RUPTURE STRESSES IN BEAMS AND CRANE HOOKS. 



223 



a beam this reduces to zero ; in that of a hook, at the principal section to the 

 suspended weight.) 



3. That the total resisting moment of these stresses must be equal to the ex- 

 ternal bending moment as measured to the neutral axis at rupture point, but that 

 these balancing moments do not differ materially from those measured to an axis 

 obtained by dividing the sectional area into tensile and compressive stress areas 

 which are in inverse proportion to the magnitude of their respective ultimate direct 

 stresses. 



The advantage of these formulae are important. It is possible to indicate with 

 certainty the magnitude of the load which will cause rupture in a beam or a hook 

 provided there is known the point of application or the effective arm of the load, 

 the cross-section of the beam or hook, and the breaking strengths of the material 

 when subjected to the different forms of direct loading. 



TRANS. ROY SOC. EDIN., VOL. L. PART I. (NO. 7). 



31 



