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This wikibook is about Seismic fitness or Seismic sustainability which stands for ability of buildings or civil engineering structures to perform their basic operational functions with seismic risk limited to acceptable level. Seismic fitness may be considered the paramount goal of earthquake engineering  which is concerned with protecting society, the natural and the man-made environment from the earthquake hazards. For any particular structural object and earth shaking intensity, seismic fitness is not universal.
It depends on a particular type of challenge: e. Technically, earthquake engineering is the study of behavior of buildings and structures subject to seismic loading. To provide their seismic fitness, a structural engineer should:.
A seismically fit structure does not necessarily have to be extremely strong or expensive. It just has to withstand the seismic effects while sustaining an acceptable level of damage. The most powerful and budgetary tools for upgrading seismic fitness of buildings and structures are vibration control technologies and, in particular, base isolation. Seismic load is one of the basic concepts of earthquake engineering which means application of an earthquake-generated agitation to a building or other structure.
It happens at contact surfaces of a structure either with the ground or with adjacent structures or with gravity waves from tsunami . Seismic loading, which is the major challenge for seismic fitnessdepends, primarily, on:. Ancient builders believed that earthquakes were a result of wrath of gods e. As knowledge of engineering has improved, however, architects and engineers have become better at building structures with proper seismic performance.
Earthquake simulation is a vibrational input that possesses essential features of a real seismic event. The very first earthquake simulations were performed by statically applying some horizontal inertia forcesbased on scaled peak ground accelerations I Love Music - Various - Disco Anthems, to a mathematical model of a building. 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, or hybrid ones. Therefore, there is a strong incentive to engage an earthquake simulation, like, e.
Earthquake simulations have been widely used in the research supported by The George E. Sometimes, Pianonsoittaja (The Lady I Am) - Sonja Lumme - Päivä Ja Yö simulation is understood as a re-creation of local effects of a strong ground shaking .
Seismic performance is an execution of a structure's ability to sustain its due functions, such as safety and serviceability, at and after a particular earthquake exposure. A structure is, normally, considered safe if it does not endanger the lives and wellbeing 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 engineeringimplemented in the major building codes, assume that a building should survive The Big One the most powerful anticipated earthquake though with partial destruction. Drawing an analogy with a human body, it will have dislocated joints, fractured ribs, traumatized spine and knocked out teeth but be alive and, therefore, quite O.
This situation is a major barrier to implementation of any structural innovations in the earthquake engineering technologies employing the seismic vibration control and, particularly, the most effective brands of base isolation. However, alternative performance-based design approaches already exist and are implemented at earthquake engineering research. Some of them, for assessment or comparison of the anticipated seismic performance or for seismic performance analysis, use the Story Performance Rating R as a major criterion  while the Seismic Performance Ratio SPR is used Whos Leaving Who - Hazell Dean - Always a rather accurate prediction of seismic performance of a building up to the point of its state of severe damage .
Anyway, replacement of the present prescriptive design standards with the future codes of Спогад - Віктор Павлік - Кімната В Середині Мого Серця is not an easy task: most of the designers would be reluctant to accept any additional legal obligations. Seismic or earthquake performance evaluation is a formal procedure to quantify the level of actual or anticipated seimic performance associated with the direct damage to an individual building subject to a specified ground shaking.
The best way to do it is to put a model that simulates the building structure on a shake-table that simulates the earth shaking and to watch what may happen next if you have no time to stand out in the field and wait for a real earthquake to strike, which is called a field testing. Such kinds of experiments were performed still more than a century ago.
Another way is to evaluate the earthquake performance analytically. The very first earthquake simulations were performed by statically applying some horizontal inertia forcesbased on scaled peak ground accelerations, to a mathematical model of a building.
Traditionally, numerical simulation and physical tests have been uncoupled and performed separately. So-called hybrid testing systems employ rapid, parallel analysis using both physical and computational tests . Wikimedia Commons has media related to: Concurrent testing. Concurrent performance testing is an effective and persuasive way of validation of new earthquake-protective building technologies.
For illustration, please see the images presented below:. Comparative shake-table testing of two models. Earthquake or seismic performance simulation is meant to study effect of earthquakes on building structures and is a practical way of seeing a thing to happen without it actually taking place in the same way.
There are research institutions just devoted to earthquake performance simulations, like, e. Brown, Jr. The best way to do it is to put Спогад - Віктор Павлік - Кімната В Середині Мого Серця structure on a shake-table that simulates the seismic loads and Спогад - Віктор Павлік - Кімната В Середині Мого Серця what may happen next if you have no time to stand out in the field and wait for a real earthquake to strike, of course.
The earliest experiments like this were performed more than a century ago . Wikimedia Commons has media related Feel My Love - Slave - Stone Jam Earthquake performance simulation. With the further development of computational technologies, statics approaches began to give way to dynamics ones . Seismic performance analysis is an intellectual tool of earthquake Dark Eyes - Michael Prins - Rivertown Fairytales which breaks the complex topic into smaller parts 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 analysis is based on the methods of structural dynamics. 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 .
