Deformation Capacity of Web Perforated H-Shaped Beams

<p>When designing web perforated H-shaped beams, it is common to reinforce the holes due to the deficit in section’s area. However, previous studies revealed that non-reinforced web-perforated H-Shaped beams had similar performances as non-perforated H-shaped beams without holes when the position and shape of holes were designed considering the relationship between the acting stress for beams and the strength at the reduced sections. While this design method of non-reinforced web perforated H-shaped beams assumes a stress state of beams in the elastic state, it cannot always guarantee an appropriate performance in the ultimate stage similarly to non-perforated H-shaped beams. So the purpose of this study is to confirm the ultimate behavior of perforated H-shaped beams by experiment and FEM.</p>

A model of cytoskeletal reorientation in response to substrate stretching

Living adherent cells change their orientation in response to substrate stretching such that their cytoskeletal components reorganize in a new direction. To study this phenomenon, we model the cytoskeleton as a planar system of elastic cables and struts both pinned at their endpoints to a flat flexible substrate. Tensed (pre-strained) cables represent acting stress fibers, whereas compression-bearing struts represent microtubules. We assume that in response to uniaxial substrate stretching the model reorients and deforms into a new configuration that minimizes its total potential energy. Using the Maxwell's global stability criterion, we find global minima configurations during static extension and compression of the substrate. Based on these results, we predict reorientation during cyclic stretching of the substrate. We find that in response to cyclic stretching cells either reorient transversely to the direction of stretching, or exhibit multiple configurations symmetrically distributed relative to the direction of stretching. These predictions are consistent with experimental data on living cells from the literature.