Shear strengthening of reinforced concrete beams with PBO-FRCM composites with anchorage

Abstract

In this paper results of tests carried out on beams strengthened in shear with PBO-FRCM composites were presented and compared with theoretical calculations according to the ACI549.4R-13 standard. PBO-FRCM (Fibre Reinforced Cementitious Matrix) composites consist of mineral mortar and PBO (p-Phenylene Benzobis Oxazole) composite fibres. The mineral mortar makes them a good alternative to the commonly used FRP composites, especially in structures exposed to high temperatures and in historic buildings. FRCM composites mostly fail due to the debonding (without rupture) of the fibres from the mineral mortar. Proper anchorage should be employed to prevent the premature debonding of the composite and to increase the effectiveness of the FRCM reinforcements. As part of this research tests were carried out on 10 RC T-beams strengthened in shear with PBO-FRCM composites with different anchorage system. The mechanisms of failure of the beams were analysed and described. A theoretical model based on ACI549.4R-13 (the only existing standard for FRCM composites) was described. Shear capacity was calculated on basis of the characteristics of the materials and elements used in the tests. The results of the calculations based on ACI549.4R-13 showed the shear capacity of the T-beams with transverse steel reinforcement and anchored composites to be considerably underestimated. The theoretical model needs to be refined and verified on a larger number of elements. The results and the probable causes of the discrepancies between the experimental results and the analytical ones are discussed.