Load capacity predictions of continuous concrete deep beams reinforced with GFRP bars

YesNine continuous concrete deep beams reinforced with glass fibre reinforced polymer (GFRP) bars were experimentally tested to failure. Three main parameters were investigated, namely, shear span-to-overall depth ratio, web reinforcement and size effect. The experimental results confirmed the impacts of web reinforcement and size effect that were not considered by the strut-and-tie method (STM) of the only code provision, the Canadian S806-12, that addressed such elements. The experimental results were employed to evaluate the applicability of the methods suggested by the American, European and Canadian codes as well as the previous studies to predict the load capacities of continuous deep beams reinforced with GFRP bars. It was found that these methods were unable to reflect the influences of size effect and/or web reinforcement, the impact of which has been confirmed by the current experimental investigation. Therefore, a new effectiveness factor was recommended to be used with the STM. Additionally, an upper-bound analysis was developed to predict the load capacity of the tested specimens considering a reduced bond strength of GFRP bars. A good agreement between the predicted results and the experimental ones was obtained with the mean and coefficient of variation values of 1.02 and 5.9%, respectively, for the STM and 1.03 and 8.6%, respectively, for the upper-bound analysis.Higher Committee of Education Development in Iraq (HCED

Influence of Shear Reinforcement on Reinforced Concrete Continuous Deep Beams

yesTest results of 24 reinforced concrete continuous deep beams are reported. The main variables studied were concrete strength, shear span-to-overall depth ratio (a/h) and the amount and configuration of shear reinforcement. The results of this study show that the load transfer capacity of shear reinforcement was much more prominent in continuous deep beams than in simply supported deep beams. For beams having an a/ h of 0.5, horizontal shear reinforcement was always more effective than vertical shear reinforcement. The ratio of the load capacity measured and that predicted by the strutand-tie model recommended by ACI 318-05 dropped against the increase of a/h. This decrease rate was more remarkable in continuous deep beams than that in simple deep beams. The strut-and-tie model recommended by ACI 318-05 overestimated the strength of continuous deep beams having a/ h more than 1.0

Influence of Type and Replacement Level of Recycled Aggregates on Concrete Properties.

yesTest results of nine recycled aggregate concretes and a control concrete using only natural aggregates are reported. The recycled aggregates used were classified into three different types according to their measured specific gravity and water absorption, namely, RG I for recycled coarse aggregate having a specific gravity of 2.53 and water absorption of 1.9%; RG III for recycled coarse aggregate having a specific gravity of 2.4 and water absorption of 6.2%; and RS II for recycled fine aggregate having a specific gravity of 2.36 and water absorption of 5.4%. The replacement levels of both recycled coarse and fine aggregates were 30, 50, and 100% in separate mixtures. Slump loss and the amount of bleeding with time were recorded for fresh concrete. Compressive and tensile strengths, moduli of rupture and elasticity, and unrestrained shrinkage strain were also measured for hardened concrete. The properties of fresh and hardened concrete tested, together with a comprehensive database reported in the literature, were evaluated with respect to the relative water absorption of aggregates combining the quality and volume of recycled aggregates used. In addition, the properties of hardened concrete with different replacement levels and quality of recycled aggregates were compared with the design equations of ACI 318-05 and empirical equations proposed by Oluokun for natural aggregate concrete, whenever possible. Test results clearly showed that the properties of fresh and hardened concrete containing recycled aggregates were dependent on the relative water absorption of aggregates. In addition, the moduli of rupture and elasticity of recycled aggregate concrete were lower than the design equations specified in ACI 318-05, when the relative water absorption of aggregates is above 2.5% and 3.0%, respectively

Influence of inclined web reinforcement on reinforced concrete deep beams with web openings.

yesThis paper reports the testing of fifteen reinforced concrete deep beams with openings. All beams tested had the same overall geometrical dimensions. The main variables considered were the opening size and amount of inclined reinforcement. An effective inclined reinforcement factor combining the influence of the amount of inclined reinforcement and opening size on the structural behaviour of the beams tested is proposed. It was observed that the diagonal crack width and shear strength of beams tested were significantly dependent on the effective inclined reinforcement factor that ranged from 0 to 0.318 for the test specimens. As this factor increased, the diagonal crack width and its development rate decreased, and the shear strength of beams tested improved. Beams having effective inclined reinforcement factor more than 0.15 had higher shear strength than that of the corresponding solid beams. A numerical procedure based on the upper bound analysis of the plasticity theory was proposed to estimate the shear strength and load transfer capacity of reinforcement in deep beams with openings. Predictions obtained from the proposed formulas have a consistent agreement with test results

