Experimental study on flexural behaviour of reinforced concrete beams strengthened with passive and active CFRP strips using a novel anchorage system

Bartosz Piątek,Tomasz Siwowski

doi:10.1007/s43452-021-00364-7

Abstract

The paper presents the research on reinforced concrete (RC) beams strengthened with carbon fibre reinforced polymer (CFRP) strips with various configurations in terms of anchoring and tensioning. The five full-scale RC beams with the total length of 6.0 m were strengthened with passive strips, without and with mechanical anchorages at their ends, as well as with strips tensioned by the novel prestressing system with three various prestressing levels ranging from 30 to 50% of the CFRP tensile strength. All RC beams were tested under static flexural load up to failure and they were investigated in a full range of flexural behaviour, including the post-debonding phase. The main parameters considered in this study include the use of mechanical anchorages, the effect of tensioning the strips and the influence of the various prestressing levels. Several performance indicators have been established to evaluate the beams’ behaviour. The study revealed that the RC beams strengthened using tensioned CFRP strips exhibited a higher cracking, yielding and ultimate moments as compared to the beams with passively bonded CFRP strips. Moreover, increasing the beams’ prestressing level has a significant positive influence on the performance of strengthened beams. However, it did not affect the ultimate load-bearing capacity of the beams. The optimal prestressing level for the novel system has been determined as 60% of CFRP tensile strength.

Highlights

The flexural strengthening of reinforced concrete (RC) structural elements with externally bonded carbon fibre reinforced polymer (CFRP) strips or sheets has been developing for about 30 years, the first attempts were made by Saadatmanesh and Ehsani [1] and Triantafillou et al [2]
The experimental study on the RC beams strengthened passively and actively with the novel CFRP prestressing system was presented in the paper
The five full-scale RC beams were strengthened with passive strips, without and with mechanical anchorages at their ends, as well as with strips tensioned by the novel CFRP prestressing system with three various prestressing levels ranging from 30 to 50% of the CFRP tensile strength

Summary

Introduction

The flexural strengthening of reinforced concrete (RC) structural elements with externally bonded carbon fibre reinforced polymer (CFRP) strips or sheets has been developing for about 30 years, the first attempts were made by Saadatmanesh and Ehsani [1] and Triantafillou et al [2]. It is a widely used and highly effective method for retrofitting RC structures throughout the world and it is a suitable alternative for conventional strengthening methods as steel plate bonding or external prestressing [3]. Lots of other solutions are still in the development phase like systems tested by Woo et al [21] or Yang et al [22]

Methods

Discussion

Conclusion