Art. 112. 



END CONDITIONS. 



185 



of the flat bearing, a round end becomes a hinged -end. A hinged 

 end is also formed by a pin connection in which the clearance 

 between the pin and the pin hole is small. A ball and socket joint 

 is hinged in all directions, while a pin joint is hinged in but one 

 direction. When the end of a column is a plane normal to its 

 axis, and it rests squarely on a plane surface, it is flat ended. Un- 

 der certain conditions a flat end might be a fixed end, but this 

 cannot be accomplished perfectly by fastening the column to its 

 bearing on account of the elasticity of the fastenings.. 



In structural work, columns have pin or hinged ends, flat 

 ends, riveted ends and fixed ends. Pivoted ends do not occur. 

 On account of frictional resistance, a pin-ended column occupies 

 an intermediate place between pivoted and flat-ended columns. 

 This frictional resistance depends upon the size of the pin, being 

 largest for large pins. Compression members in riveted trusses 

 are columns with riveted ends. Such columns are usually as- 

 sumed to be flat-ended. The ends are not fixed on account of the 

 elasticity of the connections and the deflection of the truss. When 

 n, truss deflects, the angles between the members change and some 

 bending is induced in them because their ends are not pivoted. 



(b) (c) 



Fig. 138. 



