What prevents a Suspension Bridge and an Electrical Transmis

What prevents a Suspension Bridge and an Electrical Transmission towers failing structurally ?

Solution

In a Suspension Bridge the tension in cables holds the bridge in position and prevent bridge from failing structurally.

In a transmission Tower the axial Forces( Truss Action) in its members resists the various loads a tower is subjected to like wind loads, electric cable loads. Earthquake forces etc.