Improvements in Postearthquake Building Safety Evaluations: Lessons Learned From Recent Damaging Earthquakes and Guideline Development Effort

Abstract eng:
The ATC-20 report, Procedures for Postearthquake Safety Evaluation of Buildings, was published by the Applied Technology Council in 1989 specifically for use by qualified professionals who would be required to make on-the-spot evaluations and decisions regarding continued use and occupancy of damaged buildings. Since 1989, the ATC-20 methodology has been used worldwide in response to earthquakes of varying magnitudes, and a family of ATC-20 documents has been developed, including a second edition of a field manual (ATC-20-1) in 2005. This paper will reflect on lessons learned during recent development exercises, such as the development of an adaptation of the ATC-20-1 methodology for Bhutan which considered the country’s vernacular buildings, made adjustments for its cultural and governmental context, and provided an extensive set of images of varying degrees and types of building damage with the recommended posting category. The paper will also summarize and synthesize lessons learned from postearthquake safety evaluations conducted after recent damaging earthquakes, such as 2010 in Chile, 2011 in New Zealand, 2014 in Napa, California, and 2015 in Nepal. The original ATC-20 methodology has been adapted to other structural and governmental contexts, including documents funded by the local governments of New Zealand and Nepal. Each of these adaptations offered enhancements to the existing methodology and utilized different methods of communication. This paper will present a best practices overview from observed modifications. For example, following the magnitude-6.2 22 February 2011 Christchurch, New Zealand earthquake, local officials, despite being initially caught off guard and unprepared for the scope and severity of the damage, made over 72,000 building inspections in 10 days. Many useful practices were instituted, including an emphasis on shelter-in-place, the addition of usability categories to placards, use of indicator buildings to help determine if reinspections after major aftershocks were warranted, and the forming of specialized teams to deal with specific concerns (such as buildings in danger of collapse). The approach taken by the New Zealand government in assessing buildings in Christchurch and subsequent modifications they made to their approach presents a major opportunity to learn from the experience, and this paper will present how this information can be used to update and improve the ATC-20 procedures. In Nepal, a variety of postearthquake evaluation practices were observed, with extensive volunteer efforts both by engineers from Nepal and from many other countries. Nepal’s guidelines include photographs of damaged buildings consistent with Nepal’s building stock with the damage clearly linked to the recommended placarding categories of INSPECTED, RESTRICTED USE, and UNSAFE.

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