In this study the efficiency of the use of Ultra High Performance Fibre Reinforced Concrete (UHPFRC) for the strengthening of existing Reinforced Concrete (RC) beams has been investigated. Experimental work has been conducted to determine UHPFRC material properties. Dog-bone shaped specimens have been tested under direct tensile loading, and standard cubes have been tested in compression. These results have been used for the development of a numerical model using Finite Element Method. The reliability of the numerical model has been validated using further experimental results of UHPFRC layers tested under flexural loading. Further numerical study has been conducted on full-scale beams strengthened with UHPFRC layers and jackets, and these results were compared to respective results of beams strengthened with conventional RC layers and with combination of UHPFRC and steel reinforcing bars. Superior performance was observed for strengthened beams with UHPFRC three side jackets, and the efficiency of this technique was highlighted by comparisons with other strengthening techniques.

No abstract

Constructing concrete jackets is a common technique when strengthening reinforced concrete (RC) columns, particularly in seismic regions. However, there are many uncertainties concerning the behavior of the composite specimen, particularly at the interface between the old and new concrete. In this paper, monotonic finite element (FE) analyses are performed to examine the behavior of strengthened columns under monotonic and cyclic loading. Through investigating two independent series of experimental results, it is demonstrated that monotonic FE analysis with appropriate assumptions can simulate both monotonic and cyclic loading conditions to a reasonable degree of accuracy. According to the results of this study, it is found that a simulation of the interface between the old and the new concrete is vital and cannot be ignored by simply considering a perfect bond at the interface. In the case of strengthened RC columns subjected to cyclic loading, strength degradation at the interface has to be included and can be effectively modeled by reducing the coefficients of friction and adhesion by using a proposed formula. Finally, the effect of jacket concrete shrinkage is simulated that leads to a reduced maximum load and stiffness of strengthened columns.The cross-sectional dimensions of the original columns were 200 mm× 200 mm and their height was 1350 mm. The thickness of the jackets was 35 mm and they were placed to a height of 900 mm. The initial columns were symmetrically reinforced with three longitudinal bars of 10 mm diameter near each compressive or tensile face. Stirrups were of 6 mm diameter and spaced at every 150 mm. The longitudinal reinforcement of the concrete jacket was also three bars of 10 mm diameter near each compressive or tensile face and the stirrups were of 6 mm diameter spaced

No abstract

No abstract