Available Balance
Humans threaten the biosphere and biodiversity is being reduced

Human beings in populations have a tendency to modify ecosystems that are existing for purposes centered around their own. They clear forests and grasslands for the growing of crops. They build their houses on what used to be farmlands, and they convert small towns into overcrowded cities. Human being populations continue to increase in size and so they require ever greater amounts of material good and energy input with each passing year. As each second goes y original organisms become fewer and fewer until eventually some ecosystems have been completely altered. If this type of progression continue what will remain will be human beings and their domesticated plants and animals were there were once diverse populations.

As human being populations increase more and more ecosystems are threatened. The destruction of world’s rain forests are of great concern. The destruction is due mainly to over logging. As years go by we are realizing even though slowly, that we are dependent on intact ecosystems and how they service us. A prominent example and a useful one, is the purpose and essence of our rain forests. They are  absorb of carbon dioxide. This gas is a pollutant if allowed to build up in our atmosphere. If it is allowed to build up it effects are grave such as increasing our daily atmosphere temperature.

When human beings interfere by modifying existing ecosystems they are contributing to the reduction of biodiversity. The term biodiversity is defined as the total number of species, the variability of their genes, and the ecosystems in which they live. Species become extinct meaning they die, when such species is unable to successfully adapt to a change in their environmental conditions. A shocking example is that seaside development, pollution, and over fishing are causing valuable fin fishes to become commercially extinct. This means that those that remain are too few to justify the cost of catching them.

Human beings need to realize that we are totally dependent on other species for food, clothing, medicines, and various raw materials. There it shows we have no vision when we allow other species to become extinct. We should preserved ecosystems and the species living in them because that is how the human species will continue to survive.

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Things to Know About Power Generation Station Part 3 – Round UP
November 28, 2017
0
light-161751_1280 Idea-When People Don't get Their wayPeople will try to intimidate others in order to get to get those individuals to their way. Featured Image Credit: Pixabay.com

Penstocks

The  penstocks  are  made  up  of  steel  or  concrete  and  arranged  in  the  form  of  conduits,

supported by the anchor blocks. The penstocks are used to carry water to the turbine. For the low

head (less than 30 m) power stations, the concrete penstocks are used. The steel penstocks are

suitable for any head.

There are certain protective devices attached to the penstocks.

The automatic butterfly valve completely shuts off the water flow if the penstock bursts.

The air valve maintains the air pressure inside the penstock equal to the outside atmospheric

pressure.

The anchor block supports the penstock and holds it in the proper position.

The surge tank also protects the penstock from sudden pressure changes.

Water Turbines

The main two types of water turbines are,

  1. i) Impulse and ii) Reaction

In  an  impulse  turbine,  the  entire  pressure  of  water  is  converted  into  a  kinetic  energy  in  a

nozzle. Then the water jet is forced on the turbine which a large velocity which drives the wheel.

It contains elliptical buckets mounted on the periphery of a wheel. The force of water jet on

the  buckets  drives the wheel and the turbine.  There is a needle or spare at the tip of the nozzle.

The  governor  controls  the  needle  which  controls  the  force  of  the  jet,  according  to  the  load

demand. The impulse turbines are used for the high head power stations.

In  the  reaction  turbines,  the  water  enters  the  runner,  partly  with  pressure  and  partly  with

velocity head. There are two types of reaction turbines.

  1. i) Francis and ii) Kalpan

The reaction turbine consists of an

outer ring  of  stationary  guided  blades  and  an  inner  ring  of  rotating  blades.  The  guided  blades

control  the  flow  of  water  to  the  turbine.  Water  flows  radially  inwards  and  changes  to  a

downward direction when it passes through the rotating blades. While pass ing over the rotating

blades,  the  pressure  and  velocity  of  water  are  decreased.  This  causes  reaction  force  to  exist

which drives the turbine. For large variation of  head, Kalpan  is used as  its efficiency does not

vary with change in load. For fairly constant head, a Francis or propeller turbine is used.

The reaction turbines are used for the low head power stations.

 

Advantages

  1. If the proper site is selected, the continuous water supply is available.
  2. Requires no fuel as water is used.
  3. No burning of fuel hence neat and clean site as no smoke or ash is produced.
  4. It does not pollute the atmosphere.
  5. The operating cost is very low as free water supply is available.
  6. The turbines in this plants can be switched on and off in a very short period of time.
  7. It is relatively simple in construction, self-contained in operation and requires less

maintenance.

  1. It is robust and has very long life.
  2. It gives high efficiency over a considerable range of load. This improves the overall system

efficiency.

  1. It provides the additional benefits like irrigation, food control, afforestation etc.
  2. Being simple in design and operation, highly skilled workers are not necessary for the daily

operation. Thus a man power requirement is  low.

Disadvantages

  1. Due to the construction of dam, very high capital cost.
  2. The low rate of return.
  3. Uncertainty of availability of water due to unpredictable rainfall.
  4. As its location is in hilly areas and mountains, the long transmission lines are necessary for the

transmission of generated electrical energy. This requires high cost.

  1. The large power stations disturb the ecology of the area by the way of disforestation,

destroying vegetation and uprooting people.

  1. Highly skilled and experienced persons are necessary at the time of construction.
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Things to Know About Power Generation Station Part 2
November 28, 2017
0

General Arrangement of Hydro-electric Plant

Though hydro-electric power station simply involves the conversion of hydraulic energy to

the mechanical energy, it requires many types of supporting arrangements. The Fig. 2 show s the

schematic  arrangement  of  hydro -electric  power  station  which  uses  water  supply  from  an

artificially constructed dam.

Fig. 2  Schematic arrangement of hydro-electric power plant

The dam is constructed across the river and water from catchment area is collected  behind

the wall of the dam, in high mountains. A pressure channel is taken from such a water reservoir

which takes water to a surge tank. The surge tank is a controlling room which controls the flow

of water i.e. adjusts the discharge of water according to   the need of the turbine and load on it.

Trash  rack  does  not  allow  floating  and  other  impurities  to  pass  to  the  turbine.  The  pressure

channels plays a very important role. It relieves the pressure on the penstocks when the turbine

valves  are  open  or  closed  suddenly.  The  water  is  then  taken  to  a  valve  house  from  where  the

penstocks start. The valve house contains main sluice valve and the automatic isolating valves.

These valves also regulate the flow of water to the power house and isolates the supply of water

if there  is any  emergency  such  as  bursting of a  penstock. Through the penstocks, the water  is

taken to the power house which consists of turbine and the alternator. The  penstocks are  nothing

but the steel pipes which are arranged in the form of open or  closed conduits, supported by the

anchor blocks.

