EARTHQUAKE-PROOF BUILDING'DESIGN.

Earth quake building design is necessitated necessity of the buildings and there is no reliable means of predicting an earthquake as to the time of occurrence, place of occurrence or it's intensity have yet been discovered. It is however, considered that in the localities where earthquake have occurred once they are likely to reoccured again at a future date. An earthquake map of India has been prepared by the Meteorological Department showing zones liable to severe, moderate and minor earthquakes. Earthquakes consists of vertical and horizontal wavelike motions of the ground. The horizontal motions are much greater than the vertical from five to ten times and may be in any direction. The most destructive force is therefore the horizontal motion. GENERAL PRINCIPLES OF DESIGN:-- Buildings should be as light as engineering considerations and considerations of health and comfort permit. Continuity and lightness of structure are of more importance than thickness of walls or low height The maximum height of any building shall not exceed 27 metres. Excessive length in proportion to width is undesirable. A square or a compact rectangular plan should be adopted. A ratio of length to breadth should not exceed 3to 1 normally. A closed shape, square or nearly so, is prepared to U or L shapes. All parts of building should be firmly tied together and stiffly braced at corners in such a manner that the whole structure will tend to move as a unit. Parapets, cornices, cantilevers and projections exceeding 75 cm should be avoided. Chimneys should be of RCC or metal and well tied with the main structure. Exterior bearing walls and other walls of masonry should be adequately tied together at the level of each floor line from outside wall to outside wall of structure by continuous metal rods or RC ties of adequate strength and should be tied to all intervening partition walls. Cement mortar should be used in all masonry structures. A rigid structure comes to rest very quickly and is preferable to a flexible structure. In the case of a rigid frame with rigid joints made by means of knee braces and gusset plates, the horizontal girders by means of transverse walls serve to stiffen the buildings at the expense of adding to the bending moments of the horizontal girders and vertical columns. Diagonal braces are most effective in increasing the rigidity of the structure.