Bond properties of 500 MPa steel bars in engineered cementitious composites

Abstract

Fibre-reinforced engineered cementitious composites are increasing being used in construction due to their superior toughness and durability. For composite structural members additionally reinforced with steel bars, the bond–slip relationship between the composite and reinforcing bars is an important parameter for designers. To understand the bond behaviour between Chinese 500 MPa steel bars and composites, pull-out tests were conducted to study the influence of the bar diameter, cover thickness and embedded length on bond properties under tension. The results indicated that the process of the bond–slip failure for 500 MPa steel bars in composites can be divided into three stages: Ascent, descent and remnant. The bond strength increased with a decrease in bar diameter, while shortening of the embedment length enhanced the bond strength. Specimens with a larger cover thickness achieved higher bond strength, but the enhancement in bond strength was negligible for specimens with a cover thickness greater than 55 mm. A formula for calculating the bond strength for Chinese 500 MPa reinforcing bars in composites was developed based on the experimental results and a consistent model for the bond stress–slip relationship was also obtained.