Cracking behaviour of FRC members reinforced with GFRP bars under sustained loads

GFRP bars are regarded as an alternative to steel reinforcement in marine and aggressive environments. However, there are some shortfalls to the use of GFRP reinforced members in flexure, which the addition of fibres can redress. This paper is concerned with the effect of synthetic fibres on the cracking behaviour of GFRP reinforced members. A number of FRC beams reinforced with GFRP bars were tested in flexure, considering different synthetic fibre contents and GFRP bar diameters. The flexural loads applied were representative of service conditions and were sustained for 90 days. The short- and long-term cracking behaviour was analysed in terms of crack spacing, distribution and development in pure bending sections. It was concluded that synthetic fibres increased the cracking moment capacity by up to 20% and reduced the crack width and crack spacing by up to 63% and 31%, respectively.

The accuracy of the models available in current codes to predict crack width and crack spacing was assessed by comparing the experimental results to theoretical predicted values. The accuracy of crack spacing, and crack width predictions was found to vary with fibre content, and higher discrepancies were associated with higher fibre contents. This study shows that current prediction models for crack width and spacing need updating to make them better suited to elements reinforced with GFRP bars adequately considering the contribution of synthetic fibres.