Which structural control method involves the use of Base Isolation to protect a building?
- AIncreasing the thickness of all shear walls.
- BDecoupling the structure from the ground using flexible bearings to increase its natural period.Correct
- CAdding extra mass to the top of the building to reduce vibrations.
- DUsing higher grades of concrete in the foundation.
Solution
Concept
Base Isolation System
Formula
N/A
Step-by-step solution
1. Review the concept of Base Isolation in seismic protection of buildings. 2. Understand that base isolation decouples the superstructure from ground motion using flexible bearings, increasing the natural vibration period. 3. Select Option B as the correct choice.
Explanation
Base isolation works by separating the building from the ground using flexible bearings or pads. During an earthquake, these bearings absorb the ground's shaking movement and increase the building's natural period, reducing the amount of force and vibration transferred to the structure above.
Shortcut
To remember the concept of Base Isolation, use the key phrase "Base Isolation = Break the Base Bond": - Base: Isolation happens at the bottom/foundation level. - Isolation: Decouples (separates) the building from the ground using flexible bearings. - Period Increase: Increases the natural period of the building, reducing earthquake forces.
Common mistake
A common mistake is selecting Option C by confusing Base Isolation with Tuned Mass Dampers, which use an added mass at the top of a building to reduce vibrations. Another frequent error is choosing Option A or D by confusing structural isolation with traditional seismic strengthening methods, such as stiffening shear walls or strengthening foundations, rather than decoupling the superstructure from ground motion.
Correct answer: B) Decoupling the structure from the ground using flexible bearings to increase its natural period.