Guardrail Post to Concrete over Metal Deck Connection

[theisland808]

Hi,

Does anyone have a detail for vertically cantilevering a steel guardrail pos off a concrete over medal deck. In my situation, we're using 1.5" metal deck with 2.5" concrete topping. Arch said that they would take care of guardrail and now that shop drawings are coming along is asking me to verify/revise the connection..

Tried searching through the guardrail threads but couldn't find something that fits this.

Currently they're using pipe 1 std and (2) 1/4"x2" HILTI KB to mount the post to the concrete over metal deck. I think they're being pretty hopeful trying to cantilever that post with (2) 1/4"x2" bolts. Trying to think of a alternative.

Would moving to (4) 1/4"x2" bolts with a square base plate be any better? I'm thinking not with how shallow the conc depth is. You bolt over a ridge and there's one 2.5" of conc.

Any suggestions are appreciated...

 

[phamENG]

1) Before you do anything else, check the deck and concrete section. Can it take the moment? If not, then you have bigger problems than the base plate anchorage.

2) Unless you've got detailed measurements of all locations showing exactly where the guardrail is in relation to the deck flutes, assume it's in the worst position because at least one of them probably will be.

3) You can check the 4 bolt option, but unless it's in an industrial setting I have my doubts that the arch will be willing to accept it.

4) If embedding the bolts doesn't work (which it may not), then you could potentially drill all the way through and put a plate on the bottom of the deck and through bolt everything.

 

[JLNJ]

Do you have 1” diameter std pipe or is that a typo? Seems too small if 1” for a 42” high guardrail.

 

[dik]

Off the top... I don't know what your guardrail design forces are... in Canada, the proposed one will not work... fasteners vastly undersized, depending on the orientation of the attachment plate, and connection to deck will be problematic.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

I should have included the rail and post section (same)

For a sloped guardrail, the horiz forces are increased a bit... setting rise=0, accounts for a horizontal guardrail. I also treat it as a Class 1 or Class 2 Section.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[XR250]

As PhamENG noted, I have had to thru bolt that with a plate in the past.

 

[dik]

Yes... rather than KB3s... Because the connection forces are so high... I rely on bolts and not Hilti Fasteners... through bolting also avoids the issue of lifting the deck and topping. The grade and size are part of my 'cut and paste' programming; I'd never use 1" A490 bolts...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[JLNJ]

1” pipe is 35 ksi yield, not 50 ksi as with HSS shapes. It’s just 1.315 OD which is less than 60% the strength of the 1.25 pipe (1.66 OD) dik calculated and just 40% of 1 1/2” dia std pipe strength (1.900 OD).

 

[dik]

Thanks... The 1" pipe will not work... The HSS 1.66x0.125 barely works... I was using HSS, not pipe. The problem is the anchorage and not the rail and post... it doesn't work as initially posted. The example I posted is overstressed and I would let it go because of continuity within the system... that's why I check capacity and capacity increased by 1/(phi s)(, arbitrary on my part... I just want to have an idea of how much to allow overstress, else it changes depending on how many coffees I've had.)

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik