Base Isolation

The idea behind base isolation is to detach (isolate) the building from the ground in such a way that earthquake motions are not transmitted up through the building, or at least reduced greatly. The concept of base isolation is described through an instance of building resting on roller .The roller freely roll When the ground shakes but the building above does not move. If the gap between the building and the vertical wall of foundation pit is small, vertical wall of the pit can hit the wall.

                Hypothetical building

Therefore, in practice 100% frictionless rollers are not provided. The building is rested on flexible pads that offer resistance against lateral movements as shown in given figure. This reduces some ground shaking effect to the building. The flexible pads are known as base-isolators, whereas structures protected by these devices that are called base-isolated buildings.

                                    Base isolated building