Basics of earthquake & structural and non structural guidelines for building construction in eq...

BASICS OF EARTHQUAKE +

STRUCTURAL AND NON-STRUCTURAL GUIDELINES

FOR BUILDING CONSTRUCTION IN EQ

PRONE AREAS

An academic purpose compilation byProf. Bhasker V. Bhatt

PG In-charge (ME TCP) & Assistant Professor in Civil Engineering Department, SCET, Surat

Earthquake

What is an Earthquake?

A Vibrations produced in the earth’s crust when rock’s elastic strain has

ruptured and rebounded

What causes an earthquake?

Earthquakes are usually caused by sudden movement on faults

What causes an earthquake?A sudden release of energy accumulated in deformed

rocks causing the ground to tremble or shake.Causes rupturing or brittle failure of crustal rocks.

Energy is released.Movement of fault blocks takes place along a

fault plane.

After energy is released, friction between the adjacent fault blocks prevents further movement. Stress resumes and

builds up again.Friction between the blocks is overcome. Another earthquake

occurs.

Gujarat Earthquake

Concrete Building

Mexico Earthquake

Apartment Building

Soft-story Collapse

Gujarat EQ

Mexico Earthquake

School Building

Gujarat EQ

Large blocks piled up using weak bond

Gujarat EQ

Many casualties occurred in stone masonry buildings

Gujarat EQ

Strong Structure – Weak Joint with masonry

Gujarat EQ

Soft story

Liquefaction

Nigata, Japan

Our Earth is Alive

Plate Tectonics

What is Mechanism of Earthquake ?

Different Plates around the World

Earthquake Occurrence

Himalayan Mountains

Earthquake

Seismic Waves

Measuring Earthquakes

Site Effect

The shape, amplitude, and the duration of a seismic movement are affected, among other things, by its

magnitude, the distance to the hypocenter, and the local site conditions

Buildings Configuration Problem

Irregular Shape

Torsion

Overturning

Building Seldom Overturn- They fall apart or pancake

Soft-story Collapse Mechanism

Ductility

Lateral Force Resisting Systems

Architectural

consideration in

Building Layout

and Configuration

Building Configuration

2

3

2

1 1

3Symmetrical buildings in plan and elevation are better than

asymmetrical ones.

Irregularity and Seismic Joints

Asymmetry (false symmetry) due to the location of structural elements

Unsuitable plan Suitable plan

In order to make unsuitable building plans seismically acceptable, they need to be divided into a number of

rectangular or symmetrical units.

Building Configuration

Pounding Effect

Building Configurationcontd....

The same principle can be applied to the elevations of the buildings

b

h h

b

Height of the building should be less than 3b

Building Configurationcontd....

Ideal Earthquake Resistant Building

Small mass Low Height-to-base ratio Low center of mass relative to the

ground Balanced lateral resistance Direct load paths Symmetrical Plan Uniform section and elevation Uniform floor heights, and Maximum rotational resistance Short spans

Building

Configuration

Do and Don’t do

Abrupt stiffness change in elevation due to infills

Increase of Ground Floor stiffness and strength

or

Asymmetry of building

in Plan

Seismic Joints

Or

Strengthening of Connection

Abrupt Stiffness change in building in

Plan

Seismic Joints

No Yes

Interaction of Structural Elements of Different Stiffness

Seismic Joint

Proper Design OR Strengthening of Flexible Element

Significant difference between stiffness in x and y Balanced stiffness in x and y

Asymmetric arrangement of Vertical element (Torsional Vibration)

symmetric arrangement of Vertical element

No Yes

Small contribution of Shear wall in Torsional resistance

Increase of Torsional resistance

Incorrectly supported columns Uniform Column

No Yes

Unclear Frame Behavior Good Frame Behavior in x and y

Strong beam-weak Column (column Failure mechanism)

Weak (comparatively) beam-strong Column (Beam Failure mechanism)

No Yes

Stitch at L-junctions and T-junctions should be designed to mitigate

the problem

Masonry Buildings

Masonry Buildingscontd.….

