COLUMNS AND STRUCTURES 293 



an arch. That is why the arch is not assumed to act unless the 

 wall across the break has depth enough to insure it acting as a 

 beam to span the opening. 



In the three cases, therefore, the lower lintels must be designed 

 to carry the area of wall shown between the dotted lines, and the 

 lintrls for the upper openings are designed to carry the small 

 shaded triangular areas at /> and C and the rectangular area 

 shown at the top at A. 



A few things pertaining to the design of buildings have not been 

 discussed because they are to be found in the steel and lumber 

 handbooks, without which no designer can work. With the 

 assistance of those books the student should have no difficulty 

 in handling all the ordinary problems arising in the design of 

 structures. It is hoped that the application of the MOMENT 

 has been treated so consistently throughout this book that the 

 student will have no difficulty in analyzing any problem that 

 may come up in his work. 



