Ponding of Concrete Deck Floors

Ruddy, John L. (1986). "Ponding of Concrete Deck Floors," Engineering Journal, American Institute of Steel Construction, Vol. 23, pp. 107-115.

Floor construction consisting of concrete over metal decking and supported by steel beams and girders is a frequently employed structural system. When temporary shoring is not used, the steel framing and decking deflects during placement of the concrete floor slab. If the concrete were placed to the specified uniform thickness, the result would be a floor surface defined by the deflected shape of the supporting members. The purpose of this paper is to present an interim report concerning studies toward an ultimate objective of predicting concrete volumes required to produce an acceptably level slab which is placed over a flexible substrate. As concrete is placed, the supporting system deflects. As more concrete is placed to compensate for the deflection, additional displacements occur. The situation may be considered analogous to the rainwater ponding phenomenon of roof systems. However, there are notable differences between the rainwater ponding phenomenon and the concrete placement operation. Concrete is plastic, not liquid, consequently it does not seek a constant level. Also, the concrete placement process is controlled by man and rainwater deposition is not.