Glass Handrail

[stan45]

I am currently designing a glass railing consisting of an aluminum shoe and 1/2" tempered glass. I determined wind pressure requirementss based on ASCE 7-05 "solid sign" and the loads are coming up very high. 75 psf for a railing at an elevation of 30 ft. (140 mph) Since this is not really a sign I was wondering if there is a better approximation.

Any ideas??

 

[msquared48]

Sounds like you might need a few more stanchions.

Mike McCann
MMC Engineering

 

[PMR06]

I've used component & cladding wind for guardrails.

And don't forget the load combination D + 0.75(L + W). I guess that load combo takes into account crazy reporters out on the balcony filming hurricanes as they come in, then slipping and falling into the guardrail!

 

[Ron]

stan45...I wouldn't be trying to minimize the load with a glass guardrail 30 feet off the ground...I'd be trying to justify more load!!

For occupant safety, you only need to meet the standard guardrail criteria; however, it is a component of the building, is subject to wind load and does transfer load to the building.

I would treat it as a component and cladding as PMR06 noted and design it as a solid sign. If you are looking at the typical aluminum slot design with the anchor bolts in the middle of the slot, you have to be careful what you are anchoring into. If solid concrete, not a problem other than they might need more than standard anchors. If hollow core, that can be a problem.

Specify stainless steel hardware/anchors and specify compliance with ASTM E985 – Standard Specification for Permanent Metal Railing Systems and Rails for Buildings.

 

[ishvaaag]

If you see glass panel work as guard against fall in malls you may see 1.1 m free height tall cantilever fixed in some steel U fitting below, maybe over 20 cm embedment, 32 mm thickness laminated glass, some brass handrail, and no wind. It is assumed people can do every kind of violent movement, maybe skating head on unto the glass, enter unto a fight, or ram it with a heavy piece of wood or heavy furniture or mechanical tool.

So be conservative.

 

[Ron]

ishvaaag...such assumptions are not used in the design of glass guardrails in the US. They are only designed for a 200 lbf concentrated lateral load or 50 lbf/linear foot in any direction. They are not designed for impact loading nor extraordinary loadings other than for wind loads on the exterior.

 

[ishvaaag]

The loads are similar here for open balconies. It was mainly a reminder, just in case he had some of these risks at hand.

I for example rembember a draftsman that worked with me that rammed a glass to his balcony (I vaguely remember it being steel mesh reinforced, so it may be was a lower panel of a window, but I remember it as a balcony) with some implement of furniture.

So these risks exist and really under the current code could lead to worrying consequencies when some accident happens, for in reason of economy these underwaist panels are still dimensioned thin and then one day or another the newly stated TRUE requirement of general safety imposed by the CTE code (that exacts that everything is to be safe and perfect, hah, first day to end) is going to play against the designer and other parties involved.

By the way, it is interesting to note that reinforced glass with a mesh is LESS resistent to impact and bending than unreinforced. Only that keeps most of the broken glass in place (or it should).

 

[unclesyd]

Here is a little information from the IBC on the Stainless Railings site.

http://www.stainless-railing.com/ibc.html

Anecdotal:

Several years ago I assisted in the installation of a glass railing/panel system on second story deck of a beach house to better observe the wild life. I upgraded the mounting hardware as the original appeared to be lacking even though the manufacturer assured us it would take 120 mph hurricane winds. We had the hurricane which took out the beach house but we found the deck essentially in one piece railing and all with only one broken stanchion.

 

[hokie66]

unclesyd,
Surprised you didn't get blamed for losing the house because you built the balustrade too strong.

 

[ARKeng]

stan45,

Just curious have you run the wind loads for a parapet at the same height? I don't know if the loads for parapets are better or worse than signs - but it seems like the wind on a rail would be very similar to a parapet situation. As I recall, the sign wind loads are pretty crazy.