Advances in dynamic instability of beams subjected to tensile loading

Instability caused by tensile axial loads acting on beams, for highly shear deformable beams and for beam-columns in the presence of a single structural junction allowing transversal deflection discontinuities, has been highlighted in a very few papers in the literature This paper is a contribution to the knowledge of dynamic instability arising from tensile loads of a beam-column in the presence of an arbitrary number of internal sliders endowed with translational elastic springs. First, closed form expressions of the eigen-modes and the characteristic equation under the action of axial forces, for different boundary conditions, are presented. Furthermore, besides the case of conservative tensile dead load, a non conservative axial load of the Beck type has been also considered and the following relevant question is asked: Can a beamcolumn undergo tensile flutter instability? While tensile axial loads with conservative character induce divergence type instability, this paper shows that a cantilever beam-column, under a non conservative tensile load only, undergoes flutter instability, as well as under compressive loads, when transversal displacement discontinuities along the span are allowed. A comprehensive parametric analysis is conducted. Finally, the contemporary presence of conservative and non conservative loads is investigated to study the reciprocal influence. Ranges where the structure switches from divergence to flutter instability, both in tension and in compression, are predicted and discussed in detail.