Inclined reinforcement around web opening in concrete beams

YesTwelve reinforced-concrete continuous deep beams having web openings within interior shear spans were tested to failure. The main variables investigated were the opening size and the amount of inclined reinforcement around openings. An effective inclined reinforcement factor combining the influence of the amount of inclined web reinforcement and opening size is proposed and used to analyse the structural behaviour of continuous deep beams tested. It was observed that the end support reaction, diagonal crack width and load capacity of beams tested were significantly dependent on the proposed effective inclined reinforcement factor. As this factor increased, the end support reaction and increasing rate of diagonal crack width were closer to those of companion solid deep beams. In addition, a higher load capacity was exhibited by beams having an effective inclined reinforcement factor above 0.077 than the companion solid deep beam. A numerical procedure based on the upper-bound analysis of the plasticity theory was proposed to estimate the load capacity of beams tested. Comparisons between the measured and predicted load capacities showed good agreement

Structural Behaviour of Reinforced Concrete Continuous Deep Beams with Web Openings.

yesTen reinforced-concrete continuous deep beams with openings were tested to failure. The main variables investigated were the shear span-to-overall depth ratio, and the size and location of openings. Two failure modes influenced by the size and location of web openings regardless of the shear span-to-overall depth ratio were observed. The normalised load capacity of beams having a web opening area ratio of 0·025 within exterior shear spans was approximately similar to that of their companion solid beams. Continuous deep beams having web openings within interior shear spans exhibited a higher load capacity reduction with the increase of the opening size, similar to simply supported deep beams with web openings. Formulae based on the upper bound analysis of the plasticity theory were proposed to predict the load capacity of continuous deep beams with web openings. Comparisons between the measured and predicted load capacities showed a good agreement

New Method of Synthesis of Calix-4-arenes as Analytical Reagent for Spectrophotometric Determination of Iron (III)

A compound of Calix-4-arenes was prepared, as a sensitive and selective spectrophotometric method was proposed for the rapid determination of Iron (III) in analytical sample, the proposed method was based on the formation blue complex with Calix-4-arenes as a chromogenic reagent that has a highly absorption at λmax 592 nm. The reaction was instantaneous at pH=7.0, the absorbance of complex was stable for about 24hr. Linearity was observed from 1.18 -8.0 μg.ml-1 with detection limit of 0.75μg.ml-1. Recovery and relative error values of precision and accuracy of method were found to be R.S.D.% = 0.92%, Re% = 99.45% and Erel = 0.55 % . The nature of complex showed that (Metal : Ligand) ratio was 1:1 at pH=7and the stability constant of ( 0.422x1010 L1.mole-1). The influence of chemical iand physical parameter and are evaluated . The proposed method was applied successfully to determine Fe (III) in analytical sampl

Shear strength of reinforced concrete dapped-end beams using mechanism analysis.

yesA mechanism analysis based on the upper-bound theorem of concrete plasticity is developed to predict the critical failure plane and corresponding shear capacity of reinforced concrete dapped-end beams. Failure modes observed in physical tests of reinforced concrete dapped-end beams are idealised as an assemblage of two moving blocks separated by a failure surface of displacement discontinuity. The developed mechanism analysis rationally represents the effect of different parameters on failure modes; as a result, the predicted shear capacity is in good agreement with test results. On the other hand, empirical equations specified in the Precast/Prestressed Concrete Institute design method and strutand-tie model based on ACI 318-05 highly underestimate test results. The shear capacity of dapped-end beams predicted by the mechanism analysis and strut-and-tie model decreases with the increase of shear span-to-full beam depth ratio when failure occurs along diagonal cracks originating at the bottom corner of the full-depth beam, although the shear span-to-full beam depth ratio is ignored in the Precast/Prestressed Concrete Institute design method

Application of Plasticity Theory to Reinforced Concrete Deep Beams

yesThis paper reviews the application of the plasticity theory to reinforced concrete deep beams. Both the truss analogy and mechanism approach were employed to predict the capacity of reinforced concrete deep beams. In addition, most current codes of practice, for example Eurocode 1992 and ACI 318-05, recommend the strut-and-tie model for designing reinforced concrete deep beams. Compared with methods based on empirical or semi-empirical equations, the strut-and-tie model and mechanism analyses are more rational, adequately accurate and sufficiently simple for estimating the load capacity of reinforced concrete deep beams. However, there is a problem of selecting the effectiveness factor of concrete as reflected in the wide range of values reported in the literature for deep beams