An experimental investigation of deformation and shear failure in peripherally clamped centrally supported (PCCS) blast loaded circular plates is presented. In particular, the timing of shear failure events and the associated magnitude of the shear forces are reported. The plates exhibited three distinct modes of failure: mode I (large ductile deformation), mode II (boundary failure after large deformation) and mode III (boundary failure prior to large deformation). Approximate energy analyses for mode I deformation of annular and PCCS plates are presented. An expression for dimensionless impulse, applicable to annular and PCCS plates, is derived. The experimental data and analytical predictions exhibit satisfactory correlation.