Design of Truss and Structure

Question

Hello! 
 
 I'm a CE student and im trying to design a structure made up of steel. 
 I would like to know what connection do I actually use for the support on trusses, and on STAAD.Pro do I place the truss on my structure or do I analyze the structure by two parts first the truss then transfer the loading to the steel columns? 
 
 Thank you!

Sye · Answer

There is no need to model the truss separately. You can model the truss on top of the supporting structure. The structure can be modeled as a space frame or a plane frame. Truss specification can be assigned to the braces or ties of the truss structure. Avoid assigning the truss specification to the top and bottom chords of the truss as these may actually take up bending. The loads applied on the trusses would automatically be transferred to the supporting structure. Depending on what forces (or moments ) are transferred by the truss to the supporting structure, you may need to specify appropriate member releases.

Sye · Answer

This error typically means that some of the members in your structure may not have a material assigned to it. Go to the menu option Select > By Missing Attributes > Missing Elasticity to see these members. Ensure that you assign the section property and material to all entities in your model. There is no need to recreate the file.

Rajat · Answer

Please go through the following post and modify your model accordingly 
 http://communities.bentley.com/products/structural/structural_analysis___design/w/structural_analysis_and_design__wiki/21481.error-section-properties-not-entered-for-member 
 Thank you.

Sye · Answer

Since your truss support is 15 cm high, why don't you model these supports using short vertical members. These would connect your truss and the base frame.

Sye · Answer

Yes that should work.

Sye · Answer

The reason you are getting these zero stiffness warnings is that you have certain nodes where there are no stiffness associated with certain degrees of freedom. For example if you look at the node 10, all the members connecting to that node are trusses lying in the XY plane. So if there is a load in the Z direction at that node, there is no way for the structure to resist that load which is why you get the zero stiffness warning at that node for direction 3 ( which represents translation in Z ). In addition since all the members at that joint are trusses, there is no rotational stiffness about any of the global directions ( 4, 5 & 6 ). 
 In your model there are no abnormal displacements and the static check seems to be satisfied. So as far as I can see, the zero stiffness did not have an impact on the analysis. 
 You find more on zero stiffness at the following wiki 
 https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/29020/zero-stiffness-warning 
 Instructions on uploading files in Bentley Communities forum is available at 
 https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/28129/how-can-i-upload-files-in-the-bentley-communities-forum

Design of Truss and Structure

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