Used in a graphical analysis of a joist or joist girder. It is a notation for denoting truss joints, members, loads, and forces. Capital letters are placed in the spaces between truss members and between forces. Each member and load is then designated by the letters on opposite sides of it.
Found on http://www.areforum.org/up/GeneralStructures/JOIST%20AND%20STRUCTURAL%20GLO
No exact match found