Why soldiers are not advised to do march past on the suspension bridge?

Suspension bridges are designed to handle a certain amount of weight, and this weight is evenly distributed across the bridge. When soldiers march in formation, they create a concentrated load that can exceed the bridge's capacity. This can cause the bridge to sway or even collapse.

In addition, the rhythmic motion of soldiers marching can create a resonance effect that can amplify the bridge's vibrations. This can make the bridge even more unstable and increase the risk of collapse.

For these reasons, soldiers are not advised to do march past on suspension bridges.