Short Members

Detailing short beams and short cantilevers can be problematic, as lap lengths may become longer than the actual span. The solution is to create Design Super Members. This approach can also be used to reduce the amount and complexity of reinforcement.

In the ground-beam arrangement shown below, members 2, 5, 7 & 17 are clearly analytical elements. The following super members would significantly simplify and improve the design;

Super-member 1 : M2   + M3 Super-member 2 : M5   + M6 Super-member 3 : M7   + M8 Super-member 4 : M14 + M17   You could go one stage further and for example design members M1, M2 & M3 as one super member even though you clearly have two design members.  This would have the advantage of simplifying the reinforcement, especially if the overall spans are short.

Points of caution to note regarding super members are:

•Links will not stop either side of the internal support.

•You can not redistribute moments at the internal support.