Seismic Induced Pounding of Structures and Its Mitigation

Abstract

Limited availability of land resources and increasing population have led to closely spaced buildings in cities, in which the stipulated separation distance is most often not available between the buildings. When subjected to an external excitation, such as from wind or earthquake, the differences in the dynamic characteristics of these adjacent buildings cause phase differences in their responses, leading to chances of structural collision or pounding. Pounding between closely spaced buildings under earthquake excitation has been identified as a serious hazard, due to falling of building material, as well as a major cause of structural damage, that may range from minor, affecting non-structural components only, to heavy. There have been reports of significant pounding damage during several past earthquakes in not only buildings but between decks and abutments and at expansion joints of bridges as well. There is, thus, a necessity of mitigating the effects of pounding at the design stage, or in existing structures, through construction details or by the installation of vibration control devices. In this chapter, first, the various situations in which structural pounding can arise under seismic excitation are presented, followed by the types of pounding, such as one-sided pounding and two-sided pounding. A summary of the pounding damage that has been reported in past earthquakes is provided. The different pounding models developed by researchers are examined, and the effects of varying dynamic properties and separation distance on pounding are studied. Codal specifications on the minimum separation distance are highlighted and a discussion is made on the various mitigation strategies for seismic pounding.