EARTHQUAKE RESISTING STRUCTURES

BY- VARUN

EARTHQUAKE RESISTING STRUCTURES TECHNIQUES

Base Isolation Method- separate building from ground by some rubber devices.

Energy Dissipation Device (Seismic Dampers)- Special devices introduced in building to absorb the energy produced by seismic waves.

BASE ISOLATION

Introduces flexibility to the structures.

Building is rested on flexible pads (Base Isolators).

When earthquake strikes the building does not moves.

It is suitable for hard soil only.

TYPES OF BASE ISOLATOR

Lead Rubber Bearing:-

Frequently used for base isolation.Made from layers of rubber sandwiched together with layers of steel.Very stiff and strong in the vertical direction.Flexible in horizontal direction.

Spherical Sliding Isolator

It uses bearing pads that have a curved surface and low-friction materials.During an earthquake the building is free to slide both horizontally and vertically It will return to its original position after the ground shaking stops.

ENERGY DISSIPATION DEVICE• These are used in place of structural elements

such as diagonal braces• Acts like the hydraulic shock absorbers in cars• When seismic energy is transmitted through

them, dampers absorb part of it, and thus damp the motion of the building.

TYPES OF SEISMIC DAMPERSViscous Dampers (energy is absorbed by silicone-based fluid passing between piston cylinder arrangement) Friction Dampers (energy is absorbed by surfaces with friction between them rubbing against each other) Yielding Dampers (energy is absorbed by metallic components that yield)

SEISMIC DESIGNGeneral Principles of Seismic Design:Structures should not be brittle or collapse

suddenly.Resisting elements must be provided evenly

throughout the building.All elements such as walls should be tied

together so as to act as an integrated unit during earthquake shaking.

The building must be well connected to a good foundation and the earth.

SEISMIC DESIGNING • Planning stage– Plan building in symmetrical way (both axis)– Avoid weak storey and provide strong diaphragm– Conduct soil test to avoid soil liquefaction – Simple Design

• Design stage– Avoid weak column and strong beam design.– Provide thick slab which will help as a rigid

diaphragm. Avoid thin slab and flat slab construction.

– Provide cross walls which will stiffen the structures in a symmetric manner.

– Provide shear walls in a symmetrical fashion.

•Construction stage- Compact the concrete by means of needle vibrator.

- Cure the concrete for at least a minimum period.

SHEAR WALL

Vertically oriented wide beams.

It carries seismic loads down to the bottom of foundation.

Provides large strength and stiffness to buildings.

Should be symmetrical in plan along both the axes.

Effective when located along the exterior perimeter of building.