Bond–Slip Law Between Steel Bar and Different Cement-Based Materials Considering Anchorage Position Function

Jie Xiao,Haibo Jiang,Lingfei Liu,Zikang Huang,Ming Ye,Fan Mo,Xiang Long,Dejun Deng

doi:10.3389/fmats.2021.801452

Abstract

The bond performance between steel bar and cement-based materials was the prerequisite for the two materials to work together, and previous studies showed that the bond behavior of the steel bars and cement-based materials will vary with the kinds of cement-based materials. For this reason, this paper adopted 12 direct pullout test specimens including three types of concrete and two types of steel bars. The strain of the steel bar at six measuring points was measured with a strain gauge. Based on the measured strain and free end slip of the steel bars, the distribution of steel stress, bond stress, and relative slip and the bond slip relation along the anchorage length were obtained and analyzed for different concrete and different steel bars. Based on these test results of steel strain and relative slip at six measuring points, the anchorage position function could be established in consideration of anchorage position, which was conducive to the establishment of an accurate bond–slip relationship. In addition, the anchorage length of the steel bar in Engineered Cementitious Composites (ECC) calculated from the equilibrium equation of critical limit state is only half of the anchorage length calculated in the current Code for Design of Concrete Structures (GB 50010-2010) in China. It is suggested to establish the critical anchorage length formula suitable for ECC in future studies.

Highlights

Cement-based materials are widely used in civil buildings, bridges, tunnels, and other fields because of its advantages of convenient supply of raw material, low cost, good durability, and so on (Fu et al, 2021; Lei et al, 2021; Lam et al, 2021; Wang et al, 2020; Wang et al, 2021a; Wang et al, 2021b; Zhang et al, 2021)
The strain of the steel bar at six measuring points was measured with strain gauges
We found that when the anchorage length reached 100 mm, some of the steel bars reached the yield point

Summary

INTRODUCTION

Cement-based materials are widely used in civil buildings, bridges, tunnels, and other fields because of its advantages of convenient supply of raw material, low cost, good durability, and so on (Fu et al, 2021; Lei et al, 2021; Lam et al, 2021; Wang et al, 2020; Wang et al, 2021a; Wang et al, 2021b; Zhang et al, 2021). Wang et al (2015) carried out pullout tests to evaluate the influences of the properties of matrix materials on the bond behaviors between BFRP bars and cementitious materials and found that the bond strength of the ECC specimen was higher than that of the cement mortar specimen under the same cover thickness and embedment length. Bonding stress could be calculated by these strains of the steel bar Based on these test results of steel strain and relative slip at six measuring points, an accurate bond–slip relationship could be established in consideration of anchorage position. The pullout test was employed to study the bond performance between steel bar and cement-based materials. The average relative slip of the steel bar and the matrix along the anchorage section could be expressed as follows:

EXPERIMENTAL RESULTS AND DISCUSSION

CONCLUSION

DATA AVAILABILITY STATEMENT