Earthquake Design Philosophy: Progressive Collapse

CHAPTER-1
INTRODUCTION
GENERAL
The term “progressive collapse” has been used to describe the spread of an initial local failure in a manner similar to a chain reaction that leads to partial or total collapse of a building. The fundamental characteristic of progressive collapse is that the final state of failure is disproportionately greater than the failure that originated the collapse. Progressive collapse as “the spread of an initial local failure from element to element resulting, finally in the collapse of an entire structure or a disproportionately large part of it”. The disproportionality refers to the condition in which failure of one member causes a major collapse, with an amount disproportionate to the original event. Thus, “progressive collapse” is an incremental type of failure in which the total damage is out of proportion to the original cause. In some countries, the term

Under moderate but infrequent shaking, the main members may withstand repairable damage, while the other parts of the building may be damaged such that they may even have to be substituted after the earthquake; and Under strong but rare shaking, the main members may withstand severe (even irreparable) damage, but the building should not collapse. Thus, after minor shaking, the building will be completely functioning within a short time and the repair costs will be small. And, after restrained shaking, the building will be functioning once the repair and strengthening of the damaged main members is accomplished. But, after a strong earthquake, the building may become dysfunctional for further use, but will stand so that people can be displaced and property recuperated