Blast Loading and Response of Underground Concrete-Arch Protective Structures

摘要

The purpose of this project was to evaluate the effects of a kiloton-range nuclear airburst on buried reinforced-concrete arch structures located in the high overpressure region. Since these were to be considered as personnel protective structures, they were evaluated for their resistance to blast, radiation, and missile hazards. Four structures, with the top of the arch crown 4 feet below ground surface, were positioned at three different overpressure ranges for the Priscilla Shot, a 36.6 kt, 700-foot-high burst. All four arches were semicircular in cross-section, with an inside span of 16 feet and an arch thickness of 8 inches. Three of the structures were 20 feet long and the fourth was 32 feet long. A 20-foot-long structure was placed at each of the predicted ground-surface air overpressure levels of 50-, 100-, and 200-psi, while the 32-foot-long structure was placed at the predicted ground-surface air overpressure level of 50 psi. It was specified that all structures be designed to withstand a 50-psi peak blast overpressure using 3,000-psi concrete. The four structures were instrumented for measurements of air overpressures, earth pressure, deflections, accelerations, strains, radiation, and missiles. The four structures received actual air overpressures of 56, 124, and 199 psi and suffered only minor damage, all remaining structurally serviceable. The structure at the 199-psi pressure level exhibited obvious cracking of the floor slab and minor tension cracking of the arch intrados; however, even though the damage was slight, the peak floor slab acceleration of 13.4g may have been physiologically hazardous to personnel.