The beams were intentionally designed to be weak in flexure so that when tested

The beams were intentionally designed to be weak in

This preview shows page 246 - 248 out of 623 pages.

ered here for strengthening. The beams were intentionally designed to be weak in flexure, so that when tested, all non-strengthened beams fail in flexure only. There- after, NSM technique was adopted here as the mechanism to strengthen beams in flexure, using three different types of rods for strengthening. Parameters listed in Table 1 were kept constant for all beam specimen. Apart from abovementioned parameters, two anchor bars of 10 mm diameter (Fe-415 grade) are provided in all beams to hold shear reinforcement. The details of beams tested (Strengthened as well as non-strengthened) are as mentioned in Table 2 . There were three beams tested for each material used for strengthening, and since each of them showed more or less similar results and behaviour, the results of the best among the tested three are considered in this manuscript. Initially, non-strengthened beams were tested, so as to evaluate its performance. Eventually, for each strengthening material adopted using NSM technique, beam specimens were tested so as to ascertain the performance of the strengthened speci- men. For strengthening of SF-1, SF-2, and SF-3, Extruded GFRP, Fe-415, and pul- truded BFRP bars were used, respectively, and no confinement at ends was provided in any of the cases. However, for SF-4, pultruded BFRP bars were used, and confine- ment was provided at the ends using 5 cm wide CFRP wrap, using U-wrap technique, Table 1 Parameters kept constant L 2000 mm d 239 mm F ck 25 N/mm 2 B 200 mm l 1800 mm S 200 mm F y 415 N/mm 2 D 270 mm f y 250 N/mm 2 d 25 mm A st 339.12 mm 2 (3 Nos of 12 mm diameter bars) Table 2 Nomenclature of beams S. No. Beam nomenclature Bar used for NSM strengthening Diameter of bar Remarks 1 NSF Non- strengthened 3 SF-1 Extruded GFRP rod 12 mm ø Strengthened 2 SF-2 Fe-415 rod 12 mm ø Strengthened 4 SF-3 Pultruded BFRP rod 12 mm ø Strengthened 5 SF-4 Pultruded BFRP rod and CFRP wrap 12 mm ø Rod, 50 mm wide CFRP Wrap Strengthened
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246 J. R. Patel et al. with an objective to evaluate the change in behaviour and performance of the beam element. 3 Material Properties and Detailing of NSM Groove Grooves of 20 mm × 20 mm size were used for NSM, and epoxy adhesive com- prising of base and hardener having properties mentioned in Table 3 was used for experimental work carried out. Properties of extruded GFRP bars, Fe-415 bars and pultruded BFRP bars used for the experimental program, are included in Table 4 . Properties of CFRP wrap used for end confinement in SF-4 beam are as mentioned in Table 5 . It is evident that in actual beam element, is it practically impossible to introduce a groove beneath the supports, hence groove for NSM at the soffit of the beam for flexural strengthening, was introduced for a length of 1800 mm, leaving a distance Table 3 Properties of epoxy adhesive Density 1.30 kg/l Elastic modulus Flexural 3800 MPa Tensile 4500 MPa Bond strength Concrete fracture (>4 MPa) Tensile strength 30 MPa Elongation at break 0.9% Table 4 Properties of bars used for strengthening Property Fe-415 rod GFRP rod BFRP rod Density (g/cm 3 ) 7.8 1.9 1.95 Modulus of elasticity (MPa) 2 × 105 30,000 55,000 Poisson’s ratio 0.3 0.3
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