92 BROOMALL : 



values. The maximum stress lines iu the web would, there- 

 fore, cut the junction of web and flange at nearly the same 

 angles as the corresponding lines in the flange. As commonly 

 the web is thinner than the flange, it results that the unit 

 longitudinal shear on plane B is greater than on plane A, 

 which means a different angle of cutting. A consideration 

 of Formulas (i) and (2) will show. whether the lines in the 

 web will make a greater or less angle with the longitudinal 

 direction than the corresponding lines in the flanges. 



In case the Channel is used the other side up, that is, 

 flanges directed downwards, the same line of reasoning may 

 be used and lines corresponding to those already shown may 

 be easily sketched. We will leave it to the fertile imagination 

 of the reader to picture them. 



Another common unsymmetrical cross section to examine 

 is that of the Angle Beam. We will consider it in one posi- 

 tion only, for example, horizontal leg on top, and vertical leg 

 directed downwards, referring to same as flange and web 

 respectively. Since the Angle is to all intents nothing more 

 than part of a Channel, the nature of its stresses may be 

 easily indicated by reference to the previous figures. In the 

 Angle Beam the shearing planes will be similar to those in the 

 web and upper half flange of the I Beam or in the web and 

 upper flange of Channel Beam on edge. The maximum 

 longitudinal shear will occur at the neutral axis, which of 

 course passes through the centre of gravity of the section. 



The lines of maximum stress in the web of the Angle will 

 resemble those of the flanges of the Channel Beam laid flat. 

 Figure 3 inverted and with stresses appropriately reversed will 

 indicate them very well. 



In the flange, looked at from above, the lines can be eas- 

 ily shown to have the characteristics of the corresponding 

 lines in the upper flange of the Channel Beam on edge, 

 Figure 2, upper sketch. 



In beams of thin cross section with the parts vertically 

 and horizontally disposed, it is not difficult, as we have seen, 



