If a single diagonal, or brace, is used, it must be able to resist tension (stretching) and compression (squashing) caused by sideways forces in both directions on a frame.
If you had the Flash Shockwave plugin you would be able to see an animation of force being applied to a braced frame
If you had the Flash Shockwave plugin you would be a ble to see an animation of force being applied to a braced frame
Single diagonals in a 3-storey frame.
Strengthening Buildings Braced Frames Single Diagonals