CHAPTER VII 

 SLAB, BEAM, AND COLUMN TABLES 



72. Illustrative Problems. Some of the illustrative problems 

 of preceding articles will be partly worked out under this heading 

 to show the amount of numerical computations which may be 

 avoided by the use of tables. Working stresses recommended 

 by the Joint Committee will be employed throughout. 



1. Design a rectangular beam to span 40 ft. and to support 600 Ib. per 

 foot (including weight of beam). Beam is assumed to be simply supported. 



From Table 2, f or n = 1 5, f a = 16,000, and / c = 650. 



K = 107.4 



Assume 6 = 18 in. 



18 



Area of cross-section, 6d = (18)(27.5) =495 sq. in. 

 a a = (495) (0.0077) =3.81 sq. in. 



We shall select four l|-in. round rods = 3.98 sq. in. (See Table 1 or 

 Table 13.) 



To make clear the method of reviewing beams, let us review the beam 

 we have designed. 



From table 3, for this value of p, 



A; = 0.384 j = 0.872 

 Then, 



1,440,000 

 /a = (3^8H0.872)(27.5) = 15 ' 100 lb " per SqUare mch 



,. (2) (15, 100) (0.0080) 



fc = = 630 Ib. per square inch 



U.oo4 



Column 4 of Table 3 shows that/ s =15,600 when/ c =650. 



*Table 8 could also be used in the design of above beam. 



Table 3 may be employed to find minimum allowable depth of beam for 

 a given percentage of steel and various assumed widths. Also, this table 

 may be employed to determine the amount of steel for a beam with given 

 loading, the stress in the concrete being limited to 650 Ib. per square inch 

 and the stress in the steel to 16,000 Ib. per square inch. 

 14 187 



