×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

STEEL PORTAL FRAME STABILITY IN RESIDENTIAL FRAMING

STEEL PORTAL FRAME STABILITY IN RESIDENTIAL FRAMING

STEEL PORTAL FRAME STABILITY IN RESIDENTIAL FRAMING

(OP)
I AM WORKING ON A DESIGN WHEREBY THE ARCHITECT IS REMOVING 18' OF INTERIOR BEARING WALL AND REPLACING IT WITH A STEEL BEAM. SUPPORTING 2ND FLOOR AND CEILING FRAMING. THE ARCHITECT WOULD LIKE TO USE A TS4X4 (APPROX. 16' TO BASEMENT FOOTING). A SIMPLY CONNECTED BEAM SITTING ON TOP OF A POST CAP PL IS BY ITSELF UNSTABLE. I WOULD HAVE TO RELY ON THE HOUSE FRAME STABILITY FOR STABILIZING THIS SIMPLE FRAME. IS IT APPROPRIATE TO USE 2% OF THE POST LOAD AS THE FORCE REQUIRED TO BRACE FOR STABILITY IN 2 DIRECTIONS?? WOULD IT BE MORE APPROPRIATE TO CONSTRUCT A MOMENT FRAME OR WOULD THAT BE TOO CONSERVATIVE.  

RE: STEEL PORTAL FRAME STABILITY IN RESIDENTIAL FRAMING

If its just a gravity frame, and you properly tie into the diaphragm in both directions and the beam is properly braced, I don't see a glaring issue from your description.

RE: STEEL PORTAL FRAME STABILITY IN RESIDENTIAL FRAMING

dspe01,

you have not given enough information to give a complete answer but it sounds like you need an experienced structural engineer.

The answer depends on if the 18' of wall is required for stability. If it is then you need to also consider deflection of the frame under the lateral loads.It is common practice here to use a picture frame (4 sided frame) in these situations.

RE: STEEL PORTAL FRAME STABILITY IN RESIDENTIAL FRAMING

(OP)
Thanks, the top flange of the beam will be braced to the wood floor joists at 4'oc. It is an old house with t&g flooring & wall sheathing on a diagonal so I am not sure if that will provide adaquate diaphragm and shear wall action. The load is just residential gravity load.

RE: STEEL PORTAL FRAME STABILITY IN RESIDENTIAL FRAMING

(OP)
I am a Structural Engineer however I don't typically work with residential framing. I understand that bracing columns in both directions is always critical. I am just not sure if it is common practice to rely on the house floors and walls to provide stability support (no external lateral forces beyond stability).
thanks

RE: STEEL PORTAL FRAME STABILITY IN RESIDENTIAL FRAMING

You have to make that judgement call when you view the building. Personally I would only rely on diapragm action from Tand G floors for a limited span.

RE: STEEL PORTAL FRAME STABILITY IN RESIDENTIAL FRAMING

If you're removing 18' of wall, stability of the whole building will have to be assessed.
If the house is stable, your frame likely to be stable if tied to the floors.

RE: STEEL PORTAL FRAME STABILITY IN RESIDENTIAL FRAMING

OI would consider abandoning the steel and going with an upset wood Glulam or Microlam (top would be flush with underside of the floor diaphragm.  Just have to temporarily shore on either side of the beam to cut the joists to get the beam in, placing the cut joists on joist hangers.  Gives more headroom this way.  This solution will avoid mixing steel and wood beams, something I like to avoid if at all possible.

I assume from you post that the TS 4X4 is the end column, not the beam.  If it is the beam, it probably will not work considering deflection limitations.   

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: STEEL PORTAL FRAME STABILITY IN RESIDENTIAL FRAMING

If you are tying the steel beam into the floor diaphragm and the diaphragm is adequatley braced the yes, I would say the portal frame is sufficiently restrained.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources