Prestress Loss of Post-Tensioned Near-Surface-Mounted Carbon Fiber-Reinforced Polymer for Bridge Strengthening

This paper presents short-term and long-term prestress losses in post-tensioned near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP) composites for strengthening a decrepit bridge. Predictive models are developed to examine the time-dependent behavior of the NSM CFRP, comprising carbon fibers and a resin matrix at macro- and microscales (analytical and closed-form mathematical approaches, respectively). Emphasis is placed on the relaxation of the CFRP, which is a primary component in prestress loss. Parameters influencing the relaxation (characteristic time, and viscous and plastic moduli) are calibrated using the Generalized Reduced Gradient Method. The anchor set of the post-tensioned NSM CFRP is the major attribute for short-term prestress losses, followed by the elastic shortening of the bridge. Regarding long-term losses, the relaxation of the NSM CFRP accounts for 92% of the total time-dependent loss (major relaxation takes place within the first-year period after strengthening), and the creep and shrinkage components are responsible for the remaining portions of 5% and 3%, respectively. The contribution of the fibers to the composite’s relaxation is negligible, whereas that of the matrix is noticeable. According to a parametric study, unlike the characteristic time, the plastic and viscous moduli affect the relaxation responses. Design recommendations are proposed with relaxation losses varying from 3% to 8% of the initial post-tension stress, depending on matrix properties.

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    • Abstract reprinted with permission from the American Concrete Institute.
  • Authors:
    • Kim, Yail J
    • Kang, Jae-Yoon
    • Park, Jong-Sup
    • Jung, Woo-Tai
  • Publication Date: 2018-9

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  • English

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  • Accession Number: 01692054
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jan 2 2019 2:39PM