Stepwise Bond Model Including Unconfined and Partially Confined Hooks


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Title: Stepwise Bond Model Including Unconfined and Partially Confined Hooks

Author(s): Armin Erfanian and Alaa E. Elwi

Publication: Structural Journal

Volume: 115

Issue: 1

Appears on pages(s): 103-112

Keywords: bond; confinement; in-place pressure; partial confinement; slip; splitting; stepwise

Date: 1/1/2018

A contact interface model including hook reinforcement under monotonic, unconfined, in-plane compression and tension is presented, which is in close agreement with experimental test results. Unconfined in-plane compression accompanies unconfined hooks under the bent portion of a hook and creates splitting in the same plane as the hook. Although the effect of pressure on bond capacity of unconfined concrete is investigated in the literature, there is little information on reliable bond-slip behavior for this case. fib 2010 does not provide bond-slip equations for unconfined and partially confined concrete under compression, although it considers the case of confined concrete under pressure. Laborious effort was made in this research to formulate a procedure that works in the three-dimensional finite element environment without impractical limitations. In addition, a new method of computing bond stress increments is proposed to be used in cases involving slip-dependent normal pressure such as joints.