Friday, July 27, 2012

Tough Stanced Haven - Quake Proofing Your House

When a building experiences earthquake vibrations its foundation will move back and forth with the ground. These vibrations can be quite intense, creating stresses and deformation throughout the structure. A building needs to be slightly flexible and also have components which can withstand or counter the stresses caused in various parts of the building due to these horizontal movements.The foundation must laid with utmost care. It must be laid, taking the soil conditions into consideration. Also should be considered are the various forces and loading coming on it from the building is calculated. On this rubber bearings are placed. 

Thus even though the building foundation may experience horizontal movements caused by an  intensity of considerably high level on the Richter scale, the building above it would experience very low impact as if that caused by an earthquake of negligible intensity.Frames of the superstructure are generally made of steel sections and is designed for the stresses acting on the structure with cross bracing and shear walls where required. The slabs used are again supported by steel sections and made of wooden sections, this system provides nominal flexibility and thus safety, since in an extreme condition a falling plank from the roof has less chances of giving a fatal injury than a falling concrete slab. All connections and joints are designed to withstand shear forces and where required flexible joints are provided so that there are minimum chances of slab failure.

The walls are again made of wood, toughened glass with flexible anchorage systems or of any other material taking precaution that in case of extreme condition of breakage they have minimum chances causing the total failure of the structure system. The walls are also designed to be tough enough to protect you from the impacts of nature such as cyclones, storms and hurricanes and of course from people trying to break into your home.

While designing the structure precaution also needs to be taken to ensure that in case any one structural component buckles it does not trigger a chain reaction of failures of other components and thus collapse of the total building structure. Thus structural isolation zones should be created for additional safety and additional supporting systems be created where considered critical.

While designing the building with seismic isolation bearings the total building has to be isolated from the surrounding ground thus a gap is provided all around the building. This gap should be 1.5 times the expected movement of the ground and building relative to each other and this has been recorded to be up to 49 cm. The gap should also be sized with respect to maintenance and easy accessibility for repairs and maintenance of the sub structure. This gap should be covered from safety point of view with slab or steel or aluminium grill cantilevered from the building. 

All the approaches for accessing the building such as stairs and ramps are to be cantilevered from the building and should not come in contact with surrounding ground. All services such as water supply, sanitary and drainage pipes have to be connected from the municipal connection to the building with a flexible connection so that they do not break due to the movement of the ground under the building.The safety of the human life during the worst scenario should always be of the highest consideration during the selection of structural components and the design of the building. 


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