Art. 136. STRESSES IN A BALTIMORE TRUSS. 



261 



the effective length of the top chord as a column (113), and 

 also reduces the bending moment due to its own weight (115). 

 The dead load coefficients shown in Fig. 191 are obtained as 

 follows. 



It is evident that panel load 15 is equally divided at 17, 

 and is carried downward to the right and the left. The half 

 panel load carried to the right is added to load 14, making the 

 coefficient of Vi, (1^ q). 



The shear in panel 14-15 is 7^ 1=6^, and it is resisted by 

 the algebraic sum of the vertical components of the diagonals 

 in the panel which is 7 ^ =6^. 



Since D 3 , D 5 , and D 7 are the only diagonals in action in 

 their respective panels, their coefficients are the shears in these 

 panels, namely 7^ 2=5^, 7 4=3, and 7^ 6 = 1. Writing 



s. 



~_7 ~ 



-^i + <1- 



15 ft 14 ft 13 ft 12 9: 11 ft 10 a- ft 8ft 7ft Oft 6ft 4ft 3 ft 2 ft. 



rujri-s .7 .? ,,<? , |r , , +? 



Li_ __^_ ll=L_ _I li__ f A__ -i LtJlcL T ^ 



Dead Load-Coefficients 

 Fig. 191. 



the horizontal and vertical resolution equations at joints 19, 

 21, or 23, as was done in Fig. 190, it is found that the sub-panel 

 loads coming to these points are divided and carried upward 

 so that the coefficient of each sub-diagonal is \. 



Now the coefficients for the diagonals in those panels having 

 two diagonals may be gotten, for we know that the upper one 

 carries a half panel load. The shear in panel 12-13 is 7^ 3 = 

 4J, and is resisted by the algebraic sum of the vertical com- 

 ponents of D\ and Z) 4 . Since these act in opposite directions, 

 and that of D' 4 is J, that of Z) 4 must be 5. Looking at it in 

 another way, it is known that one-half the load at 13 is carried 

 by D' 4 ; then the shear carried by D 4 is 7J-2i=5. In a sim- 

 ilar manner, the shear resisted by D G is 7^ 4^=3, and by D 8 

 is 71 -6^ = 1. 



The same results may be obtained by taking resolutions at 

 joints 19, 21, and 23. 



