108 REINFORCED CONCRETE CONSTRUCTION 



equal to the diameter of the rod. There is likely to be more or 

 less tension in the concrete surrounding the rods and, besides, 

 since the concrete is not easily placed between the rods, it may 

 have a lower strength in that vicinity. A clear spacing of 1 1/2 

 diameters is advisable unless it is determined by computation 

 that the bond stress is very much lower than the bond strength 

 allowed. In the above discussion plain rods only have been 

 considered. Deformed bars, if stressed to their full bond value, 

 should be spaced farther apart than plain bars. 



For a beam uniformly loaded, the bond stress near the center 

 of the beam is low and the bars may be placed as closely together 

 as the proper placing of the concrete between them will permit. 

 Near the end of beam the bond stress should be calculated if it is 

 desired to space the rods so as to obtain the minimum width of 

 beam possible. In beams having the horizontal rods bent up, 

 the bond stress at the bending points should be considered. 

 This stress may be less than the maximum and, if so, the corre- 

 sponding spacing may be made less than 11/2 diameters in the 

 clear. With rods bent up, more liberal spacing can readily be 

 made toward the end of beam. 



The Joint Committee recommends that "the lateral spacing 

 of parallel bars should not be less than 21/2 diameters, center to 

 center, nor should the distance from the side of the beam to the 

 center of the nearest bar be less than 2 diameters." In order 

 that concrete may be readily placed between the rods and also 

 give sufficient concrete on the sides of the beam for fire protection, 

 it is also advisable to require that the spacing of rods be not less 

 than 1 in. in the clear (if the maximum size of aggregate does not 

 exceed 1 in.) and that 1 in. in the clear be also considered the 

 minimum distance of the rods from the sides of the beam. Thus, 

 the least width of beam should be the greater of the two values 

 determined from the following formulas: 



in which 6= least width of beam. 

 d i = thickness of the rods. 

 n = maximum number of rods which occurs in a hori- 



zontal layer. 

 a g maximum size of aggregate in inches. 



It should be clear that, for a 1-in. maximum aggregate, the width 



