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.
Experimental study on shear lag of curved box girder under earthquake excitation
A plexiglass cantilever curved box girder model is built to investigate shear lag effect distribution law in curved box girder. Firstly the finite element model is established based on ANSYS. Secondly the testing is performed on earthquake shaking table test under different earthquake excitations. Finally, the comparative analysis between the theoretical and experimental results is performed. From the above results, it is shown that an evident shear lag effect occur at the junction between web and flange of the cantilever curved box girder model under simulated earthquake excitations, and under the same condition, different kinds of earthquake excitations have limited influence on shear lag effect in curved box girder.
On the modeling of integrally actuated helicopter blades
This paper presents an asymptotical formulation for preliminary design of multi-cell composite helicopter rotor blades with integral anisotropic active plies. It represents the first attempt in the literature to asymptotically analyze such active structure. The analysis is broken down in two parts: a linear two-dimensional analysis over the cross-section, and a geometrically non-linear (beam) analysis along the blade span. The cross-sectional analysis revises and extends a closed form solution for thin-walled, multi-cell beams based on the variational-asymptotical method, accounting for the presence of active fiber composites distributed along the cross-section of the blade. The formulation provides expressions for the asymptotically correct cross-sectional stiffness constants in closed form, facilitating design-trend studies. These stiffness constants are then used in a beam finite element discretization of the blade reference line. This is an extension of the exact intrinsic equations for the one-dimensional analysis of rotating beams considering small strains and finite rotations, and now taking account of the presence of distributed actuators. Subject to external loads, active ply induced strains, and specific boundary conditions, the one-dimensional (beam) problem can be solved for displacements, rotations, and strains of the reference line. Analytical and numerical studies are presented to compare the proposed theory against the previously established analytical models. Discrepancies are found for general blade cross-section and discussed herein in details, especially for the piezoelectric actuation components. Direct results of the present formulation are also compared with experimental data.