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.

Shear capacity of steel fiber‐reinforced concrete beams

“…The DTFTM, which can estimate the shear contribution of steel fibers at the crack surface, was proposed in the authors’ previous studies 24–30 . The DTFTM is a microscopic approach model 17,18,24–26 and it can consider the contributions of the steel fibers separately from that of the concrete at the crack interface.…”

“…In the DTFTM the steel fibers are treated as distributed steel reinforcement embedded in concrete with their resistance capacities at the crack interface dominated by either their bond strength (i.e., pull‐out failure) or their tensile strength. Considering the bond strength and directions of the steel fibers in three‐dimensional space, the shear contribution of the steel fibers can be calculated as follows 24–30 : …”

“…The DTFTM, which can estimate the shear contribution of steel fibers at the crack surface, was proposed in the authors' previous studies. [24][25][26][27][28][29][30] The DTFTM is a microscopic approach model 17,18,[24][25][26] and it can consider the contributions of the steel fibers separately from that of the concrete at the crack interface. In the DTFTM the steel fibers are treated as distributed steel reinforcement embedded in concrete with their resistance capacities at the crack interface dominated by either their bond strength (i.e., pull-out failure) or their tensile strength.…”

“…Some researchers 1–14 carried out investigations on the basic material characteristics of SFRC and fiber directionality (or orientation) and many experimental and analytical studies on the structural behavior of SFRC beam members have also been conducted 1–11,15–23 . Furthermore, considerable research effort has been devoted in analyzing the shear behavior of SFRC members—from simple semi‐empirical strength estimation models 2,5,8,20–22 to theoretical shear behavior models 15–18,24–31 . In many traditional approaches the aggregate interlocking resistance of the cracked tension zone is considered as the governing shear resistance mechanism 31–33 .…”

“…[1][2][3][4][5][6][7][8][9][10][11][15][16][17][18][19][20][21][22][23] Furthermore, considerable research effort has been devoted in analyzing the shear behavior of SFRC members-from simple semi-empirical strength estimation models 2,5,8,[20][21][22] to theoretical shear behavior models. [15][16][17][18][24][25][26][27][28][29][30][31] In many traditional approaches the aggregate interlocking resistance of the cracked tension zone is considered as the governing shear resistance mechanism. [31][32][33] On the other hand, in some recent approaches the uncracked concrete in the compression zone of the section is considered to be the main source of shear resistance.…”