Behaviour of eccentrically loaded prestressed stayed columns with circular hollow sections

The behaviour of axially loaded prestressed stayed columns is a commonly studied area. Despite the fact that load eccentricity in columns is commonplace in practice, the amount of investigation into these systems under eccentric loading is limited. This study employed finite element analysis to investigate the interactive post-buckling behaviour of prestressed stayed columns. Critical imperfection combination with respect to the load carrying capacity was established and a comparison of a planar and a three-dimensional model was carried out to investigate key differences in the models. In this work, it has been shown that the load carrying capacity of eccentrically loaded columns can be significantly reduced when buckling in interactive mode is observed. Furthermore, it was established that increase in eccentricity results in a decrease in load carrying capacity of columns for both planar and three-dimensional models. However, a major difference between the models is the twisting effect exhibited in the three-dimensional model under out-of-plane eccentric loading. This work highlights the importance of carefully designing prestressed stayed columns’ connections to minimise loading eccentricity as it has been shown that the benefit of employing these systems over unstayed columns reduces with increasing load eccentricity.

Swelling-induced twisting and shearing in fiber composites: the effect of the base matrix mechanical response

If a helical network of fibers is embedded in a swellable matrix, and if the fibers themselves resist swelling, then a change in the amount of swelling agent will cause a corresponding twisting motion in the material. This effect has recently been analyzed in highly deformable soft material tubes using the theory of hyperelasticity, suitably modified to incorporate the swelling effect. Those studies examined the effect of spiral angle and fiber-to-matrix inherent stiffness in the context of a ground state matrix material that exhibited classical neo-Hookean behavior in the absence of swelling. While such a ground state material is nonlinear in general, its shear response is linear. As we describe here, it is this shear response that governs the matrix contribution to the twist-swelling interaction. Because gels, elastomers, and even biological tissue can exhibit complex ground state behavior in shear—behavior that may depart significantly from a linear response—we then examine the effect of alternative ground state behaviors on the twist-swelling interaction. The range of behaviors considered includes materials that harden in shear, materials that soften in shear, materials that have an ultimate shear stress bound, and materials that collapse in shear. Matrix materials that either soften or collapse in shear are found to amplify the twisting effect.

Numerical simulation of flow field in the twisting chamber of Murata vortex spinning based on the hollow spindle with different structures

The novel hollow spindle with spiral guide grooves is introduced into the manufacture of Murata vortex spun yarn for the sake of enhancing the vortex yarn’s strength. By means of numerical simulation, the airflow characteristics in the conventional twisting chamber and novel twisting chamber of Murata vortex spinning are obtained and compared in order to explain yarn formation for adoption of the novel hollow spindle. The airflow distribution near the spiral guide grooves is analyzed, and the influence of airflow changes caused by the groove structure on the movement of the free end fibers and the yarn strength is analyzed. The results show that the spiral guide grooves will influence the pressure and velocity distribution in the twisting chamber, especially near the areas of the guide grooves. The guide grooves can guide the swirling airflow moving down the conical cavity of the twisting chamber, resulting in increases of the tangential, axial, and radial velocities of airflow in the conical cavity. And it is expected to produce fiber migration in the yarn cross-section and the self-twist effect of wrapped fibers. These phenomena will strengthen the wrapping and twisting effect of the free end fibers and inter-fiber cohesive force of vortex spun yarn in the process of yarn formation, and finally improve the strength of vortex spun yarn due to adopting the novel hollow spindle.