Calculate the reactions at the supports and determine graphically the magnitude and nature of the forces in all the members of the frame structure.

The frame has a roller support at the bottom-middle joint (let's call this J5) and a pin support at the top-right joint (let's call this J3).
External forces are:

• $F_1 = 40 \text{ kN}$ downwards at the top-left joint (J1).
• $F_2 = 50 \text{ kN}$ downwards at the top-middle joint (J2).
• $F_3 = 50 \text{ kN}$ downwards at the top-right joint (J3).

The problem states that internal angles are $45^\circ$.