Confined blast loading of steel plates with and without pre-formed holes

•Influence of pre-formed holes and their geometry on the internal blast response of ductile plates.•Internal blast loadings due to cylindrical TNT charge detonations.•Venting by the pre-formed holes does not alleviate the peak pressure of the primary blast wave, but is effective in attenuating the secondary blast waves.•Dynamic fracture behaviour of plate with square holes is affected by its deformation profile and regions of equibiaxial tension. This paper presents experimental and numerical results for fully-clamped square steel plates to elucidate how the deformation and failure are affected by the presence of pre-formed holes, and the pre-formed holes’ geometry, under confined blast loading. The geometry of the pre-formed holes will be shown to play a crucial role in the deformation and failure of a plate. Numerical simulations successfully predict the inelastic deformation and crack propagation observed in experiments; and, it will be shown that venting by the pre-formed holes does not alleviate the peak pressure of the primary blast wave, but is effective in attenuating the secondary blast waves arising from multiple reverberations within the test chamber. Pressure-venting by the pre-formed holes will be shown to be ineffectual in reducing the maximum transient midpoint displacement due to impulse saturation. The crack path that develops in a plate with pre-formed square holes was found to be affected by stress triaxiality.