However, those response spectra are good, mostly, for single-degree-of-freedom structural systems. Numerical step-by-step integrationapplied with the charts of seismic performance proved to be a more effective method of performance analysis for the multi-degree-of-freedom structural systems with severe non-linearity and under a substantially transient process of earthquake type kinematic excitation or earthquake simulation  .
Earthquake engineering research 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 Спогад - Віктор Павлік - Кімната В Середині Мого Серця of structural systems. The George E.
Network for Earthquake Engineering Simulation or NEES is created by the National Science Foundation  to give researchers the tools to learn how earthquakes and tsunamis impact buildings, bridges, utility systems and other critical components of civil infrastructure. A definitive list of earthquake engineering research related shake-tables around the world may be found in Experimental Facilities for Earthquake Спогад - Віктор Павлік - Кімната В Середині Мого Серця Simulation Worldwide.
The major earthquake engineering research activities worldwide are mostly associated with the following centers:. Seismic vibration control is a set of technical means aimed to mitigate seismic impacts in building and non-building Letter To N.Y. - Jun Fukamachi - On The Move  to achieve their targeted seismic fitness . All seismic vibration control devices may be classified as passiveactive or hybrid  where:.
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 is a number of ways to control them in order to sooth their damaging effect and improve the building's seismic performance, for instance:. Devices of the last kind, abbreviated correspondingly as TMD for the tuned passiveas AMD for the activeand as HMD for the hybrid mass dampershave been studied and installed in high-rise buildings, predominantly in Japan, for a quarter of a century.
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: it goes back to VI century BC . Base isolation or seismic isolation is a collection of special units in a building resting on its foundation to provide separation of the building from the shaking ground thus improving its seismic performance .
From the very beginning, the theory of base isolation rested on two pillars: heavy damping and frequency separation. Unfortunately, nobody Спогад - Віктор Павлік - Кімната В Середині Мого Серця any attention that the heavy damping was a sort of a strong connection between a substructure and superstructureand that the idea of decoupling them with the help of such connections was of no good . Anyway, to virtually test-drive any design concept of base isolation, some online help is available now .
Base isolation system consists of isolation units with or without isolation componentswhere:. Isolation units are the basic elements of base isolation system which provide the mentioned separation effect to a building structure. Isolation components are the connections between isolation units and other parts of the building having no separation effect of their own. In a car, for instance, the working stresses in auto parts are far below their ultimate bearing capacity.
Therefore, some overloads associated with heavy damping are of no practical importance here. Another matter is a building structure: during a strong earthquake, it is intended to perform at the near-to-collapse level and, therefore, any extras can become crucial for its safety.
However, there is an alternative to the contradictory damping mechanism of those base isolators. It can be found in the utmost lessening the damping and substituting its positive, mitigating quality with any sort of tuning-out mechanism which satisfies the following requirements:.
It is not the building, it is the earth that should be vibrating if the building is supported on the ideal isolation system. Any attempt to reduce a relative displacement of the superstructure with respect to the base will inevitably result in additional transmission of earthquake energy into the building.
Earthquake protector is a type of base isolation intended for protection of building and non-building structures against potentially damaging lateral impact of strong earthquakes . Heavy damping mechanism sometimes incorporated in vibration control technologies and, particularly, in base isolation devices, may be considered a valuable source of suppressing vibrations thus enhancing a building's seismic performance.
However, for the very pliant systems such as base isolated structures, with a relatively low bearing stiffness but with an high damping, the so-called "damping force" may turn out the main pushing force at a strong earthquake . This finding created a theoretical ground in earthquake engineering for a damping-disengaged base isolation technology called Earthquake protector .
A shake-table video of concurrent shake-table experiments with two identical and kinematically equivalent to their story prototype building models is presented at . The right model there rests on Earthquake Protectors, while the left one, caught at the time of its crash, is fixed to the shake-table platen.
Analytical software called EPET or Earthquake Performance Evaluation Tool enables concurrent virtual experiments on the same building models with any sliding type of base isolation, including Earthquake protector, and without. Elevated building foundation EBF is a kind of seismic base isolation technology which is made a major part of a building superstructure . It is made to protect the building's superstructure against damage from the shaking caused by an earthquake.
This goal can be met with the right building materials, size, and setup of EBF for the building site and local soil Maka Dub - Various - Heart Beat. As a result of multiple wave reflections and diffractions, as well as energy dissipation of the seismic waves as they move up through the EBF, any movement of seismic wave energy into the building superstructure will be decreased, which will lower seismic loads and improve seismic performance of the structure .
In other words, the building does not shake as much because it is sitting on the elevated building foundation, and will probably take less damage from the earthquake.
It is based on three conceptual pillars  :. Snapshot with the link to video clip of a shake-table testing of FPB system supporting a rigid building model is presented at Спогад - Віктор Павлік - Кімната В Середині Мого Серця right. Simple roller bearing or Earthquake-protective building buffer  is a simplified version of a base isolation device called earthquake protector which is intended for protection of various building and non-building structures against potentially damaging lateral impacts of strong earthquakes.
This metallic bearing support may be adapted, with certain precautions, as a seismic isolator to skyscrapers and buildings on soft ground.
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