Simplification of Softened Strut-and-Tie Model for Strength Prediction of Discontinuity Regions

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Title: Simplification of Softened Strut-and-Tie Model for Strength Prediction of Discontinuity Regions

Author(s): Shyh-Jiann Hwang, Ren-Jie Tsai, Weng-Kin Lam, and Jack P. Moehle

Publication: Structural Journal

Volume: 114

Issue: 05

Appears on pages(s): 1239-1247

Keywords: compressive softening effect; diagonal compression; discontinuity region; reinforced concrete; shear; strength; strut-and-tie

Date: 9/1/2017

Abstract:
A geometric discontinuity caused by abrupt changes in cross-sectional dimensions and a force discontinuity caused by concentrated loads results in discontinuity regions due to the disturbance in the flow of internal forces. A softened strut-and-tie model has been developed for determining the shear strength of discontinuity regions that fail under diagonal compression. The softened strut-and-tie model requires complicated computations, consequently making it challenging to apply in engineering practice. In this paper, a further simplification of the softened strut-and-tie model is proposed to facilitate design practice. Strength predictions of the simplified model correlate well with 449 test results of deep beams, corbels, squat walls, and beam-column joints available from the literature. The simplified model incorporates the shear-resisting mechanisms as postulated by the softened strut-and-tie model, and it is a function of the concrete compressive strength, steel yield strength, shear reinforcement ratio, and geometric configuration of the discontinuity region.