Enhanced Effective Thickness for laminated glass beams and plates under torsion

Abstract The torsional response of laminated rectangular panes composed by N glass plies of arbitrary thickness, coupled by N - 1 polymeric interlayers, is here analyzed. Under the quasi-elastic approximation, that considers the secant stiffness of the polymer, we use the classical hypothesis that the all glass plies rotate of the same angle of twist to derive the shape function for the strain field, whose actual form is found by energy minimization. When the width of the pane is much less that its length, we find formulae that apply to the geometry of a beam, representing the counterpart for laminates of the solution a la de Saint Venant for elements with thin rectangular cross sections. This approach extends to the case of torsion the Enhanced Effective Thickness (EET) method, already proposed for bending, and generalizes other previously proposed engineering methods, which are only applicable for beams composed of a limited number of glass plies. Comparison with numerical results for different geometries confirms the accuracy of the proposed formulation. This method can be conveniently applied for the preliminary design of cold-bent laminated cells for facades, as well as to study the lateral torsional buckling of in-plane-bent beams.