Simulating CFRP-confinement of concrete bridge piers under sustained loads: evaluation of the compressive capacity

The present paper deals with the evaluation of the compressive behaviour of circular concrete columns strengthened with carbon fiber reinforced polymers (CFRP) under different levels of sustained loads and subsequently loaded until failure. The aim was to compare the effect of existing stress/strain states on the axial load-strain response of bridge piers after strengthening under sustained loads. An experimental investigation was carried out on circular plain concrete columns loaded up to low, medium and high ratios of the concrete compression capacity before the application of the CFRP-confinement. After the strengthening process, the columns were loaded until failure, comparing the results in terms of load-bearing and deformational capacity with that obtained by the compression tests without preload. It was found that the preload does not affect the ultimate load of the confined columns, but a reduction of the secant stiffness of the load-strain response was observed on the preloaded specimens with the increasing of the sustained load level before confinement.