1- Select the whole bridge (anything that has hinges in it)
2- On the left menu go to the "Hinges" Section
3- There should be 3 slider boxes in there, Motor Speed, Motor Strengh, and Impulse break limit. Set the impulse break limit box to 100 or so and the hinges will "break" when you put enough force on them
*forgot* go to options and set it to Advanced Mode. Then there will be impulse break limit section under hinges now. You can also set hinges to move by setting buttons (like making a wheel spin when you press a button)