Applying Castigliano's Second Theorem to Bent Beam Analysis

[closrevolution]

Homework Statement

The problem is attached

Homework Equations

Any help on setting up the problem would be appreciated

The Attempt at a Solution

U = 1/2*[(M^2)L]/[GIp]
This equation gives the energy
Using Castigliano's 2nd Theorem I need to find the partial derivative of U with respect to P
Not sure how to go about this with the beam given

 

[pongo38]

Thinking of the plane in which the bent beam lies as having x and y axes, can you formulate expressions for M as Mx and My in the sections parallel to Ox and Oy? How would you interpret the expression GIp for the 2 parts of the bent?

 

[closrevolution]

Not sure what you mean by Ox and Oy
G is the same for both parts of the beam but not sure for Ip

Thinking of the plane in which the bent beam lies as having x and y axes, can you formulate expressions for M as Mx and My in the sections parallel to Ox and Oy? How would you interpret the expression GIp for the 2 parts of the bent?