When the water from the penstock is hammered through a nozzle, on the turbine blades, the

turbine starts rotating.  At this stage the  hydraulic energy  is converted to a mechanical energy.

The  turbine  drives  the  alternator  which  is  coupled  to  the  shaft  of  the  turbine.  The  alternator

converts  the  mechanical  energy  into  an  electrical  energy.  This  electrical  energy  is  then

transmitted to the load centers. The water collected from the turbine is called tail  race. This tail

race is then taken off to the river.

 

Let us discuss the constituent and their functions in the operation of the hydroelectric power

station.

Dam

The water reservoir in  the form of a dam is the main part of the power station. It stores the

water,  provides  the  continuous  supply  of  water  and  maintains  the  necessary  water  head.  The

dams are built up of stones and concrete. The design and type of the dam us selected according

to the topography of the site and economical aspects.

Spillways

There are certain times when the river flow exceeds the storage capacity of the dam, due to

the heavy rainfall. The spillways are provided to discharge this surplus water and mai ntain safe

water level in the dam.

Surge Tank

This is an important projecting device in a hydro-electric power plant. It is built just before

the valve house. It protects the penstocks from bursting due to sudden pressure changes.

If the load on the turbine is thrown off suddenly then by the governing action, the turbine

input gates get suddenly closed. Thus there is sudden stopping of water at the lower end of the

penstock. This time the excess water at the lower end of the penstock, rushes back to the surge

tank. The surge tank water level increases. Thus the penstock is protected from bursting due to

high pressure. The surge tank absorbs this high pressure swing by increasing its water level.

On  the  other  hand,  when  the  load  on  the  turbine  suddenly  increases,  the  additional  water

required is drawn from the surge tank. This satisfies the increased water demand instantly.

Thus the surge tank controls the pressure changes created due to rapid changes in the water

flow in penstock and hence protects the penstock from water hammer effects which might burst

the penstock.

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Things to Know About Power Generation Station Part 1
November 28, 2017
0

A  power  generation  station  which  uses  the  potential  or  kinetic  energy  of  water  for  the

generation of an electrical energy is called hydro -electric power station.

Water has a kinetic energy when it is in motion. While the water stored at  high level has a

potential energy. The difference in level of water between the two points is called head. Such a

water head is practically created by constructing reservoirs across river or lake. Generally a dam

is constructed at high altitudes, which can  be used as a continuous source of the water for the

hydro-electric power stations. The water from the dam is taken through pipes and canals to the

water turbine, which is at lower level. The turbine obtains the energy from the falling water and

changes it  into a mechanical energy. This mechanical energy of the turbine is then used to drive

the  alternator,  which  converts  the  mechanical  energy  into  an  electrical  energy.

 

Factors for Selection of Site

The water reservoir like dam cannot be constructed anywhere. There are  number of factors

of affecting the choice of site for the hydroelectric power station.

  1. Availability of  water:  As  the  basic  requirement  of  hydro -electric  plant  is  the  water,  the

availability of huge quantity of water is the main consideration. The plant   must be constructed

where sufficient quantity of water is available at a good head. The previous rainfall records are

studied and the maximum and minimum quantity of water available during the year estimated.

Considering the losses such as evaporation, the water necessary for the plant is calculated. Then

by comparing both the estimations, the choice of the site is done.

  1. Storage of water : The rainfall is not consistent every year. Hence the available water should

be stored. This makes necessary to construct dams. The storage helps in equalizing the flow of

water throughout the year. So site should be provide sufficient facilities for erecting dam and the

storage of water.

  1. Head of water : For getting sufficient head, the dam or reservoir should be constructed at a

height in a hilly area. The availability of the head directly affects the cost and economy of the

power  generation.  So  site  should  be  selected  in  proper  geographical  area,  which  can  give

sufficient water head.

  1. Cost and type of land: The initial cost of the project includes the cost of the land. Hence land

must be available at a reasonable price. Similarly the type of the land must be such that it should

able to withstand the weight of the heavy equipment to be installed.

  1. Transportation facilities: For transporting the equipment and the machinery, the site selected

must be easily accessible by rail and road.

  1. Distance from load centers: The load center is connected to the site by the transmission lines.

Hence to keep the cost of the  transmission  lines  minimum and the  losses occurring  in the  line

minimum, the distance of the site from the load centers must be less. Otherwise the overall cost

increases considerably.

All these factors affect the selection of site for the hydro-electric power station.

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Physics Study – ELECTRIC CHARGES AND FIELDS

INTRODUCTION

All of us have the experience of seeing a spark or hearing a crackle when we take off our synthetic clothes or sweater, particularly in dry weather.This is almost inevitable with ladies garments like a polyester saree. Have you ever tried to find any explanation for this phenomenon? Another common example of electric discharge is the lightning that we see in the sky during thunderstorms. We also experience a sensation of an electric shock either while opening the door of a car or holding the iron bar of a bus after sliding from our seat. The reason for these experiences is discharge of electric charges through our body, which were accumulated due to rubbing of insulating surfaces. You might have also heard that
this is due to generation of static electricity. This is precisely the topic we are going to discuss in this and the next chapter. Static means anything that does not move or change with time. Electrostatics deals with the study of forces, fields and potentials arising from static charges.

ELECTRIC CHARGE

Historically the credit of discovery of the fact that amber rubbed with wool or silk cloth attracts light objects goes to Thales of Miletus, Greece, around 600 BC. The name electricity is coined from the Greek word elektron meaning amber. Many such pairs of materials were known which on rubbing could attract light objects like straw, pith balls and bits of papers.

You can perform the following activity at home to experience such an effect. Cut out long thin strips of white paper and lightly iron them.Take them near a TV screen or computer monitor. You will see that the strips get attracted to the screen. In fact they remain stuck to the screen for a while.

It was observed that if two glass rods rubbed with wool or silk cloth are brought close to each other, they repel each other [Fig. 1.1(a)]. The two strands of wool or two pieces of silk cloth, with which the rods were rubbed, also repel each other. However, the glass rod and wool attracted each other. Similarly, two plastic rods rubbed with cat’s fur repelled each other [Fig. 1.1(b)] but attracted the fur. On the other hand, the plastic rod attracts the glass rod [Fig. 1.1(c)] and repel the silk or wool with which the glass rod is rubbed. The glass rod repels the fur. If a plastic rod rubbed with fur is made to touch two small pith balls (now-a-days we can use polystyrene balls) suspended by silk or nylon thread, then the balls repel each other [Fig. 1.1(d)] and are also repelled by the rod. A similar effect is found if the pith balls are touched with a glass rod rubbed with silk [Fig. 1.1(e)]. A dramatic observation is that a pith ball touched with glass rod attracts another pith ball touched with plastic rod [Fig. 1.1(f )].

