STORAGE AND DISTRIBUTION. 



147 



7 14 I ^O 



x - x 7*c x -^ 



12 12 112 



equal, say, 7 cwt. If the external load is worked out 

 it will be found to be about no cwt. on each beam. 



Stirrups 



3% Rods 



FlG. 114. 



On the 7 in. x 14 in. beams over the span in 

 question, the safe load is found as follows : 



= '37 X 1-3 + -214 ( ;x * 4 * I4 )=i28 cwt., 



which is ample ; p being the safe stress intensity in 

 Ib. per sq. in. = 1 50 

 = i '3 cwt. 



The method of as- 

 certaining the thrust 

 on the walls due to 

 the arch, and if such 

 walls will withstand 

 that thrust, is shown 

 in fig. 1 1 6. Find the centre of gravity of the arch 

 and the load above at A. Drop a perpendicular 

 AB, and from the top of the middle third at the 

 crown draw a horizontal line to cut AB in C. Join 

 C to the bottom of the middle third at the abut- 

 ment. Find the weight of the arch (at 1 50 Ib. per 

 ft. cube) and the load above (at 112 Ib.) and set 

 off from C, CB equal to that load. Complete the 



