Variable-Property Beam Element Analysis for Improved Load Estimation in Complex Beam Structures

This study investigates displacement-based and equilibrium-based beam element formulations and their implementation to upgrade the existing beam model used in the wind turbine load analysis code, HAWC2. The two formulations are implemented and evaluated to model different beam configurations in which the structural properties vary along the beam. The performance of the different beam element formulations is evaluated in terms of static deflections and natural frequencies for tapered and pre-twisted beam configurations. The obtained results show that the beam element formulation can significantly improve the accuracy of the existing beam model used in HAWC2 when varying values of the cross-sectional properties are used to obtain the element matrices in combination with an updated element assembly. The considered displacement-based and equilibrium-based beam element formulations both include variation of the cross-sectional properties in the integration along each beam element. Of these two element formulations, the displacement-based beam element formulation is found to have a larger potential for implementation in HAWC2 due to a similar accuracy when inertial effects are included and due to a larger resemblance to the existing beam element implementation in HAWC2.