Hysteretic Modeling of Steel Struts: Refined Physical Theory Approach

The nonlinear behavior and failure mechanism of braced frames and trusses under static and dynamic loads tend to be strongly influenced by the inelastic‐buckling behavior of steel struts. The study reported herein has been concerned with analytical modeling of the nonlinear behavior of steel struts under generalized loading conditions. A computationally efficient formulation is presented for predicting the inelastic‐buckling behavior of steel struts under monotonic and cyclic loads. The proposed formulation incorporates approximate techniques to account for some critical aspects of the strut inelastic‐buckling behavior under generalized loads, including: (1) Partial plastification and degradation prior to full yielding at critical regions of struts under increasing loads; (2) sudden buckling of straight elements; and (3) degradation of strut stiffness and strength under repeated inelastic cyclic loads. The simplifying assumptions in the development of the proposed formulation were based on the observed physics of the strut behavior. The computational efficiency of the model results from its limited number of degrees of freedom as well as its compatibility with the stiffness method of structural analysis. The proposed formulation is shown to compare favorably with several monotonic and cyclic test results performed on struts with various material and geometric properties. In spite of some reliance on empirical refinements, the model has been largely based on theoretical concepts, and may thus be generally applicable and can be further refined and developed without conceptual problems.