Analysis of cracking behaviour and tension stiffening in FRP reinforced concrete tensile elements

摘要

The differences in mechanical and bond properties of FRP bars when compared to those of traditional steel reinforcement for reinforced concrete (RC) structures may affect the cracking and deformability behaviour of FRP RC members. To analyse this cracking behaviour, the reinforcement strain profile along a reinforcing bar has been experimentally recorded by using a specially manufactured reinforced concrete element in tension, in which the FRP reinforcement was internally strain gauged. Furthermore, a general procedure derived from a cracking analysis based on slip and bond stresses has been used to study the deformability of FRP reinforced concrete elements under tension. The tension stiffening effect is included via the experimental nonlinear bond-slip law obtained from pull-out test of an experimental programme previously published. The comparison between numerical predictions of the reinforcement strain profile along the reinforcing bar during a tensile test and experimental data confirms that the bond-based model adequately reproduces the redistribution of stresses after crack formation. To further prove the model reliability, numerical predictions of the load-mean strain relationship are compared to previously reported experimental data on FRP RC tensile elements and predictions furnished by the models usually adopted for the analysis of FRP reinforced concrete structures.