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Ward_s_MGH Earthquake Engineering

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1 The application of the natural and social sciences for the reduction of risk resulting from the effects of earthquakes. Although earthquake shaking and building collapse are the primary causes of loss of life and property, earthquake loss can also be caused by other effects such as ground failure (e.g., liquefaction, landsliding), tsunami, fire and hazardous materials release, and is also caused by busi- ness and social disruption, equipment and content damage, and lifeline damage (Fig. 1). Lifelines are urban services, such as water, power, gas, communications, and transportation, without which an urban region cannot function. Occasionally, effects other than shaking, such as widespread ground failure, tsunami, fire following an earthquake, landslides, or release of hazardous materials, may be the dominant agents of damage in a particular earthquake. Performance-based design High-seismic regions, such as San Francisco or Tokyo, typically experience a strong earthquake only once in many decades. Because strong earthquakes are rare events, until recently, building codes were based on allowing some significant degree of damage. If a strong earthquake occurred, structures were designed so that most would not collapse but might be dam- aged, which resulted in significant costs for repairs, business interruption, and, potentially, casualties. This degree of damage was tolerated because tools for understanding and designing Earthquake Engineering Article by: Charles Scawthorn, SPA Risk LLC, Oakland, California. Access to this content is available to Ward's World readers for free from McGraw Hill's AccessScience, an award-winning, digital STEM resource that provides immediate, authoritative answers to students' thirst for scientific knowledge on topics such as climate change, virology, pollution, and more. Ward's World and McGraw Hill have partnered to offer educators a no-obligation, free trial subscription to this product. Request your free trial today and discover how valuable AccessScience can be for you and your students. + ward ' s science Key Concepts • Earthquake engineers use information derived from seismic research to identify and mitigate structural risk from future earthquake events. • Earthquake engineering involves specific activities: seismic hazard quantification; structural and non-structural (e.g., equipment) analysis, design, and/or retrofitting; and operational planning, in order to prevent disruption due to earthquakes. • Structural vulnerability is the expected damage from an earthquake given a specified hazard (such as fault rupture or shaking), and is used to calculate the expected loss or seismic risk of the structure. • The most seismically hazardous existing building structures are low-strength masonry, unreinforced brick masonry, nonductile reinforced concrete, and certain kinds of precast concrete buildings. Earthquake engineers typically mitigate vulnerability in such buildings by structural retrofitting. • Current approaches to seismic design also include methods that modify the structural response to reduce earthquake loads, such as base isolation, supplemental damping, and active control. Fig. 1: Damage to reinforced-concrete frame buildings, M7.8 Gorkha, Nepal earthquake of April 25, 2015. (Credit: J. Bevington)

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