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Do you believe mankind can travel throughtout our solar system?

In star Trek it took mankind many year to sit aside their hate and racism for one other.

yes, i know it just Tv. but on the flip side of that they were able to come to a revolution, or some type of peace between all race on this place. now, if they where able to come together and sit aside there different and become one.

Why our race cant do the same?? but scientist what to travel throughout our solar system to see if our planets or our planet moons are capable of supposing life.

yeah, here the thing about that, before even can do that we need sit aside of hate for one other before we even thing about traveling any farther. we cant take our problem out there in space we cant for example race racism. we can take that out there. why you ask? because if we stop that whole racism thing out there with a highly weaponize , and intelligent race of species, they might not that to well. my friend that will lead us in a all out intergalactic war.

That lead me to another major problem our race have. That problem is telling other country how to run there our government. yes! people that our race big problem. That’s also a very big n… No!  if we every decide to travel to different planet such as our own or different solar system. if we did came across a whole civilization of a race aliens we cant go to there planet and tell them that we take over and you have to do what our race said. no! NO! that’s we surly started a war no question ask. right of the back that would start problem and that can leaded to war.

oh yeah there another that mankind have huge problem with interfering with other people problems. In all star trek they have a prime directive. therefore that prime directive means: Is a guiding principle where the untied Federation of planets (UFA) prohibiting the protagonists to “interfering ” with any internal development of any alien.

so that mean under any reason no government should not interfered with other country problem. only. and ONLY!!! if that country is in need of help, other then that no countries should interfered in other countries problem. if that problem don’t concern you or our countries then don’t interfered.

yes, ladies and gentle man that our lovely countries huge problem interfering with thing that don’t have anything to do with us.

Do you agree or disagree???

endless wonder

Space and time

now i’m asking you do you truly believe mankind live beside another race that’s not human?

In your mind can you picture the out come of that?

Do you believe mankind is capable to live in a different era where human and different species of alien can live together?

 

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National Center for Research on Earthquake Engineering
storm_Nationwide Earthquake Drillphoto is mine

International Institute of Earthquake Engineering and Seismology (IIEES), founded by Mohsen Ghafory-Ashtiany, is an international earthquake engineering and seismology institute based in Iran. It was established as a result of the 24th UNESCO General Conference Resolution DR/250 under Iranian government approval in 1989. It was founded as an independent institute within the Iran’s Ministry of Science, Research and Technology.[1]

Mohsen Ghafory-Ashtiany distinguished professor of earthquake engineering and risk management at International Institute of Earthquake Engineering and seismology (IIEES) which was founded by him in 1989, is Chief Editor of JSEE and IDRiM Journals; author of more than 140 papers and 3 books in the field of earthquake engineering, seismic hazard and risk analysis, risk management and planning. Ashtiany is the Director and member of the Executive committee of International Association of Earthquake engineering (IAEE), Chairman of Earthquake Hazard, Risk and Strong Ground Motion Commission of IASPEI, member of UN-ISDR Scientific and Technical commission, Director and member of board of World Seismic Safety Initiative, member of Global Earthquake Risk Model Project; Member of Geo-Hazard Initiative, Member of GSHAP, Member of Global Risk Forum-Davos, and many other scientific communities. Ashtiany was born in Tehran, Iran in 1957 and graduated from Va. Tech (USA) in 1983 with honor, and is resident of US.

On its establishment, the IIEES drew up a seismic code in an attempt to improve the infrastructural response to earthquakes and seismic activity in the country. Its primary objective is to reduce the risk of seismic activity on buildings and roads and provide mitigation measures both in Iran and the region.[1]

The institute is responsible for much of the research and education in this field by conducting research and providing education and knowledge in seismotectonic studies, seismology and earthquake engineering.[1] In addition conducts research and educates in risk management and generating possibilities for an effective earthquake response strategy.

The IIEES is composed of the following research Centers: Seismology, Geotechnical Earthquake Engineering, Structural Earthquake Engineering, Risk Management; National center for Earthquake Prediction, and Graduate School, Public Education and Information Division.
NCREE was established in 1980 by the National Science Council (NSC), and they are working together with the National Taiwan University (NTU), as well as being part of the National Applied Research Laboratories (NARL, a non-profit organisation established in June 2003), whose purpose to improve efficiency between research institutions, and they are trying to decrease the impact of earthquakes on various structures.

They have published books and printed reports with all their findings. This is to try raise public awareness. They also hold international seminars, make videos, and hold a design construction competition every year.
NCREE is aiming to improve seismic resistant designs for all constructions and to provide feedback to the engineering community through research and development. The Center was built for researchers to collaborate and check their theories by doing various experiments. Their goals are:

– Establish and provide research facilities.

– Develop and improve the seismic engineering database.

– Create and carry-out regulations relating to seismic design codes.

– Co-ordinate and Integrate academic institutes and related industries.

– Introduce, Develop and Educate on seismic-resisting technology.
NCREE’s seismic simulation laboratory has international standard facilities, such as eighteen sets of static hydraulic actuators and six sets of dynamic hydraulic actuators.
The Tri-Axial Seismic Simulator, or Shaking Table, can produce earthquake ground motions in six degrees of freedom, with motion in 3 axes.

The shaking table is 5m x 5m and has a mass of 27 tons. It can take models of large scale buildings weighing up to 50 tons, and the square shape of the table provides large bending and torsional stiffness.

Small-scale or full-scale models are placed on the shaking table. To prevent the instrument vibration on surrounding areas during experiments, the shaking table has a vibration isolation system, including 80 dampers, 96 airbags and air springs, and a reaction mass (16m x 16m x 7.6m, weighing about four thousand tons.)

Under the table are twelve actuators, which produce the shaking movement in six degrees of freedom. There are four actuators for each axis, and the hydraulic power is provided by two electrical pumps and three diesel pumps. The weight of the shaky table and the model is balanced by four static supports.

By doing these experiments, engineers can understand a structure’s response to an earthquake. The results will show how stable the building is during earthquakes, and it will also accelerate the development of seismic isolation and minimize the damage caused by an earthquake.

Reaction Wall and Strong Floor
The Reaction Wall and Strong floor make it possible to test multiple full-scale structural experiments. The wall can be used to perform seismic tests by using experimental methods, such as traditional quasi-static tests, cyclic loading tests and pseudo-dynamic tests.

