Modeling Moment and Shear Connections

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SUMMARY

This discussion focuses on modeling moment and shear connections in a 3D steel frame structure using S-Frame 11. The user encountered an "Illegal constraint to the support" error when defining moment connections, which prevent rotation and translation about all axes. The correct approach to modeling a moment connection is to define the joint as a rigid joint, allowing translation while restricting rotation. The user clarified that moment connections imply welded members, and rigid connections are the default setting in S-Frame 11.

PREREQUISITES
  • Understanding of moment and shear connections in structural engineering
  • Familiarity with S-Frame 11 software
  • Knowledge of rigid joint definitions and their implications
  • Basic principles of structural analysis under gravity and lateral loads
NEXT STEPS
  • Research how to troubleshoot "Illegal constraint" errors in S-Frame 11
  • Learn about the differences between moment and shear connections in structural design
  • Explore modeling techniques for rigid joints in 3D structural analysis
  • Study the impact of joint constraints on structural behavior under various loading conditions
USEFUL FOR

Structural engineers, civil engineering students, and professionals involved in modeling steel frame structures will benefit from this discussion.

CivilSigma
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Homework Statement


I am trying to model a structure that has moment connections between some beams and columns, and shear connections between the remaining beam and columns in 3D.

The software I am using (S-Frame 11) gives me an error when running the analysis for the nodes that I have defined as moment connections :
  • No rotation about x,y,z axis
  • No translation about x,y,z axis
The error is : "Illeagel constraint to the support"

Homework Equations


I know that a moment connection prevents rotation and translation about all axis

The Attempt at a Solution



Can some one please provide guidance to how I can define a moment connection or if my understanding of a moment connection is correct?

This figure represents the definition I used for a Moment connection at one of the nodes:
upload_2018-3-21_12-35-7.png


This is my general model of the steel frame building I am going to analyze under gravity and lateral loads. If you can see, I have some nodes as fixed (line with dash underneath - those are the moment connections).

upload_2018-3-21_12-30-37.png
 

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For those who are interested: to model a moment connection, you simply define the joint as a rigid joint.

You do not play around with the degrees of freedom at the joint (only if it is fixed in real conditions, like at the foundation/base). But a moment connection implies that the members are welded together = a rigid joint (that is still able to translate about x,y,z). Also a rigid connection is the default condition set when you model a member connecting into a joint!
 

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