Art. 136. 



STRESSES IN A BALTIMORE TRUSS. 



265 



The one of these two values which is the greater is the one to 

 be used. It depends upon the relation of the live load to the 

 dead load. 



The live load coefficients are shown in Fig. 192. Having 



Us 24 



L 5 11 L 6 10 L 7 9 L s 8 7 6 

 Live Load Coefficients 



Fig. 192. 



all of the coefficients, it is a simple matter to find the stresses. 

 The following loads will be used in figuring the stresses: 



Weight of trusses and bracing =2200 Ibs. per ft. of bridge. 

 Weight of floor system =1100 Ibs. per ft. of bridge. 



Total dead load =3300 Ibs. per ft. of bridge. 

 Live load =4000 Ibs. per ft. of bridge. 



From these we get the following constants : 



Dead load panel load = X20 =33,000 Ibs. 



Live load panel load = =X20 =40,000 Ibs. 



_|X2200 

 5 ' 3300 

 Diagonal length =64.03 ft. 



,. 64 



sec tr= . 



50 



40 



tan 0= =0.8. 



D' 



D 7 - 



(74 



(7 



( * 



(5i 



(5 



(31 



(3 



(lJ 



X 33,000 + 74 X 40,000) sec =700,800 Ibs. 

 X 33,000 +7 X40,000) sec =654,000 Ibs. 



X33,000 -f \ X40,000) sec = 46,700 Ibs. ( +) 



X 33,000+ f^X 40,000) sec 0=523,500 Ibs. (-) 



X33,000+f|X40,000) sec (j =476,800 Ibs. (-) 



X33 ; 000+ff X40,000) sec 0=359,000 Ibs. (-) 



X 33,000+ f|X 40,000) sec 0=312,300 Ibs. (-) 



X 33,000 +ff X 40,000) sec 0=207,400 Ibs. (-) 



X 33,000 +fjX 40,000) sec = 160,600 Ibs. (-) 

 =,]j' s = (i x 33,000 + 4 X40,000) sec =46,700 lbs.( -) 



