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The following is an indeterminate frame consisting of two beams that are rigidly connected to each other at the corner support.

enter image description here

I want to find the support reactions.

enter image description here

As far as I can see, this is a symmetric structure with symmetric loading (please do correct me if I am wrong).

And as I understand it, a symmetric structure with symmetric loading has symmetric reactions.

From here, the chain of logic I would follow is:

  1. The corner roller support has a vertical reaction (V2) of 0, for symmetry to be possible.
  2. Similarly, H1 = 0, for symmetry.
  3. V1 = - H2, again for symmetry of reactions.

Then, from equilibrium, we can say:

enter image description here

However, this is incorrect. The mark scheme for this question has a different solution.

Could someone please tell me where in my process I have made a mistake?

EDIT: This is what the mark-scheme says: enter image description here

VJ123
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1 Answers1

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The members and loads of the frame are symmetric about joint "B", but the supports are not, which is the source that causes non-conforming deflections when loaded. The sketches below depict each case of the deflection of the frame.

enter image description here

ADD:

The roller support at "B" is free to move in x-dir. The sketches below show the lateral displacement and corresponding joint rotation due to the respective loads "F" and "H".

enter image description here

Simplified Frame Model:

enter image description here

r13
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