Ultimate strength assessment of stiffened panels using Equivalent Single Layer approach under combined in-plane compression and shear

Abstract

Equivalent Single Layer (ESL) approach is extended to model ultimate strength of stiffened panels under a combination of in-plane compression and shear. Ultimate strength under this combined loading depends on the loading path and could be lower than for only uni-axial compression since shear load can produce axial forces. Thus, to account for this effect, the recent ESL model is extended to include A13 stiffness component as non-zero value. Procedure to accurately obtain A13 is presented. In ESL approach, a stiffened panel is transformed into a two-dimensional (2D) single layer with the same stiffness obtained from unit cell simulations. To obtain non-linear stiffness matrix of ESL, elastic–plastic material properties and initial imperfection were applied to the unit cell. ESL responses were validated by comparing numerical and experimental results from the literature. Several stiffened panel configurations were analyzed to obtain different collapse modes. Combined loads were applied for shear to compression ratio of 0, 1, and 2. Lateral pressure loading was also considered in the simulations. Analyses were carried out based on the load sequences consisting of: 1) compression and shear loaded simultaneously and 2) shear applied first, followed by compression. The results show that the modified ESL can well capture the effect of shear load on ultimate strength in comparison to a detailed 3D FEM model of stiffened panels. The accuracy of the ESL varies depending on the collapse mode of stiffened panels.