Experimental and analytical investigations on bond–slip behavior of steel reinforcement in <scp>UHPFRC</scp> considering yielding

Abstract The bond behavior between ultra‐high‐performance fibre‐reinforced concrete (UHPFRC) and steel rebars plays an important role in the load‐bearing capacity and serviceability of structural members. A suitable bond–slip model is essential for predicting the load resistance and deformation capacity of members, after cracking of the UHPFRC. This paper studies the bond strength between ribbed steel bars and the surrounding UHPFRC before and after yielding of the steel reinforcement. To determine the corresponding bond–slip relationship, pull‐out tests, with varying embedment lengths of the reinforcement, namely 2 times and 10 times the rebar diameter, and diameter of reinforcing bars ranging from 10 mm to 16 mm were conducted. The bond stress, strain and slip along the embedment length of the steel rebars were measured by strain gauges and displacement transducers. Based on the test data, a bond stress–slip model was derived before (elastic stage) and after (inelastic stage) yielding of the reinforcement. The slip at the yield point is suggested through theoretical equations. The post‐yield bond–slip model is based on yield bond stress and frictional bond stress. The two‐part model was validated through iterative procedures and is able to predict the applied force, bond stress and strain distribution along the reinforcing bar. A comparison between the test data and analytical results demonstrates a good predictive capacity on the bond behavior of reinforcement in UHPFRC both before and after yielding of the reinforcement.