# Homework Help: Frames with inclined legs using slope-deflection method

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1. Mar 4, 2015

### Ashu2912

1. The problem statement, all variables and given/known data
This is a diagram from "Structural Analysis" by Aslam Kassimalli while solving frames using slope-deflection method. In the figure, the tangent to the deflected shape at C` is parallel to the original member AC implying that the slope at C is zero. However, later they have considered θC (the slope at C) as an unknown while writing the slope deflection equations. Why so?

2. Relevant equations

3. The attempt at a solution

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2. Mar 8, 2015

### pongo38

I don't think you can assume that the tangent at C' (the prime symbol ' is not clear enough in the figure) is parallel to AC. The tangent at D' is not visibly parallel to BD, and shouldn't be. In general, I would expect both C and D to rotate somewhat, because the rotation is only partially restrained by the stiffness of the attached members.