Abstract: An underground shock-resistant structure comprises a vaulted roof having a ring configuration as viewed from above and a ring-shaped base member, such as a flat floor, joined to the inner and outer edges of the vaulted roof. The external surface of the vaulted roof has a continuous convex configuration with a slowly varying radius of curvature and no change of signal such that over pressures and shockwaves striking the external surface of the vaulted roof apply compressive pressures to the vaulted roof and are deflected by the surface. Optionally, there may be one or more basement levels below the flat floor which are enclosed by inner and outer walls having a ring configuration which are joined to the inner and outer edges of the vaulted roof. In another option the flat floor may be replaced by an arch with its concavity facing upwards joined to the inner and outer edges of the vaulted roof.

Abstract: A combination door and door frame primarily designed for blast shelters wherein the hinged door, which in locked position is designed to withstand external overpressures resulting from detonation of either nuclear or conventional weapons, swings inwardly when opened, thus avoiding the objection of outwardly opening doors which can be blocked by rubble, debris, soil, etc. projected by the force of the explosion piling up against the door resulting in the occupants becoming entombed in the shelter.