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PRACTICAL STRUCTURAL DESIGN 



The stress in the braces increases from the ends to the center, 

 as in the case of the Queen truss, and may be figured the same 

 way. The vertical rods at the joints are in tension and the braces 

 are in compression. The center panel is usually as wide as the 

 height, which decreases the angles at which the braces are set 

 as they approach the ends. 



Steeply pitched roofs of the Howe truss type may be figured 

 by the method of coefficients when the loads are uniform and 

 symmetrically placed. They may be figured by the cumulative 

 load method or by the shear method when unsymmetrically or 



.4P W 



Fig. 85A. (a) King Truss: (6) (c) (d) Queen Trusses, 

 irregularly loaded. In Fig. 85A the truss with one vertical is 

 a King truss. When the vertical is a post it is a King Post truss 

 and when the vertical is a tie it is a King Rod truss. At (6) and 

 (c) are shown Queen trusses, these being known by the number 

 of panels into which they are divided and, like the King truss, 

 being Queen Post or Queen Rod trusses, as the verticals may be 

 posts or rods. 



In a system of roof framing all longitudinal members are called 

 purlins and all members extending from the eaves to the ridge 

 are rafters. The top chord of a truss is composed of rafters. 

 Main purlins extend from truss to truss, resting on the joints at 

 the upper ends of verticals. Intermediate rafters rest on the 

 main purlins when the spacing between trusses is considerable 

 and across the rafters sheathing is placed to carry the roof cover- 

 ing. By so doing all loads are concentrated at the upper ends of 

 the verticals, so the truss rafters (upper chord) are in compres- 



