Reinforced concrete flat plate slabs and slabs with drop panels often exhibit radial cracking in the vicinity of column supports under normal service/construction loading. This behavior has been observed in slabs in which design and/or construction errors have been identified, and in properly designed and constructed slabs. As such, the occurrence of radial cracking is not itself indicative of either design of construction errors, much less unanticipated performance. Negative flexural stresses are typically responsible for a concentration of cracking in the immediate vicinity of the columns, which commonly manifests in a "star-burst" pattern of radial cracks, interspersed with orthogonal or circumferential cracking. Such cracking can be found in reinforced concrete flat plate slabs in buildings that have been in service for decades, as well as in new buildings shortly after removal of shoring. While this cracking may be of potential concern to building owners, building officials, and design professionals as it may signify high flexural stresses and may result in undesirable exposure of the negative flexural reinforcing to moisture and chlorides, it is normally not indicative of a serious structural problem, and can be readily shown by analysis to occur under normal service conditions. Despite this, radial slab cracking appears to be mistaken as indicative of design or construction errors, structural overload, or punching shear failure nearly as often as it is recognized as normal behavior.
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