Bending and shear behavior in one-way dapped-end reinforced concrete slabs

Six one-way reinforced concrete slabs, simply supported along the short sides by means of corbels (dapped ends), were recently tested for bending and shear behavior in Milan under two different crosswise load distributions and with three partially different reinforcement layouts in the supporting corbels and in the main body (size 2200 x 1300 mm [7.22 x 4.27 ft]; thickness/length ratio close to 1/14; corbel depth and overhang/length ratio close to 1/23). The tests in bending under the service loads and in shear up to and beyond the peak load show that load crosswise-distribution plays a minor role. In shear, the quite complex crack patterns in the D-regions close to the dapped ends clearly indicate the formation of very effective strut-and-tie systems if the bottom bars of the main body are bent up, and of shallow arch-and-tie systems if the same bars are straight. In the former case, a proper introduction of the bond along the tension bars of the corbels is a must to define the position of bond-related joints and to make strut-and-tie models more reliable in predicting the bearing capacity, while in the latter case, the design equations provided by the codes for constant-section shear-unreinforced beams (ACI 318, EC2, and fib Model Code 2010) prove to be adequate also in the case of corbels.