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The general objective of the study was to test a rigid structure in as large a field test as possible and to compare the results with those obtained from tests of the same type of structure in a laboratory simulation device. To accomplish the field-test part of the objective, three 30-in.-diameter reinforced concrete arches were buried in dense dry sand with 15 in. of cover over the crown and subjected to the effects of a 500-ton TNT blast (Project 3.2, Operation SNOWBALL) at overpressures of 105, 205, and 320 psi. In the laboratory, three structures were tested in the U.S. Army Engineer Waterways Experiment Station's Large Blast Load Generator, an explosively operated plane-wave loader, at overpressures of 92, 190, and 301 psi. It was found that the gross motion experienced in the field compared favorably with that obtained in the laboratory. Thrust and moment in the arch ring correlated; however, moment distribution in the arch ring appeared to be related to the impingement angle of the stress wave. Shock-spectrum comparison indicated that the free-field spectrum in the field and laboratory when compared with spectrum at a point on the structure generally exhibited an empirically predictable ratio. Consequently, the shock-spectrum envelope at certain points on these structures can be constructed for field loadings based on laboratory and free-field data. (Author).
The determination of the loads on and behavior of shallow-buried arch structures is complicated by the geometry of the arch and by existence if soil structures arches interaction effects. A common approach to the analysis of buried is to idealize the structure as a lumped parameter single degree of freedom (SDOF) system. The parameters which must be assumed for input into the SDOF model include a loading function and a structural resistance deflection relationship. The applied load on a buried arch due to overpressure at the ground surface includes a radial and a tangential component. The radial component can be measured experimentally; however, there seems to be no available transducers to measure the tangential component or interface friction. Two 1/12-scale model reinforced concrete arches were tested statically in a sand backfill. The arches were semicircular with an inside radius of 1 foot 9 inches and a thickness of 2 inches. One arch was covered with two layers of 1/32-inch-thick Teflon at the soil-structure interface to significantly reduce the interface friction, and the loading and behavior of the two arches were compared. Pretest finite element calculations were conducted to estimate the arch behavior. Based on both the experimental data and posttest calculations, it appears that interface friction on a shallow buried arch has an effect on its behavior, at least for the case of static loads. The load path at sections in the arch with a lower friction coefficient at the interface tended more toward pure compression than it did in the other arch. Keywords: Air blast simulation; Concrete structures; Hardened installation. (SDW).
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An overview of recent developments in constitutive modelling, numerical implementation issues, and coupled and dynamic analysis. There is a special section dedicated to the numerical modelling of ground improvement techniques, with applications of numerical methods for solving practical boundary value problems, such as deep excavations, tunne