These beams are more efficient than having two side-by-side simple beams. If the length of cantilever L, - 0.172L (where L is the span length), then magnitudes of positive and negative moments will be M,- M- My- 0.086wL' which is less than the maximum moment Mna= wL18 = 0.125wL in a simply-supported beam. COLUMN HINGE CANTILEVER BEAM SYSTEM FRAMING PLAN CANTILEVER PORTION SUSPENDED SMne BEAM PTON COLUMN CONNECTION SECTION urORM LOAD teCANTILEVER LENOT SMPLE BEAM MOMENT FOR COMPARISON M M O Ar INGE Figure 6.25 Twospan eantilever heam aystem. Cantilevered beams are not recommended for floors because of difficulty with cambering and transfer of vibrations from one span to the other span. AITC recommends the use of simple beams for floors. 10 bonus points towards homework: For the two-span cantilever beam (shown above) under uniform load, show that when L =0.1721, M,= M;= M;=0.086wL?. Also, draw the shear and moment diagrams. Due next Friday (Oct. 12).