The wall is L-shaped and has 4 sections: 15m x 15.5m, 12m x 15.5m, 9m x 12m and 6m x 12m. The strong floor is a reinforced block of concrete 60m x 29m x 1.2m. The compressive strength of the concrete for both the reaction wall and the strong floor is 350 kg/cm2

During experiments, full-scale and large-scale constructions are mounted onto the strong floor. Hydraulic actuators then exert forces on the test objects, making it possible to see the resistance of various structures and performances of seismic isolators and energy dissipaters. The experimental data has helped proved that seismic theories can be applied, and are a reference to earthquake resistant building designs.Building Engineering Studies

– Seismic evaluation and retrofit technologies of existing buildings.

– Development of advanced innovative construction.

– Revision of building seismic design codes.

Bridge Engineering Studies

– performance-based design of bearing systs in bridges.

– Seismic evaluation and retrofit technologies of existing bridges.

Structural Control and System Identification Studies

– Studies on structural health monitoring and structural control.

– Seismic evaluation and retrofit technologies for high-tech industrial structures.

Geotechnical and Strong Ground Motion Studies

– Studies on earthquake prediction models.

– Establishment of Engineering Geological Databases for TSMIP (EGDT). TSMIP stands for Taiwan Strong Motion Instrumentation Program.

– Seismic behaviour of the investigation of soils in the large bi-axial shaking table shear box.

Earthquake Scenario Studies

– Establishment and application of geotechnical earth science hazard database.

– Development of Taiwan seismic scenario database and its applications.

– Development of Taiwan Earthquake Loss Estimation System.

Experimental Technology Studies

– Collaborative experiment technology using the Internet.

– Application of optical fiber sensors in civil engineering structures.

Information Technology Studies

– Establishment of an earthquake engineering database.

– Integration of numerical and experimental stimulation.
To educate people about earthquakes, there are published books, printed reports, international seminars and videos. NCREE also holds IDEERS and ITP to raise public awareness.

IDEERS Edit
IDEERS stands for “Introducing and Demonstrating Earthquake Engineering Research in Schools” and is held every year by the British council in Taipei, NCREE and the Bristol University. It is a science-based project with a competition developed by the Earthquake Engineering Research Centre of the Bristol University. The students participating are undergraduate students majoring in civil engineering related subjects and high school students. Students entering the competition will make their models using cheap materials which then will be put on the tri-axial seismic simulator (shaking-table). Models will be shaken to destruction, and the best-designed models will win prizes.

ITP Edit
ITP stands for The International Training Program (for Seismic Design of Structures and Hazard Mitigation) and is held by The National Science Council (NSC) and the Democratic Pacific Union. It is a short-term workshop to train government officials and engineers from different countries (In 2006, thirty-three people attended from fourteen different countries). The Program will try to improve the disaster-preventing technology and the earthquake-resisting ability of those countries and try reduce the impacts and losses caused by major earthquakes.

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National Center for Research on Earthquake Engineering
storm_Nationwide Earthquake Drillphoto is mine

International Institute of Earthquake Engineering and Seismology (IIEES), founded by Mohsen Ghafory-Ashtiany, is an international earthquake engineering and seismology institute based in Iran. It was established as a result of the 24th UNESCO General Conference Resolution DR/250 under Iranian government approval in 1989. It was founded as an independent institute within the Iran’s Ministry of Science, Research and Technology.[1]

Mohsen Ghafory-Ashtiany distinguished professor of earthquake engineering and risk management at International Institute of Earthquake Engineering and seismology (IIEES) which was founded by him in 1989, is Chief Editor of JSEE and IDRiM Journals; author of more than 140 papers and 3 books in the field of earthquake engineering, seismic hazard and risk analysis, risk management and planning. Ashtiany is the Director and member of the Executive committee of International Association of Earthquake engineering (IAEE), Chairman of Earthquake Hazard, Risk and Strong Ground Motion Commission of IASPEI, member of UN-ISDR Scientific and Technical commission, Director and member of board of World Seismic Safety Initiative, member of Global Earthquake Risk Model Project; Member of Geo-Hazard Initiative, Member of GSHAP, Member of Global Risk Forum-Davos, and many other scientific communities. Ashtiany was born in Tehran, Iran in 1957 and graduated from Va. Tech (USA) in 1983 with honor, and is resident of US.

On its establishment, the IIEES drew up a seismic code in an attempt to improve the infrastructural response to earthquakes and seismic activity in the country. Its primary objective is to reduce the risk of seismic activity on buildings and roads and provide mitigation measures both in Iran and the region.[1]

The institute is responsible for much of the research and education in this field by conducting research and providing education and knowledge in seismotectonic studies, seismology and earthquake engineering.[1] In addition conducts research and educates in risk management and generating possibilities for an effective earthquake response strategy.

The IIEES is composed of the following research Centers: Seismology, Geotechnical Earthquake Engineering, Structural Earthquake Engineering, Risk Management; National center for Earthquake Prediction, and Graduate School, Public Education and Information Division.
NCREE was established in 1980 by the National Science Council (NSC), and they are working together with the National Taiwan University (NTU), as well as being part of the National Applied Research Laboratories (NARL, a non-profit organisation established in June 2003), whose purpose to improve efficiency between research institutions, and they are trying to decrease the impact of earthquakes on various structures.

They have published books and printed reports with all their findings. This is to try raise public awareness. They also hold international seminars, make videos, and hold a design construction competition every year.
NCREE is aiming to improve seismic resistant designs for all constructions and to provide feedback to the engineering community through research and development. The Center was built for researchers to collaborate and check their theories by doing various experiments. Their goals are:

– Establish and provide research facilities.

– Develop and improve the seismic engineering database.

– Create and carry-out regulations relating to seismic design codes.

– Co-ordinate and Integrate academic institutes and related industries.

– Introduce, Develop and Educate on seismic-resisting technology.
NCREE’s seismic simulation laboratory has international standard facilities, such as eighteen sets of static hydraulic actuators and six sets of dynamic hydraulic actuators.
The Tri-Axial Seismic Simulator, or Shaking Table, can produce earthquake ground motions in six degrees of freedom, with motion in 3 axes.

The shaking table is 5m x 5m and has a mass of 27 tons. It can take models of large scale buildings weighing up to 50 tons, and the square shape of the table provides large bending and torsional stiffness.

Small-scale or full-scale models are placed on the shaking table. To prevent the instrument vibration on surrounding areas during experiments, the shaking table has a vibration isolation system, including 80 dampers, 96 airbags and air springs, and a reaction mass (16m x 16m x 7.6m, weighing about four thousand tons.)

Under the table are twelve actuators, which produce the shaking movement in six degrees of freedom. There are four actuators for each axis, and the hydraulic power is provided by two electrical pumps and three diesel pumps. The weight of the shaky table and the model is balanced by four static supports.

