Connection of deck guardrail posts

[crss]

Hello,
Anyone has a detail for connecting guardrail posts to a flush beam at the edge of the deck framing with the post on top of the beam? The connection must be able to resist the 200# load at the top

 

[JAE]

This isn't a post-on-top-of-beam detail - but it is what Simpson Strong-Tie suggests for their product>

With the post on top of the beam - you'd almost have to fabricate a custom bracket of some sort to create the necessary moment connection.

 

[crss]

I use this Simpson bracket when possible. I wish they would come up with a manufactured connector for the post on top of the beam. I figure the only way will be to have a custom made connector with a plate knifed into the post welded to a base plate with screws or bolts to the beam. Unless someone else has an alternative out there.

 

[CELinOttawa]

I had a colleague who was forced to do this... We came up with a detail using flat strapping on the two faced, and bracing between. Looked like garbage, but made the Architect happy. Never knew what thee client thought...

 

[jittles]

Regarding that Simpson detail - how does that work for the 200 lb load in any direction?

It looks good when the force is applied to the left, relative to the detail. The tension tie acts in tension. But when the load is reversed, the bottom bolt is in tension and is just all by its lonesome down there with no tension tie to help it out.

 

[woodman88]

I agree with jittles, the Simpson detail does not meet the 200 lbs in any direction requirement.

As for the OP, I have done both the knife plate (with a 4x6 posts) and straps details.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[crss]

CelinOttawa: I am collecting suggestions and saw one which is less "crappy looking". I will post once I have it drawn and verified.

Jittles: I believe the concept is that since the posts are at edges of decks, the 200# load will not occur in both directions unless something comes flying from the outside to push that post towards the deck. I also was told by contractors that using a HDU2 is cheaper than the DTT2Z bracket.

 

[woodman88]

crss: You may have a valid point on the main direction of the 200 lb load. But can you get a statement from the Building Official agreeing with you? Even if you could, I would not use the detail.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[crss]

Well, building departments here in California accept the Simpson bracket, no questions. And I believe in applying some common sense to code requirements.

 

[crss]

Thinking about further about the Simpson bracket, it actually can resist the load on both directions. The post can push the bracket and it will work the same.

 

[crss]

Here is a suggested detail with calculations.

 

[CELinOttawa]

That bracket had best have some pretty good press stiffereners to take the stress reversal, but if Simpson says it is a go you are relyingon their testing and warranty. Nothing wrong with that, just make a note that it is what is being done, is: "Install all material in accordance with the manufacturer's written instructions. Variations from the manufacturer's written instructions shall not be permitted nor analysed by the Engineer. All such variations shall be removed and make good with all costs borne by the Contractor."

Doesn't always stick, but I love having it to point to with the client. You can pay twice, but just don't blame me...

 

[jayrod12]

That detail is all well and good on paper. In reality I don't believe this will provide the fixity you are hoping for, even if they tighten down the bolts as much as possible there may still be a bit of wobble in the connection. That being said I don't have a better recommendation.

 

[woodman88]

Regarding the Simpson DTT2Z, per Simpson own (at

http://www.strongtie.com/FTP/bulletins/T-GRDRLPST10.pdf)

"Do the Simpson Strong-Tie
details address load applied in all directions?
The details in this technical bulletin address an outward force
on the guardrail. An additional connector can be installed on
the lower bolt to resist an inward force."

So the detail is not code (IBC/IRC) compliant.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[crss]

Thank you all for the inputs. It is not an easy connection at all. I don't like deck additions. Nothing works. From the posts supporting the decks(if no diagonal braces),to the railing posts. And clients always think a deck addition is a simple project.I have convinced my client to drop the beam and have the posts installed within the joists with the Simpson bracket. For connection on top of a beam, in my opinion, it is best to use a steel post with base plate. Or a plate inserted into the post and welded to a base plate.

 

[SAIL3]

As far as the 200# load in any direction requirement I would tend to agree with crss in using common sense and engineering judgement....the primary function of the guardrail is to prevent personnel from falling off the platform...I have difficulty visualizing a situation where this "any direction" catch-all phrase would pose a danger to personnel. At the same time, I am not endorsing that particular conn without running my own analysis.

 

[woodman88]

SAILS3: I have helped move things in and out of second story apartments. Also on and off of decks. I can say that I have caused at least 150 lbs force if not more than 200 lbs in an inward direction on the handrails. I am very glad that the rail did not fail in my cases.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[crss]

woodman88: how were those posts that you hit connected?

 

[woodman88]

crss: Duct tape and baling wire as far as I know.
So just write me off as a dumb engineer who wants to design per the code as the public has selected it.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[SAIL3]

Woodsman....I understand your point....I guess I was looking at it from a strictly personnel impact situation, but, being that the guardrail is there and convenient to be used for a variety of other uses that 200# in any direction makes sense with the result that one has a robust design in anticipation of that possibility.