LXV. 



294*15 

 Stress per sq. in. flanges = * = 10*21 tons per sq. in. 



28"8 



Shearing stress — 



Area of Web = 117" x §" = 44 D " 



229 

 Shearing Force = — - = 111 tons. 



Shearing stress per sq. in. = — — = 2£ tons per sq. in 



The Author in Reply. 



Mr. Bowman's comparison of the plate girder, as designed by 

 himself, and the bridge referred to in the paper by the Author, 

 by which the former is shown to be equally strong, but some 

 50 per cent, lighter than the latter, is erroneous, as the following 

 statement will prove. 



The weight of the bridge as tested was 62,703 kgs. = 61-45 

 tons made up as follows : — 



(1) 2 main girders ... ... = 31*75 tons. 



(2) Cross girders, rail bearers, dia- 



phragm stiffeners and wind 



bracing ... ... = 16*76 tons. 



(3) Decking of corrugated iron, etc. = 9 80 tons. 



(4) Oak planking on footpaths = 3*14 tons. 



Total 61*45 tons. 



Mr. Bowman does not include items (3) or (4) at all, and only 

 portion of item (2), though, of course, his design is incomplete 

 without the stiffeners and wind bracing. 



According to Mr. Bowman one of his main girders would 

 weigh 15*26 tons, whilst the Vierendeel girder weighs 15*87 tons. 



The latter bridge had flange plates 12*6 inches wide, whilst 

 Mr. Bowman's were 10 inches, thereby necessitating, in the latter 

 case, heavier diaphragm stiffeners, and owing to continuous web 

 surface of Mr. Bowman's design, heavier windbracing than in 

 the case of the Vierendeel girder. Had these facts been taken 

 into consideration, it will be readily seen that Mr. Bowman's 



