> I look at the glass from a minimum tensile stress, and for
> simplicity assume that any stresses are tensile.
Fair enough, I do about the same thing for brittle materials, but
tensile principal stress is the actual failure criterion. OTOH, the
determination of a real failure criteriaon for real world glass
probably isn't all that precise anyway
> Finally, point loads aren't part of the guardrail standard for the
> building code, only pressures (50lbs over 1 ft^2), unless it is
> used at the rail itself, in which case you can apply a point load
> in FEM and see the stress contours.
Gotta be careful with point loads and FEA. point loads are
singularities in elasticity theory. The stresses under a point load
diverge with decreasing mesh size--best to estimate the contact area
and use a pressure loading that gives you the same force.
Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw@skypoint.com | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
http://www.skypoint.com/members/chrisw/
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