Experimental study on bond performance between vertical deformed steel bar and modern rammed earth based on in-situ pull-out test

Abstract

This study investigates the bond strength–slip behavior between vertical deformed steel bar and modern rammed earth in modern rammed earth wall. Firstly, in-situ pull-out tests were conducted on seven modern rammed earth walls, taking into account the effects of the relative anchorage length of steel bars, the cube compressive strength of modern rammed earth, and the diameter of steel bars on the bond strength and slip of vertical deformed steel bars and modern rammed earth. The experimental results indicate that the bond force–slip behavior between vertical deformed steel bars and modern rammed earth can be divided into four stages: elastic bonding stage, nonlinear rising stage, nonlinear decreasing stage, and residual stage. Based on the experimental results, six characteristic values were defined: ultimate bond strength τu, cracking bond strength τs, residual bonding strength τr, ultimate bond slip Su, cracking bond slip Ss, residual bond slip Sr. An average bond strength-slip constitutive model for vertical deformed steel bars and modern rammed earth was proposed. The model was compared with the experimental results and can be used to predict τu, τs, Su, Ss. Due to the anisotropic characteristics of modern rammed earth, there will be a large deviation in the prediction of τr and Sr. There are three types of failure in the pull-out specimens, namely, pull-out failure, splitting failure and conical failure. The relative anchorage length of steel bar, the cube compressive strength of modern rammed earth and the diameter of steel bar have different degrees of improvement on τu, τs, but have little effect on τr. Due to the brittle failure of modern rammed earth specimens, the above three factors have little effect on the slip value.