Buckling strut response for frame elements

In Abaqus/Standard frame elements defined with pipe sections support switching to an optional uniaxial buckling strut response during the analysis.

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Frame elements
Frame section behavior

ProductsAbaqus/Standard

Frame elements admit an optional force response in which axial force only is supported by the element. Furthermore, the axial force is constant along the element; all transverse forces and all moments in the element are zero. The axial forces in the element may be linear elastic or may admit a buckling strut response where the force versus axial strain is characterized by a buckling envelope with hysteresis, as described below. For details on the standard frame element response, see Frame elements with lumped plasticity.

In compression the buckling strut response models, in a simple way, the highly nonlinear buckling and postbuckling damage of slender members when loaded monotonically or cyclically. In tension the response is modeled by isotropic hardening plasticity. The buckling strut envelope is phenomenological, derived from experiments with pipe-like members. Since the description of the buckling envelope includes the outer pipe diameter and the pipe thickness, only pipe cross-section types are permitted with buckling strut response.

The buckling strut response is linear elastic until the compressive loading exceeds Pcr, the critical load to cause buckling. The value of Pcr is determined with the ISO equation, as described below.