By doing these experiments, engineers can understand a structure’s response to an earthquake. The results will show how stable the building is during earthquakes, and it will also accelerate the development of seismic isolation and minimize the damage caused by an earthquake.

Reaction Wall and Strong Floor
The Reaction Wall and Strong floor make it possible to test multiple full-scale structural experiments. The wall can be used to perform seismic tests by using experimental methods, such as traditional quasi-static tests, cyclic loading tests and pseudo-dynamic tests.

The wall is L-shaped and has 4 sections: 15m x 15.5m, 12m x 15.5m, 9m x 12m and 6m x 12m. The strong floor is a reinforced block of concrete 60m x 29m x 1.2m. The compressive strength of the concrete for both the reaction wall and the strong floor is 350 kg/cm2

During experiments, full-scale and large-scale constructions are mounted onto the strong floor. Hydraulic actuators then exert forces on the test objects, making it possible to see the resistance of various structures and performances of seismic isolators and energy dissipaters. The experimental data has helped proved that seismic theories can be applied, and are a reference to earthquake resistant building designs.Building Engineering Studies

– Seismic evaluation and retrofit technologies of existing buildings.

– Development of advanced innovative construction.

– Revision of building seismic design codes.

Bridge Engineering Studies

– performance-based design of bearing systs in bridges.

– Seismic evaluation and retrofit technologies of existing bridges.

Structural Control and System Identification Studies

– Studies on structural health monitoring and structural control.

– Seismic evaluation and retrofit technologies for high-tech industrial structures.

Geotechnical and Strong Ground Motion Studies

– Studies on earthquake prediction models.

– Establishment of Engineering Geological Databases for TSMIP (EGDT). TSMIP stands for Taiwan Strong Motion Instrumentation Program.

– Seismic behaviour of the investigation of soils in the large bi-axial shaking table shear box.

Earthquake Scenario Studies

– Establishment and application of geotechnical earth science hazard database.

– Development of Taiwan seismic scenario database and its applications.

– Development of Taiwan Earthquake Loss Estimation System.

Experimental Technology Studies

– Collaborative experiment technology using the Internet.

– Application of optical fiber sensors in civil engineering structures.

Information Technology Studies

– Establishment of an earthquake engineering database.

– Integration of numerical and experimental stimulation.
To educate people about earthquakes, there are published books, printed reports, international seminars and videos. NCREE also holds IDEERS and ITP to raise public awareness.

IDEERS Edit
IDEERS stands for “Introducing and Demonstrating Earthquake Engineering Research in Schools” and is held every year by the British council in Taipei, NCREE and the Bristol University. It is a science-based project with a competition developed by the Earthquake Engineering Research Centre of the Bristol University. The students participating are undergraduate students majoring in civil engineering related subjects and high school students. Students entering the competition will make their models using cheap materials which then will be put on the tri-axial seismic simulator (shaking-table). Models will be shaken to destruction, and the best-designed models will win prizes.

ITP Edit
ITP stands for The International Training Program (for Seismic Design of Structures and Hazard Mitigation) and is held by The National Science Council (NSC) and the Democratic Pacific Union. It is a short-term workshop to train government officials and engineers from different countries (In 2006, thirty-three people attended from fourteen different countries). The Program will try to improve the disaster-preventing technology and the earthquake-resisting ability of those countries and try reduce the impacts and losses caused by major earthquakes.

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Have you heard about earthquake engineering
Science behind the happinessThe Science Of Happiness

Earthquake engineering is an interdisciplinary branch of engineering that designs and analyzes structures, such as buildings and bridges, with earthquakes in mind. Its overall goal is to make such structures more resistant to earthquakes. An earthquake (or seismic) engineer aims to construct structures that will not be damaged in minor shaking and will avoid serious damage or collapse in a major earthquake. Earthquake engineering is the scientific field concerned with protecting society, the natural environment, and the man-made environment from earthquakes by limiting the seismic risk to socio-economically acceptable levels.[1] Traditionally, it has been narrowly defined as the study of the behavior of structures and geo-structures subject to seismic loading; it is considered as a subset of structural engineering, geotechnical engineering, mechanical engineering, chemical engineering, applied physics, etc. However, the tremendous costs experienced in recent earthquakes have led to an expansion of its scope to encompass disciplines from the wider field of civil engineering, mechanical engineering and from the social sciences, especially sociology, political science, economics and finance.

The main objectives of earthquake engineering are:

Foresee the potential consequences of strong earthquakes on urban areas and civil infrastructure.
Design, construct and maintain structures to perform at earthquake exposure up to the expectations and in compliance with building codes.[2]
A properly engineered structure does not necessarily have to be extremely strong or expensive. It has to be properly designed to withstand the seismic effects while sustaining an acceptable level of damage.
Seismic loading means application of an earthquake-generated excitation on a structure (or geo-structure). It happens at contact surfaces of a structure either with the ground,[4] with adjacent structures,[5] or with gravity waves from tsunami. The loading that is expected at a given location on the Earth’s surface is estimated by engineering seismology. It is related to the seismic hazard of the location.
Earthquake or seismic performance defines a structure’s ability to sustain its main functions, such as its safety and serviceability, at and after a particular earthquake exposure. A structure is normally considered safe if it does not endanger the lives and well-being of those in or around it by partially or completely collapsing. A structure may be considered serviceable if it is able to fulfill its operational functions for which it was designed.

Basic concepts of the earthquake engineering, implemented in the major building codes, assume that a building should survive a rare, very severe earthquake by sustaining significant damage but without globally collapsing.[6] On the other hand, it should remain operational for more frequent, but less severe seismic events.

Seismic performance assessment Edit
Engineers need to know the quantified level of the actual or anticipated seismic performance associated with the direct damage to an individual building subject to a specified ground shaking. Such an assessment may be performed either experimentally or analytically.

Experimental assessment Edit
Experimental evaluations are expensive tests that are typically done by placing a (scaled) model of the structure on a shake-table that simulates the earth shaking and observing its behavior.[7] Such kinds of experiments were first performed more than a century ago.[8] Only recently has it become possible to perform 1:1 scale testing on full structures.

Due to the costly nature of such tests, they tend to be used mainly for understanding the seismic behavior of structures, validating models and verifying analysis methods. Thus, once properly validated, computational models and numerical procedures tend to carry the major burden for the seismic performance assessment of structures.
Seismic performance assessment or seismic structural analysis is a powerful tool of earthquake engineering which utilizes detailed modelling of the structure together with methods of structural analysis to gain a better understanding of seismic performance of building and non-building structures. The technique as a formal concept is a relatively recent development.

