Development of Progressive Collapse Analysis Procedure and Condition Assessment for Structures

摘要

Progressive collapse denotes an extensive structural failure initiated by local structural damage, or a chain reaction of failures following damage to a relatively small portion of a structure. This can be also characterized by the loss of load-carrying capacity of a relatively small portion of a structure due to an abnormal load which, in turn, triggers a cascade of failures affecting a major portion of the structure. From an analytical viewpoint, progressive collapse occurs when a structure has its loading pattern or boundary conditions changed such that other structural elements within the structure are loaded beyond their capacity and fail. The residual structure is forced to seek alternative load paths in order to redistribute the loads applied to it. As a result, other elements may fail causing further load redistribution. This process might continue until the structure can find equilibrium either by shedding load, as a byproduct of elements failing, or by finding stable alternative load paths. Perhaps, the most dramatic example of progressive collapse occurred in 1968 when an internal gas explosion seriously damaged the Ronan Point residential apartment building in London, UK. The explosion occurred on the 18th floor as a result of build up gas from a domestic cooker, and the exterior panels of the kitchen blew outwards. The result was that the entire corner of the building above and below the location of the explosion collapsed.