In this paper a mixed finite element based on Generalised Beam Theory (GBT) is proposed to analyse the first-order behaviour of naturally curved beams with circular axis (without pre-twist) and having deformable thin-walled cross-sections. The element applies the assumed strain concept to the longitudinal strains terms that are not present in straight members and cause locking. The additional strain DOFs are condensed out and therefore the stiffness matrix of the mixed element shares the DOFs of the standard (displacement-based) GBT finite element. The superior predictive capacity of the proposed mixed element with respect to the standard element with reduced integration is demonstrated through several examples involving complex global-distortional-local cross-section deformation.
- Bars with circular axis
- Cross-section deformation
- Generalised beam Theory (GBT)
- Mixed finite elements
- Thin-walled curved members