Investigation on effectiveness of reinforced HSFRC overlay in flexural strengthening of RC beams

Abstract

At first, Hybrid Steel Fibre Reinforced Concrete (HSFRC) mixtures are developed and characterized for developing HSFRC overlay strips for flexural strengthening of Reinforced Concrete (RC) beams. HSFRC is developed using cement, sand and coarse aggregates of size 10 mm down, short straight-and long hooked-ended steel fibres in 1:3 proportion and densified silica fume to replace 7% by weight of cement. The fibre content is varied as 0.5, 1, 1.5 and 2% volume fraction. In order to assess the suitability of the HSFRC mixture developed for retrofit application, the mechanical and fracture characteristics of HSFRC are compared with that of plain concrete of same mixture proportion without fibres. Based on the merits, HSFRC with 1.5% volume fraction of fibres is chosen for the development of HSFRC overlay strips. The performance of a reinforced concrete beam after flexural strengthening with an innovative reinforced HSFRC overlay strip is compared with that of an unstrengthened control beam. Numerical model of RC beam retrofitted with reinforced HSFRC strip is developed and validated by comparing the results of numerical study with experimental results. A parametric study is carried out to evaluate the influence of thickness of overlay strip, level and strength of overlay reinforcement on the load carrying capacity and stiffness of the retrofitted beam. The parametric study brings out the potential of reinforced HSFRC overlay in flexural strengthening of RC beams and its ability to emerge as economic, feasible and promising retrofit strategy.