Which of the following is an example of a dynamic load on a bridge?

• A. Traffic-induced vibrations.
• B. Dead weight of the bridge.
• C. Permanent supports weight.
• D. Static wind load.

Answer: (A)

Dynamic loads are forces that change with time and can make a structure respond with vibrations. Traffic-induced loads fit this, because as vehicles move across the bridge deck the forces on it rise and fall, causing vibrations and a transient dynamic response rather than a steady, unchanging load. The other options are static in nature: the bridge’s own dead weight remains constant; the weight of permanent supports is fixed; and a static wind load implies a steady force rather than a time-varying one. In real-world scenarios, wind can be dynamic, but the term used here indicates a constant load, so traffic-induced vibrations are the clear example of a dynamic load.