250 STRESSES IN PRATT TRUSS BY COEFFICIENTS. Art. 130.^ 



Chord Stresses. 



7 2 = 1JX 5,400=+ 7,200 D. L. 

 =^_o X 14,400= +20,600 L. L. 



+27,800 Total. 



7 3 = JX 5,400=+ 1,800 D. L. 

 = f x 14,400=+ 12,300 L. L. 



+ 14,100 Total. 



L l =L 2 =3Ptand=3x 4,630 = - 13,890 D. L. 

 =3P tan =3 X 12,340 = -37,020 L. L. 



-50,910 Total. 



-L 3 = + 7 2 =5P tan 6 =5 X 4,630 =23,150 D. L. 

 =5P ton 6 =5 X 12,340 =61,700 L. L. 



84,850 Total. 



= 6Pto#=6X 4,630 =27,780 D.L. 

 = 6P tan 6 =6 X 12,340 =74,040 L. L. 



101,820 Total. 



If it is not required to keep the dead and live load chord 

 stresses separate, the total may be gotten by one operation. 



t* 



LL 



(l-q)P +8 (l3?)P (ifyP (1W (1*)P 



i P 1-2 of L 8 P L 4 







8 Equal Panels 



Fig. 184. 



A truss diagram with stresses marked on the members is 

 called a stress diagram. Sometimes only the total stresses are 

 given and sometimes both dead load and live load stresses. 

 The character of each stress must be indicated. 



When the total stress is to be an equivalent static stress, 

 the live load stress must be kept separate from the dead load 

 stress until the impact stress has been added, as this is usually 

 a certain percentage of the live load stress. (88.) (5.) 



Fig. 184 shows a Deck Pratt truss with the coefficients 



