44 s PROBLEMS 



PROBLEM 18. DEAD LOAD STRESSES IN A WARREN TRUSS BY GRAPHIC 



RESOLUTION. 



(a) Problem. Given a Warren truss, span I2o'-o", panel length 

 2o'-o", depth 2o'-o", dead load 700 Ibs. per ft. per truss. Calculate 

 the dead load stresses by graphic resolution. Scale of truss, i"-i6'-o". 

 Scale of loads, i" = 12,000 Ibs. 



(b) Methods. The loads beginning with the first load on the 

 left are laid off from the bottom upwards. The calculation of the 

 stresses is started at the left reaction, and the stress diagram is closed 

 at the right reaction. For additional information on the solution see 

 page 70. 



(c) Results. The top chord is in compression, the bottom chord 

 is in tension ; all web members leaning toward the center of the truss 

 are in compression, while the web members leaning toward the abut-, 

 ments are in tension. All web members meeting on the unloaded chord 

 (top chord) have stresses equal in amount but opposite in sign. The 

 stresses in the lower chord are the arithmetical means of the stresses 

 in the top chord. The Warren truss is commonly made of iron or steel, 

 the most common section for the members being two angles placed back 

 to back. 



PROBLEM i8a. DEAD LOAD SRESSES IN A WARREN TRUSS BY GRAPHIC 



RESOLUTION. 



(a) Problem. Given a Warren truss, span i26'-o", panel length 

 i8'-o", depth 2o'-o", dead load 700 Ibs. per ft. per truss. Calculate 

 the dead load stresses by graphic resolution. Scale of truss, l" = 

 i5'-o". Scale of loads, i" = 12,000 Ibs. 



