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|Title:||Tests and analyses of 1/4-scale upgraded nine-bay reinforced concrete basement models|
|Authors:||United States. Federal Emergency Management Agency.|
Woodson, Stanley C.
Flat plate model
Two-way slab model
Nuclear blast shelters
|Publisher:||Structures Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Technical report (U.S. Army Engineer Waterways Experiment Station) ; SL-84-6.|
Abstract: Methods that can be used to increase (upgrade) the blast resistance of existing two-way reinforced concrete slab systems to a value near 50-psi overpressure from a 1-mt weapon were evaluated. Two nine-bay prototype structures, a flat plate and a two-way slab with beams, were designed in accordance with the 1977 ACI Code. Each structure had a basement area 60 feet square. A 1/4-scale model of each prototype was constructed, upgraded with 4- by 4-inch timber posts, and statically tested in the Large Blast Load Generator at the U. S. Army Engineer Waterways Experiment Station. The timber posts placement scheme was based upon yield-line analyses, a study of moment-thrust interaction diagrams for sections of the slabs, and punching shear evaluations. The upgraded flat plate was tested first, and the upgrading scheme was then modified for the slab with beams model. The flat plate was upgraded at locations 1/4 of the span length, and the two-way slab with beams structure was upgraded at locations 1/3 of the span length. The flat plate model and the slab with beams model withstood approximate static overpressures of 79 and 40 psi. Allowing some plastic deformation from a long duration load such that the peak dynamic load capacity approaches static capacity indicates that required hardness can be achieved through simple upgrading techniques. The flat plate test indicated that the 1/4-span-length spacing was conservative for a required 50-psi overpressure capacity. The ability of the upgraded flat plate to deflect without punching shear failure occurring at the upgrading columns allowed the model to withstand overpressures greater than expected. Rupture occurred in the two-way slab with beams model. The ruptured area was approximately 40 inches square, and was the consequence of either an upgrading column punching into the slab or the slippage of the column such that it no longer supported the slab. The test indicated that the 1/3-span-length spacing of upgrading columns was inadequate for a 50-psi overpressure requirement.
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