28-09-2012, 05:55 PM
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28-09-2012, 05:55 PM
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29-09-2012, 03:27 PM
To get more information about the topic "earthquake resistant structures"
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07-11-2012, 02:27 PM
EARTH QUAKE RESISTANT STRUCTURES
EARTH QUAKE.pptx (Size: 1.22 MB / Downloads: 152) Introduction The worst of all natural disasters, earthquake have become more pronounced and have claimed a large number of lives from the start of the history. This is a subject of growing concern among civil engineers and architects. This is important because it is not the earthquake that kills the people but it is the buildings they live in. This paper involves the various techniques that can be adapted to make the buildings more resistant to the earthquakes. Dynamic Analysis Dynamic analysis may be performed either by the Time History Method or by the Response Spectrum Method Time history method of analysis is performed using accepted principles of dynamics based on the appropriate ground motion. Response spectrum method of analysis is performed using a site-specific design spectrum value Inverse Pendulum Effect: It is analysed to have more flexibility hence too weak to carry earthquake force due to its collapse at ground storey and this effect termed as inverse pendulum effect. Open ground storey buildings are inherently poor systems. In the current practice, stiff masonry walls are avoided and bare frames are considered in design calculations. In practical, steel sections will be raised as vertical reinforcement and hollow blocks will be hoisted as partitions. Thus, the inverted pendulum effect is not captured in design Short Column During past earthquakes, reinforced concrete (RC) frame buildings that have columns of different heights within one storey, suffered more damage in the shorter columns as compared to taller columns in the same storey. Poor behavior of short columns is due to the fact that in an earthquake, a tall column and a short column of same cross-section move horizontally by same amount. Stiffness of a column means resistance to deformation – the larger is the stiffness, larger is the force required to deform it. This behavior is called into the columns vertically above. Short Column Effect. As per Indian Standard the reinforcement must extend beyond the short column Basic Structural Concepts Extra attention to analysis and details is not likely to improve significantly the performance of a poorly conceived structural system In precise it is to have a check on Control over mass and stiffness, Continuity in load transfer Regularity of the system Redundancy of the structural element Damping of the building Moment resisting frames When seismic resistance is provided by moment resistant frames, lateral forces are resisted primarily by the joints between columns and beams. At joints, to avoid damage as shown below we can go for the anchorage of the bars at the ends and to avoid congestion micro concreting can be done. Pre Tensioning Technique In case of domes and shell structures, the lateral thrust experienced will be more. This fault is answered well by pre tensioned concrete. In case of huge structures like nuclear rectors, large spanning domes we will be having a thin walled cylindrical tube of diameter about 10 to 15 cm and steel rods will be packed tightly |
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