The mechanics of DNA supercoiling is a subject of crucial importance to uncover the mechanism and kinetics of several enzymes. It is therefore being investigated using several biochemical and biophysical methods including single molecule experimental techniques. An interesting problem within this realm is that of torsional buckling and plectoneme formation in DNA as it is simultaneously put und...

We report on molecular dynamic calculations of combined tension–torsion of chiral single-wall nanotubes. We work within the framework of objective structures that exploits symmetry groups to enable torsion of chiral nanotubes, in addition to non-equilibrium extension. We apply the method to study the mechanical response and failure of nanotubes of various chiralities. We find that three distinc...

Nonlinear torsional-flexural modal ;nteractions of a torsionally excited cantilever beam are studied in the case of one-to-one internal resonance. Discrete two DOF model is derived from the equations of motion for the continuous canthwer beam by using the Galerkin mode approx;mat;on method. The method of averaging is used to obtain the approx;mat;on to the response of the discrete model. Steady...

Simply supported steel beams with rectangular hollow section (RHS) are investigated, taking into account large twist and cross-sections distortions. A closed-form expression for the critical value of external couple inducing lateral torsional buckling is found; homotopy perturbation method (HPM) used to investigate post-buckling non-linear path. The linear paths given by HPM compared those of: ...

An analytical study along with a numerical investigation is conducted to determine the lateral buckling strength of thin-walled open-section I shape composite beams. Based on Vlasov-type linear hypothesis beam stiffness coefficients, which account for a cross section geometry and material anisotropy of the section, are obtained. In this study the axial and bending coupling terms ( A,, , A,, , D...

Eurocode (EC3) bending moment design model of mono-symmetric corrugated web girders (CWGs) is based on the critical failure mode among tension flange yielding, compression yielding and lateral-torsional buckling (LTB) flange. Recently, LTB behaviour S460 laterally-unrestrained CWGs with fully-effective flanges has been investigated by authors, from which EC3 modified to better represent their a...

An attempt is made to explain the observed torsional oscillations of an airscrew by means of the 'wake' theory. It is shown that the aerodynamic torsional damping becomes negative at certain blade angles and frequencies; the frequencies, or speeds, at which a single blade becomes unstable are shown to differ slightly from the critical frequencies of a multi-blade airscrew. At low incidences it ...