I am establishing a MatLab FEA code for determining the stiffness of a structure. Diagram of the structure is added below. I have established a code for determining the stiffness of the structure, but I am unsure of how to treat node B. Element AC is one continuous beam with element BD connected to it through a pin connection. That is, element BD will only experience axial forces (= no angular displace), while element AC at node B will experience axial forces AND bending moment, causing angular displacement. So how do I treat this node? I can not say angular displacement is 0, because it is not for element AC. But if I say it is different from zero, the connection will act as if it was welded together.

Please let me know if you need more information.


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  • $\begingroup$ Welcome to Engineering! Are you using the direct stiffness method for your analysis? $\endgroup$ – Wasabi May 12 at 15:52
  • $\begingroup$ If you by, the direct stiffness method, mean hand calculations, then no. I establish a 6x6 matrix for every element with given values. Afterwards I rotate them into the global system and make then correspond with the global DOFs. Then at last sum up the element stiffness matrices. Thanks. $\endgroup$ – Frederik Christensen May 25 at 21:51
  • $\begingroup$ That's the definition of the direct stiffness method. I'll try to find time to answer this tomorrow. $\endgroup$ – Wasabi May 26 at 0:49

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