lateral load for glass balustrade in shopping mall

[ajk1]

What is the appropriate lateral load to design a glass balustrade guard in a shopping mall? By NBC of Canada it appears to be 0.75 kN/m (50 plf) or a concentrated load of 1.0 kN (225 pds) applied at any point, whichever governs. We are designing the base connection; the glass design is by others. The 0.75 kN/m is only 25% of the Code load required for grandstands bleachers and arenas, so I am wondering if it is enough for shopping mall where people could crowd around watching a performance on the floor below, etc.

 

[racookpe1978]

"Standard" (US units) code requirement for commercial railings is the same for iron and wood rails as for glass panels: 50lbf per foot at the top of the guard rail, 200 lbfs per post - with the posts obviously "assumed" every four feet. Thus, the "panels" are capable of resiting at least 200 lbs force per panel, plus the company's safety factors and margins.

Usually, much more "Code words" are spent writing about the spaces and openings and heights for the guard railings, the handrails, the stair rails, and the decorative iron (glass) to keep children from getting their heads stuck than defines the basic forces they must resist. (4 inch rules, 6 inch stair rules, etc.)

"Impact" forces and dynamic forces (from a crowd running into the rail) are not mentioned in any code I've read, US or international.

Canadian rules? Don't know them.

 

[Ron]

ajk1...in general, the requirement in the US is similar. It is 50 plf in any direction or a 200 lbf point load at any point in any direction. The glass infill for the guardrail has to meet 100 psf at any location.

The more difficult of all of these is the lateral application of the 200 lbf point load or the 50 plf distributed load in the horizontal outward direction if the post spacing exceeds 48 inches.

 

[ajk1]

ok, thanks. I take it that you are both saying the 0.75 kN/m and
1 kN requirements are fine to apply to large shopping mall barriers.

 

[DBronson]

ajk1:

In the US under the IBC the infill force is 50lb acting on a one sq ft area (not 100lb). The infill force and the railing force do not act simultaneously. Also, the IBC requires a safety factor of 4 on glass rail assemblies.

Regards,

DB

 

[Ron]

DBronson....we both got that one wrong!! Your 50 lbf applied on a 1 square foot area is correct; however, with glass, a factor of safety of 4 is required by the code. None of the loading has to be concurrent.

 

[hokie66]

ajk1, I think you are right to be concerned that the generic standard is not enough for shopping malls. If there is a standard for grandstands, I would tend to use it, as some performances in big shopping centres can attract crowds similar to those attending concerts in stadiums.

 

[ajk1]

Well that is a big increase in load...4 times. We cannot find a fastener that will work for that, under our conditions.

 

[hokie66]

The Australian Standard for loading on balustrades, AS1170.1, requires 3.0 kN/m for "Areas susceptible to over-crowding", which are defined specifically as "theatres, cinemas, grandstands, discotheques, bars, auditoria, shopping malls, assembly areas, studios, etc".

The attached gives loading for one glass balustrade system used in Australia.

http://harkk.com.au/common/javascript/tiny_mce/plugins/filemanager/files/Harkk_Design_Guidelines.pdf

 

[ajk1]

To Hokie66 - that is very clear and helpful information, and in my mind makes a lot of sense. Especially where here is an event (such as a mall concert as I sometimes see on Utube) on the floor below and everyone is leaning over the balustrade to watch it. On this occasion and others, the Australian Code seems to have useful information not found in North American Codes.

We will have to see what we can do with our project.

It would still be interesting to know what other engineers in North America are using for shopping mall balustrade design loading.

 

[thaidavid40]

Since this is a glass structural member, I would be equally as concerned with deflection under lateral load as I would be with the maximum allowed loads. What information does the manufacturer provide. I would bet that they have at least some backup design for use information. The right relationship with the manufacturer can make for a much simpler design experience.

Thaidavid

 

[ajk1]

I think your comments are perhaps more applicable to the glass balustrade design than the Hilti base bolts for the track holding the base to the concrete. Any movement of the bolts at the base frame will of course contribute to the deflection of the top of the glass, but I would expect that it is very marginal relative to the deflection of the glass itself.

Be interested to hear what engineers who have designed shopping mall balustrades have used for the lateral load in the design.

 

[Agent666]

In New Zealand we use the same standard referenced by Hokie66. Its worth mentioning there is a relaxation if the pedestrain flow is parallel to the barriers, for example a barrier at the end of a hallway needs to be designed for the full load as people can stack up against it (i.e. overcrowding), but those on the sides can be designed for less load as it should only be subject to a normal load (i.e. just people leaning against it).

This might be of some help, its based on the NZ Building Code requirements, which reference AS/NZS1170.1 for the loading as per Hokie66 noted.
Link

 

[ajk1]

To Agent666 - that is quite interesting. Thanks.