In general, seismic structural analysis is based on the methods of structural dynamics.[9] For decades, the most prominent instrument of seismic analysis has been the earthquake response spectrum method which also contributed to the proposed building code’s concept of today.[10]

However, such methods are good only for linear elastic systems, being largely unable to model the structural behavior when damage (i.e., non-linearity) appears. Numerical step-by-step integration proved to be a more effective method of analysis for multi-degree-of-freedom structural systems with significant non-linearity under a transient process of ground motion excitation.[11]

Basically, numerical analysis is conducted in order to evaluate the seismic performance of buildings. Performance evaluations are generally carried out by using nonlinear static pushover analysis or nonlinear time-history analysis. In such analyses, it is essential to achieve accurate non-linear modeling of structural components such as beams, columns, beam-column joints, shear walls etc. Thus, experimental results play an important role in determining the modeling parameters of individual components, especially those that are subject to significant non-linear deformations. The individual components are then assembled to create a full non-linear model of the structure. Thus created models are analyzed to evaluate the performance of buildings.

The capabilities of the structural analysis software are a major consideration in the above process as they restrict the possible component models, the analysis methods available and, most importantly, the numerical robustness. The latter becomes a major consideration for structures that venture into the non-linear range and approach global or local collapse as the numerical solution becomes increasingly unstable and thus difficult to reach. There are several commercially available Finite Element Analysis software’s such as CSI-SAP2000 and CSI-PERFORM-3D and Scia Engineer-ECtools which can be used for the seismic performance evaluation of buildings. Moreover, there is research-based finite element analysis platforms such as OpenSees, RUAUMOKO and the older DRAIN-2D/3D, several of which are now open source.
Research for earthquake engineering means both field and analytical investigation or experimentation intended for discovery and scientific explanation of earthquake engineering related facts, revision of conventional concepts in the light of new findings, and practical application of the developed theories.

The National Science Foundation (NSF) is the main United States government agency that supports fundamental research and education in all fields of earthquake engineering. In particular, it focuses on experimental, analytical and computational research on design and performance enhancement of structural systems.
The Earthquake Engineering Research Institute (EERI) is a leader in dissemination of earthquake engineering research related information both in the U.S. and globally.

A definitive list of earthquake engineering research related shaking tables around the world may be found in Experimental Facilities for Earthquake Engineering Simulation Worldwide.[13] The most prominent of them is now E-Defense Shake Table[14] in Japan.
NSF also supports the George E. Brown, Jr. Network for Earthquake Engineering Simulation

The NSF Hazard Mitigation and Structural Engineering program (HMSE) supports research on new technologies for improving the behavior and response of structural systems subject to earthquake hazards; fundamental research on safety and reliability of constructed systems; innovative developments in analysis and model based simulation of structural behavior and response including soil-structure interaction; design concepts that improve structure performance and flexibility; and application of new control techniques for structural systems.[15]

(NEES) that advances knowledge discovery and innovation for earthquakes and tsunami loss reduction of the nation’s civil infrastructure and new experimental simulation techniques and instrumentation.[16]

The NEES network features 14 geographically-distributed, shared-use laboratories that support several types of experimental work:[16] geotechnical centrifuge research, shake-table tests, large-scale structural testing, tsunami wave basin experiments, and field site research.[17] Participating universities include: Cornell University; Lehigh University; Oregon State University; Rensselaer Polytechnic Institute; University at Buffalo, State University of New York; University of California, Berkeley; University of California, Davis; University of California, Los Angeles; University of California, San Diego; University of California, Santa Barbara; University of Illinois, Urbana-Champaign; University of Minnesota; University of Nevada, Reno; and the University of Texas, Austin.[16]
The equipment sites (labs) and a central data repository are connected to the global earthquake engineering community via the NEEShub website. The NEES website is powered by HUBzero software developed at Purdue University for nanoHUB specifically to help the scientific community share resources and collaborate. The cyberinfrastructure, connected via Internet2, provides interactive simulation tools, a simulation tool development area, a curated central data repository, animated presentations, user support, telepresence, mechanism for uploading and sharing resources, and statistics about users and usage patterns.

This cyberinfrastructure allows researchers to: securely store, organize and share data within a standardized framework in a central location; remotely observe and participate in experiments through the use of synchronized real-time data and video; collaborate with colleagues to facilitate the planning, performance, analysis, and publication of research experiments; and conduct computational and hybrid simulations that may combine the results of multiple distributed experiments and link physical experiments with computer simulations to enable the investigation of overall system performance.

These resources jointly provide the means for collaboration and discovery to improve the seismic design and performance of civil and mechanical infrastructure systems.

Earthquake simulation Edit
The very first earthquake simulations were performed by statically applying some horizontal inertia forces based on scaled peak ground accelerations to a mathematical model of a building.[18] With the further development of computational technologies, static approaches began to give way to dynamic ones.

Dynamic experiments on building and non-building structures may be physical, like shake-table testing, or virtual ones. In both cases, to verify a structure’s expected seismic performance, some researchers prefer to deal with so called “real time-histories” though the last cannot be “real” for a hypothetical earthquake specified by either a building code or by some particular research requirements. Therefore, there is a strong incentive to engage an earthquake simulation which is the seismic input that possesses only essential features of a real event.

Sometimes earthquake simulation is understood as a re-creation of local effects of a strong earth shaking.
Theoretical or experimental evaluation of anticipated seismic performance mostly requires a structure simulation which is based on the concept of structural likeness or similarity. Similarity is some degree of analogy or resemblance between two or more objects. The notion of similarity rests either on exact or approximate repetitions of patterns in the compared items.

In general, a building model is said to have similarity with the real object if the two share geometric similarity, kinematic similarity and dynamic similarity. The most vivid and effective type of similarity is the kinematic one. Kinematic similarity exists when the paths and velocities of moving particles of a model and its prototype are similar.

The ultimate level of kinematic similarity is kinematic equivalence when, in the case of earthquake engineering, time-histories of each story lateral displacements of the model and its prototype would be the same.
Seismic vibration control is a set of technical means aimed to mitigate seismic impacts in building and non-building structures. All seismic vibration control devices may be classified as passive, active or hybrid[20] where:

passive control devices have no feedback capability between them, structural elements and the ground;
active control devices incorporate real-time recording instrumentation on the ground integrated with earthquake input processing equipment and actuators within the structure;
hybrid control devices have combined features of active and passive control systems.[21]
When ground seismic waves reach up and start to penetrate a base of a building, their energy flow density, due to reflections, reduces dramatically: usually, up to 90%. However, the remaining portions of the incident waves during a major earthquake still bear a huge devastating potential.

