Multiscale Modeling of Concrete in Anchorage Region of Post-Tensioned NSM CFRP

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Title: Multiscale Modeling of Concrete in Anchorage Region of Post-Tensioned NSM CFRP

Author(s): Yail J. Kim, Yongcheng Ji, Wei-Tze Chang, Jae-Yoon Kang, Jong-Sup Park, and Woo-Tai Jung

Publication: Structural Journal

Volume: 113

Issue: 6

Appears on pages(s): 1233-1242

Keywords: bridge girder; carbon fiber-reinforced polymer (CFRP); damage; multiscale modeling; near-surface-mounted (NSM); post-tensioning

Date: 11/1/2016

Abstract:
This paper presents a multiscale modeling approach to understand the behavior of anchorage concrete in prestressed concrete bridge girders strengthened with post-tensioned near-surfacemounted (NSM) carbon fiber-reinforced polymer (CFRP) strips. The macroscale, mesoscale, and microscale responses of the concrete are represented by continuum finite element, discreteobject physics, and analytical representative element models, respectively. Domain decomposition and integration are implemented in accordance with an information-passing mechanism. The post-tensioned NSM CFRP results in macroscale strain softening near the anchorage and it also causes a regional net strain increase responsible for macroscale and microscale damage. The existence of a rapid crack-propagation phase is ascertained in the anchorage concrete from a mesoscale standpoint, which influences stress transfer from the anchor bolt to the contiguous concrete. The microscale damage of the concrete rapidly propagates when mechanical distress is applied due to post-tensioning the NSM CFRP and stabilizes with a decrease in stress transfer from the cementitious binder to aggregate inclusion in the representative element. The concept of effective stress is proposed to link the macroscale and microscale responses of the anchorage concrete.