# Symmetry to determine the support reactions of a statically indeterminate frame

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

I want to find the support reactions.

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:

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:

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.