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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 73 Abstracts search results
March 1, 2011
A. Bilotta, F. Ceroni, M. Di Ludovico, E. Nigro, M. Pecce, and G. Manfredi
The paper deals with the results of an experimental program aimed at the investigation of the bonding behavior of different types of FRP materials for strengthening: externally bonded carbon (EBR) plates, and bars or strips externally applied according to the Near Surface Mounted (NSM) technique.
The overall experimental program consists of 18 bond tests on concrete specimens strengthened with EBR carbon plates and of 24 bond tests on concrete specimens strengthened with NSM systems (carbon, basalt and glass bars and carbon strips). The performances of each reinforcement system are presented, discussed and compared in terms of debonding load, load - slip relationship, and strain distribution; the failure mode of each system is also analyzed. The results of the experimental program allow a comparison of the effectiveness of the various EBR and NSM strengthening systems tested and evidence of some differences in the bond behavior.
Slamah Krem and Khaled Soudki
Fiber reinforced polymer (FRP) reinforcements, with their excellent mechanical and non-corrosive characteristics are being increasingly used as a replacement for conventional steel reinforcement. ACI 440.1R-06 equation for determining the development length of FRP bars is based on Glass FRP (GFRP) bars and may not be applicable for Carbon FRP (CFRP) bars. This paper presents the results of an experimental study on the flexural behavior, bond characteristics, and development length of concrete beams reinforced with CFRP bars. Twelve beams were fabricated and tested. All beams were tested up to failure using a four point bending regime. The results indicated that the average bond strength of CFRP bars in concrete is about 15% higher than those of GFRP bars at comparable concrete strength. The ACI 440.1R-06 over estimated the development length of the CFRP bars by slightly above 30%, while CAN/CSA-S6-06 equation was unconservative by 50%.
Yungon Kim, Kevin T. Quinn, Christopher N. Satrom, Wassim M. Ghannoum, and James O. Jirsa
Several tests were conducted to evaluate the shear performance of beams strengthened externally with carbon fiber reinforced polymer (CFRP) laminates and CFRP anchors. Results are presented for five tests conducted on 24-in.(610-mm) deep reinforced concrete T-beams constructed and tested at Phil M. Ferguson Structural Engineering Laboratory at the University of Texas at Austin. Monotonically increasing load was applied to the reinforced concrete members at a shear span-to-depth ratio of three (a/d = 3) until failure. Overall, a 40-45% increase in shear strength was observed when anchored CFRP laminates were installed on the RC members. In all cases, CFRP anchors prevented a premature de-bonding failure in the CFRP laminates, thus increasing the useable capacity of the CFRP laminates. Theoretical calculations predicting the shear strength of the retrofitted concrete members were carried out and compared with the measured strengths of the members.
Ying-Wu Zhou, Yu-Fei Wu, Yan-chun Yun, Li-Li Sui, and Feng Xing
An analytical model is developed in this work to derive the bond-slip relationship at the reinforcement-substrate concrete interface (joint) for externally bonded FRP (EB-FRP). The model is generally applicable to both long joints (infinite bond length) and short joints. The bond-slip relationship for short joints with a limited bond length is a general model for EB-FRP joints. When the bond length approaches infinity, the model degenerates to a well-known existing analytical model. It is concluded from the modeling that the existing model for long joints is not applicable to short joints that have a bond length that is less than the effective bond length, or at locations in long joints that are closer than the effective bond length to the free end of the reinforcement. The bond-slip relationship is verified with test results.
Jianwei Huang and Riyad Aboutaha
In current International Codes for FRP Reinforced Concrete, an environmental reduction factor is applied to the tensile strength of GFRP bar to account for its long-term durability. In this paper, the approaches for the durability design of GFRP bars are discussed and corresponding limitations are addressed, followed by presentation of a newly developed design approach, which incorporates the effects of relative humidity, exposure temperature, and design life. By using time extrapolation and time-temperature shift approaches, a new equation for design strength of GFRP bar under various exposure time and temperature was proposed. The effect of moisture, in the form of relative humidity, was incorporated into the new equation by investigating the relationship between the relative humidity and concrete pore water. On the basis of reported durability data for E-glass/VE GFRP bars embedded in moist concrete, reduction factors linked to service life, temperature and relative humidity were obtained. By utilizing the new approach presented in this paper, more refined and accurate design values for long-term tensile strength of a GFRP bar could be achieved.
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