In recent years, proprietary systems have been developed that address the above problems.  This bolt-on corbel has a capacity of up to 1500 kN.  A serrated plate cast into the column matches serrations on the corbel.  It allows the mould to be simple, but still requires treatment to provide fire resistance. 

Other heavy duty systems consist of a steel box cast into the end of the beam.  Inside this is a steel, loadbearing, plate or ‘knife’.  During erection, the knife is extended beyond the beam to engage in a corresponding box in the column face.   The complete assembly is then grouted to give protection against fire and corrosion.  Capacities go up to 950 kN.  Since the load is applied at the column face, the induced moments in the column are considerably lower than for corbels or billets having a higher eccentricity.   This can be a considerable advantage when designing the column, allowing a more slender section.

The main advantage of both these systems is that they do not require work on the column mould, and result in a simpler section.   The three-storey columns shown below are considerably lighter from not having corbels.