Hi good morning sir and my dear colleagues… I and my friend vaibhavsharma stood before you to present a topic on Earth quake resistent techniques and technology.. Earth quake is natural disaster as you all know so constructions should be made to resist the eq…so let me enter in to the topic
The contents are introduction is all about terms in eq….different types of seismic waves and wave formsSeismograph…how to measure the eq…Impacts of earth quakes Technological aspects like dampers and technical like shear wallss!!
Vaibav Your ppt will start from hereExplanation: All of you know what an earth quake is…but it is defined as shaking of earth due to movement of rocks along a fault which results in breaking of rocks. Rocks in earth quake due to stresses accumulate strain energy and breaks along the fault plane which causes movement of rocksLet us see what is focus and epicenter
As on the slide focus is the point along the fault plane where the earth quake startsEpicenter is the point above the focus on the earth surface….you can clearly watch it on the imageFocal distance is distance from the focus and epicenter…it’s a vertical distance
Seismic waves are the responsible waves for all the damages done during earth quakesThey r of two typesBody waves and Surface wavesBody waves are also dividend into two types 1. primary waves 2. secondry wavesConsider the a undisturbed material as shown in the figureThe primary waves causes compression and expansionSecondry waves travel perpendicular to the surface making shearing of rocks
Let us now watch how actually the s and p waves travelAs I said before p waves travel in compression and expansion you can see the trendAnd also s waves which travel in the perpendicular direction which makes the wires break
Second type of waves are surface waves which travel on surface of earth and are the main cause for damageThey r also divided into rayleigh wave and love wavesPatterns are seen in the images..
Vaibav read it as above no separate explanation required
Earth is divided in to several plates called tectonic platesThere are mainly seven plates and several small plates as shown here..pacific plate is the place where earthquakes occurs widely as u can see the red points Earth quakes starts generally from these points…
Earth quake is measured in Magnitude and intensity
Richter scale measures total amount of energy released by an earthquakeAs shown in the figure the amplitude, magnitude and distance between p-s waves is co related and magnitude is find out..The amplitude and distance is known from seismogram which u can see in the coming slides
Intensity refers to the amount of damage done in an earthquake…Mercalli Scale is used to express damageImages shows mercalli intensity map during an earth quake
Seismograph is the instrument used to measure the earthquake magnitude..There are mainly two types of seismograph vertical and horizontal used for various purposesNow the digitalized seismograph is available which can give directly the magnitude..Normal type of seismograph consists of drum, marker, suspended mass cable and support
Seismogram is the graph that is given by the seismograph… As I said already amplitude and distance between p and s waves are shown here clearly used to get the magnitude by co relation..As seen in the graph p waves reach first, s waves reach next and body waves the last
Now just have a look at seismograph working..See earth quake occurs at a point and reaches the station and the waves are recorded in the seismogram
To locate the epicenter of an earthquake three seismic stations are required…On each station a circle is drawn with a radius equal to distance is drawn The intersections of the circles is the epicenter as shown here on the arrow
In this image u can see the epicenter and the seismic locations centers
Now coming to the impact of earth quakes it mainly causes the structures to collapse…As in the slide u can see the damage
It even causes landslides u can see in the slide…now rest of the part will be completed by my colleague akhilesh
As u all know when plates move away…cracking on earth will occur
Liquefaction is the movement of particles along with water due to presure created by the earth quakes…see in this slide the two apparments are shrinking down due to the earth quake
Large waves are generated in the ocean due to the quake in the ocean or under water
Coming to the techniques
For a general understanding consider a coconut tree…it is able to resist against wind loads due to the continuous fibers in it…suppose as shown in the figure if it is weak at joints what will happen..it will break the same happens in the column beam joint..
The weak joints are shown in the figure…higher grade of steel should be used or reinforcement should be increased by 0.5%
Lower San Fernando dam (left, SC) suffered an underwater slide during the San Fernando earthquake, 1971. The soil that under go liquefaction are highly dangerous in earth quake prone areas..so better to avoid the site..!!
The weight of the Mass damper counteracts The Natural resonant frequency of the buildingConsider a bike..u all know how indian roads generally be with ditches…what make u feel a safe ride in those ditches too..yes shock absorbers…the same works here….
Here are the three types of dampers…first is the viscous damper works with vicous action…second is the friction damper…as shown in the picture these are used to create friction and absorb the seismic waves..!!The third is the yielding dampers where it uses metallic yield of the materials
Viscous dampers in s
A real example of friction damper and yielding dampers
Shear wall concept comes form the idea of box…When seismic waves or wind forces acting on a building this make them to act as a box like structure where the building moves as a box resulting in less damage
The two functions of shear wall are explained clearly….it stops the side sway and resist the shear
The location of the shear wall should be symmetrical so that the box action occur to resist the seismic waves
Here are some classification of shear walls
There is a famous saying in seismology earth quake don’t kills but the structure kills…But damage can be reduced using latest techniques and technologies…though strctures may damage but ultimately our lifes can be saved
WHAT IS AN EARTH QUAKE?o Shaking of earth due tomovement of rocks along a fault.o Associated with faulting orbreaking of rockso Rocks under stress accumulatestrain energy and breaks.
FOCUS:The point within Earth where faulting begins is the focus, or hypocenterEPICENTER: The point directly above the focus on the surface is the epicenterFOCAL DISTANCE: Vertical distance from focus and epicenter
The waves that causes vibrations on earth are seismic wavesTypes of seismic waves1. Body Waves travel through interior1.1 Primary or "P" Waves:oHighest velocityoCauses compression and expansion1.2 Secondary or "S" Waves:oSlower than P waves but faster than surface waves.oCauses shearing of rock perpendicular to direction of wave
2. Surface Waves or "Love" (“L”) Wavesotravel on surface of earthoCause vertical & horizontal shakingoCause maximum damage
Where Do Earthquakes Occur and How Often?o 80% occur in the circum-Pacific belto ~15% occur in Mediterranean-Asiatic belto Remaining 5% occur in the interiors of plateso More than 150,000 quakes strong enough to be felt are recorded each year Indonesia after Tsunami 2004
Richter scale measures totalamount of energy released byan earthquakeAmplitude of the largest waveproduced by an event iscorrected for distance andassigned a value on an open-ended logarithmic scale
oIntensity refers to theamount of damage done in anearthquakeoMercalli Scale is used toexpress damage Modified Mercalli Intensity Map 1994 Northridge, CA earthquake, Magnitude 6.7
Vertical type Normal type seismographHorizontal type Digitalize type seismograph
Three seismograph stations are needed to locate the epicenter of an earthquakeA circle where the radius equals the distance to the epicenter is drawnThe intersection of the circles locates the epicenter