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Earthquakes and Structures
  Volume 8, Number 3, March 2015, pages 619-637

Relationship between hardness and plastically deformed structural steel elements
Hassan Nashid, Charles Clifton, George Ferguson, Micheal Hodgson, Chris Seal and Jay-Hyouk Choi

    A field based non-destructive hardness method is being developed to determine plastic strain in steel elements subjected to seismic loading. The focus of this study is on the active links of eccentrically braced frames (EBFs). The 2010/2011 Christchurch earthquake series, especially the very intense February 22 shaking, which was the first earthquake worldwide to push complete EBF systems into their inelastic state, generating a moderate to high level of plastic strain in EBF active links for a range of buildings from 3 to 23 storeys in height. Plastic deformation was confined to the active links. This raised two important questions: what was the extent of plastic deformation and what effect does that have on post-earthquake steel properties? A non-destructive hardness test method is being used to determine a relationship between hardness and plastic strain in active link beams. Active links from the earthquake affected, 23-storey Pacific Tower building in Christchurch are being analysed in the field and laboratory. Test results to date show clear evidence that this method is able to give a good relationship between plastic strain and demand. This paper presents significant findings from this project to investigate the relationship between hardness and plastic strain that warrant publication prior to the completion of the project. Principal of these is the discovery that hot rolled steel beams carry manufacturing induced plastic strains, in regions of the webs, of up to 5%.
Key Words
    deformed steel; eccentrically braced frames; earthquake; hardness; plastic strain; residual stress; portable hardness tester
Hassan Nashid, Charles Clifton, George Ferguson, Micheal Hodgson: Civil and Environmental Engineering, The University of Auckland, New Zealand

Chris Seal: School of Mechanical, Aerospace and Civil Engineering, University of Manchester, United Kingdom

Jay-Hyouk Choi: School of Architecture, College of Engineering, Chosun University, Republic of Korea

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