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Re: Point supported glass design

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On Mar 12, 2009, at 12:32 PM, Jordan Truesdell, PE wrote:

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(--nospam--at)skypoint.com   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania 1864)
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