Perma Coliumn SW series anchor bracket

[JStructsteel]

Has anyone used the Perma Column SW base brackets? It seems rational for the posts and the reactions, but dang it seems to make the concrete anchor loads big for the moment.

Looks like uplift too, it magnifies your anchor load by the prying action.

Who has used these items?

 

[Eng16080]

Is there a particular detail that you're concerned about?

I assume you're using these to attach a railing/guardrail post with a concentrated load applied at the top? If that's an accurate assumption, then the tension and compression forces in the anchors should be roughly: T/C = Ph/x where P is the concentrated load at the top of post, h is the post height, and x is the moment arm (conservatively assumed to be the distance between anchors). This assumes that the load P is being applied in the direction parallel to a line through the anchors. If it's applied in the other direction then, the moment arm would be much less.

I very quickly looked at the manufacturer's literature and they seem to indicate that a factor of 2 should be used to account for prying action with an uplift force. Their literature seems to be very detailed especially concerning the analysis of the connector.

 

[JStructsteel]

Thanks, ive looked into these more, I think my dilemma is they give moment capacities etc for these, yet say the building must be a diaphragm building or braced by other means. For a post/frame building, I am not relying on a diaphragm. If I have bracing, then why do I need a post base thats moment resisting, or how do I limit the amount of load they take?

I am waiting on a call from their engineer.

 

[Eng16080]

...they give moment capacities etc for these, yet say the building must be a diaphragm building or braced by other means

I agree that's confusing. I wonder if this is a roundabout way to say that these connectors should not be used as part of the lateral force resisting system of the building but may be used for other applications, like for a guardrail post base connection.

 

[JStructsteel]

Yea, if they want them to be used in pole or post framed buildings, they need better engineering support.

 

[XR250]

I have a similar job coming up.
What do y'all think about taking a 6x6x1/4 HSS as the shoe for a 6x6PT post?
If the corners of the post are shaved down, it should fit in there nicely and add some thru bolts for fixing.
Then I can use a large base plate with epoxy or CIP anchors.
Seems a lot more economical and has some wiggle room for the install.

 

[JStructsteel]

XR250, I still dont think you get a fully restrained connection, which is the premise of the permacolumn.

My situation I am low on shear, so more than likely the metal roofing is going to help tremendously. I have perlins 2'-0" o.c. so the roofing could be spec'd for that fastener spacing.

 

[XR250]

XR250, I still dont think you get a fully restrained connection, which is the premise of the permacolumn

Similar to the perma-column, I would likely only be counting on the thru bolt capacity for the connection. The HSS is just a convenient, cheap and easy bolt holder that also will add a fair bit of belts and suspenders.

 

[JStructsteel]

Gotcha. Whats your span?

 

[XR250]

Span of what?

 

[JStructsteel]

Your building

 

[Eng16080]

What do y'all think about taking a 6x6x1/4 HSS as the shoe for a 6x6PT post?

I think that's a reasonable connection. I would use galvanized HSS for contact with PT. I would also add drain holes at the bottom if the connection is subject to moisture. I think a connection like this is your best bet for a rigid base connection for a wood post.

 

[XR250]

I think that's a reasonable connection. I would use galvanized HSS for contact with PT. I would also add drain holes at the bottom if the connection is subject to moisture. I think a connection like this is your best bet for a rigid base connection for a wood post.

For sure - thanks