200 lb & 50 plf Loads For Handrail / Guardrail 2

[BHandke]

Does anyone know where the 200 lb concentrated load or 50 plf load in OSHA/IBC originated from?

With this loading and the time frame that it has been around, these loads can most likely be thought of as service loads. In IBC 2006, there was a 1/3 stress increase allowed. This 1/3 stress increase suggests that the loads are ultimate loads rather than service loads. However, this 1/3 stress increase has since been removed from IBC for handrails, but no changes have been made with respect to the loads and how they are applied or factored.

Are these loads to be taken as service loads or ultimate loads? I have seen it calculated where the yield stress is factored and the loads are taken as ultimate, but have also seen them calculated where both the yield stress as well as the loads are factored.

Any insight into the proper application would be greatly appreciated.

Thanks

 

[JStephen]

Usually, the loads in OSHA are based on a "must withstand that load" kind of thing, not "must maintain a specified low stress level", but it is kind of left up to the designer.
OSHA also specifies minimum member sizes and spacing, and if you equate those to the specified loads, they are based on fairly high stresses, as I recall.

Building codes also specify handrail loads and may control.

 

[JAE]

The loads are service loads. Not sure why IBC 2006 has the 1/3 stress increase allowance in there - it was not in ASCE 7-05.

 

[SlideRuleEra]

See the AISC "Modern Steel" magazine, February 2009 issue. It includes the following explanation of the 1/3 stress increase and the reasons it has been deleted:

"Since its inception in 2000, the IBC has permitted the allowable stresses for handrails and guardrails to be increased by one-third when the design is based on working stress. This provision, which does not appear in any other codes or specifications, is based on a perceived disparity between allowable (working) stress design (ASD) and load and resistance factor design (LRFD) for both steel and wood, and on the lack of widespread use of LRFD for wood. While this provision actually results in non-conservative and potentially unsafe design for critically important components, it has been continued in the 2006 IBC. Informally, there are efforts to remove this provision from the 2009 edition. Engineers are strongly urged not to use this stress increase."

Here is the link:

http://www.modernsteel.com/uploads/issues/february_2009/022009_feb09_handrails_web.pdf

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[Bagman2524]

The earliest record of 50 plf that I can find is ANSI 58.1-1972 section 3.1.3. ANSI 58.1 is the precursor to the modern ASCE-7.
The earliest record of 200 lbs. concentratrated load that I can find is ANSI A1264.1-1995 section 5.6.1. This section references ASTM E985, which I suspect is the original source. ANSI A1264 is a combination of older ANSI specs A12.1 (1967) and A64.1 (1968), which also may have the 200 lbs. in it. Most of the requirements in OSHA were taken from ANSI standards such as A1264

There is ample precedent in the history of science for the overwhelming bulk of the scientific community strongly believing in imaginary entities postulated by a favovered theory. -Michael Behe

 

[JStephen]

The AISC Manual, 5th Edition, Sixth Printing, 1948, includes the 50 lb/ft for handrails. It references A58.1-1945.

 

[Bagman2524]

A Model Performance Standard for Guardrails (1976) by S.G. Fattal provides some description of tests used to provide rail design loads. Basically amounts to someone falling on the rail. See link

There is ample precedent in the history of science for the overwhelming bulk of the scientific community strongly believing in imaginary entities postulated by a favovered theory. -Michael Behe

 

[JStephen]

The 1973 version of API-650 includes the 200# requirement for handrail. This would presumably have been taken from some other specification of the day.