by recalibrating the yield surfaces and hardening rules to match the uniaxial backbone curve and by adjusting the unloading-reloading rules.