×
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

Finding Element Stress of Space Frame Stiffness Method

Finding Element Stress of Space Frame Stiffness Method

Finding Element Stress of Space Frame Stiffness Method

(OP)
Hi all

If I have interconnected frames, when using stiffness matrix for frame I can find the reaction at each node of the space frame.
So now I have these reaction forces at each node.

Then lets say there is this node A connecting 3 frame elements a, b and c.
I know the reaction force at A equal x.
So the value of x would be the sum of reaction forces of element a, b and c at end point A.

But what would be the reaction (moment, torque, axial, shear) at node A with respect only to the element a?
, what would be the reaction at node A with respect only to the element b?
and
, what would be the reaction at node A with respect only to the element c?

I need this value to find the stress components of each member a, b and c at point A.

Thank you in advance.

RE: Finding Element Stress of Space Frame Stiffness Method

If you post a well annotated sketch I'm sure someone could help you.

...Probably not me though

RE: Finding Element Stress of Space Frame Stiffness Method

The output from the stiffness method is the deflections and rotations at each node. You then apply those deflections and rotations to both ends of each beam, which gives you end actions of each beam. So you set up the stiffness matrix for each beam and multiply it by the displacement vector of the two end nodes.

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

RE: Finding Element Stress of Space Frame Stiffness Method

1) what s/ware are you using that doesn't give element loads ?

2) the load at the node is going to be shared between the elements according to stiffness. I would calculate the stiffness of each element (axial only ?) then project into the three global axes (that match the nodal loads). Three elements (or less) into a node are solvable, more than three are redundant (but you may be able to use other nodes to infer the load in one, or more, elements and so solve these too.

3) get a better FE s/ware !

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

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