Glass design charts are available for annealed, monolithic glasses. In order to use these design charts, strength of a laminated glass unit needs to be adjusted by a strength factor. This paper presents a study on strength factor and the effect of various factors oil the strength factor, like ambient temperature, width and length of the beam. The effect of nonlinearity on the strength factor is also investigated by considering the nonlinear behavior of fixed end laminated glass beams since the simply supported glass plates behaves nonlinearly. From the study, two factors are crucial in the estimation of relative strength of laminated glass with respect to monolithic glass: one of two factors is the plasticizer content and therefore the transition temperature of the PVB layer used in the manufacture of laminated glass unit, and the other is the effect of nonlinearity as observed in the analysis conducted with fixed end beams in this study. (c) 2005 Elsevier Ltd. All rights reserved.