Art. 122. BRIDGE TRUSSES NOW OUT OF DATE. 219 



first bridge having all members of wrought iron was built, and 

 cast iron was gradually abandoned. About 1870 steel began to 

 be used, and wrought iron went out of use about 1890. 1 



The early bridge builders were very successful in ^view of the 

 fact that they knew nothing about stresses in trusses. To Mr. 

 Squire Whipple belongs the credit of having first analyzed the 

 stresses in a truss. In a small book which is published at Utica, 

 New York, in 1847, he gave the correct analysis of bridge stresses 

 and the details of design for a Wipple truss bridge (Fig. 159). 

 In this design, pin connections were first introduced. Mr. Whip- 

 pie not only gave, in his small book, much sound theory and good 

 practice, but built many bridges of the Whipple and bow-string 

 types. 



The following are the most important of the older types of 

 trusses; for others, and for an account of the evolution of the 

 modern truss, reference should be made to the works cited in the 

 foot note below. 



TRUSS 



Fig. 155. 



Fig. 155 shows the B oilman truss, which was patented about 

 1850 and introduced as an * ' iron suspension truss bridge. ' ' Each 



FINK TRUSS 



Fig. 156. 



'For historical data concerning American bridge building, see a 

 paper by C. C. Schneider, Pres. Am. Soc. C. E., in the Engineering 

 Record, Vol. LI, p. 707. Also see paper by Theo. Cooper, M. Am. Soc. 

 C. E., in Trans. Am. Soc. C. E., Vol. XXI, p. 1; Johnson's Modern 

 Framed Structures Chapt. I, and Merrim.an and Jacoby's Roofs and 

 Bridges, Part I, Chapter V, sixth Edition. 



