stress reduction when designing handrail and railing

[gazibu]

As it is known commonly when designing handrails as per the code one designs for a concentrated force of 200 lb, or uniform load of 50 lb/ ft.My question is does the nyc code allow for 1/3 stress reduction in this case? can the 200 lb load be considered temporary, to allow for the stress reduction?

 

[gooddammer]

Which "code"? OSHA requires handrails to "withstand" a 200 lb force in any direction, including its fastenings. You can define "withstand" any way you wish. I use material & conn yield point as "failure to withstand". Thus, there's a factor of safety from 'yield' to 'ultimate' of any assembly, even one of glass or rubber. State codes may vary from this basic document, but not degrade from it. Other trade spec's are more vigourous in these regards than that 200 lb "withstand" standard. NOBODY credits rail systems with ability to "withstand" any lower load.

 

[gazibu]

I Know the nyc (new york city ) code specifies the 200 lb, concentrated and 50 lb uniform load, but can the determined stresses be reduced by 1/3 , similarly to wind and seismic forces? that is my question.

 

[Ron]

Not sure you can figure this out without calling the NYC building department. I've looked at the NYC building code and it's a pain in the a$$. The latest version of its revisions seems to follow the International Building Code (which does allow a 1/3 overstress on railings); however, wading through all the changes will take a while. It seems to be available online, at least for referenced purposes.

Dig through it...good luck.

 

[slickdeals]

I know the Florida Building code allows a 1/3 stress increase in the non-high velocity regions (non HVHZ) for handrails. Mysteriously the 1/3 increase is not permitted in the HVHZ.

 

[Ron]

Hey Slickdeals....it's because they don't want the rail to fail while you're standing on the balcony with 120 mph wind blowing on you. Doesn't everyone stand on the balcony or stairs during a hurricane?

Our good ol' Florida Building Code gets a little goofy at times.

 

[slickdeals]

We have had building reviewers here not allow the use of 1/3 stress increase even inside stair towers (one which is completely shielded from wind forces). I don't know if you have ever heard of the infamous Coral Gables Building Department.

 

[MikeHalloran]

The FBC reflects the nature of the population.

After kneeling on a tin roof driving screws to keep it fastened through just one more hurricane, as the hurricane arrived, I resolved to get a battery powered screwdriver.

Double insulated drills will tickle you a little in a driving rain...



Mike Halloran
Pembroke Pines, FL, USA

 

[Lion06]

IBC 2006 allows a 1/3 stress increase when using "allowable stress design". I read this to EXCLUDE steel since IBC 2006 recognizes AISC 360-05, in which ASD means allowable STRENGTH design. I think it would apply for wood, or masonry, or anything else that you can design by ASD.

 

[Ron]

SD...have had to deal with several building departments in Dade/Broward...mostly with Threshold Inspection issues.

Mike...just move a little farther north...you realize hurricanes only hit Dade/Broward

Don't ever design anything that straddles the north Broward county line...two designs in one!

 

[WillisV]

Yes - the 1/3 stress increase in IBC is for ASD design, but that is how most stair designers still design. Anyway, it is recommended not to use it and it was pulled from IBC 2009"

http://www.modernsteel.com/Uploads/Issues/February_2009/022009_Feb09_Handrails_web.pdf

 

[gazibu]

Thanks guys appreciate your input.