A review on various formulations of displacement based multi-fiber straight Timoshenko beam finite elements
Résumé
Specific kinematic assumptions are often adopted in structural analysis of civil engineering structures in order to simplify the global equilibrium equations and reduce the required number of degrees of freedom. The classical Timoshenko beam hypothesis, considering that plane sections remain plane after deformation but not necessary normal to the beam axis, is often chosen because it can (approximately) take into account the influence of shear strains. On the contrary, the Euler-Bernoulli assumption (sections remain plane and perpendicular the beam axis) neglects their influence and provides therefore accurate results only for the case of slender beam structures. This work is focused on the Timoshenko beam theory in the context of a multi-fiber approach: The section is considered as multi-fiber, it can have an arbitrary shape and each fiber has a local constitutive law representing a specific material. Various formulations of displacement based multi-fiber straight Timoshenko beam finite elements are re-visited. After a presentation of the shape functions leading to the stiffness matrices and the consistent nodal forces relative to each formulation, comparisons are made using elastic or elastic perfectly plastic constitutive laws. The advantages and disadvantages of each formulation are highlighted and general conclusions on the use of displacement based Timoshenko multi-fiber beams in engineering are drown.
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