A page for readers who check the numbers. Why shape matters more than wall thickness.
Design load: 100 kPa blast overpressure with fragment retention
Undergoing certification testing to ДСТУ 9329:2025
Testing with the State Emergency Service is in progress. We do not call the shelter certified until the document is in our hands.
Protection from fragments, blast wave and structural debris. Protection from a direct hit is not claimed.
A doubly-curved shell carries uniform external pressure mainly through membrane forces — in-plane compression. Bending moments concentrate only around openings and at the support edge, so reinforcement is concentrated there rather than spread across the whole surface. This is the fundamental difference from a flat wall, where bending governs and dictates thickness.
Considered: 100 kPa overpressure with a normative rise time; fragment and secondary-debris impact; static load of the earth berm and traffic surcharge above; lifting and transport; ground shock from a nearby detonation as an impulsive base acceleration.
Real civilian casualty data is dominated by fragments and debris, not by peak overpressure. A shell with a large compression reserve is rarely the weak link. The opening is: the door, its frame, its anchorage and the valves. That is why Premium uses Temet doors and valves, and why we test that assembly together with the shell rather than separately.
C40/50 concrete with polypropylene fibre, which restrains inner-face spalling under dynamic load. Two layers of reinforcement mesh. The internal polyurea membrane does two jobs: waterproofing, and holding any concrete spall in place.