Cracking in Concrete Fill on Metal Decks, Cracking in Flat Plate Concrete Slabs, and Cracking in Concrete Walls

The fact that concrete cracks under the influence of everyday service loads is a truism that engineers, architects, contractors, and building owners often forget or fail to recognize. Three very common types of cracking — cracking in concrete fill on metal decks, cracking in flat plate concrete slabs, and cracking in concrete walls — are discussed in this paper. In the case of concrete fill on metal decks, cracking is often erroneously attributed to excessive dead and live loads, design or construction errors, or even earthquake loads. Actually, cracking in concrete fill is most commonly related to restraint against shrinkage and to the location of the supporting steel members. Due in part to curvature of the section induced by drying shrinkage of concrete, cracking typically occurs directly atop the supporting beams and girders, even when the decking is not shored during construction. Cracking at that location reduces the local moment of inertia at the crack, leading to incremental rotation of that cross-section and widening of the crack.