Post-tensioned NSM CFRP for Upgrading Concrete Bridges: Modeling, Testing, and Field Application

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Title: Post-tensioned NSM CFRP for Upgrading Concrete Bridges: Modeling, Testing, and Field Application

Author(s): Yail J. Kim, Hee Young Lee, Wonseok Chung, Jae-Yoon Kang, Jong-Sup Park, and Woo-Tai Jung

Publication: Special Publication

Volume: 327

Issue:

Appears on pages(s): 4.1-4.18

Keywords: bridge; carbon fiber reinforced polymer (CFRP); near-surface-mounted (NSM); site application, strengthening; upgrade

Date: 11/1/2018

Abstract:
This paper presents an on-going research program to develop an effective strengthening method using post-tensioned near-surface-mounted (NSM) carbon fiber reinforced polymer (CFPP) composites for constructed bridges girders. Various technical aspects associated with strengthened girders are examined through computational modeling, laboratory experiments (small- and full-scale tests), and a field project that is the world’s first site application of post-tensioned NSM CFRP. The flexural behavior of the bridge girders is improved by strengthening (that is, cracking, yield, and ultimate loads, as well as serviceability) relative to unstrengthened control girders, and the post-tensioned NSM CFRP should cover at least 60% of the girder length. The influence of CFRP post-tensioning on the girder concrete adjacent to the anchorage exponentially decays and becomes negligible beyond a distance of 800 mm (31 in.), irrespective of girder size. The presence of initial damage in the girder does not affect the efficiency of the strengthening system until failure occurs. The site application is dedicated to upgrading the design live load capacity of a 56-year old bridge in South Korea from 318 kN (72 kips) to 424 kN (95 kips). Step-by-step procedures are detailed for the technology transfer. Long-term performance monitoring for this upgraded bridge is underway and corresponding results will be reported when sufficient data are available.