Abstract
Due to inadequacies of reinforcement design in older structures and changes in building codes, but also the change of building use in existing structures, reinforced concrete (RC) beams often require upgrading during building renovation. The combined shear and flexural strengthening with composite materials, fibre-reinforced polymer sheets (FRP) and textile reinforced mortars (TRM), is assessed in this study. An experimental campaign on twelve half-scale retrofitted RC beams is presented, looking at various parameters of interest, including the effect of the steel reinforcement ratio on the retrofit effectiveness, the amount of composite material used for strengthening and the effect of the shear span, as well as the difference in effectiveness of FRP and TRM in strengthening RC beams. Significant effects on the shear capacity of composite retrofitted beams are observed for all studied parameters. The experimental study is used as a basis for developing a detailed finite element (FE) model for RC beams strengthened with FRP. The results of the FE model are compared to the experimental results and used to design a parametric study to further study the effect of the investigated parameters on the retrofit effectiveness.
Highlights
The strengthening of reinforced concrete (RC) elements is becoming a topic of increased importance due to the ageing of the European building stock and the associated need for building renovation to comply with modern standards, changes of use or the deterioration of materials
The results indicate a complex interaction between steel reinforcement ratio and fibre-reinforced polymer (FRP) strengthening effectiveness that could not be predicted by FRP-strengthening code equations that add together the contributions of steel and FRP to the shear capacity of beams
An experimental study on twelve half-scale beams was designed to assess the effect of various parameters on the effectiveness of combined flexural and shear strengthening with composite materials
Summary
The strengthening of reinforced concrete (RC) elements is becoming a topic of increased importance due to the ageing of the European building stock and the associated need for building renovation to comply with modern standards, changes of use or the deterioration of materials. Experimental evidence suggests that other important parameters are not sufficiently addressed in any guidelines, including crack patterns, the shear span-todepth ratio [8] and the amount of flexural FRP strengthening [25], as well as the interaction of external FRP and internal steel reinforcement [26] Models including such features have been proposed by [4,27,28]. Four main variables were evaluated in the experiments, namely: (a) the effect of steel shear reinforcement ratio; (b) the interaction between flexure and the shear capacity; (c) the effectiveness of TRM vs FRP and (d) the effect of the composite retrofit material arrangement These parameters were found to be critical in the literature and are assessed here by means of comparisons of experimental results. The obtained results are used to calibrate a non-linear finite element model (FEM) which is used for a parametric study to further study the effect of the investigated parameters on the retrofit effectiveness
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