×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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!

*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

Octagonal Roof Support

Octagonal Roof Support

Octagonal Roof Support

(OP)
Does anyone have any experience in designing a octagonal room that can be built without the use of tie beams from wall to wall supporting a kingpost at the center of the tie beam and supporting the roof planes at the peak.

I was wondering if I could use some metal braces which would be fastened to a triple top plate at each of the eight wall intersections, which would form a continuous ring preventing any outward thrust from the roof eight roof planes. Has anyone ever heard of doing this or something similar? Do you think you think it would work? We would like to do something similar to this to keep the cathedral ceiling in the octagonal room open as much as possible, without any obstructions of tie beams or kingpost. Thanks

RE: Octagonal Roof Support

A ring beam roof is the way to design the structure without any central support or cross ties.

A tie (tension) ring beam is located at the top of the walls and a compression ring is located close to the top of the structure near the crown.  The main rafters will meet at the crown and run down to each corner of the octagon with the purlins running around the roof structure. The ceiling follows the line of the rafters.

The purlins are designed to carry in-plane forces and if the roof is required to provide support to the tops of the walls then bracing within the plane of the roof structure can be added to transfer the loads.

RE: Octagonal Roof Support

I have to agree with Ginger. Use a ring beam to restrain the horizontal thrust.

RE: Octagonal Roof Support

(OP)
Actually, the morning room is a decagon (10-sided) structure. Each of the wall sections are 4'6-9/16" in length, 14'-0" across the flats, w/ a 9/12 roof slope, 40# snow load & 15# dead load. We want to frame the roof with 2x12's.

I guess what I am asking for is any input on the design and/or construction of a structure similar to the one I described. I guess the way I see it I only need to support the top half of each of the ten roof planes with the bracing, which from what I can tell, on a polygon hip roof is 25% of the total roof weight, which would be the top half of the roof rafters. By supporting the top half of the roof planes with the use of bracing on the corners of the stud walls should eliminate the outward thrust of the roof rafters, similar to how a load bearing ridge beam works. The other 75% or lower half of the rafter would bear down on the stud wall.

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! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close