Prestressed CFRP reinforcement of RC beams under secondary loads considering environmental impact
Based on the issues encountered in actual building reinforcement projects,where it is difficult to completely unload before strengthening,this study investigates the flexural stiffness and load-bearing capacity of reinforced concrete beams subjected to secondary loading after being strengthened with prestressed carbon fibre-reinforced polymer(CFRP).A finite element analysis model for the strengthened beams is established using the software ABAQUS,and the simulation results are compared with experimental results to validate the accuracy of the model.Numerical analyses are conducted on the strengthened beams considering environmental influences,different reinforcement ratios,CFRP quantities,concrete strengths,prestress levels,and initial loads.The research findings indicate that the simulation results of the finite element model are generally consistent with the experimental results,with similar load-strain curves for both the steel reinforcement and CFRP,thereby validating the model's accuracy.In the initial loading stage before the yielding of the steel reinforcement,the mid-span displacements of the experimental beams are relatively small for different reinforcement ratios,concrete strength grades,and CFRP quantities.After the yielding of the steel reinforcement,as the three variables increased,the slopes of the load-displacement and load-strain curves became steeper,and the rate of displacement increase slowed down.A higher prestress ratio results in smaller displacements at failure,while a higher preloading ratio led to larger displacements at failure.Under the same load conditions and in high-temperature and high-humidity environments,the degree of damage at the bonding interface is greater,with the damage rate accelerating significantly compare to room temperature conditions.The initiation of delamination still occurs at the mid-span regions,consistent with observations in low-temperature environments.The stress in CFRP is symmetrically distributed about the mid-span,with higher stress levels in the mid-span region and gradually decreasing stress levels near the anchorage ends.Under high-temperature and high-humidity conditions,the structural failure results in reduced displacements.
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