EARTHQUAKE RESISTANT CONSTRUCTION OF BUILDINGS

by - Bishal Ghimire

OVERVIEW• Internal Structure of Earth

• Plates

• History of Plates

• Earthquake - Global Seismic hazard map

• Earthquake History in Nepal

• Site Selection

• Liquefaction

GLOBAL SEISMIC HAZARD MAP

PLATES

HISTORY OF PLATES

“५ सम्म बाल..६ आए पाल...7 आए बेहाल...8 आए काल...”

EARTHQUAKE• At the boundaries where the plates are coming close to

each other (convergent plate boundaries), the movement of different plates increases the stresses in the plates.

• In the course of time, such stress goes on increasing and a stage comes when the plates can not bear further stress and they suddenly break producing a strong vibration.

BODY WAVE

Traveling through the interior of the earth, body waves arrive before the surface waves emitted by an earthquake. These waves are of a higher frequency than surface waves.

The first kind of body wave is the P wave or primary wave. This is the fastest kind of seismic wave, and, consequently, the first to 'arrive' at a seismic station. The P wave can move through solid rock and fluids, like water or the liquid layers of the earth. It pushes and pulls the rock it moves through just like sound waves push and pull the air.

P waves are also known as compressional waves, because of the pushing and pulling they do. Subjected to a P wave, particles move in the same direction that the the wave is moving in, which is the direction that the energy is traveling in, and is sometimes called the 'direction of wave propagation'.

The second type of body wave is the S wave or secondary wave, which is the second wave you feel in an earthquake. An S wave is slower than a P wave and

can only move through solid rock, not through any liquid medium. It is this property of S waves that led seismologists to conclude that the Earth's outer core is a liquid. S waves move rock particles up and down, or side-to-side--perpindicular to the direction that the wave is traveling in (the direction of wave propagation).

SURFACE WAVES• Traveling only through the crust, surface waves are

of a lower frequency than body waves, and are easily distinguished on a seismogram as a result. Though they arrive after body waves, it is surface waves that are almost entirely responsible for the damage and destruction associated with earthquakes. This damage and the strength of the surface waves are reduced in deeper earthquakes.

The first kind of surface wave is called a Love wave, named after A.E.H. Love, a British mathematician who worked out the mathematical model for this kind of

wave in 1911. It's the fastest surface wave and moves the ground from side-to-side. Confined to the surface of the

crust, Love waves produce entirely horizontal motion.

The other kind of surface wave is the Rayleigh wave, named for John William Strutt, Lord Rayleigh, who mathematically predicted the

existence of this kind of wave in 1885. A Rayleigh wave rolls along the ground just like a wave rolls across a lake or an ocean. Because it rolls,

it moves the ground up and down, and side-to-side in the same direction that the wave is moving. Most of the shaking felt from an earthquake is due to the Rayleigh wave, which can be much larger

than the other waves.

Finding the Distance to the Epicenter and the Earthquake's Magnitude

︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎︎EARTHQUAKE RECORD IN NEPAL ( 1911 - 1991 )

Magnitude (Richter) No Of Events Frequency

( Years )

5 to 6 41 2

6 to 7 17 5

7 to 7.5 10 8

7.5 to 8 2 40

More than 8 1 81

HOW MUCH BIGGER…?

• How much Bigger ?

• http://earthquake.usgs.gov/learn/topics/calculator.php

• What are the different magnitude scales, and why are there so many?

• http://www.usgs.gov/faq/categories/9828/3357

CEMENT

• A cement is a binder, a substance that sets and hardens and can bind other materials together.

• The most important uses of cement are as a component in the production of mortar in masonry, and of concrete, a combination of cement and an aggregate to form a strong building material.

CURING (SETTING)• Cement sets or cures when mixed with water which causes a series

of hydration chemical reactions. The constituents slowly hydrate and crystallize; the interlocking of the crystals gives cement its strength.

• Maintaining a high moisture content in cement during curing increases both the speed of curing, and its final strength.

• The time it takes for cement to cure varies as little as twenty minutes, while full cure can take over a month. Cement typically cures to the extent that it can be put into service within 24 hours to a week.

CONCEPT OF STIFFNESS & DUCTILITY

Stiffness is a property of a body by which it can resist the deflection. If a body can resist sufficient amount of displacement then the body is called stiff.

Ductility is a proper ty of a material by which it can take more force without any sudden damage but with the gradual elongation of the material. By ductility an element can absorb larger amount of energy in it without sudden breaking of the element.