Allowable deflection of steel posts providing lateral support to glass balustrade panels
Allowable deflection of steel posts providing lateral support to glass balustrade panels
(OP)
1. Does anyone know of any published requirement, or recommendation, for the maximum allowable horizontal deflection of steel posts that are to provide lateral support to glass balustrade panels? Posts are about 1.5 m on centres.
2. We calculate the posts will deflect horizontally h/80 (1070 mm / 80 = 13 mm) under the Code specified horizontal loading (since the posts are cantilevers, this would correspond the about L/160 for a single span member). Is that ok, or should the post be stiffer to avoid cracking the glass?
2. We calculate the posts will deflect horizontally h/80 (1070 mm / 80 = 13 mm) under the Code specified horizontal loading (since the posts are cantilevers, this would correspond the about L/160 for a single span member). Is that ok, or should the post be stiffer to avoid cracking the glass?






RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
Most glass panels attach through drilled bolt holes in the glass lined with a plastic or soft rubber grommet, or are inserted into a liner-edge of metal. The liner edge (a u-shaped strip) has a inner liner of rubber of plastic, sometimes a felt-like material that wraps around the glass edge and provides movement, some expansion allowance, and an softer impact surface agianst low velocity accidents.
Your manufacturer will tell what movement is allowed in their system, and how to mount the posts for their system - usually at 4 ft intervals. They have to meet the codes listed above = there minimum standards solve your question.
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
- Are you saying that the glass connection details allow for such gross deflections?
- Do you know how the h/12 limit came about?
- Is a metal handrail the same as a balustrade guarding a drop?
- Where does the 4 foot usual spacing come from? Any publication?
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
I have never really understood the large allowable deflection per the ASTM.
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
But I am still interested if anyone knows how the h/12 deflection limit was derived.
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
This article is interesting, doesn't resolve the issue but they do a good job of summarizing:
http://www.pieglobal.com/guardrail-deflection-limi...
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
Most glass guards that I've encountered would be relatively insensitive to post deflection perpenducular to the guarded edge. They are attached at two vertical elevations on the post and, as such, would see only rigid body rotation as a result of post deflection. The curvature of the posts would not be transmitted to the glass.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
Great spirits have always encountered violent opposition from mediocre minds - Albert Einstein
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
It's also important to remember that the code loads for handrails and guard rails are not serviceability level loads. True serviceability level loads would be much less and are not specified in codes.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
In reality, 2L/175 could be quite conservative depending on your glazing detail.
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
http://www.metroglasstech.co.nz/media/48424/tb31%2...
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
http://www.documents.dgs.ca.gov/dsa/pubs/IR_24-1_r...
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
OSHA is not a design spec; it was written by non-engineers under the supervision of politicians. And OSHA is essentially impervious to feedback, unlike ASME, API, and ASIC. Thus some stupid criteria like "withstand 200# lateral loading". To a real engineer, this means that a failure at 205# is deemed acceptable. Oops.
Handrails, per OSHA, are to be 42" - period. Thus a 46" tall handrail does not meet their criteria. Even though it is safer; at 42", at least 1/4th of American men have their center of gravity above the railing. So if the taller guy is jostled, he will flip over the railing and fall. Next time you go to a shopping mall, put a tape measure on the mezzanine-level handrail. It is taller than the mandatory 42", because their insurance carrier said it had to be; in violation of the OSHA standard. And when you apply a 250# lateral load to that rail, it will not fail, nor deflect significantly. Because 200# is idiotic.
RE: Allowable deflection of steel posts providing lateral support to glass balustrade panels
I guess the Australian Standard for deflection limit has to be read in conjunction with their code loading for guards. Does anyone have that information? Ours is 50 pounds per foot of horizontal rail but not less than a concentrated load of 225 pounds (0.75 kN/m, and not less than pounds 1.0 kN).
I think the deflection limit for the glass will be dependent on how it is mounted, and how it is supported.