Based on the proposed mechanical hypothesis and the analytical model of the grid stiffened composite panels,a new smeared stiffened theory was derived for analysing the global stability of grid-stiffened panels.The theory fully considered the effects of shell-stiffener interaction and influence of midplane shift.In this theory,the method is applicable for different types of grid stiffened elements.A general eigen function was deduced for computing global buckling load combined with a Rayleigh-Ritz method.Th...