596 



Professor Ernest G. Coker 



[Feb. 18, 



The form which these ends shall take to ensure the maximum possible 

 strength is a problem which has exercised the minds of many engineers, 

 particularly those engaged in the construction of large span-bridges of 

 the pin-connected type, where such members occur in considerable 

 numbers and of great size. In fact, the main tension members of 

 the majority of the great bridges in the United States, Canada, and 

 Australia are simple links of this kind. 



Some of the forms of ends which have been very generally used 



are shown on the diagram, and their diversity indicates the uncer- 

 tainty which is felt as to the best possible shape ; nor is it easy to 

 devise a method of selection unless the stresses in these forms can 

 be measured. 



An optical investigation of a model does this effectively and 

 quickly. A very common form is that in which the swelled end has 

 a contour bounded by a circle concentric with the pin, and if we use 

 proportions very widely adopted, it is easy to see from the colour 

 effects on the loaded model now shown, that the stress distribution is 

 unsatisfactory ; in fact at the principal transverse section (Fig. 13) 



