The objective of this study is to gain knowledge of the strength and deformability of confined fibre reinforced highstrength concrete (HSC) after exposure to a thermal cycle at high temperature. A total of 126 confined cylindrical specimens (150 mm diameter, 450 mm height) were cast and tested. The confined concrete specimens were reinforced with six 8 mm diameter bars as longitudinal reinforcement and 6 mm diameter hoops equally distributed along the height. After exposing the specimens to the desired elevated temperature ranging from room temperature to 8008C, they were allowed to cool naturally in the furnace before testing them under axial compression the next day. The variables considered in this experimental study included maximum exposure temperature, volume fractions of steel and polypropylene fibres and the use of hybrid fibres. The effects of temperature on confined fibre reinforced HSC were studied and quantified with respect to strength and ductility. Important observations have been made about the residual thermal and mechanical behaviour of confined fibre reinforced HSC. The results show that the residual post-fire strength and strain capacities of confined fibre reinforced concrete were better than those of comparable confined non-fibre concrete.
NotationA c cross-sectional area of concrete in the column specimen section A cc cross-sectional area of core concrete in the column specimen section A cuc area under the stress-strain curve of confined concrete A cuo area under the stress-strain curve of unconfined concrete A g gross area of column cross-section A st sectional area of longitudinal steel f 9 c cylinder compressive strength of concrete f yl yield strength of longitudinal steel f yh yield strength of hoop reinforcement P applied load P c peak concrete load in the load-strain curve after deducting the contribution of steel P cc peak confined concrete load P max maximum load capacity of the confined specimen P o theoretical concentric capacity of specimen ¼ (0 : 85 f 9 c (A g À A st ) þ f y A st ) P oc gross concrete area force P occ core concrete area force P st tensile load-carrying capacity of longitudinal steel V f fibre volume fraction å9axial strain corresponding to P max å cc axial strain at peak confined load P cc å co strain at peak load of unconfined concrete specimen å c50c axial strain at which the load drops to 50% of the peak confined concrete load å c85c axial strain at which the load drops to 85% of the peak confined concrete load å9 sp axial strain at the beginning of mechanical spalling å 0 sp axial strain on completion of mechanical spalling T temperature difference between surface and centre of specimen r s volumetric ratio of hoops
Concrete undergoes time-dependent deformations that must be considered in the design of reinforced/prestressed highperformance concrete (HPC) bridge girders. In this research, experiments on the creep and shrinkage properties of a HPC mix were conducted for 500 days. The test results obtained from this research were compared to different models to determine which model was the better one. The CEB-90 model was found better in predicting time-dependent strains and deformations for the above HPC mix. However, in a far zone, some deviation was observed, and to get a better model, the experimental data base was used along with the CEB-90 model database to train the neural network. The developed Artificial Neural Network (ANN) model will serve as a more rational as well as computationally efficient model in predicting creep coefficient and shrinkage strain.
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