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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 12 Abstracts search results
April 1, 2003
C. Kassem, E. El-Salakawy, and B. Benmokrane
This paper presents the test results of 14 full-scale concrete beams. The beams were 3300 mm long with a rectangular cross-section of 200-mm width and 300-mm depth. Twelve beams were reinforced with carbon FRP composite bars and two reinforced with steel as control. Two newly developed types of CFRP bars with different surface textures were considered: the sand-coated ISOROD bars and the ribbed-deformed C-BAR. The beams were tested to failure in four-point bending over a clear span of 2750 mm. The results presented focus on the deflection behaviour of beams reinforced with CFRP bars, which have different bond, elasticity modulus, strain, and strength characteristics. The test results were compared to the predictions of some of the available models (ISIS-M03-01 design manual, ACI 440.1R-01 guidelines, and Razaqpur model). Based on the findings of the study, the validity of the design guidelines and the effectiveness of using the new CFRP bars as reinforcement for concrete beams were established.
February 1, 2003
J. R. Yost, S. P. Gross, and D. W. Dinehart
Deflection behavior of high strength concrete (HSC) flexural members reinforced with glass-fiber polymer bars (GFRP) is investigated. Because serviceability plays a significant role in establishing design acceptance for GFRP reinforced concrete beams, accurate modeling of flexural stiffness is critical and he effect of influencing parameters must be considered. This study accounts ofr variations in reinforcement ratio ( r ) for HSC beams. Experimental results from twelve simply supported concrete beams reinforced with GFRP bars are compared with published deflection models to establish analytic accuracy. All samples have a hear-span-to-depth ratio of 9.4 and are overreinforced with respect to a balanced strain design. Results show that the ACI 318 and ACI 440 effective moment-of-inertia expressions greatly overestimate flexural stiffnes, with the degree of inaccuracy dependent upon on reinforcement ratio.
D. Kaminetzky and P. C. Stivaros
Throughout the history of concrete construction, numerous construction failures have occurred involving excessive deflections and cracking of the completed structure. This paper presents two building construction cases where concrete slabs developed extensive cracking and excessive deflections soon after the slab construction and formwork removal. The effects of the shoring-reshoring operations, the rate of concrete strength development, as well as the effects of design details on the slab cracking and deflections, are investigated. The ACI 318 requirements of minimum thickness and deflection control are applied to both construction cases, and the adequacy of these code requirements is discussed. Based on the findings of this work it was concluded that the ACI 318 long term creep and shrinkage deflection calculation method does not adequately account for the early-age high construction loads.
F. A. Malhas and A. Rahman
ACI 318-99(1999) and EC2-92(1992) building design codes are the two major design code documents of reinforced concrete structures worldwide. Therefore, a detailed comparative analysis of these codes is justified and can be useful in understanding rational behind both codes. This type of comparative work can help identify iiscrepancies in either code and would substantiate their validity. In this regard, deflection computations and estimation of the flexural stiffness would be particularly attractive for detailed comparison. The analytical procedure adopted by ACI is particularly characterized by inconsistent correlation with test results, due to the fact that a number of factors affecting deflection have been ignored. In this study, detailed comparison with parametric analysis is conducted using the deflection provisions of ACI318-99 and EC2-92. First, the permissible deflections are compared and significant differences between the limits of the two codes are noted. The differences in the rationale of the deflection limits are identified. The span-to-depth ratio limits adopted by the two codes were found to have significant differences, with EC2 exhibiting more conservative limits. In comparing the two procedures for computing flexural deflection, all the pertinent quantities are investigated. These include: the cracking moment, the modulus of elasticity, the gross and cracked moment of inertia, the effective moment of inertia. A special form of the effecive moment of inertia equation is used to facilitate a parametric comparison between the two equations. Long-term flexural deflection is aslo compared and exhibits the differences between the two codes in relation to the impact of shrinkage, creep and compression reinforcement. This study is concluded by a numerical example that shows the differences between the codes in estimating short and long term deflection.
D. D. Kleinhans, A. Prota, and A. Nanni
Serviceability of FRP-reinforced concrete structures remains a highly relevant issue as more structures are constructed using the technology. With the recent publication of the ACI 440 doocument "Guide for the Design and Construction of Concrete Reinforced with FRP Bars," the need to examine serviceability-related issues and validate the accuracy of these design guidelines is heightened. A short-span concrete slab bridge was constructed in St. James, Missouri, using precast panels reinforced with FRP bars. The bridge was designed to meet AASHTO load and deflection requirements using the "Guide for the Design and Construction of Concrete Reinforced with FRP Bars." Carbon FRP, as tensile reinforcement, and glass FRP, as shear reinforcement, were utilized. Laboratory testing of one bridge panel that is identical to those installed in the field was conducted using a four-point loading configuration. Field testing of the bridge was also conducted to examine its behavior under service load. A loaded dump truck was placed at various locations along the bridge while deflections were measured and recorded. Similar field tests will be conducted annually fo rthe next three years in an effort to monitor the ong-term performance of the bridge. The results of the laboratory and field tests are summarized herein; a comparison between the theoretical and measured deflection values is made to illustrate the conservative nature of the prescribed design guidelines.
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