Issue 46

S.Y. Jiang et alii, Frattura ed Integrità Strutturale, 46 (2018) 275-284; DOI: 10.3221/IGF-ESIS.46.25 275 Experimental research on the instantaneous and long-term deflections of pre-cracked concrete beams enhanced by carbon fibre reinforced polymer Shiyong Jiang, Tao Cai, Shijuan Wu, Weilai Yao Department of Military facilities, Army Logistics University of PLA, Chongqing 401331, China jiangshiy@163.com , Caitao5474@foxmail.com, wudzon@163.com, futureYWL@hotmail.com A BSTRACT . This paper aims to disclose the influence law of cracks on instantaneous and long-term deflections of reinforced beam. For this purpose, four concrete beams were created, pre-loaded to varied degrees of cracking, and reinforced with carbon fibre reinforced polymer (CFRP). Then, a 300-day load test was carried out on these samples to measure the instantaneous and long-term deflections. The experimental results show that the pre-cracking degree has little influence on instantaneous deflection; whether a beam is pre- cracked or intact, the final deflection of the beam is mostly affected by its initial deflection before the reinforcement; the pre-cracking degree is negatively correlated to the magnitude of additional deflection under sustained load. The research findings lay the basis for judging whether a reinforced beam can be used normally in the long run. K EYWORDS . Carbon fibre reinforced polymer (CFRP); Pre-cracked beams; Creep; Long-term deflection. Citation: S.Y. Jiang, T. Cai, S.J. Wu, W.L. Yao, Experimental research on the instantaneous and long-term deflections of pre-cracked concrete beams enhanced by carbon fibre reinforced polymer, Frattura ed Integrità Strutturale, 46 (2018) 275-284. Received: 31.05.2018 Accepted: 12.07.2018 Published: 01.10.2018 Copyright: © 2018 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION hanks to its light weight, high strength and good corrosion resistance, carbon fibre reinforced polymer (CFRP) has been widely used to strengthen and reinforce concrete structures [1]. For instance, the reinforcement of flexural members (beams) with CFRP plate is now a common engineering practice. The CFRP reinforcement can greatly improve the short-term beam performance, e.g. the ultimate bearing capacity [2~5]. In the long run, however, it is inevitable for concrete and other materials of the beam to creep under external load. The resulting deflection of the beam will accumulate over time, and eventually surpass the limit state of normal use. Thus, the reinforced beam cannot satisfy safety requirements after long-term use. At present, the long-term deformation behaviours of reinforced beam have not been extensively studied at home or abroad. There are a few studies on directly reinforced beams with no initial crack or deformation. For example, Nikolaos Plevris et al. [6] investigated the effect of fibre reinforced plastic (FRP) on long-term beam deflection through a 250-day load test on various fibre-reinforced concrete beams. Sungnam Hong et al. [7] conducted a 550-day creep experiment on three concrete beams, namely, concrete beams reinforced by the CFRP, concrete beams enhanced by glass fibre reinforced polymer T