GRAPHIC CALCULATION OF STRESSES 93 



puted by applying wind loads at the points above referred to, the wind 

 loads being equal to the total wind loads divided by the number of 

 panels. The stresses are computed as in a cantilever truss. The brac- 

 ing in the plane of the lower chord is designed to prevent undue de- 

 flection of the end columns and to brace the lower chords of the trusses. 

 All wind braces should be designed for, say, 5,000 pounds initial stress 

 in each member, and the struts and connections should be proportioned 

 to take the resulting stresses. 



It should be noted that a mill building can be braced so as to be 

 rigid without knee braces if the bracing be made sufficiently strong. 



GRAPHIC CALCULATION OF STRESSES. Data. To il- 

 lustrate the method of calculating the stresses in a transverse bent by 

 graphic methods, the following data for a transformer building similar 

 to one designed by the author will be taken. 



The building will consist of a rigid steel frame covered with cor- 

 rugated steel and will have the following dimensions: Length of 

 building, So' o"; w r idth of building, 60' o"; height of columns, 

 20' o"; pitch of truss, % (6" in 12"); total height of building, 

 35' o" ; the trusses will be spaced 16' o" center to center. The trusses 

 will be riveted Fink trusses. Purlins will be placed at the panel points 

 of the trusses and will be spaced for a normal roof load of 30 Ibs. per 

 square foot. The roof covering will consist of No. 20 corrugated steel 

 with 2^-inch corrugations, laid with 6-inch end laps and two cor- 

 rugations side lap, with anti-condensation lining (see Chapter XVIII). 

 The side covering will consist of an outside covering of No. 22 corru- 

 gated steel with 2^/2 -inch corrugations, laid with 4-inch end laps and 

 one corrugation side lap ; and an inside lining of No. 24 corrugated 

 steel with I ^4 -inch corrugations, laid with 4-inch end laps and one 

 corrugation side lap. For additional warmth two layers of tar paper 

 will be put inside of the lining. Three 36-inch Star ventilators placed 

 on the ridge of the roof will be used for ventilation. The general ar- 

 rangement of the framing and bracing will be as in Fig. I and Fig. 8l. 