After the seismic waves enter a superstructure, there are a number of ways to control them in order to soothe their damaging effect and improve the building’s seismic performance, for instance:

to dissipate the wave energy inside a superstructure with properly engineered dampers;
to disperse the wave energy between a wider range of frequencies;
to absorb the resonant portions of the whole wave frequencies band with the help of so-called mass dampers.[22]
Devices of the last kind, abbreviated correspondingly as TMD for the tuned (passive), as AMD for the active, and as HMD for the hybrid mass dampers, have been studied and installed in high-rise buildings, predominantly in Japan, for a quarter of a century.[23]

However, there is quite another approach: partial suppression of the seismic energy flow into the superstructure known as seismic or base isolation.

For this, some pads are inserted into or under all major load-carrying elements in the base of the building which should substantially decouple a superstructure from its substructure resting on a shaking ground.

The first evidence of earthquake protection by using the principle of base isolation was discovered in Pasargadae, a city in ancient Persia, now Iran, and dates back to the 6th century BCE. Below, there are some samples of seismic vibration control technologies of today.
People of Inca civilization were masters of the polished ‘dry-stone walls’, called ashlar, where blocks of stone were cut to fit together tightly without any mortar. The Incas were among the best stonemasons the world has ever seen[24] and many junctions in their masonry were so perfect that even blades of grass could not fit between the stones.

Peru is a highly seismic land and for centuries the mortar-free construction proved to be apparently more earthquake-resistant than using mortar. The stones of the dry-stone walls built by the Incas could move slightly and resettle without the walls collapsing, a passive structural control technique employing both the principle of energy dissipation and that of suppressing resonant amplifications.

Rate This Content
Have you heard about earthquake engineering
Science behind the happinessThe Science Of Happiness

Earthquake engineering is an interdisciplinary branch of engineering that designs and analyzes structures, such as buildings and bridges, with earthquakes in mind. Its overall goal is to make such structures more resistant to earthquakes. An earthquake (or seismic) engineer aims to construct structures that will not be damaged in minor shaking and will avoid serious damage or collapse in a major earthquake. Earthquake engineering is the scientific field concerned with protecting society, the natural environment, and the man-made environment from earthquakes by limiting the seismic risk to socio-economically acceptable levels.[1] Traditionally, it has been narrowly defined as the study of the behavior of structures and geo-structures subject to seismic loading; it is considered as a subset of structural engineering, geotechnical engineering, mechanical engineering, chemical engineering, applied physics, etc. However, the tremendous costs experienced in recent earthquakes have led to an expansion of its scope to encompass disciplines from the wider field of civil engineering, mechanical engineering and from the social sciences, especially sociology, political science, economics and finance.

The main objectives of earthquake engineering are:

Foresee the potential consequences of strong earthquakes on urban areas and civil infrastructure.
Design, construct and maintain structures to perform at earthquake exposure up to the expectations and in compliance with building codes.[2]
A properly engineered structure does not necessarily have to be extremely strong or expensive. It has to be properly designed to withstand the seismic effects while sustaining an acceptable level of damage.
Seismic loading means application of an earthquake-generated excitation on a structure (or geo-structure). It happens at contact surfaces of a structure either with the ground,[4] with adjacent structures,[5] or with gravity waves from tsunami. The loading that is expected at a given location on the Earth’s surface is estimated by engineering seismology. It is related to the seismic hazard of the location.
Earthquake or seismic performance defines a structure’s ability to sustain its main functions, such as its safety and serviceability, at and after a particular earthquake exposure. A structure is normally considered safe if it does not endanger the lives and well-being of those in or around it by partially or completely collapsing. A structure may be considered serviceable if it is able to fulfill its operational functions for which it was designed.

Basic concepts of the earthquake engineering, implemented in the major building codes, assume that a building should survive a rare, very severe earthquake by sustaining significant damage but without globally collapsing.[6] On the other hand, it should remain operational for more frequent, but less severe seismic events.

Seismic performance assessment Edit
Engineers need to know the quantified level of the actual or anticipated seismic performance associated with the direct damage to an individual building subject to a specified ground shaking. Such an assessment may be performed either experimentally or analytically.

Experimental assessment Edit
Experimental evaluations are expensive tests that are typically done by placing a (scaled) model of the structure on a shake-table that simulates the earth shaking and observing its behavior.[7] Such kinds of experiments were first performed more than a century ago.[8] Only recently has it become possible to perform 1:1 scale testing on full structures.

Due to the costly nature of such tests, they tend to be used mainly for understanding the seismic behavior of structures, validating models and verifying analysis methods. Thus, once properly validated, computational models and numerical procedures tend to carry the major burden for the seismic performance assessment of structures.
Seismic performance assessment or seismic structural analysis is a powerful tool of earthquake engineering which utilizes detailed modelling of the structure together with methods of structural analysis to gain a better understanding of seismic performance of building and non-building structures. The technique as a formal concept is a relatively recent development.

In general, seismic structural analysis is based on the methods of structural dynamics.[9] For decades, the most prominent instrument of seismic analysis has been the earthquake response spectrum method which also contributed to the proposed building code’s concept of today.[10]

However, such methods are good only for linear elastic systems, being largely unable to model the structural behavior when damage (i.e., non-linearity) appears. Numerical step-by-step integration proved to be a more effective method of analysis for multi-degree-of-freedom structural systems with significant non-linearity under a transient process of ground motion excitation.[11]

Basically, numerical analysis is conducted in order to evaluate the seismic performance of buildings. Performance evaluations are generally carried out by using nonlinear static pushover analysis or nonlinear time-history analysis. In such analyses, it is essential to achieve accurate non-linear modeling of structural components such as beams, columns, beam-column joints, shear walls etc. Thus, experimental results play an important role in determining the modeling parameters of individual components, especially those that are subject to significant non-linear deformations. The individual components are then assembled to create a full non-linear model of the structure. Thus created models are analyzed to evaluate the performance of buildings.

The capabilities of the structural analysis software are a major consideration in the above process as they restrict the possible component models, the analysis methods available and, most importantly, the numerical robustness. The latter becomes a major consideration for structures that venture into the non-linear range and approach global or local collapse as the numerical solution becomes increasingly unstable and thus difficult to reach. There are several commercially available Finite Element Analysis software’s such as CSI-SAP2000 and CSI-PERFORM-3D and Scia Engineer-ECtools which can be used for the seismic performance evaluation of buildings. Moreover, there is research-based finite element analysis platforms such as OpenSees, RUAUMOKO and the older DRAIN-2D/3D, several of which are now open source.
Research for earthquake engineering means both field and analytical investigation or experimentation intended for discovery and scientific explanation of earthquake engineering related facts, revision of conventional concepts in the light of new findings, and practical application of the developed theories.

