A DYNAMIC ULTIMATE STRENGTH STUDY OF SIMPLY SUPPORTED TWO-WAY REINFORCED CONCRETE SLABS.
Final technical rept.,
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS
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Static and dynamic airblast-loaded behavior of simply supported, two-way reinforced concrete slabs was investigated. Four static and seventeen dynamic tests were conducted on slabs with clear span dimensions of 7 feet 6 inches and a thickness of 2-58 inches. Three series of slabs corresponding to three different percentages of steel reinforcement were subjected to uniformly distributed static loads varying from 7.1 to 11.8 psi and dynamic airblast overpressures ranging from 7.3 to 13.2 psi. Measurements of pressure, deflection, concrete surface and reinforcement strains, acceleration, and velocity were made. Three damage ranges negligible, moderate, and severe, defined in terms of permanent midpoint deflection, are used to discuss the condition of the slabs after static and dynamic loading because none of the slabs actually collapsed or failed. Crack patterns present in the severe damage range indicated that the slabs would fail primarily in a flexural mode. However, tensile membrane action developed in the center region of the slabs at a midpoint deflection approximately equal to the depth of reinforcement, and this action accounts for the increased slab resistance when deflections become large. Static ultimate strengths of Series I, II, and III slabs were approximately 1.43, 1.38, and 1.51, respectively, times the ultimate strength predicted by a yield-line analysis with an X crack pattern. Dynamic ultimate strengths of the slabs were estimated to be 11, 13, and 15 psi for the Series I, II, and III, respectively, and these values are approximately 1.43, 1.38, and 1. 27 times the static ultimate strengths. Author
- Structural Engineering and Building Technology