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Re: Glass Hand Rail

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leave seaint

please please

----- Original Message ----- 
From: "Drew A. Norman, SE" <DNorman(--nospam--at)dnormanse.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Thursday, February 15, 2001 4:52 AM
Subject: Re: Glass Hand Rail


> Joseph,
> 
> There are several different proprietary structural glass guardrail systems
> out there.  In UBC jurisdictions, ref. section 2406.6 of the 1997 UBC.  In
> general, keep in mind that glass is an inelastic and brittle material with
> structural properties highly dependent on the nature and amount of
> impurities in the silica from which it is made as well as the way it is
> tempered during cooling.  Structural glass panels are often laminated and/or
> heat strengthened.  Stress concentrations at notches, edges and restraints
> are critical considerations.
> 
> In my experience, field load testing to "certify" completed glass guardrails
> installations is commonly required, but the design team still needs to
> specify something that is likely to pass the test.  This is usually done on
> the basis of empirical data provided by the manufacturer/supplier of the
> system (or of each of its components).  They should be able to provide
> copies of test data to support the ability of the system to provide the
> required factor of safety against failure under the code specified design
> load.  For the glass itself, the data I have seen on past projects (usually
> from PPG if I recall) has always been probabilistic rather than absolute
> (i.e., for a particular product, the glass manufacturer will tell you what
> the probability of failure is at a given stress), and I would be suspicious
> of any data I got in an the form of an allowable stress or ultimate
> strength.
> 
> I am currently working a project involving the system Nels referred you
> (Julius Blum).  I think you will find that they make hardware (base fittings
> and top rails) but do not sell or warrant the structural glass balustrade
> itself.  They will probably give you an old (1985) Wiss Janney Elstner
> report to substantiate the ability of their cast aluminum base "shoes" (and
> the machine screws used to attach them to structural steel backing) to
> resist the moment created by the code required rail load.  You will have to
> design and detail the backing (e.g., an edge of slab embed or torsionally
> restrained edge beam) to receive the screws and resist the cranked in
> moment.
> 
> A word of caution:  the WJE tests were made with steel panels rather than
> glass.  In evaluating the resulting data and suggested details, you should
> keep in mind that the structural characteristics of the materials used to
> grip the bottom of the panels of glass may be critical.  Blum supplies
> plastic setting blocks and (I believe) stainless steel channel caps to fix
> glass within the glazing channel at the center of their shoe, and using any
> other method to secure it could create a different distribution of stress in
> the glass at a critical location -- leading to premature brittle failure.  I
> recommend that you make sure that the system you are using has been tested
> in the exact configuration you will have and that the contractor understands
> that the installation must be exactly per the manufacturer's
> recommendations.
> 
> Drew Norman, S.E.
> Drew A. Norman and Associates
> Pasadena
> 
> ----- Original Message -----
> From: "Joseph Ward" <joseph_ward(--nospam--at)leavittengineers.com>
> To: <seaint(--nospam--at)seaint.org>
> Sent: Wednesday, February 14, 2001 7:25 AM
> Subject: Glass Hand Rail
> 
> 
> > Has anyone out there seen a design method for glass hand rails?
> >
> >
> >
> 
> 
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