166 REINFORCED CONCRETE CONSTRUCTION 



Hence, from formula in Art. 63, the length of haunch 



220,000 , 10 



Since maximum negative moment occurs in middle of column and 

 necessary length of haunch is only 4.75 in., no haunch will be introduced 

 outside of the column. 



PROBLEMS 



53. Determine the economical depth of a T-beam in a floor system. Thick- 

 ness of floor slab is 4 in. Maximum shear = 16,000 Ib. Maximum 

 moment = 600,000 in.-lb. Assume the ratio of unit cost of steel to 

 cost of concrete = 60. Use working stresses recommended by the 

 Joint Committee. 



54. A T-beam has the following dimensions: 6=48 in., t = Q in., d = 22 in., 

 and b' = 10 in. the steel consisting of six 3/4-in. round rods. Take 

 f 8 = 15,000, / c =600, and ft = 15. What is the safe resisting moment 

 of the beam? 



55. Change t of Problem 54 to 4 in. and find the safe resisting moment. 



56. Make a complete design of a T-beam with span of 30 ft. Live load = 

 3800 Ib. per foot. Assume dead load = 1000 Ib. per foot. The beam 

 is simply supported and the flange does not form a part of a floor 

 system already determined. Use working stresses recommended by 

 the Joint Committee. Take 6' = 17 in. and t = W in. Select required 

 steel area from 1 1/8-in. and 1-in. round rods. 



57. A beam of which 6 = 14 in. and d = 20 in. has 2 per cent of tensile 

 steel and 1 per cent of compressive. What is the safe resisting moment 



of the beam? Assume , =0.1 and use stresses recommended by the 



Joint Committee. 



58. Suppose the beam in Problem 57 were subjected to a bending moment 

 of 1,500,000 in-lb.; what would be the resulting fiber stresses, f c , / s , 

 and/%? 



59. Suppose the conditions met in Problem 58 occurred at the supports 

 of a continuous beam with equal spans of 30 ft. Design the necessary 

 haunch. Take d = 23 in. 



