RAPID/Collaborative Research: Investigation of the Effects of Rockfall Impacts on Structures During the Christchurch Earthquake Series

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This award funds collaborative U.S. - New Zealand research that will investigate the effects of earthquake-induced rockfalls on residential and small commercial structures. The 2010-2011 Canterbury, New Zealand Earthquake Sequence included four major earthquakes that produced high levels of ground shaking in the Christchurch metropolitan region. These earthquakes triggered thousands of rockfalls, which impacted several hundred buildings and resulted in both human and capital losses. However, the impact of these rockfalls on structures varied widely. In some instances boulders became enmeshed within a building's structural system, causing damage but preserving life-safety. In other situations boulders fully penetrated building systems and caused structural collapse. While a rockfall's interaction with a building system may be conceptually understood to be a function of both impact energy and structural capacity, it still remains unclear exactly how these factors govern a building's resistance to these impacts. There is virtually no information on this in the engineering literature. This work will be the first extensive, well-documented study of the subject and will be of immediate use to engineers in all parts of the world where rockfalls are a potential threat. To this end, this research seeks to acquire, process, and archive data pertaining to the impact of rockfalls on a series of common residential and commercial structures. This study will be accomplished through geo-referenced, 3D, ground-based LIDAR scans and Structure from Motion (SfM) photographic acquisition at approximately 30 damaged buildings. In addition to documentation at high detail, the resulting database will provide a substantial increase in the number of high-quality case histories of rockfall-structure interaction. This work additionally aims to identify the factors that govern the resilience of a wide range of common structures through a preliminary series of coupled runout/structural impact model simulations of the rockfall process. The project includes a range of broader impacts including most notably development of preliminary guidelines on building system resilience to rockfalls. These guidelines will have important implications for building codes worldwide and more immediately will serve to inform local rebuilding and recovery efforts in Christchurch. The work will be done in close cooperation with researchers from GNS Science, New Zealand.