ahypek
Structural
- Aug 11, 2016
- 57
We currently have an interior stair railing that was specified by the EoR for us to fabricate that does not pass NYCBC calculations now that some dimensional changes have occurred. We're trying to avoid a major change order here as we have ordered all of the pipe.
The rail has two end posts 1-1/4SCH80 and a top rail 1-1/4SCH40.
Typical calculations as per AMP521 + AISC LRFD involve using overly conservative assumptions like simply supported guardrails and cantilevered posts free to translate/rotate at one end.
At the moment these railing are 1.14 required/available under those assumptions and most certainly less than 1 with more thorough analysis.
Typically I'd reduce the 1.6 load factor to make it work for the EoR but unlike ASCE/AISC, NYCBC lists the rail loads under "LIVE LOADS." Since this is a single span endpost there's no reduction factor either.
Being that I am not currently using any structural analysis software, everything works if I idealize this post as fixed at one end, free to deflect but not rotate at other. (which is how I expect it to behave as opposed to it being free to rotate at one end)
Does anyone have a problem with my assumption of the guardrail providing significant rotational restraint and insignificant lateral restraint?
EDIT: Just wanted to reiterate that I have absolutely zero concern about the strength and stability of the system.
The rail has two end posts 1-1/4SCH80 and a top rail 1-1/4SCH40.
Typical calculations as per AMP521 + AISC LRFD involve using overly conservative assumptions like simply supported guardrails and cantilevered posts free to translate/rotate at one end.
At the moment these railing are 1.14 required/available under those assumptions and most certainly less than 1 with more thorough analysis.
Typically I'd reduce the 1.6 load factor to make it work for the EoR but unlike ASCE/AISC, NYCBC lists the rail loads under "LIVE LOADS." Since this is a single span endpost there's no reduction factor either.
Being that I am not currently using any structural analysis software, everything works if I idealize this post as fixed at one end, free to deflect but not rotate at other. (which is how I expect it to behave as opposed to it being free to rotate at one end)
Does anyone have a problem with my assumption of the guardrail providing significant rotational restraint and insignificant lateral restraint?
EDIT: Just wanted to reiterate that I have absolutely zero concern about the strength and stability of the system.
