COKRESPONDENCE. 



161 



James Yicars, b.c.e. — Since the discussion on Professor 

 Warren's Paper, I have prepared the diagram given on Plate 16, 

 to show more clearly the manner in which the loads are trans- 

 mitted through the various members of the truss to the points of 

 support. The forces acting at each apex, due to the dead load, 

 are resolved in the directions of the several members meeting at 

 these points, in accordance with the principles of the parallelogram, 

 or rather triangle of forces. The diagram shows a portion of 

 load (1) transmitted to the right support, B, through Z 2 and Y 2 , 

 the direction of their resultant stress being a line from their 

 apex to B; a portion of load (2) together with the vertical 

 component of Y< 2 transmitted to B through Z A and Y 3J the line 

 from their apex to B being the direction of their resultant stress ; 

 and similarly that all loads transmitted to B pass through mem- 

 bers of the system Y 2 , Y s , Y 4 , Y 5 and 1~ 6 , while all loads 

 transmitted to A use members of the other system Y 7 , Y 8 , Y 9 , 

 Y x and Y x x ; but since the diagonals are not connected up, the 

 stresses in members of the one system cannot affect the stresses 

 in members of the other system. The maximum stress on Y s 

 obtained by this method, with live loads at V 1 and V a is 

 (3*1 + 6-3) due to dead load and (4 + 7*8) due to live load, or a 

 total of 21 2 tons against 21*19 tons given in the paper. The 

 stresses on the various members obtained are given in the table 

 appended, which agrees generally to the first place of decimals 

 with those given in the paper. 



Table of Stresses for Dead Loads. 



Bar. 



Stresses obtained by triangle of forces. 



Stresses given 

 in paper. 



Stresses. 



Total. 



x x 



V93-4 







x 2 

 x 7 



x s 



93-4 



93-53 



x, 



x 6 



| 93-4 + (15-7 -13-4) 



95-7 



95-88 



x, 

 x 5 



J 95-7 + (8-1 -8-1) 



95-7 



95-85 



z x 



z* 



i 22 5 + 56-7 + 26-5 



105-7 



106-08 



Zi 

 Zi 



i 22-5 + 56-7 + 11-4 



90-6 



90-77 



z, 

 z* 



1 17 + 34 + 14-7-1- 7-4 



73-1 



73-22 



\z± 



\z 6 



| 17-6 + 26-6 + 15-7 + 159 



75-8 



76-28 [ 



K— September 3, 1890. 



