CE2045 Prefabricated Structures-Progressive Collapse-Makendran C

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Information about CE2045 Prefabricated Structures-Progressive Collapse-Makendran C

Published on February 16, 2014

Author: makendran

Source: authorstream.com

CE2045 Prefabricated Structures UNIT-V Design for Abnormal Loads Progressive collapse: CE2045 Prefabricated Structures UNIT-V Design for Abnormal Loads Progressive collapse Prepared by C.Makendran Assistant Professor Progressive collapse: Progressive collapse Progressive collapse typically, Progressive disproportionate collapse is the result of an abnormal loading event. Four general classes of abnormal loads are 1.Accidential Impact 2.Faulty construction 3.Foundation failure 4.Violent change in air pressure 1.Accidental Impact: 1.Accidental Impact Several causes of progressive (disproportionate) collapse have been caused by accidental impact. An example of this form of abnormal loading is an automobile striking a key members in a structure( i.e.,Buildings , Bridge etc.) 2.Faulty Construction: 2.Faulty Construction There have been several instances throughout history where poor construction practices have led to progressive collapse. A notable example of this was the skyline plaza apartment in building in fairfax country, virginia . This failure was attributed to premature removal of supporting forms. This leads to localized failure, followed by a progressive collapse of the northwest corner of the structure. 3.Foundation failure: 3.Foundation failure Failure of a small portion of a structures foundation can result in a loss of primary support. This failure could be the result of problems with erosion , geology , cartering due to explosion etc.. If the remainder of the structure is unable to redistribute this change in load caused by the loss in support , extensive damage to the structure could be much greater. 4.Violent change in Air pressure: 4.Violent change in Air pressure An extreme change in air pressure can stem from any sources such as explosions caused by gas, high explosives etc.. An example of a progressive disproportionate collapse that resulted from a sever change in air pressure was the 1995 terrorist bombing of the A.P.Murrah Federal Building in Oklahoma City, Oklahoma. Causes of Progressive Collapse: Causes of Progressive Collapse There are usually multiple factors that take place in order to initiate a progressive collapse. Often, these collapses will take place during the construction phase of a building. Miscommunication between contractors and engineering documents can cause a progressive collapse. In this case, workers may improperly install specific structural elements that can lead to weakened structural members throughout the building. Some contractors may be pressed for time to where they may improperly address key connections or finishing techniques to adequately install the structure. Causes of Progressive Collapse: Causes of Progressive Collapse Construction technology may also fail, as it did in many cases where buildings used lift-slab technology to construct the building. Improper inspection or overlooking structural issues also leads to factors that initiate a progressive collapse. In some cases proper inspection may find a faulty member or connection yet may not properly document it or resolve the issue do to poor miscommunication. Causes of Progressive Collapse: Causes of Progressive Collapse Another root cause of progressive collapse takes place in the design phase of a building. If structures go for years without receiving proper maintenance, rust or other material failures can occur which weaken the structure and make it more susceptible to a progressive collapse. Causes of Progressive Collapse: Causes of Progressive Collapse Engineers may under-design specific elements because of an underestimation of loads or load paths which in turn cause higher stresses on specific structural elements. Often times engineers design for a specific live load or construction load that is exceeded on the job site due to storage of materials. Progressive Collapse Examples: Progressive Collapse Examples 1.World Trade Centre 1 and 2 2.Ronan Point 3.A.P.Murrah Federal Building

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