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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 23 Abstracts search results
Document:
SP180-20
Date:
October 1, 1998
Author(s):
B. Aarup and B. C. Jensen
Publication:
Symposium Papers
Volume:
180
Abstract:
CRC (Compact Reinforced Composite) is a special concept for high performance concretes, where ductility is achieved through incorporation of a large content of short, stiff and strong steel fibres (6 vol.%). This ductility combined with high strength (150-400 MPa) - and the ability of the small fi-bres to provide an effective reinforcement against even small cracks, makes it possible to obtain exceptional bond properties for deformed reinforcing bars. Results show that full anchorage is achieved with an embedment length of only 5-10 diameters for ribbed bars, which has led to applications in buildings, where CRC is used for in-situ cast joints between pre-cast decks -joints which can transfer full moments with a width of 100 mm. This type of joint, which was used for a university building, has been extensively tested for different loading situations and for behaviour in a standard fire. As the fibre reinforced matrix provides a strong, ductile joint which responds well to dynamic loads it is expected to perform well under seismic loads.
DOI:
10.14359/5889
SP180-15
E. Vintzileou and N. Psilla
This paper presents the results of an experimental investigation on the anchorage of deformed steel bars embedded in bed joints of masonry. The effect of bar diameter, anchorage length and vertical load on the mortar joint is investigated. Although the horizontal bars in masonry are under unfavourable conditions, such as low strength of mortar, small cover values, lack of bond at places where the bars pass over large holes of the masonry unit, tests have proved that embedment lengths as low as 30 to 40 times the bar diameter seem to be sufficient for the bars to develop their yield strength.
10.14359/5884
SP180-13
D. Darwin, J. Zuo and M. L. Tholen
The results of the first major reevaluation of reinforcing bar geometry in the United States in nearly 50 years is described. The study involves experimental and analytical efforts designed to broaden the understanding of factors that control bond strength, improve the development characteristics of reinforcing bars, and develop practical design expressions that more accurately represent development and splice strength than existing expressions. The research has established that deformation pattern has little effect on the bond strength of uncoated bars that are not confined by transverse reinforcement. Deformation pattern, however, as represented by the relative rib area, does have a major effect on the bond strength of bars that are confined by transverse reinforcement. Increases in relative rib area, obtained with either higher ribs, closer ribs, or a combination thereof, result in an improved bond strength for confined bars. The study has also established limits on how closely ribs can be placed without resulting in a pullout failure. High relative rib area bars provide a reduction in development/splice length of 20 percent for all coated bars, independent of the presence or absence of confining transverse rein-forcement. Based on the experimental work, expressions are developed that accurately characterize development/splice strength. In the development of the expressions, f’,t/4 is shown to be superior to f$2 for characterizing the contribu-tion of concrete strength to bond. The resulting design expressions are accurate for compressive strengths between 2500 and 16,000 psi (17 and 110 MPa). The most accurate representation of the effect of transverse reinforcement on bond strength includes parameters that account for the number of transverse reinforcing bars that cross the developed/spliced bar, the area of the transverse reinforcement, the number of bars developed or spliced at one location and the relative rib area, and size of the developed/spliced bar. The yield strength of the transverse reinforce-ment does not play a measurable role. Practical comparisons illustrate reductions in splice lengths of 20 percent for conventional bars and 30 percent for high relative rib area bars compared to current requirements in AC1 3 18-95.
10.14359/5882
SP180-14
S. Sritharan, J. M. Ingham, M. J. N. Priestley and F. Seible
Until recently, bridge design specifications in California permitted longitudinal column reinforcement to be terminated in monolithic cap beam/column joints with straight bar development not extending fully up the joint height. Since the development length could be construed not to comply with AC1 3 18 requirements, it was suspected that the anchorage length provided for the column bars was insufficient to develop the full moment capacity of the column at the joint interface. Considering that this detailing was widely used in bridges in California, an experimental investigation was initiated at the University of California, San Diego, where response of a bridge knee joint incorporating as-built reinforcement details was examined under simulated seismic loading. Following inadequate performance of the test unit, the behavior of the knee joint was investigated based on the experimental readings, giving consideration to bond slip of the longitudinal column reinforcement. The response of the test unit indicated that the bond conditions developed when anchoring the longitudinal reinforcement of circular bridge columns is unlike that developed along the beam reinforcement anchored into building joints.
10.14359/5883
SP180-18
J. Cairns, J. 0. Jirsa and S. L. McCabe
Fusion bonded epoxy coated reinforcement (FBECR) has been developed ! to help combat problems of corrosion in reinforced concrete structures. The surface i texture of the coating is smoother than the normal mill scale surface of reinforcing bars and alters bond characteristics of the bar. Although FBECR has now been in use for more than 30 years and production Standards have been established, rules for design using the material are not well developed. CEB Task Group 2/5 is currently reviewing data on bond and structural performance of elements reinforced with FBECR with the aim of deriving recommendations for design practice which will enable structures reinforced with FBECR to achieve equivalent performance to that of structures reinforced with millscale surface ribbed bars. This paper presents proposals for amendments to the CEB-FIP Model Code 1990 for design of anchorages and splices of coated bars, and briefly reviews other aspects of structural performance influenced by the different bond characteristics of FBECR.
10.14359/5887
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