Foundation, Concrete and Earthquake Engineering

What is Pounding? Structural and Foundation Issues of Pounding

What is pounding?

Collision of adjacent buildings during earthquake is generally called pounding. This is occurred when they have different dynamic properties and there have not sufficient or no separation distance from adjacent one. The damage due to pounding may be of local and global; local damage is associated with collision force but global damage of buildings depends on their dynamic properties at the time of taking place of collision. Global damages caused by transfer of energy and momentum between two system generated by collision.

Seismic pounding between buildings is one of the most common causes of severe structural damages due to earthquake. Pounding involves movement along or transverse to separation joints provided between neighbor structures and may cause non-structural damages. From the above discussion, seismic pounding between adjacent buildings occur during earthquake when

• Buildings have different dynamic characteristics

• They vibrates out of phase relative to each other

• The separation between buildings at rest is not sufficient

• Insufficient energy dissipation system, if any, to restrain movement within allowable separation distance. 

Why is pounding of buildings concerned?

Past building codes didn’t provide definite recommendation or guidelines to account pounding effect and to counteract this phenomenon. As a result in many densely populated areas to achieve maximum land usage and for economic consideration, many buildings over the world already built extremely close to neighbor and in some region even no space is left. These building are vulnerable to pounding damage during future seismic activity. A large separation distance is not expected from both technical point of view within same facility having large expansion joints and economical point of view considering loss of land. In many cities the highly congested structures become a major concern for pounding damage. This is why, it is now widely accepted that this unexpected phenomenon has to be mitigated or prevented (Abdel Raheem, 2006).

What is seismic gap?

The distance provided between two adjacent building structures is called separation joint; often same facility is divided into two wings and sometime more depending on dimension of buildings. This permits an independent movement of structures relative to each other. A seismic gap is nothing but a separation joint kept to provide room for relative lateral movement due to seismic agitation.

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