92 



CAMBRIA STEEL. 



REINFORCED CONCRETE FLOOR SLABS. 



Axis 



NOTATION. 



w= Total weight in Ibs. per sq. ft. including slab weight. 



L = Span in feet c. to c. of beam supports. 

 M = Bending Moment for 12" width of slab (inch pounds). 

 EC = Modulus of Elasticity for concrete. 

 Es= " " " " steel. 



r = Ratio. Es -r EC. 



C = Extreme fibre stress of concrete in compression. 



S = " steel in tension. 



K = Constant for a given steel and concrete. 



d = Effective depth of slab in inches. 



p = Ratio of steel area to effective slab area. 



x = Distance, Top of slab to Neutral Axis *- d. 



j = " between centers of stress -j- d. 



V = Maximum Shear, 12" width of slab. 



v = Unit shear. 



u = Unit bond stress. 

 So = Sum of perimeters of bars (hi 12" width of slab). 



FORMULAE. 



M = 1.5 wL 2 for slabs freely supported. 



= 1.2 wL 2 " " continuous over supports. 



P 



2S(Cr + S) 



Sp /2Cr + 3S\ 

 = ~~ 



M Steel Area (12" width of slab) = 12 dp 



12 K 

 y 

 v = 12 . d (not to exceed GO Ibs. for stone or 25 Ibs. for cinder concrete). 



u = . . - (not to exceed 60 Ibs. for stone or 30 Ibs. for cinder concrete). 

 For Square and Round Bars, refer to pages 451-457. 



NOTE. Best practice indicates that Spans of Floor Slabs should not ex- 

 ceed seven feet between steel beams or steel girders. Generally speaking, 

 the span should in no case exceed 10 feet for ordinary work. 



