CAMBKIA STEEL. 



93 



REINFORCED CONCRETE FLOOR SLABS. 



Values deduced from formulae, page 92, using unit stresses based 

 on modern safe practice. 



THICKNESS OF CONCEETE BELOW STEEL. 



SPACING OF REINFORCING BARS. 



The lateral spacing of parallel bars should not be less than two and one-half 

 diameters, center to center, nor greater than 2^ X thickness of slab; nor 

 should the distance from edge of slab to center of nearest bar be less than one 

 and one-half diameters. The clear spacing between two layers of bars should 

 not be less than one-half inch. 



Cross reinforcement of steel rods of small diameter (W) laid parallel to 

 the principal beams upon which the slab rests, should be used to prevent 

 shrinkage and temperature cracks and to give added strength. They should 

 be spaced about two feet, center to center. 



DISTRIBUTION OF LOAD FOR SLABS OF FOUR SIDES SUPPORT. 



Where length of slab exceeds 1.5 width, the entire load should be carried 

 by transverse reinforcement. Slabs of smaller ratio of dimension may well 

 be reinforced in both directions. Distribution of the load may be determined 

 by use of the formula 



in which r = proportion of load carried by transverse reinforcement, 1 = 

 length and b = breadth of slab. 



Using values thus determined, each set of reinforcement is to be calculated 

 as in slabs having two supports only. 



NOTE. In all cases of two-way reinforcement, intersections of rods should 

 be securely tied with heavy wire. 



