K-stiffener

[rowingengineer]

Attached is a detail of a K-stiffener arrangement. My understanding is that if I use this type of detail I no longer need horizontal stiffeners to take the compression/tension loading if the load is greater than the web strengh.

Anyone used this arrangement before, am I correct? Does anyone know it by another name? Any references on this type of stiffener and design requirements for detailing?

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it

 

[apsix]

Row
If you save the file as a .doc or pdf more of us will be able to open it.

As it is I can't open it, and I have no idea what a K-stiffener is meant to be.

 

[rowingengineer]

sorry in doc form this time, let us know if this didn't work

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it

 

[asixth]

Why would you want to detail it this way. In my experince of designing moment connections, the diagonal stress developed across the web rarely exceeds the capacity so when detailing this connection I have only provided horizontal stiffeners for the large flange forces. When I say that, I mean that I have detailed 18" deep (460mm) I-beam knee joints transferring close to the moment capacity from the beam to the column.

The K-stiffeners would be more efficient because they can facilitate the flow of flange forces around the joint more efficiently. I have seen diagonal stiffeners detailed [\] so that the web is stiffened for gravity loads at edge columns but it doesn't help you out when wind loads are large contributors (wind blowing both ways).

 

[rowingengineer]

I have no job in which I wish to use this detail; however I am currently deep in ASI (equivalent to the ASIC) manual for the design of steel connections and it give this opinion for detailing. However I am getting confused about the design requirements for the stiffeners if the horizontal stiffeners are not present. Thus I am looking for how this K-stiffener works such I can be confident of the application if required.

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it

 

[abusementpark]

I've have never used that detail before or seen it used in a design example.

I'm not sure if it eliminates the possibility of web panel zone shear completely. If flange local bending in both flanges is a concern you will need to develop the forces in those stiffeners along the web of beam. So, IMO, even in this scenario some panel zone shear behavior can occur between the stiffeners. However, what effect the does the triangular shape of the panel have on it ability to develop a shear failure mechanism. I would think it reduces its susceptibility for that type of failure, but I'm not sure how to quantify it.

As one might expect, this detail is only applicable when there is girder framing from one side. If panel zone shear is problem, the most economical solution is usually to use a column with a thicker web.

 

[nutte]

Blodgett talks about using a diagonal stiffener in lieu of a web doubler. In that case, you still have two horizontal stiffeners, one at each flange. You also have a diagonal stiffener, which takes out the panel zone shear.

 

[rowingengineer]

abusementpark,
Your thinking is along the same lines as mine, I can mind testing for the Morris stiffener, which is more efficient I believe, however nothing for the K-stiffener. The most common situation I would want to have the ability to use this stiffener is a portal frame connection, with wind reversal; hence the Morris is no longer a viable option.


An expert is a man who has made all the mistakes which can be made in a very narrow field

 

[Ron]

RE...a couple of thoughts...

1. Assuming this is a bolted connection, as long as the bolt pattern is symmetric and outside the "K", then not an issue with clearance. If you have a double line of bolts and one is inside the "K", then clearance becomes and issue.

2. Yes, the "K" configuration does help alleviate the shear issue; however, only if the angle in your sketch approaches 45 degrees. Any angle helps, but the larger the angle, the more efficient it becomes....unfortunately that's constrained by the beam geometry relative to the column geometry.

3. The weld joint at the apex of the "K" is possibly not prequalified, so you might want to check that. Depending on the "K" angle opening, the other weld joints might not be prequalified or easily accessible.

4. "K" stiffener uses more material and is more difficult to construct...fab shop bitchiness will kick in.

Do you really need it over conventional horizontal stiffeners? Since you want reversal, the Morris stiffener is not a great option, but conventional will handle either, as will the "K".

This would be one of those situations where you might want to model it a couple of ways and consider von Mises distribution as was discussed in one of the other threads. (No real reason other than personal edification!)

For what its worth, I would probably just add another horizontal if stress levels were too high to justify a conventional configuration.

 

[asixth]

RE

Are you considering detailing a K-stiffer in the future?

 

[rowingengineer]

Asixth,
If I had the right ratio's and need the stiffeners, maybe. My preferred option would be to use a reverse K with horizontals.


An expert is a man who has made all the mistakes which can be made in a very narrow field