RECTANGULAR BEAMS 



117 



may be considered secure against slipping. Stirrups are unnecessary at a 

 distance from the center of support equal to 



_ 1 _ (40) (7) (0.865) (11. 5) 

 *i~T~ "695 



= 5-4.0=1.0 ft. = 12 in. 



The minimum spacing of stirrups will occur at the supports and will be equal 

 to 



(3) (2) (0.049) (16,000) (0.865) (1 1.5) 



= 6.7 in. 



(2) (5) (695) 



The stirrups are needed for such a short distance from each end of the beam 

 that two stirrups near the ends will suffice, as shown in Fig. 54. 



Perhaps we may be able to provide web reinforcement by means of bent 

 up rods. Let us investigate. 



The total stress to be taken by the inclined rods is represented by the 



. 4 



Center Line of Support 



FIG. 54. 



triangle ABC, Fig. 55. <7 represents two-thirds of the horizontal shear 

 at the support per 1-in. length of beam. 



BC = -- =-- = - (695 X 5 ) 

 3 bjd 3 ^'d 3 " (0.865) (11. 5) 



r = (0.7)(AZ>) = (0.7)(12) =8.4 in. 

 Hence total stress to be taken by the rods 



= 233 Ib. 



But the area of one rod multiplied by 16,000 gives its tensile value, or 



tensile value of one rod = (0.250) (16, 000) =4000 Ib. 



Thus, only one bent up rod is required. For the two straight rods the 

 maximum bond stress 



U = (2) (4) (0.5) (7/8) (11. 5; =86 lb ' per square inch ' which is 

 factory. 



in / t \ 



^\l-\fTjZ\ =2.12 ft. 



