abstracts: engineering 009 



ENGINEERING.— T'es/s of large bridge columns. J. H. Griffith 

 and J. G. Bragg. Bur. Stand. Tech. Paper No. 101. Pp. 139. 

 1918. 



Tests were made upon eighteen large bridge cohunns which were 

 half-size models of chord sections of raih'oad bridges recently erected 

 at St. Louis, Mo., Metropolis, 111., and Memphis, Tenn. The speci- 

 mens were constructed of nickel, Mayari, chrome, silicon, and high 

 carbon steels. They varied in length from 15| feet to 24| feet, and 

 in cross-sectional areas from 42 to 119 square inches. The slenderness 

 ratios varied from 15 to 44. The columns were of modern design 

 and were constructed in accordance with approved methods of shop 

 practice and were tested in the 10,000,000 Olsen compression machine 

 of the Bureau at Pittsburgh. 



The strengths of the columns varied from a minimum of 31,200 

 pounds per square inch for the carbon steel to a maximum of 657,000 

 pounds per squafe inch for the Mayari steel members, the intermediate 

 values corresponding to the grades of steel used in the construction of 

 the columns. The strengths for twelve columns failing as units were 

 approximately defined by the yield points of the individual steels used 

 in the construction, being confined within a zone determined b^- the 

 upper and lower limits obtained by independent tests of the com- 

 ponent steels. The mean deviation was found to be 0.5 per cent from 

 the mean-yield points determined for the columns at failure, the range 

 of variation being from four to twelve per cent. Of the remaining six 

 columns four failed by local bending at the ends and two by body 

 failures due apparentl}^ to the unsymmetrical action of lattice bars. 



A full discussion is given of the effects of initial eccentricity, the laws 

 of stress distribution from bending of columns, and the laws of distribu- 

 tions in pin plates and lattice. The analj^ses were conducted from the 

 point of view of the column formula used in design and the more 

 rational formula based on initial eccentricity in a column. 



J. H. G. 



