At 0.5% drift, cracks in the concrete corbels opened and gradually evolved under cyclic reversals. Crack width and length increased with increasing drift amplitudes, propagating from the steel dowels to approximately midheight of the corbel. This mechanism resulted in a partial expulsion of the corner of the corbels at the first two floor levels. A similar damage pattern developed at the top floor (Fig.10), causing the concrete to crush at the interior side of the columns. A slightly less inclined crack was observed in the latter case because the beams were directly seated on the tops of the columns, and, hence, no restraint was provided between the bottom face of the beam and the edge of the column, thus varying the inclination of the resulting struts. By contrast, in the former case, the beam-column gap had to be taken up before the end of the beam made contact with the side of the column, resulting in a delay in the load pickup. After a relative horizontal displacement of about 15 mm (0.59 in.), the rotation at the end of the beam was restrained by the edge of the column, resulting in a stress concentration on the column or an additional demand on the connection, depending on the direction of the loads. In actual structures, this behavior is expected to be worse if diaphragms are grouted with a cast-in-place concrete topping.