Title: Simplification of Buckled Bar Tension Test through Fiber Modeling

Author(s): Diego Sosa, Jurgen Varela, and Mervyn Kowalsky

Publication: Materials Journal

Volume: 119

Issue: 3

Appears on pages(s): 161-171

Keywords: buckling; critical bending strain; fiber models; fracture; reinforcing bar

DOI: 10.14359/51734616

Date: 5/1/2022

Abstract:
Buckled reinforcing bars exhibit bending strains across the bar section. The bending strain threshold that triggers brittle bar fracture in tension, referred to as the critical bending strain, can be obtained with the buckled bar tension (BBT) test. However, the BBT test requires three-dimensional (3-D) position measurement systems that are not widely available. To make the BBT test more accessible, this paper uses fiber-based models to develop empirical equations for curvature, neutral axis depth, and bending strains in buckled reinforcement. These equations may be employed in the BBT test without the need for advanced instrumentation systems. This study shows that bending strains calculated from fiber models of buckled reinforcing bars have a 95% probability of having less than 20% variation compared with experimental measurements. Furthermore, the determination of the bending strains for the BBT test is simplified to equations with three input parameters: bar fixed length, bar diameter, and bar axial displacement.