Horizontal band at sill, lintel and eve level should be designed for out of plane bending


Stitch and band give more integrity to the building elements and protect the building from corner opening and out of

plane failure


Vertical bars at corners T-joints and around the openings should be designed

for tensile stress developed

RC Buildings

Brittle failure of RC building

RC Buildingscontd…..

Failure of building at beam column joints

Joint ReinforcingUnreinforced beam-column joints may not be able to

develop the strength of the connected members, and this can lead to sudden brittle failure of the joint

Damage at Joint and Column


What is our practice?


Joint Reinforcing...


Failure at cold Joint


What we are constructing?

Cold joint...


Cold joint...

Shear key and rough surface give better performance


Column tie spacing and tie hooks

Can only longitudinal bars save the column?


Column tie spacing and tie hooks….

Comparison of damage of two columns


Column tie spacing and tie hooks….


Short column effect…...


Column-bar splices

Non structural Damage and its Mitigation

Broken Glass in Kitchen

Room

In Bed RoomsFurniture overturned throwing outside the contents

Bureau Toppled

Office

In officeFurniture, file cabinets overturned

Shops

In shops and departmental storesMany liquor and bottles broken

Non-structural damage

In Book Store and Libraries

Non-structural damage

Shattered glasses

Water Heaters Tip Easily During Earthquakes

Significance: Life Safety

If a ten-rupees flowerpot , not fastened well to the building, falls on someone’s head, it can be a killer!

Significance: Property Loss

Very important in case of commercial and Institutional buildings

Property losses in 25 commercial buildings due to the 1971 San Fernando earthquake:Structural damage 3%Electrical and mechanical

7%Exterior finishes 34%interior finishes 56%.

Significance: Loss of functionCritical facility

HospitalTelecommunication etc.

Mitigation Measures : Removal

A hazardous material that could be spilled, could be stored perfectly well outside the premises

One solution would be stronger fastening or the use of stronger supports,

But the most effective solution would be removal and replacement

A very heavy object on top of a shelf could fall and seriously injure someone

If it is relocated to a floor-level shelf it would not represent any danger to human lives or to property. Store large, heavy or fragile objects on

lower shelves or in low closed cabinets

Relocation

Anchorage of Battery Rack+ Anchorage of Book shelve SOURCE: EERI

Anchorage

Anchorage

SOURCE: PAHO/WHO

Restricted Mobilization

It does not matter if the cylinders shift as long as they do not fall and break their valves. Sometimes back-up power generators are mounted on springs to reduce the noise and vibrations when they are working, but these springs would amplify ground motion.

Flexible Couplings

The use of flexible piping in critical areas

such as between buildings and

equipment helps to prevent breakage

PAHO/WHO

Supports

Damage to ceilings

Supports

Substitution

A heavy tiled roof does not only make the roof of a building heavy, it is also more susceptible to earthquake shaking. The individual tiles tend to come off, creating a hazard for people and for objects.

One solution would be to change it for a lighter, safer roofing material.

Modification

Rolls of transparent adhesive plastic may be used to cover the inside surfaces and prevent them from shattering and threatening those inside.

Reinforcement

Useful forUnreinforced infill wallChimney may be strengthened

Redundancy

Redundancy or duplication of items is advisable.

An emergency response plan requiring storage of emergency supplies is a good idea.

It is possible/necessary to store extra quantities of certain products, providing a certain level of independence from external supply which could be interrupted in the case of earthquakes.

Limit Sliding & Rocking Movements

Restraints and fasteners for smaller equipment

Simple improvement can save life and property

Nonstructural Vulnerability Reduction

BHASKER BHATTConsulting Town Planner and Civil EngineerC:+91-98258-35364 E: [email protected]

Promote & Practice Safe Construction…Thanks…

Basics of earthquake & structural and non structural guidelines for building construction in eq...

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