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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Title: Prestress Loss of Post-Tensioned Near-Surface-Mounted Carbon Fiber-Reinforced Polymer for Bridge Strengthening
Author(s): Yail J. Kim, Jae-Yoon Kang, Jong-Sup Park, and Woo-Tai Jung
Publication: Structural Journal
Appears on pages(s): 1495-1506
Keywords: bridge; carbon fiber-reinforced polymer (CFRP); long-term; loss; near-surface-mounted (NSM); post-tension; retrofit; strengthening
Abstract: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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