COLUMNS FIXED AT THE BASE 



87 



Having the stresses K, U , and L, the remaining stresses in the 

 truss can be obtained by ordinary algebraic or graphic methods. 



For a simple graphic solution of the stresses in a bent for Case I, 

 in which these stresses are computed graphically, see Fig. 54 for wind 

 horizontal, and Fig. 56 for wind normal to all surfaces. 



Case II. Columns Fixed at the Base. With columns fixed 

 at the base the columns may be (i) hinged at the top, or (2) rigidly 

 fixed to the truss. 



(i) Columns fixed at the base and hinged at the top. It will be 

 further assumed that the deflections at the foot of the knee brace and 

 the top of the column, Fig. 52, are equal. 



<---t 14- S 



'WTI^H"*" ~fi-r "f'H 



i (a) i i/ b) 



(a) 



External Forces 



H 1 



<c\ 

 Leeward Col. Beam 



FIG. 52. 



H' 



(d) (e) 

 5hear Moment 



In Fig. 52 we have as in Case I 





V and F 1 are not as easily found as in Case I, but will be cal- 

 culated presently. 



The leeward column will be considered and will have horizontal 

 external forces acting on it as shown in (c) Fig. 52. For convenience 

 we will consider the leeward column as a beam fixed at a and acted 

 upon by the horizontal forces B and C as shown in (c) Fig. 52, the de- 

 flection of the points b and c being equal by hypothesis. 



From the fundamental condition of equilibrium, summation hori- 

 zontal forces equal zero, we have 



B = H 1 + C (31) 



