Probabilistic Assessment of Residual Strength of Damage Reinforced Concrete Beam using Glass Fibre Reinforced Polymer (GFRP) with Flexural Deficciency
Publication Date : 28/04/2020
In this work, structural reliability analysis for reinforced concrete beam strengthened with Glass Fibre Rienforced Concrete Polymer (GFRP), due to flexural deficiency as a result of corrosion was undertaken. A simply supported reinforced concrete beam was specifically used for the investigation. Corrosion rate ranging from 0.1mm/years were considered in the study. Likewise, the investigation was based on exposure time ranging from 0 to 30 years. The uncertainties in the basic design variables for bending resistance of the un-strengthened and the GFRP strengthened beam, as well as the applied bending action were fully accommodated in the analysis. First Order Reliability Method (FORM) was adopted for the computation of the safety indices. The search for the optimum safety level using FORM was enhanced by constrained nonlinear optimization strategies, using Genetic Algorithms (GA). FORM and Optimization Algorithms were developed and implemented using MATLAB Simulinks. Limit state function for flexural mode of failure was developed based on Eurocode 2 (2004). Corrosion damage model for the reinforcing steel was included in the limit state function. It was confirmed that flexural strengthening of reinforced concrete beam with GFRP can restore its capacity losses. From the study, the safety index of the beam after 30 years of corrosion exposure and before strengthening with GFRP was 0.5. However, after flexural strengthening of the beam with GFRP, using 3mm, 3.5mm, 4mm and 4.5mm GFRP sheets, the safety indices respectively increased to 1.1 (175% increase in flexural reliability), 1.7 (245% increase), 2.2 (323% increase) and 2.6 (550% increase). In conclusion, GFRP thickness of 4.5mm will achieveved a target safety index of 3.8 recommended by Eurocode 0 (2002) at a corrosion exposure time of 11 years. The research also established that for corrosion affected reinforced concrete beam, the amount of reinforcement is not significant after 30 years, since the safety of the beam tends towards zero.
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