Abstract

In this paper we derive the field of displacements and strains for thin-walled open composite beams with composite laminated material including in their kinematics flexural and torsional shear deformations effects. The equilibrium equations are defined through the variational formulation and show that is possible to formulate Co finite elements taking into account the torsional shear deformation. Stress-strain relationships for the cross-section of thin-walled composite beams are obtained by extending first-order laminate (FSDT: first-order shear deformation) theory and using a «free stress resultant condition at the boundary». Three different one-dimensional finite elements with Co continuity are formulated for the study of thin-walled open composite beams and they are labelled as BSW (beam with shear and warping). The influence of the integration strategy in the BSW elements is evaluated via the shear-locking phenomenon and the rate of convergence for displacements and rotations. The stiffness matrix integration is compared using exact and reduced integration methods. Examples of pure torsion and flexo-torsion in a cantilever composite beam are performed. Numerical results are compared to those reported by other authors.

Abstract

High demand for living and working space as well as the corresponding infrastructure, caused by a growing population and increasing prosperity worldwide, leads to increased consumption of mineral resources. This is accompanied by high usage of grey energy and a high output of greenhouse gas emissions. Adaptive structures represent a promising approach for mass and resource savings. Through the interaction of actuators, sensors and control units, the structure can adapt to the external loads to reduce stresses and deformations. As a result, the building material required can be reduced. For actuators integrated into slabs, new challenges arise due to the multi-axial load transfer. In particular, the aim is to achieve the largest possible effective range of the applied moment to reduce the number of actuators required. One approach is to optimize the geometry of the force-introducing surfaces inside the structural element. This paper presents a study about the correlations of the geometric parameters using numerical simulations. This enables the pre-dimensioning of the actuator and is thus a first step in its design.