Pocketbook of Useful Formulæ and Memoranda
for Civil and Mechanical Engineers

183 OF ENGINEERING FORMULÆ, Bridges of Large Span. (‘ Min. Inst. Civ. Eng.,’ vol. liv. Clarke.) Comparative Weights of different Types. Span 700 feet clear. With 250 feet of viaduct at each end. Double line of railway; live load 3400 lbs. per foot; wind pressure, 40 lbs. per square foot; iron strained to 10.0U0 lbs. per square inch (say 4- J6 tons). STRAIGHT GIRDER. 715 feet main girder .. ,. 4900 tons. 500 feet viaduct __________ 500 „ STIFFENED SUSPENSION BRIDGE. 715 fe t of suspension girder and Kick chains 3000 tons. 500 ,, viaduct .. ..................... Ö00 „ Total .. .. 350Q „ Total .. .. 350Q „ BRACED ARCH. 715 feet of arch and shore abutments .. 2800 tons. 500 „ viaduct ......................... 500 „ ’ BRACED ARCH. 715 feet of arch and shore abutments .. 2800 tons. 500 „ viaduct ......................... 500 „ ’ Total .. .. 330(j )( Total .. .. 33oo ) (