loads on building guardrails

huangyhg

loads on building guardrails
i remember reading in a code somewhere that the guardrail must resist the prescribed load "without failure or permanent set".  does anyone else remember reading this phrase as it relates to the design of building-type guardrails (e.g. osha, ubc, ibc, etc.)?  if so, do you remember where you read it?
in my opinion, a guardrail is there purely to save someone's life - not to give you a feeling of confidence in its strength or stiffness.  (if the engineer advises, and the owner agrees that it should be designed to exceed the code minimums, then by all means that is fine, of course.)  
if the phrase i remember is correct, then the intent of the code body that wrote the statement would probably be:
"we want the rail to stop a 200 pound force without breaking or deforming, but we really don't care if it exceeds some typical 'allowable stress' limit."
designing the rail to stop a 200 pound force without breaking or permanently bending would probably mean letting the bending stress get pretty close to fy, and the deflection could be most anything, as long as it stayed in the elastic range so it springs back once the load is gone.
the question then becomes what do you design the connections for?
i wonder if anyone would care to comment on this.
btw - for what it's worth, i do design rails and connections using the allowable stress method, and the full 200 pound (or 50#/ft, if greater) load.  i use the ibc 2000 allowable overstress of 1/3 (1607.7.1.3).  i personally think this more than satisfies the 'without failure or permanent set' idea.
i agree. but i also check deflections.
the requirement is single load of 200 lbs applied in any direction ( cfr 1910.23(e)(5)(iv)), at any section of the top rail.
check out osha requirements:
thanks for the references.
can you tell me what recent legislation you are referring to?
thanks!
i agree also but depending on railing material i limit deflction to l/200.  i find it necessary to use a 3d frame anaysis program to model many railings and/or stairs.  a railing post is not a flag pole, nor does it have to be designed as such.
the 1/3 stress increase was a load combination adjustment factor that accounted for the reduced probability that two or more loads, other than dead load, acting concurrently will each attain its maximum at the same time.
the new 2000 ibc building code (1605.3.1.1) does not permit this factor unless you have two or more "transient" loads applied.  current boca also does not allow the increase for seismic loading conditions unless using load factor design.  many states have adoped this code change.  florida also recently changed (rule 9b-72) to multiply the steel values by 0.75 to negate the 1/3 stress increase
boo1,
sorry to tell you this, but ibc does allow this increase in handrails & gaurdrails.  see section 1607.7.1.3
btw, i limit the deflection to l/180 which is only a quarter inch (most cases).  if i hit the rail with 200# of force, it's going to hurt so freakin bad i don't care how much it deflected as long as i don't fall.
chip
interesting! had not noticed the 1/3 increase allowed for railings myself...... thanks!
check this link
alohabob said "check deflections".
my question is: what is the criteria for the deflection of a post or guardrail??.  i know we all have our "comfort" levels. but when it comes down to rejecting the rail design (we don’t design it, but as the ser we check it), i can't, in good faith reject it on the basis of deflection, because i have never found deflection criteria. i even wrote a letter to osha, to see if they had a recommendation. they didn't get back to me.
has anyone got a reference for deflection of a guardail??
there are only two "official" deflection recommendations that i am aware of.  
one is in the military engineering manual 385-1-1 , paragraph 21.b.02.  this is available at: