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Concrete cracks when it is restrained to conract, or expand. We all kow that. But, I never imgained that the failure to give due regard to cater for this property of concrete at deisgn phase can lead to grave consequences. A structure was provided expansion/seismic joint at a distance of about 200ft. It is normal practice to do that. But normally, two columns are provided at the joint to suport end-spans. But, in this case, the end panel was supported on corbel which was attached to the column loacated next to exapnsion/contraction joint. Floors of the building contracted, approximately, 4 months after the pour. This resulted in the damage of corbel, or the beams supported on corbel. Damage to two corbels was limited to the spalling of concrete, as depicted in attached pictures. In two joints, end of beams also cracked along with the corbel. A part from contraction of concrete, observation also shows the importance of frictional forces. There is a huge opening at one of floor. Could this lead to un-equal contraction of floors, leading to an increase in stresses? What could have been done to improve the performance? Any ideas.

Teflon plates would do a much better job. The connection at corbel in that case would be bearing only. Thanks.

IMHO, the solution was not hard at all. Just smoothing of top bearing surfaces of the corbels, and provision of double layer of good quality building paper over them, would have avoided the damage observed.