Seismic movement

The hot duct consists of three sections of metallic pipes, two of which are covered with thermal barrier. The assembly is attached to the core barrel and extends through the crossduct to the steam generator vessel. The hot duct includes bellows to accommodate thermal and seismic movements and seals to prevent bypass flow. The hot duct assembly also includes a set of two shrouds, one of which is part of the elbow installation device, and both of which form a channel for the gas being directed to the main circulator. 

Random vibrations, such as tho.se caused by an earthquake, cause shocks and ground movements and are termed seismic disturbances. Shocks and turbulence caused by a heavy sea, landslides and volcanic eruptions are also examples of shocks that may cause vibrations and result in tremors, not necessarily earthquakes. Nevertheless, they may require design considerations similar to those for an earthquake, depending upon the applieation (e.g. naval applications, hydro projects, dams and bridges). 

This is a response spectrum obtained during a test in a laboratory while exciting the shake table with ground movements as in the RRS. The test object is mounted on the shake table. The test object should respond normally during such movements. The test conditions (i.e. TRS) should closely overlap the required seismic conditions (i.e. RRS) of Figure 14.25. 

Now that it is possible to establish test facilities in a laboratory to simulate the time history of an earthquake seismic tests are conducted by creating the ground movements in the test object. Other methods, such as by analysis or by combined analysis and testing, are also available. Refer to IEEE 344 and lEC 60980 for more details. For this purpose a shake table, able to simulate the required seismic conditions (RRS) is developed on which the test object is mounted and its performance observed under the required shock conditions. Since it is not easy to create such conditions in a laboratory, there are only a few of these facilities available. The better equipped laboratories are in Japan, the USA, the UK, Greece, Germany, India and China. In India the Earthquake Engineering Department (EQD) of the University of Roorkee (UoR) is equipped with these facilities. 

This is the duration sufficient to simulate seismic conditions. It depends upon the algorithm used to find time history from the reqtiired response spectrum (RRS). The minimum duration of a strong movement, as recommended by IEEE 344, is 15 seconds as illustrated in Figure 14.24(b). This will require a total duration of the order of 20 seconds, including the movement s times of rise and time of decay. A duration of 20.48 seconds, as noted in the figure, is typical of a test conducted at University of Rorkee. The following tests may be conducted ... 

Seismic effects and earthquake engineering is covered in this part to study the behaviour of an object under seismic conditions and its suitability for critical installations. The formation of the earth and movements of tectonic plates that cause earthquakes and volcanic eruptions are described,... 

The occurrence of earthquakes is a highly studied phenomena by geologists. The role of solid surfaces in such phenomena is obvious. Especially, faults are known to contribute to many earthquakes. Faults are treated as shear cracks, the propagation of which may be understood through the application of fracture mechanics. The stability of any fault movement, which determines whether the faulting is seismic or aseismic, is determined by the frictional constitutive law of the fault surface. It is well established that, once a fault has been formed, its further motion is controlled by friction (between the solid surfaces), which arises from contact forces across the two solid surfaces. 

The seismic wave generated by an explosion is a compression wave the vibration is parallel to the direction of propagation of the wave. On the surface, the initial movement of this wave corresponds to a lifting of the ground. However, this is not the only propagation mode for seismic waves. Three other types are possible shear wave. Love wave and Rayleigh wave. 

Other causes of waves include undersea landslides, volcanic eruptions, and movement along faults on the ocean floor. Fault movements can suddenly raise or lower the seabed, resulting in earthquakes and displacing water. The displaced water forms a gigantic wave called a tsunami (sometimes referred to as a seismic or tidal sea wave). 

Seismic reinforcement RubCon s high elasticity makes for a most impressive material in structures threatened by seismic activity. Where conventional concrete is brittle and tends to crack easily, RubCon s unique rubberlike binder offers a very high deflection rate, equipping the material with the freedom of movement necessary to rebound from seismic activity. 

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