49. Constructing a fixed-pinned stiffness matrix

Direct Stiffness Method - 3D Braced Frames
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Questions and discussion for this lecture live here. Fire away by hitting Reply below :fire:

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Hi Sean,

Thanks for the clear explaination of how to implement pinned connections. How does the stiffness matrix change if say the rotation is only released in one axis rather than for both Ry and Rz? and also what happens to the stiffness matrix if it is released in the FY direction only for example? Is there a rule of thumb for modifying the stiffness matrix to take into account any combination of beam releases?

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Hey @nicben,

I wouldn’t say a ‘rule of thumb’, but there is a process for you to work out what the modified stiffness matrix looks like. After watching this lecture, head over to the 2D beam and frame course and watch the section on calculating the pinned-end stiffness matrix…it starts here…

Between that section and the this lecture in the 3D course, you’ll understand how to build the required element stiffness matrix.

Seán

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Thanks Sean. It is clear now!