ASeminar

On

“Base Isolation and Seismic Consideration in Civil Engineering”

APPLIED MECHANICS DEPARTMENTS. V. NATIONAL INSTITUTE OF TECHNOLOGY

SURAT – 395 007

Prepared By: ANKIT JAIN (U10CE078)

Seismic Forces is generated due to Earthquake.

Earthquake is a natural disaster. It is a violent shaking of earth. It happens due to mass shifting in

bedrock. Because it is a natural disaster so

we can’t control it. Only we can try that the damage should be minimum.

WHAT IS SEISMIC FORCE?

Bhuj Earthquake, 2001

Different Seismic Zones In India

MAGNITUDE AND INTENSITY OF EARTHQUAKE

1. MAGNITUDEThe Magnitude (M) is a quantitative measure of its strength in terms of energy released . 2. INTENSITYThe intensity of an earthquake is measured qualitatively in terms of damages caused by it at a particular location. In general, larger the earthquake, greater is the intensity.

Magnitude of an earthquake is a measure of its size. While intensity is an indicator of the severity of shaking generated at a given location.

HAZARDS DUE TO EARTHQUAKE

a) Liquefaction of Soils

b) Ground Shaking

c) Surface Rupture

d) Landslides

e) Lateral Spreading

f) Shear Failure of Foundation

g) Settlements of Structures

h) Failure of Retaining Wall

i) Tsunamis And Seiches

LIQUEFACTION OF SOIL

Liquefaction is a state of saturated cohesion less soil when its shear strength is reduced to zero due to pore water pressure caused by vibration during an earthquake. The soil starts behaving like a liquid.

Soil Liquefaction During New Zealand Earthquake, 2011

PREVENTION OF LIQUEFACTION

a. Providing Deep Foundation

b. Compaction of Soil

c. Replacing the Liquefaction Soil

d. Grouting The Soil

e. Ground Water Pumping

f. Drainage of Soil

g. Providing Stone Columns

EARTHQUAKE-RESISTANT DESIGN

Objective of Earthquake-Resistant Design is to make such buildings that can resist effect of ground motion and would not collapse during the strong Earthquake.

All the components of the structure and foundations are designed to resist inertia forces in addition to the normal forces.

All the walls must be jointed properly, so that they can act together against the earthquake shaking at the time of seismic force transferring to the ground.

BASE ISOLATION METHOD

The idea behind the 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 greatly reduced.

If a building is rested on flexible pads that offer resistance against lateral movements, then some effect of the ground shaking will be transferred to the building above. If the flexible pads are properly chosen, the forces induced by ground shaking can be a few times smaller than that experienced by the building built directly on ground.

EFFECT OF BASE ISOLATION METHOD

View of Basement in Bhuj Hospital Building

BASE ISOLATION METHOD

SEISMIC DAMPERS

Seismic Dampers are fixed in place of structural elements as diagonal braces.

They absorb a part of seismic energy when it is transmitted through them.

TYPES OF SEISMIC DAMPERS:

a. Viscous Dampers

Energy is absorbed by silicone-based

fluid passing between piston-cylinder

arrangement.

Viscous Damper

SEISMIC DAMPERS

SEISMIC DAMPERS

b. Friction Dampers

Energy is absorbed by surfaces with

friction between them rubbing against

each other

c. Yielding Dampers

Energy is absorbed by metallic

components.

Friction And Yielding Dampers

SEISMIC DAMPERS