86 STANDARD SPECIFICATIONS 



358. Spacing of Reinforcement: 



(a) Slabs. The minimum spacing of parallel bars shall not be 



less than 3 in. Two layers of bars perpendicular to 

 each other shall be in contact, the bars forming the 

 main reinforcement being in all cases placed under- 

 most. 



(b) Beams and Girders. The minimum distance from the 



center of any bar to the edge of beam shall be 2 diam- 

 eters, or 1J in. The minimum distance c. to c. of 

 any bar in the same layer shall be 2J diameters for 

 round bars and 3 diameters for square bars, and not 

 less than 2 diameters between centers of bars in different 

 layers. The longitudinal spacing of stirrups or bent 

 rods, where used, shall not exceed three-fourths (j) 

 of the depth of the beam. 



(c) Columns. In columns having longitudinal reinforcement 



only, the rods shall be securely tied together at inter- 

 vals not exceeding 20 diameters of rods. In columns 

 having circumferential reinforcement the clear spacing 

 of such shall not exceed one-fourth () the diameter 

 of the inclosed column. 



The circumferential reinforcement shall be securely 

 held in position by means of spacing bars, or other 

 adequate means. 



359. Fireproofing. The minimum thickness of a fire-retard- 

 ing coating, covering the reinforcement, shall be as follows: 



For slabs, not less than 1J diams. of rods, or f inch 

 " beams, " 1J , or 1J " 



" girders, " 1J , or 1J " 



" columns, " 1 , or 1J " 



" columns having no reinforcement, 2 " 



The above coverings shall not be considered as effective area; 

 they shall be made of concrete in which no limestone is used, 

 but in which the coarse aggregate may consist of hard-burned 

 cinders or other material that will resist high temperatures. 

 All aggregates shall be so small that the reinforcement is thor- 

 oughly covered, leaving no voids or cracks. 



For further fire-resisting purposes all external angles shall be 

 either beveled or rounded. 



