Impact load results from which type of effect of the loads applied?
Try it first: pick an option, then read the explanation.
Asked in SSC JE 25/01/2018 (Morning)
Detailed Explanation
A static load is applied slowly and then stays constant. When a load is applied suddenly, moves, or strikes the structure, inertia comes into play and the stresses exceed the static values. This extra effect is called impact.
Why “Dynamic” Is Correct
Impact arises from the dynamic effect of the loads — option (b). Examples: vehicles on road and railway bridges, crane loads, machinery. Designers allow for it with an impact factor added to the live load.
Why the Other Options Are Wrong
- A. Static: A purely static load causes no impact.
- C. Static and dynamic: Impact is specifically the dynamic part, not a mix.
- D. Neither static nor dynamic: It is a dynamic effect.
Key Point
Impact = dynamic effect of moving or suddenly applied loads; allowed for by an impact factor.
Key Concepts for Students
- A suddenly applied load produces twice the stress of a gradually applied one.
- IRC and Indian Railway codes specify impact factors for bridges.
- Impact factor is larger for short spans.
Practice more: this is question 32 in Bending Moment and Shear Force MCQs – Part 3. Try the whole set and check every answer instantly.