Work Access Walkway
Work Access Walkway
(OP)
I work at a fabrication facility and need to design a gangway for workers to safely access a project. The span must be 120LF which if I follow the building construction code of L/360 I get 4.0in max deflection (delta). Given my load conditions the required Ix=15,600in^4 which is very large (W40x211!). Deflection is my controlling case.
Am I being too conservative on my deflection? Does anyone know what the general rule of thumb would be for TS&CD that would satisfy any inspection and give workers good access?
FYI: I am a young engineer so keep that in mind before you say "i can't believe you engineer these and dont know!" I do have bosses that review these....
Am I being too conservative on my deflection? Does anyone know what the general rule of thumb would be for TS&CD that would satisfy any inspection and give workers good access?
FYI: I am a young engineer so keep that in mind before you say "i can't believe you engineer these and dont know!" I do have bosses that review these....






RE: Work Access Walkway
Are you looking at deflection under live load? dead load? combined? What live load are you using? Have you reduced the live load at all? You probably won't be loading all 120' at the same time.
I don't have a code book in front of me, but I believe that L/360 is the standard when you have sensitive finishes (plaster, glass, etc) that could be damaged by the deflection. I'd consider L/180 to be the starting point in an industrial facility.
RE: Work Access Walkway
RE: Work Access Walkway
(I am not affilated with this company).
Even is you decide not to go this way this will give you some ideas of cost and design issues for elevated walkways.
www.SlideRuleEra.net
www.VacuumTubeEra.net
RE: Work Access Walkway
A truss might be the economical way to go. 120' is pushing it for a rolled beam, in terms of economy. We recently did a bridge with a 145' span using rolled beams - clearance issue - and it required a very tight beam spacing.
Take a look at AASHTO's guide spec for pedestrian bridges. It gets into LL reduction and vibration criteria, which is important for a ped bridge.
RE: Work Access Walkway
Use a horizontal truss at floor level to carry lateral forces over the 120' span.
Consider the natural frequency of the structure and avoid resonance problems.
BA
RE: Work Access Walkway
RE: Work Access Walkway
RE: Work Access Walkway