Re: Bent Beam/Frame

Gentlemen,

 

        I agree with Josh on this one.  The major impact is that all horizontal wind and earthquake loads must be resisted elsewhere since this frame can resist no horizontal loads.

 

Regards,

 

H. Daryl Richardson

----- Original Message -----

From: Josh Comfort

To: seaint@seaint.org

Sent: Friday, September 07, 2007 11:36 AM

Subject: RE: Bent Beam/Frame

If the tube steel members are connected together with a full pen weld at the apex, you have a "fixed" condition at the peak and your FBD should not show any lateral reactions unless there is an external lateral force.  Assuming you are not using the bent beam/frame to support any lateral forces, I don't see any problem with design the supports for the vertical reaction only.  You would want to consider the horizontal deflection of the frame though and take that into account when designing the support posts.

 

If you had a "pinned" condition at the apex you would have lateral forces do the the ridge beam reaction that would need to be resolved.

 

Josh Comfort, P.E.
Golden, Graper & Burton, Inc.
1500 W. Fourth Ave., Suite 509
Spokane, WA 99204
(509)624-3224 (509)624-3225 Fax

-----Original Message-----
From: William.Sherman@CH2M.com [mailto:William.Sherman@CH2M.com]
Sent: Friday, September 07, 2007 10:18 AM
To: seaint@seaint.org
Subject: RE: Bent Beam/Frame

No, you cannot just ignore the horizontal reactions from the rigid frame.  Greater rigidity may reduce the force but it does not eliminate it.  You should analyze the horizontal reactions based on frame analysis for the stiffnesses provided, and follow the load path and design for it.

 

 

Bill Sherman

CH2M HILL / DEN

720-286-2792

 

---

From: erik gibbs [mailto:erik.gibbs@gmail.com]
Sent: Friday, September 07, 2007 11:04 AM
To: seaint@seaint.org
Subject: Bent Beam/Frame

We are providing a steel bent beam/frame in a custom home to support the ridge beam within the ceiling instead of the typical king post to ceiling beam. The Steel frame is sized to fit within the depth of the R.R. and it is a 3/12 pitch, made with 2 square steel sections and a full penetration weld connection is provided at the apex, where the 2 beams meet. The bearing of the frame is at a 4x post at each end, hidden within the wall. 

 

Now my question is, if you determine the reactions using a simple FBD there will be an x & y reaction at the bearing points at the 4x posts, but if the steel frame is designed as stiff as possible to limit the deflection to negligable amounts then I am assuming that there will only be vertical reactions in the y direction. Therefore a wood post can be used without designing the connection for a very large reaction in the horizontal direction. 

 

Am I right in this assumption?  

 

Erik Gibbs