Earthquake Vibrations

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 making the upper edges of the building swing from a few mm to many inches dependent on their height size and mass. This is uniformally applicable for buildings of all heights, whether single storeyed or multi-storeyed in high-risk earthquake zones.

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 horizontal movements caused by earthquakes.

In Mexico earthquake it was observed that buildings of different sizes and heights vibrated

This expansion joint is provided for relieving stresses caused due to expansion or contraction of construction material owing to temperature changes. At this point the buildings are totally separated and a gap of 1 to 2" is provided which is filled with a flexible material. However this is causing a major problem ie. the deflection of these independent buildings during earthquake is much more in high rise buildings than the expansion joint and since at this point these buildings are separate and of varying size they would swing and hammer with each other and weaken the buildings. Structural components around the expansion joint would be severely damaged and there shall be a chain reaction of forces in the total structure for which the structure has not been designed.

These cracks can be easily observed by just going around Delhi and Gurgaon and various cities of Gujarat. The damage caused in the recent earthquake by the seismic forces in the high rise residential and commercial buildings at the position of expansion joints is clearly visible and indicates to the gravity of the

Here again engineers designing one's house cannot be aware of the forces due to earthquake which will come from the neighbouring house, who will be sharing your external wall or structural frame with his. This system is totally against the principle of earthquake proof construction and design since this puts in an unknown factor regarding moments and horizontal forces for which the walls or building frames are to be designed. Further this is also against the provision of the I.S Code where a building or structure is to be separated every 30m for allowing expansion caused due to properties of building materials.

Thus it is advised that in areas where high intensity earthquakes are expected the following precautions be taken:

1. Municipal and other housing bodies should insure that a suitable gap is provided between two adjoining buildings at the time of