This paper reports the results of scaled tests on mild steel square plates with different edge restraint subjected to uniformly distributed triangular pulse pressure loading producing large inelastic deformations without tearing or rupture. The loading is representative of overpressure loading arising from a confined hydrocarbon explosion. A scale factor of 0.5 was examined in this series of tests on 16 plates, eight 1 m by 1 m × 2 mm thick and eight 0.5 m × 0.5 m × 1 mm thick. Both static and dynamic test results are presented. A quasi-static rigid–plastic and elastic–plastic analysis of a fully restrained square plate is also presented and compared with the test results. The transient response of the plates under dynamic loading show some divergence from the laws of geometrically similar scaling while the permanent deformations in both the static and dynamic tests show good compliance with the laws of similitude, within the accuracy expected in such tests.