This paper addresses the influence of adjacent plates on the strength of a single plate by studying the strength of panels composed of three and five plates transversely connected and loaded along the longitudinal direction,. The influence of adjacent plates is studied in two limiting cases of the shapes of initial imperfections in those plates. First, a comparison between the strength of panels having asymmetric imperfections in adjacent plate elements and of single plates is made, which allows evaluating the ability of the single plate to properly simulate the panel strength. Following this, the results obtained for a panel model having symmetric imperfections in adjacent plates are confronted with the results of the asymmetric imperfections. The asymmetrical and symmetrical models of the panel give, respectively, the lowest and highest strengths possible (imperfections in adjacent plates with different amplitudes have intermediate strengths), allowing to establish limits to the variation of the strength. The results show that using a single plate for assessing the strength of a panel made of those plates can be conservative or nonconservative, depending on the plate slenderness and shape of initial deflections. It is concluded that for design purposes, it will in general be enough to consider assemblies of three plates, as the results for five plate assemblies are not much different.