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Title: Tests and evaluation of upgraded flat-plate and waffle-slab floor systems
Authors: United States. Federal Emergency Management Agency.
Woodson, Stanley C.
McVay, Mark K.
Keywords: Buildings
Reinforced concrete
Concrete slabs
Deep slabs
Slabs on grade
Dynamic loads
Flat plate
Waffle slabs
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-83-7.
Description: Technical Report
Abstract: Several tests were performed at the Waterways Experiment Station (WES) for the Federal Emergency Management Agency (FEMA). The tests were conceived and recommended by Scientific Services Incorporated (SSI) to provide information for use in the Shelter Upgrading Manuals being prepared for FEMA by SSI. The program consisted of tests on individual 19- and 30-inch-square panels taken from waffle slabs, 19-inch panels taken from one-way ribbed joist slabs, two center portions of a waffle slab, and the center portion of a flat plate. Also included were tests to determine the punching strength of 4-inch-thick basement slabs on grade. The individual 19- and 30-inch waffle panels and the 19-inch one-way slab panels were 3 inches thick, which is the minimum thickness used in standard construction. Each panel was cast as the center portion of a 46-inch-diameter by 11-inch-thick concrete disk and statically loaded to failure with water pressure in the Small Blast Load Generator (SBLG). Two 4-inch-thick basement slabs on grade were cast inside 46-3/4-inch-diameter steel rings and on top of a polyurethane sheet covering 6 inches of compacted gravel on top of 18 inches of soil compacted to 95 percent optimum density. The slabs were tested by pushing a 7- by 7-inch wooden post, composed of four 4- by 4-inch posts nailed together, into the center of the slab with the 200-kip loader. One test was performed statically and one dynamically. The two center portions of a waffle slab and the one center portion of a flat plate were designed with the maximum diameters that would allow placement inside the 22-foot 10-inch-diameter Large Blast Load Generator (LBLG). The flat-plate test specimen was constructed to include the positive moment area from a 22-foot-square slab designed according to the Third Edition of the CRSI Handbook. The waffle-slab specimens were constructed to include positive moment areas from 24-foot-square slabs. An 8-inch-thick wall, 8 feet tall, supported the slabs along their perimeters, and wooden posts were wedged in place under each specimen where SSI predicted upgrading supports would be needed in an actual slab. It should be noted that these test specimens were not under boundary conditions similar to those in actual structures. However, SSI was interested in testing the response of the slabs' center portions whete upgrading supports were applied. The 19-inch-square by 3-inch-thick waffle-slab panel failed in shear under a peak pressure of 900 psi and at a peak displacement of 0.15 inch. The 19-inch-long by 3-inch-thick one-way ribbed joist panel failed in shear at an average peak pressure of 400 psi and a displacement of 0.054 inch. The 30-inch-square by 3-inch-thick waffle panels failed at an average peak pressure of 320 psi and a deflection of 0.087 inch. The wooden posts punched through the 4-inch-thick slabs on grade under a peak static load of 79.0 kips and a peak dynamic load of 135.0 kips. After punching through the slabs, the wooden posts were still capable of supporting load. The static load capacity of the center portion of an upgraded waffle slab under the given boundary conditions was 44.0 psi. Failure seemed to be caused by collapse of the wooden columns and then shearing of the slab around the rigid boundary. The dynamic load capacity of an identical slab was near an average pressure of 34 psi. Movies of the underside of the slab indicated that the wooden columns failed and the slab collapsed at nearly the same time. The static load capacity of the center portion of an upgraded flat plate was 38.0 psi. The wooden columns collapsed allowing the slab to deflect. These test results will be incorporated into the manuals SSI is preparing on upgrading of shelters. NOTE: This file is large. Allow your browser several minutes to download the file.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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