A curved shell finite element for the geometrically non-linear analysis of box-girder beams curved in plan
A four-noded curved shell finite element for the geometrically non-linear analysis of beams curved in plan is introduced. The structure is conceived as a sequence of macro-elements (ME) having the form of transversal segments of identical topology where each slice is formed using a number of the curved shell elements which have 7 degrees of freedom (DOF) per node. A curved box-girder beam example is modelled using various meshes and linear analysis results are compared to the solutions of a well-known computer program SAP2000. Linear and non-linear analyses of the beam under increasing uniformly distributed loads are also carried out. In addition to box-girder beams, the proposed element can also be used in modelling open-section beams with curved or straight axes and circular plates under radial compression. Buckling loads of a circular plate example are obtained for coarse and successively refined meshes and results are compared with each other. The advantage of this element is that curved systems can be realistically modelled and satisfactory results can be obtained even by using coarse meshes.
Curved girders are special
Abstract Horizontally curved l-girders have been used in highway bridges for over 30 years. Their structural behaviour is known to be quite different from straight girders because of the always present nonuniform torsion. Early studies of these members were based on a strength of materials approach. Modifications of these results were made to account for distortion and amplification effects. More recent investigations in Japan have involved inelastic finite element studies. From these studies various modifications of straight I-girder bending strength equations have been presented. Bending tests of curved beams are compared to these equations. It is suggested that current research may lead toward the thought that curved girders are the general case, and straight girders may be considered a special case.
Nonlinear analysis of composite thin-walled helicopter blades
Abstract Nonlinear theoretical modeling of laminated thin-walled composite helicopter rotor blades is presented. The derivation is based on nonlinear geometry with a detailed treatment of the body loads in the axial direction which are induced by the rotation. While the in-plane warping is neglected, a three-dimensional generic out-of-plane warping distribution is included. The formulation may also handle varying thicknesses and mass distribution along the cross-sectional walls. The problem is solved by successive iterations in which a system of equations is constructed and solved for each cross-section. In this method, the differential equations in the spanwise directions are formulated and solved using a finite-differences scheme which allows simple adaptation of the spanwise discretization mesh during iterations.