Study on flexural behaviour of reinforced high strength concrete beams
  V.V. Arora, Brijesh Singh and Vikas Patel
  The High Strength Concrete (HSC) is generally defined as concrete above M55. Bureau of Indian Standard (BIS) code IS 456:2000 in clause 6.1 (Table 2) has identified concrete grade M10 to M80. However, note: 2 under Table 2 of IS 456:2000 states that for concrete of grades higher than M55, design parameters given in the code of practice may not be applicable and values may be obtained from specialized literatures and experimental results. Whilst there are many publications proposing stress block models for HSC beams, a universally accepted stress block model is yet to be developed. In most design standards, the conventional rectangular stress block developed for Normal Strength Concrete is still being used for design of HSC beams. The aim of this study was to develop design parameters for High Strength Concrete for incorporation in Indian Standard for Design (IS 456:2000). In this paper, model proposed in European design standard EC: 02-2004 have been analysed to compare the experimental and theoretical moment capacities considering actual Fck and Fy values obtained from the tests done. Based on this studies, new approach is suggested by working out strain in HSC and steel. Twelve numbers Reinforced Concrete Beams of size 200 x 200 x 2400 mm using concrete mix with four different w/c ratios (0.47, 0.36, 0.27 and 0.20) were cast for study. For flexural strength assessment, the beam was placed in simply supported condition over two fixed steel pedestals to get a clear span of 2000 mm. Keeping in view the specimen size to be tested and failure load, the loading was decided to be applied at the rate of 0.2 mm/minute in displacement control machine. The LVDT was placed in centre of beam to measure mid-point deflection.
 

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