Since the 1980’s, several buildings throughout the world have been subject to gas explosions, impact by trucks or airplanes, or car bomb attacks. In many cases the effect of the impact or explosion has been the failure of one or more critical structural members at the perimeter of the building. After the failure, the load supported by that member could not be redistributed and part or all of the structure has collapsed in a progressive manner. The phenomenon that occurs when local failure is not confined to the area of initial distress, and spreads horizontally and/or vertically through the structure, is termed progressive collapse. The phenomenon of progressive collapse has been extensively studied for cast in-situ buildings, and literature is available. However, for precast concrete structures, much less design information exists, and addresses mainly bearing wall structures. For precast structures in general and skeletal structures in particular, nearly no practical design guidelines exist. The fib commission on Prefabrication has recently published in Bulletin 63 a Guide to Good Practice on “Structural Integrity of Precast Concrete Structures under Accidental Actions”. The present knowledge on the subject and guidelines for the design of precast structures against progressive collapse are dealt with in a series of three articles. The first article describes the classification of possible accidental actions, properties for a good structural response and strategies to cope with accidental actions in the design. The second article discusses in detail the three design methods for mitigating the risk of progressive collapse after a severe initial damage. The third article gives an overview of international standard requirements concerning the categorization of buildings into consequences classes and indicates corresponding design strategies. It concludes with a critical analysis of typical connections in precast concrete structures.
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