Stability of Tensile Cracks in Concrete Beams

A tensile crack in a concrete member may be harmless or may lead directly to failure. A method of analysis is presented by means of which the development of a tensile crack in a concrete member can be studied quantitatively and conclusions can be formed concerning its stability. The assumptions on which the method is based are stated in general terms and specific examples are presented to illustrate the application of the method. Examples include the following cases: Flexural crack in an unreinforced beam; flexural crack in a reinforced beam; cracks originating in a zone of combined shear and moment in a reinforced beam; and cracks at the top fiber of prestressed concrete beams at transfer. The implications of the calculations are evaluated and a set of conclusions is presented concerning their significance.