Ultimate Strength Study of Two-Way Concrete Slabs

The study reported herein is one phase of an effort to develop criteria that will be helpful in evaluating or predicting the air-blast load-carrying capacity of conventional floor slabs in existing Defense Civil Preparedness Agency approved shelters. Twelve tests, four static and eight dynamic, were conducted on slabs with totally fixed edges and a clear span of 29 in. (737 mm) and a thickness of 0.89 in. (22.6 mm). Two series of slabs (I and II) corresponding to two different percentages of steel reinforcement (0.78% and 1.17%) were used. The slabs were subjected to uniformly distributed static loads up to 36.5 psi (252 kN/m²) using water pressure and to dynamic airblast overpressures ranging from 26.5 psi (183 kN/m²) to 56.8 psi (392 mm kN/m²) using explosives. Measurements of pressure, deflection, and reinforcement strains were made, and results are presented herein. The primary mode of failure studied was the response of the slabs in the area beyond yield. This included the effects of tensile membrane action.