An experimental study on bond–slip in moderately confined concrete subjected to monotonic and cyclic loading using an experimental plan

Abstract

This paper presents results from an experimental investigation of the bond–slip performance of moderately confined concrete under monotonic and cyclic loading. The effects of six factors on the bond–slip response and on the bond mechanisms are investigated. These factors are grouped into two categories: the first category of four factors is related to the confining conditions, the second category to the loading conditions. A total of 43 pullout tests under monotonic and cyclic loadings were performed. Results show that the quantity of confining steel and the distance between the tested bar and the confining steel are the most important factors affecting the overall bond response. Bar spacing and height of concrete cast below the bar have less significant effects on the overall response, affecting mainly the initial response phase. The height of concrete cast below the tested bar is found to affect the maximum bond resistance to the same extent as in well-confined concrete. Cyclic bond behaviour of moderately confined concrete is found to be similar in shape and in cyclic degradation to that of well-confined concrete. It was also found that most of the bond response parameters, such as maximum bond resistance and the post-peak (softening) phase, can be predicted with excellent accuracy in terms of the factors investigated.