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Application of transfer relations to structural analysis of arch bridges

Zhang J.-L., Hellmich C., Mang H. A., Yuan Y., Pichler B.

Computer Assisted Methods in Engineering and Science

2017

Vol. 24, no. 3

199--215

Transfer relations, representing analytical solutions of the linear theory of slender circular arches, have facilitated structural analysis of segmented tunnel linings. This is the motivation to apply such relations to two examples of circular arch bridges in which the bridge deck is held from the arch by equally spaced hangers. First, the number of hangers is optimized to minimize the maximum bending moment of the arch, thus allowing the latter to come as close as possible to the desired thrust-line behavior. Next, analytical solutions for a “uniform temperature change” are derived and used to demonstrate that a temperature increase of 30 K results in minor redistributions of the inner forces but in significant additional deflections. The two examples have shown that the transfer relations are useful for structural analysis of circular arch bridges, because they reduce the complexity of the analysis to that of structural systems consisting of straight beams.

The influence of the microfibril angle on wood stiffness: a continuum micromechanics approach

Hofstetter K., Hellmich C., Eberhardsteiner J.

Computer Assisted Mechanics and Engineering Sciences

2006

Vol. 13, No. 4

523-536

Wood exhibits an intrinsic structural hierarchy. It is composed of wood cells, which are hollow tubes oriented in the stem direction. The cell wall is built up by stiff cellulose fibrils which are embedded in a soft polymer rnatrix. This structural hierarchy is considered in a four-step homogenization scheme, predicting the macroscopic elastic behavior of different wood species from tissue-specific chemical composition and microporosity, based on the elastic properties of nanoscaled universal building blocks. Special attention is paid to the fact that the fibrils are helically wound in the cell wall, at an angle of 0°-30°, generally denoted as microfibril angle. Consideration of this microfibril angle in the continuum micromechanics model for wood is mandatory for appropriate prediction of macroscopic stiffness properties, in particular of the longitudinal elastic modulus and the longitudinal shear modulus. The presented developments can be readily extended to the prediction of poroelastic properties, such as Biot and Skempton coefficients.