Expert: Veto Varma - 4/16/2007

Question
explain shear failure of soil and beams under vertical loads

Answer
Shear Strength of soil:

Shear strength  of soil is measured in terms of two soil parameters cohesion and angle of internal friction. Practically speaking it is the resistance to mass deformation developed from a combination of particle rolling, sliding, and crushing and is reduced by any pore pressure that exists or develops during particle movement.

It is expressed as

s= c+ stress x tan(angle of internal friction)

you can get more info on these from any standard text books

Shear Strength of Beams:

For vertical loading  it depends on the section of the beam. Different section has different strength depending on the geometry. to get the shear stress on the section use following formulas

s= F Ay/(I b)

where  F=Shear force
Ay= moment of area of the section about neutral axis
I= inertia of the section
b= width of section

This will give you stress distribution across the section. Allowable shear stress depends on the material used, factor of safety involved and area of section. Again any standard text book will give you information about it.

Hope this helps

Regards
veto