Art. 169. 



PORTAL WITH SIMPLE X BRACING. 



D'= 26,400 + 16,700= 43,100 



M 2 = 9,700X4.75 = 46,000 in. Ibs. = 3,830 ft. Ibs. 

 M 2 f =43,100X4.75 =205,000 in. Ibs. =17,100 ft. Ibs. 



13,270 =M 2 '-M 2 



From equation (173) 



H = 10,000 -5,560 =4,440 Ibs. 

 3830 



X 1 = 



4440 



,, 

 =0.86 ft. 



5560 



2d Trial: 



M^= 9,900 as before. 

 M/= (26,400 + 16,700) =16,200 ft. Ibs. 



From equation (174) 

 V =-J [10,000(28-0.86) -5,560(3.07-0.86) +26,100] 



= 16,600 Ibs. 



D= 26,400 -16,600= 9,800 Ibs. 

 D' =26,400 + 16,600 = 43,000 Ibs. 

 M 2 = 9,800X4.75 = 46,500 in. Ibs. = 3,880 ft. Ibs. 

 M 2 ' =43,000 X4.75 =204,000 in. Ibs. =17,000 ft. Ibs. 



13,120 =M 2 '-M 2 



H =10,000 X 5,550 =4,450 Ibs. 

 3880 _ , 



5550 



These values differing so little from those of the first trial 

 shows that they are close enough for practical purposes. 



