EARTHQUAKE RESISTANT CONSTRUCTION

GLOBAL AND NATIONAL GUIDELINES

Earthquakes – facts and figures An earthquake is caused by the breaking and shifting of

rock beneath the Earth's surface. Earthquakes, also called temblors, it’s hard to imagine

they occur by the thousands every day around the world, usually in the form of small tremors.

Some 80 percent of all the planet's earthquakes occur along the rim of the Pacific Ocean, called the "Ring of Fire“

On average, a magnitude 8 quake strikes somewhere every year and some 10,000 people die in earthquakes annually

Ground shaking from earthquakes can collapse buildings and bridges; disrupt gas, electric, and phone service; and sometimes trigger landslides, avalanches, flash floods, fires, and huge, destructive ocean waves (tsunamis).

 Collapsing buildings claim by far the majority of lives, but the destruction is often compounded by mud slides, fires, floods, or tsunamis

Earthquake Hazards Ground Shaking: Shakes structures constructed on

ground causing them to collapse.

Liquefaction: Conversion of formally stable cohesion-less soils to a fluid mass, causing damage to the structures.

Landslides: Triggered by the vibrations

Retaining structure failure: Damage of anchored wall, sheet pile, other retaining walls and sea walls.

Fire: Indirect result of earthquakes triggered by broken gas and power lines.

Tsunamis: large waves created by the instantaneous displacement of the sea floor during submarine faulting

Earthquakes – facts and figures

Damages due to earthquake in 2011

Global seismic hazard map

India – how prone are we ?

Approach to ERC construction

Conventional Approach:- Design depends upon providing the building with

strength, stiffness and inelastic deformation capacity which are great enough to withstand a given level of earthquake generated force.

  Basic Approach:- 

Design depends upon underlying more advanced techniques for earthquake resistance is not

to strengthen the building, but to reduce the earthquake generated forces acting upon it.

Factors governing effect of Earthquake on structure

Intensity of earthquake Type of earthquake waves Type of structure Type of design Shape of structure both in plan & elevation Type of soil Type of foundation Type of material used for construction Load of structure

Methods Of creating Earthquake Resistant Structure

Increase natural period of structures by Base Isolation like : Lead Rubber Bearing Laminated Rubber Bearing High Damping Rubber Bearing Spherical Sliding Bearing Friction Pendulum System

Increase damping of system by Energy Dissipation Devices like : Viscous dampers Friction dampers Yielding dampers Visco elastic dampers

By using Active Control Devices like : Sensors H/w & S/w Actuators

Seismic designing Planning stage

Plan building in symmetrical way (both axis) Avoid weak storey and provide strong diaphragm Don’t add appendages which will create difference in Centre of mass and

centre of rigidity Conduct soil test to avoid soil liquefaction Steel to be used of having elongation of 14% and yield strength of 415

N/mm2 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. It should be in outer

boundary to have large lever arm to resist the EQ forces. Construction stage

Compact the concrete by means of needle vibrator. Cure the concrete for at least a minimum period. Experienced supervisor should be employed to have

good quality control at site

BIS guidelines for construction in India

Guideline laid down for five category of structures Part 1 General provisions and buildings Part 2 Liquid retaining tanks - Elevated and ground supported Part 3 Bridges and retaining walls Part 4 Industrial structures including stack like structures Part 5 Dams and embankments

Seismic zone identified and construction parameters amended accordingly

Foundation laying in various soil type is also specified.

Specification about material to be used including RCC, Steel, masonry work etc.

Some important IS codes IS 1893 (Part I), 2002, Indian Standard Criteria for

Earthquake Resistant Design of Structures (5th Revision)

IS 4326, 1993, Indian Standard Code of Practice for Earthquake Resistant Design and Construction of Buildings (2nd Revision)

IS 13827, 1993, Indian Standard Guidelines for Improving Earthquake Resistance of Earthen Buildings

IS 13828, 1993, Indian Standard Guidelines for Improving Earthquake Resistance of Low Strength Masonry Buildings

IS 13920, 1993, Indian Standard Code of Practice for Ductile Detailing of Reinforced Concrete Structures Subjected to Seismic Forces

Other questions to think about

How will you stop the building from collapsing? If it does not fall how will you prevent accidents

in the building as it moves? What about falling glass and rubble on the

people outside? What about problems after the earthquake (fire,

gas and water leaks, no power)? Where will you build it? Away from built up areas

or near emergency services? There are plenty of other things that you need to

think about.