Catwalk access around circular tanks
Catwalk access around circular tanks
(OP)
Hello!
I've done some structural work before, but nothing really unconventional. I've got a (slightly) oddball situation, and I'm curious about how it's normally handled. It's a catwalk for maintenance access to two FRP tanks. Due to space contraints and access requirements, they'd like the grating to be cut around a portion of the perimeter of the tanks. I'm putting together a preliminary stab at how I think it ought to look, but before I present the concept I was curious if anyone would be willing to sanity-check it.
Attached is a plan-view sketch (catwalk elevation will be ~9' above finish-floor.) The concept is braced frames for column-lines A, B, and C, a moment-frame for column-line 2. I've got beams running as sort-of "chords" around the perimeter of the tanks, ultimately stability-supported by the plan-south moment-frame. The grating will be cantilevered off of the "chords," supported by clips or angle along the main plan-south beams. Stability for the columns along column-line 1 will be provided through the long chord-beams to the moment-frame.
Does the basic idea as presented make sense? Even though it's a small, lightly loaded structure, I'm a little nervous about using a single moment-frame for E-W stability; not for any reason that I can justify, it just seems unconventional. But apart from providing base-fixity for small HSS columns (and any associated added cost with that) I'm not sure how to arrange it, apart from abandoning the concept. Would anyone with a bit more structural experience take a glance at this? Thanks a lot!
I've done some structural work before, but nothing really unconventional. I've got a (slightly) oddball situation, and I'm curious about how it's normally handled. It's a catwalk for maintenance access to two FRP tanks. Due to space contraints and access requirements, they'd like the grating to be cut around a portion of the perimeter of the tanks. I'm putting together a preliminary stab at how I think it ought to look, but before I present the concept I was curious if anyone would be willing to sanity-check it.
Attached is a plan-view sketch (catwalk elevation will be ~9' above finish-floor.) The concept is braced frames for column-lines A, B, and C, a moment-frame for column-line 2. I've got beams running as sort-of "chords" around the perimeter of the tanks, ultimately stability-supported by the plan-south moment-frame. The grating will be cantilevered off of the "chords," supported by clips or angle along the main plan-south beams. Stability for the columns along column-line 1 will be provided through the long chord-beams to the moment-frame.
Does the basic idea as presented make sense? Even though it's a small, lightly loaded structure, I'm a little nervous about using a single moment-frame for E-W stability; not for any reason that I can justify, it just seems unconventional. But apart from providing base-fixity for small HSS columns (and any associated added cost with that) I'm not sure how to arrange it, apart from abandoning the concept. Would anyone with a bit more structural experience take a glance at this? Thanks a lot!






RE: Catwalk access around circular tanks
1. How would the guardrail on the edge of the platform be supported at the cantilevered grating edge?
2. Does the tanks have a perimeter guardrail if you are walking on the top of the tank?
3. Do you have a fall protection system for 100 % tie off if there is no guardrails?
I would frame a platform around the entire outside with 2 holes for the tanks (octagon framed opening) and have guardrail around the outside perimeter.
RE: Catwalk access around circular tanks
BA
RE: Catwalk access around circular tanks
BAretired: The tanks will be fiber-reinforced plastic, so I'm avoiding making it load-bearing, especially with regard to the out-of-plane forces that would result from a cantilever from the tank wall.
RE: Catwalk access around circular tanks
BA
RE: Catwalk access around circular tanks
Suggest that you use only simple span or continuous span supported grating. Keep the framing basic so that the edges of the grating form cords around the tank exterior. Of course, there will be some gaps between the grating edges (the cords) and the circular tank. In most operational situations these gaps are of no concern. Have the edges of the grating banded. Use grating tie downs, but only to keep the grating from shifting, not for structural reasons.
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RE: Catwalk access around circular tanks
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Catwalk access around circular tanks
Faith is taking the first step even when you can't see the whole staircase. -MLK
RE: Catwalk access around circular tanks
The cantilevered frames would be tied to the tank wall and should be FRP material which offers excellent corrosion resistance. I would visualize the FRP grating spanning 2.5' between FRP beams supported on the cantilevered FRP frames. The advantage of tying the catwalk to the tank is that it derives its lateral stability from the tank itself, eliminating the need for wind resisting frames.
FRP structural shapes are available from several sources and come in similar shapes as structural steel including HSS, WF, angles, channels and others. See the following link:
http://www.strongwell.com/products/structural-shap...
BA
RE: Catwalk access around circular tanks
RE: Catwalk access around circular tanks
Mike McCann, PE, SE (WA)
RE: Catwalk access around circular tanks
Mike McCann, PE, SE (WA)
RE: Catwalk access around circular tanks
BA