Axial Compressive Behaviors Of Circular And Square Ice-Filled FRP Tube Stub Columns

A new type of component with the name of ice-filled FRP tube stub columns(IFFT)is proposed in this paper according to the problems of scarcity of common civil engineering materials and construction difficulties in permafrost areas as well as the constraint mechanism of FRP confined concrete.Besides,the ice material in permafrost region is widely existing and the material property of FRP(fiber-reinforced plastic)is excellent.The FRP tube is made by hand and the ice is poured inside.So FRP tube and inner ice share the axial load together when the monotonic axial compression test is performed on it.The main works of this paper is as follows:(1)27 circular IFFT stub columns and 3 plain ice stub columns are tested under the monotonic axial compression.The types of FRP involve CFRP(carbon fiber),BFRP(basalt fiber),GFRP(glass fiber).Each kind of fiber corresponds to three thicknesses,and the test results show that: The circular IFFT stub columns are severely damaged as the result of rupture of FRP tube;FRP can significantly improve the bearing capacity of ice as well as its ductility;the axial stress-strain curves show obvious bilinear characteristic;with the increase of the confining stiffness,the initial slope increase linearly.The intercept of stress axis,the ultimate stress and the ultimate strain increase linearly with the increase of the confining stress.(2)Based on the experimental results of the monotonic axial compression and the design-oriented stress-strain relationship of circular FRP confined concrete,the stress-strain relationship of IFFT is analyzed and the constitutive model under this experimental condition is proposed.The test result is on the whole in line with the predictive value.Taking into account the axial bearing capacity of FRP tube,the formula for the bearing capacity of circular IFFT stub column is proposed and it can make accurate prediction of test results.(3)A total of 27 square IFFT stub columns are tested under the monotonic axial compression.The types of FRP involve CFRP(carbon fiber),BFRP(basalt fiber),GFRP(glass fiber),Each kind of fiber corresponds to three thicknesses.The test results show that: The squarer IFFT stub columns are damaged by the rupture of corner of FRP tube in the end of loading which is less severe than the circular specimens.FRP can significantly improve the bearing capacity of ice as well as its ductility;the axial stress-strain curves show obvious bilinear characteristic;with the increase of the confining stiffness,the initial slope increase linearly.The intercept of stress axis,the ultimate stress and the ultimate strain increase linearly with the increase of the confining stress.(4)Based on the experimental results of the monotonic axial compression and the design-orientedstress-strain relationship of square FRP confined concrete,the stress-strain relationship of IFFT is analyzed and the constitutive model under this experimental condition is proposed.The test result is on the whole in line with the predictive value.Taking into account the axial bearing capacity of FRP tube,the formula for the bearing capacity of square IFFT stub column is proposed and it can make accurate prediction of test results...