174 QUESTIONS AND PROBLEMS. CHAPTER VIII. 



and maximum shear in the crane-runway girder of 20 ft. span. 

 The wheel base is 9 ft. and the load on each wheel is 90000 Ibs. 



Ans. 540000 ft. Ibs. and 139500 Ibs. 



27. Find the maximum moment and maximum shear in a 

 beam of 19 ft. span for a live load of four equal wheel loads o 

 40000 Ibs. each, the distances center to center of wheels being 5 ft. 



Ans. 373200 ft. Ibs. and 96800 Ibs. 



28. What is the maximum live load moment in a girder 

 of 100 ft. span for a uniform live load of 2575 Ibs. per ft.? 

 What is the maximum live load moment at 25 ft. from a support? 



29. In the preceding problem, what is the shear at 25 ft. 

 from the support for the same loading which gave the maximum 

 moment at this point? What is the maximum live load shear at 

 this point? 



30. In the preceding problem, find the maximum shear and 

 maximum moment at 25 ft. from the support when the live load 

 is combined with a uniform dead load of 760 Ibs. per ft.? What 

 is the maximum shear in the girder in this case? 



31. A continuous girder has two spans of 40 ft. each; the 

 dead load is 600 Ibs. per ft. and the live load 3000 Ibs. per ft. 

 Will it be a continuous beam when the live load covers one arm, 

 if it is impossible to have a negative reaction at the ends? See 

 Figs. 108 and 109. 



32. In the preceding example, what will be the dead-load 

 shear at 20 ft. from the end? What the maximum positive and 

 negative live-load shears at tho ends? 



Ans. -3000 Ibs. +52500 Ibs. - 7500 Ibs. 



33. In the above example, what will be the maximum posi- 

 tive and negative moments. at 20 ft. from the end? 



Ans. +540000 ft. Ibs. -180000 ft. Ibs. 



34. At what point on ths girder of problem 31 must a 

 concentrated load stand to produce zero moment at 36 ft. from 

 the left support? Ans. 2.98 ft. from left support. 



35. In Fig. Ill, what must be the value of k for a maxi- 

 mum moment at the middle support? 



Ans. fc = v'J 



36. If in Fig. 112 there is also a load P at a distance Id 

 from A', will all the reactions be positive? 



