----- Original Message -----
Sent: Friday, January 04, 2008 2:43
Subject: RE: Glass guardrail
We are having a
(local) debate on guardrails (any rail system above a drop of 2' or
more). The main concern at this time is that a lot
of off-the-shelf railing systems don't appear to conform to the code
loadings we have. Aluminum systems are especially a problem since some
manufacturers use the 6063 alloy which doesn't have adequate strength for our
loads. We need at least 6061alloy for posts and connecting plates.
Welding kicks the s... out of any connections too.
FWIW our loadings
are 1.0kN (225#) point and distributed 0.75kN/m (51.4#/ft). This means
that to minimize the post load the spacing has to be about 4'-4" ... and the
(true) design hgt will depend where the fixing is. If you use a
side connect your lever arm could increase to over 3'-9"
railings we have a requirement that a top rail be in place so that if any one
lite is removed/damaged there is still (possible) restraint. The use of
laminated glazing seems to be a way around that requirement but I haven't
yet seen where that is allowed per se in our code.
My point? If
you are being asked to design just the base connect, make sure that the
supplier's system has a written assurance by an/their engineer. If
you just do the base you may not be free of liability that the (overall)
system conforms (CYA) to any code ... engineers are meant to know
Thor A. Tandy P.Eng, MIStructE, Struct.Eng
I am looking at the support system for a guard
rail system. The system is pre-manufactured and only the attachment to
the structure needs to be designed. It is a guard in a residence and I
am told will be 36" high. I also understand that per IBC 1607.1 that I
only need to consider the 200# load requirement. The glass panels are
wide (from what I am told, they are the full width of the opening they serve
with no intermediate vertical non-glass members.
I am wondering if there is some distribution of
the 200# concentrated load that can be taken from the top of the guard to the
support attachment? with a 36" high guard can the 200# load be
distributed over, say 3 ft? or maybe something other 2ft?, 6ft? A
distribution would make my attachment to the substructure much easier since it
is a wood substructure.