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

Framework calculations in 3-D

Framework calculations in 3-D

Framework calculations in 3-D

I'm currently doing a project where i'm constructing a framework for an engine mount connecting an airplane with an engine. The project involves both calculations by hand and with CAD(Creo), and i have no problem with the CAD part as i have done the simulations.
The part with doing calculations by hand have caused some problems where i'm doing the calculations in 3-D, and its causing some problems.
The top and bottom diagonals are not to be considered in the calculation by hand. Therefore you have 6 symmetrical beams.
So far what I have done in the calculations is that i've created a equation system with help of directional cosines which seems to get me the wrong answers. So i'm looking for some help in creating the equations system for this problem.

RE: Framework calculations in 3-D

Virtual work is a good method for such things.

RE: Framework calculations in 3-D

why are the top and bottom diagonals neglected in hand calcs ?

sure their primary job is lateral load, but they'll work under vertical load, what I guess you're hand calc'ing.
sure they complicate things, but that's what truss member do to you ... create loads in unintended directions.

direction cosines should work.

but the structure is redundant so that'll be your hand calc difficulty.

you could do something iterative ...
neglect the top and bttm diagonals (for vertical load; negect the side diagonals for lateral load)
each side reacts 1/2 the vertical load and one side of the couple from moment.
direction cosines should distribute the load between the three members,
direction cosines should complete the loads in the members.
now how have the ends moved, and what loads does this create in the diagonals?
rework to remove these "unwanted" loads ...

of course you'll FEA for the proper loads

another day in paradise, or is paradise one day closer ?

RE: Framework calculations in 3-D

Simplify first!
I would start with the assumption of pin-joints on all truss members. Analyze the mount as if it were a pure truss with no beam or bending elements at all.
Furthermore, you would be giving yourself a model that DOES permit consideration of the diagonal members (and wouldn't work without them, in fact).
Will the tensile/compressive loads on all of the members, you can then do a reality check on a second model, using beam members, if you want.
Good frame design depends on alignment of all member centerlines to common points - which not only prevents secondary moments in the joints, but also makes the truss correspond to the pin-joint model, too.


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


White Paper - Strategies to Secure Connected Cars with Firewalls
White-hat hackers have demonstrated gaining remote access to dashboard functions and transmissions of connected vehicles. That makes a firewall a vital component of a multilayered approach to vehicle security as well as overall vehicle safety and reliability. Learn strategies to secure with firewalls. Download Now
White Paper - Model Based Engineering for Wire Harness Manufacturing
As complexity rises, current harness manufacturing methods are struggling to keep pace due to manual data exchanges and the inability to capture tribal knowledge. A model-based wire harness manufacturing engineering flow automates data exchange and captures tribal knowledge through design rules to help harness manufacturers improve harness quality and boost efficiency. Download Now
White Paper - What is Generative Design and Why Do You Need It?
Engineers are being asked to produce more sophisticated designs under a perfect storm of complexity, cost, and change management pressures. Generative design empowers automotive design teams to navigate this storm by employing automation, data re-use and synchronization, and framing design in the context of a full vehicle platform. Download Now
eBook - Simulation-Driven Design with SOLIDWORKS
Simulation-driven design can reduce the time and cost of product development. In this engineering.com eBook, we’ll explore how SOLIDWORKS users can access simulation-driven design through the SOLIDWORKS Simulation suite of analysis tools. 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