The National Science Foundation (NSF) is the main United States government agency that supports fundamental research and education in all fields of earthquake engineering. In particular, it focuses on experimental, analytical and computational research on design and performance enhancement of structural systems.
The Earthquake Engineering Research Institute (EERI) is a leader in dissemination of earthquake engineering research related information both in the U.S. and globally.

A definitive list of earthquake engineering research related shaking tables around the world may be found in Experimental Facilities for Earthquake Engineering Simulation Worldwide.[13] The most prominent of them is now E-Defense Shake Table[14] in Japan.
NSF also supports the George E. Brown, Jr. Network for Earthquake Engineering Simulation

The NSF Hazard Mitigation and Structural Engineering program (HMSE) supports research on new technologies for improving the behavior and response of structural systems subject to earthquake hazards; fundamental research on safety and reliability of constructed systems; innovative developments in analysis and model based simulation of structural behavior and response including soil-structure interaction; design concepts that improve structure performance and flexibility; and application of new control techniques for structural systems.[15]

(NEES) that advances knowledge discovery and innovation for earthquakes and tsunami loss reduction of the nation’s civil infrastructure and new experimental simulation techniques and instrumentation.[16]

The NEES network features 14 geographically-distributed, shared-use laboratories that support several types of experimental work:[16] geotechnical centrifuge research, shake-table tests, large-scale structural testing, tsunami wave basin experiments, and field site research.[17] Participating universities include: Cornell University; Lehigh University; Oregon State University; Rensselaer Polytechnic Institute; University at Buffalo, State University of New York; University of California, Berkeley; University of California, Davis; University of California, Los Angeles; University of California, San Diego; University of California, Santa Barbara; University of Illinois, Urbana-Champaign; University of Minnesota; University of Nevada, Reno; and the University of Texas, Austin.[16]
The equipment sites (labs) and a central data repository are connected to the global earthquake engineering community via the NEEShub website. The NEES website is powered by HUBzero software developed at Purdue University for nanoHUB specifically to help the scientific community share resources and collaborate. The cyberinfrastructure, connected via Internet2, provides interactive simulation tools, a simulation tool development area, a curated central data repository, animated presentations, user support, telepresence, mechanism for uploading and sharing resources, and statistics about users and usage patterns.

This cyberinfrastructure allows researchers to: securely store, organize and share data within a standardized framework in a central location; remotely observe and participate in experiments through the use of synchronized real-time data and video; collaborate with colleagues to facilitate the planning, performance, analysis, and publication of research experiments; and conduct computational and hybrid simulations that may combine the results of multiple distributed experiments and link physical experiments with computer simulations to enable the investigation of overall system performance.

These resources jointly provide the means for collaboration and discovery to improve the seismic design and performance of civil and mechanical infrastructure systems.

Earthquake simulation Edit
The very first earthquake simulations were performed by statically applying some horizontal inertia forces based on scaled peak ground accelerations to a mathematical model of a building.[18] With the further development of computational technologies, static approaches began to give way to dynamic ones.

Dynamic experiments on building and non-building structures may be physical, like shake-table testing, or virtual ones. In both cases, to verify a structure’s expected seismic performance, some researchers prefer to deal with so called “real time-histories” though the last cannot be “real” for a hypothetical earthquake specified by either a building code or by some particular research requirements. Therefore, there is a strong incentive to engage an earthquake simulation which is the seismic input that possesses only essential features of a real event.

Sometimes earthquake simulation is understood as a re-creation of local effects of a strong earth shaking.
Theoretical or experimental evaluation of anticipated seismic performance mostly requires a structure simulation which is based on the concept of structural likeness or similarity. Similarity is some degree of analogy or resemblance between two or more objects. The notion of similarity rests either on exact or approximate repetitions of patterns in the compared items.

In general, a building model is said to have similarity with the real object if the two share geometric similarity, kinematic similarity and dynamic similarity. The most vivid and effective type of similarity is the kinematic one. Kinematic similarity exists when the paths and velocities of moving particles of a model and its prototype are similar.

The ultimate level of kinematic similarity is kinematic equivalence when, in the case of earthquake engineering, time-histories of each story lateral displacements of the model and its prototype would be the same.
Seismic vibration control is a set of technical means aimed to mitigate seismic impacts in building and non-building structures. All seismic vibration control devices may be classified as passive, active or hybrid[20] where:

passive control devices have no feedback capability between them, structural elements and the ground;
active control devices incorporate real-time recording instrumentation on the ground integrated with earthquake input processing equipment and actuators within the structure;
hybrid control devices have combined features of active and passive control systems.[21]
When ground seismic waves reach up and start to penetrate a base of a building, their energy flow density, due to reflections, reduces dramatically: usually, up to 90%. However, the remaining portions of the incident waves during a major earthquake still bear a huge devastating potential.

After the seismic waves enter a superstructure, there are a number of ways to control them in order to soothe their damaging effect and improve the building’s seismic performance, for instance:

to dissipate the wave energy inside a superstructure with properly engineered dampers;
to disperse the wave energy between a wider range of frequencies;
to absorb the resonant portions of the whole wave frequencies band with the help of so-called mass dampers.[22]
Devices of the last kind, abbreviated correspondingly as TMD for the tuned (passive), as AMD for the active, and as HMD for the hybrid mass dampers, have been studied and installed in high-rise buildings, predominantly in Japan, for a quarter of a century.[23]

However, there is quite another approach: partial suppression of the seismic energy flow into the superstructure known as seismic or base isolation.

For this, some pads are inserted into or under all major load-carrying elements in the base of the building which should substantially decouple a superstructure from its substructure resting on a shaking ground.

The first evidence of earthquake protection by using the principle of base isolation was discovered in Pasargadae, a city in ancient Persia, now Iran, and dates back to the 6th century BCE. Below, there are some samples of seismic vibration control technologies of today.
People of Inca civilization were masters of the polished ‘dry-stone walls’, called ashlar, where blocks of stone were cut to fit together tightly without any mortar. The Incas were among the best stonemasons the world has ever seen[24] and many junctions in their masonry were so perfect that even blades of grass could not fit between the stones.

Peru is a highly seismic land and for centuries the mortar-free construction proved to be apparently more earthquake-resistant than using mortar. The stones of the dry-stone walls built by the Incas could move slightly and resettle without the walls collapsing, a passive structural control technique employing both the principle of energy dissipation and that of suppressing resonant amplifications.

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