Direct analysis by an arbitrarily-located-plastic-hinge element — Part 2: Spatial analysis

• The planar curved beam-column element is extended to three-dimensional space.
• Large deflection can be simulated through the incremental secant stiffness method.
• The proposed element can be easily incorporated into the existing software.
• Highly nonlinear material behavior can be reflected by single element per member.
• Satisfactory accuracy is verified against the examples from available literatures.

This is the part two of the two companion papers, which extends the element formulations and the applications of the curved ALH (Arbitrarily Located Hinge) element to three-dimensional space for direct analysis of the steel frames considering large deflection and inelastic behaviors. A simplified approach assuming the space frame to deform with finite but small rotations is adopted for extending the planar element to the three-dimensional space. The updated Lagrangian description and the incremental secant stiffness method are introduced for considering large deflection in the analysis, which is proven to be accurate and efficient in the convergence in iterations for equilibrium. Since the internal degrees of freedom of the proposed element are condensed, a significant reduction on the size of the global stiffness matrix can be achieved with improvement in numerical efficiency. Finally, examples are given for the verification of the proposed numerical method.