COLUMNS AND STRUCTURES 



Cantilever Footing 



The subject of cantilever footings is very simple, although a 

 number of students seem to find it difficult. In Fig. 179 the 

 column on the right is against a wall, or property line, and the 

 footing must be kept within the limits of the property. The 

 first line of interior columns 

 must, therefore, help out the 

 wall columns. First find the 

 proper size of footing under 

 each line of columns. The 

 outside footing is arranged so 

 the outer face is even with 

 the lot line. The load P, com- 



ing down the wall column, acts | !i If I 



at the center of the column Fig. 179 -Cantilever Footings 



and the distance to the center 



of the footing gives the moment due to eccentric loading, thus 

 M = Pa. 



Divide this by the load in the interior column to obtain the 

 eccentricity 6. The footing under the interior column is then 

 so located that the center of the footing will be distant 6 feet 

 from the center line of the column. Thus, 



Pa 

 o - p" 



To transfer the loads from the columns to the centers of the 

 respective footings the columns rest on a girder having a resist- 

 ing moment M r = A/6 - Pa = P'b. The girder must also be de- 

 signed for deflection, as a cantilever at each end, and for shear 

 which is usually very high. 



"Foundations of Bridges and Buildings," by Jacoby and Davis, 

 price $7.50, is the best book on the subject with which the writer 

 is acquainted. The student is advised to consult it if he needs 

 more information on this im|K>rtant subject. 



Stresses in Towers 



A tank tower, or any braced tower or pole, may be designed 

 as a vertical cantilever l>eam or truss. 



The vertical load, consisting of the weight of the water, tank, 

 and framework, is transmitted directly to the foundations through 



