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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 12 Abstracts search results
Document:
SP210-08
Date:
April 1, 2003
Author(s):
C. Kassem, E. El-Salakawy, and B. Benmokrane
Publication:
Symposium Papers
Volume:
210
Abstract:
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.
DOI:
10.14359/12578
SP210
February 1, 2003
Editor: NJ Gardner
SP-210 This Symposium Publication contains papers presented during the 2002 ACI Spring Convention in Detroit, including six papers related to predicting the deflections of concrete members reinforced with fiber-reinforced polymer (FRP) reinforcement: one paper describes two field investigations, two unique laboratory investigations, a paper on estimating the errors in calculating deflections of high-performance concrete slabs, and a comparison of the ACI and EC2 deflection provisions. This volume should be read in association with Symposium Publication SP-203, Code Provisions for Deflection Control in Concrete.
10.14359/14020
SP210-05
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.
10.14359/12575
SP210-06
H. A. Rasheed, H. Charkas, and H. G. Melhem
The use of externally bonded FRP plates has been established as an effective means to strengthen RC beams in flexure and shear. Few investigators have attempted to propose minor modifications to the current ACI empirical equation orginally developed for the effective moment of inertia of unstrengthened RC beams. In contrast, the present work develops a rational procedure for calculating the deflections of beams at any load stage. The procedure assumes a trilinear moment-curvature response characterized by section flexural crack initiation, yielding and ultimate capacity. This model incorporates some tension stiffening effects ans assumes the section to be fully cracked only upon or near steel yielding. A generalized solution is presented for the case of beams having any extent of uncracked, partially-cracked and post yielded regions. The curvature distribution is determined for each region and closed form equations are developed for the cases of 4-point bending and uniform load. Comparisons with experiments indicate the effectiveness of the procedure for properly anchored plates. Parametric studies are conducted to explore the applicability of the ACI original and modified equations for a wide range of geometric and material properties. As a result, improved ACI equations are suggested for use in practical deflection calculations.
10.14359/12576
SP210-04
M. M. Reda Taha and M. A. Hassanain
Although limit state design blends both serviceability and strength limit states, most engineers tend to be less confident in serviceability limit states than in strength limit states, especially when deflections of reinforced concrete slabs are considered. A major source of the lack of confidence is the existence of many uncertain variables in calculating slab deflections of reinforced concrete slabs are considered. A major souce of this lack of confidence is the existence of many uncertain variables in calculating slab deflections such as concrete properties (e.g., modulus of elasticity, modulus of rupture), creep coefficient, curing regime and duration, and the existence of construction loads. The absence of any reliability ocefficients in deflection calculations or deflection limits gives the impression that engineers are expected to evaluate the exact deflection that will take place on site. To make matters worse, the introduction of high-performance concrete (HPC) has increased the uncertainty about concrete properties. While HPC enhances the overall material's performance, it is usually reported to have higher shrinkage strains, and it is more susceptible to plastic shrinkage than normal-strength concrete (NSC). The possible reduction of curing periods from the recommended one week to two or three days due to tight construction schedules can result in substantial microcracking which would significantly reduce the concrete modulus of rupture. Therefore, serviceability performance is dependent on many inter-related factors that the engineer cannot control in the design assumptions. Unless the band of errors in deflection calculations is known to the engineer, the lack of confidence in deflection claculations will always be there. This paper describes a mathematical model utilizing the theory of error propagation to predict the error in the calculated deflections of simply-supported, one-way reinforced concrete slabs. Parametric studies have been carried out to examine the effect of changing the concrete properties as a result of changed site conditions on the accuracy of the estimated deflections.
10.14359/12574
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