Fixed-Angle Smeared-Truss Approach with Direct Tension Force Transfer Model for Torsional Behavior of Steel Fiber-Reinforced Concrete Members

Abstract

The existing analysis models for torsional strength or torsional behavior of steel fiber reinforced concrete (SFRC) members typically adopted a simple approach, in which the tensile constitutive model of conventional concrete was modified appropriately for the SFRC considering that the steel fibers and concrete matrix behave in a fully composite manner. In such approaches, however, the pull-out behavior of the steel fibers at crack interfaces caused by the progressive loss of bond stress developed between the fiber and surrounding concrete is hard to be described in detail, and they also requires much experimental effort and cost to derive the constitutive models of SFRCs in tension for various types of SFRCs. In this study, steel fibers are modeled as separate direct tension force transfer elements and applied to a modified fixed-angle smeared-crack truss model for torsion so that the bond mechanism between the steel fibers and concrete matrix can be reflected in the tensile behavior of SFRC further in detail. The proposed fixed-angle model approach for torsional behavior of SFRC members take into account the difference between principal stress and cracking angle, and well reflects the unique characteristics of SFRC, such as fiber directionality and bond mechanism. The proposed approach provided a good agreement with the torsional behavior of 48 specimens obtained from previous studies.