×
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

Second Moment Area of Moment Frame with Shear Truss

Second Moment Area of Moment Frame with Shear Truss

Second Moment Area of Moment Frame with Shear Truss

(OP)
Hi there,

I am trying to calculate the deflection of a moment frame made up with a shear truss.



Each bay is 3 metres, so total height is 12 metres. I am using a static horizontal load of 10000 N/m.

I am modelling it as a cantilever beam using stiffness 'K' as (8*E*I)/L^4

I need to find the second moment area of the structure. For the shear truss alone I get the correct deflection. In the literature I have found that the second moment of area is 0.9*(2*(A*1.5^2)). A is the cross-sectional area of the column, 1.5 is the distance in metres from the neutral axis. Using this I get the correct answer. However, when I add unbraced bays to each side I do not.

I guessed that the new second moment area of the total structure is 0.9*(2*(A*1.5^2)) + 2*(A*4.5^2), but I don't get the correct answer from this.

So, Could somebody please tell me what the second moment of area for this structure is, please?

Best wishes

RE: Second Moment Area of Moment Frame with Shear Truss

It doesn't really have a "second moment of the area" in the strict sense. The drift at the top is a function of many input parameters, including the types of connections between all of those members.

You could use the program to compute the drift at the top and back-calculate an "effective second moment of the area."

For example, apply P = 50 kips laterally at the top, and calculate the drift, Delta. Then use Delta = PL^3 / 3EI to back out Ieff. That's the closet thing to what you're asking.

RE: Second Moment Area of Moment Frame with Shear Truss

The usual approach to 2d truss analysis is a graphical method of great beauty. It superimposes the FBDs of each joint. The members themselves are not labelled, the spaces between them are. Sadly my google fu has failed to find the proper name for it.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Second Moment Area of Moment Frame with Shear Truss

I remember those diagrams, fondly, from my undergraduate days in the late 1960s.  "Maxwell diagrams".

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