TRANSFER AND DEVELOPMENT LENGTHS OF CFRP BARS IN SCC BEAMS

摘要

The use of self consolidating concrete (SCC) and carbon fibre reinforced polymer (CFRP) reinforcement in the precast/prestressed concrete industry in North America is becoming increasingly popular. The current ACI 440.4R-04 and the ISIS design guidelines do not consider the effect of concrete type on the bond behaviour of CFRP bars. This paper presents the results of an ongoing experimental research study on the bond and flexural behaviour of SCC beams prestressed with CFRP bars. Sixteen prestressed beams were fabricated and tested. Transfer length measurements were done by means of concrete longitudinal strain profile and draw-in measurements. Development lengths were estimated experimentally using four point flexural tests. The test results showed that the transfer length of the 12.7mm diameter sand-coated CFRP bars in SCC varies nonlinearly with the prestressing level and it was greater than that in CVC. The transfer length at 30% prestress was slightly less than prediction by ACI 440.4R-04 while at 60% prestressing, the experimental transfer length was 25% longer than the values predicted by ACI 440.4R-04. The development length of the 12.7mm diameter sand-coated CFRP bar prestressed to 30 % was very similar in both types of concrete. At 60% prestress level, the development length of the CFRP bar in SCC was longer by 25% as compared to CVC beams.