Study On Axial Compressive Behavior Of Segmental Concrete-Filled Basalt Fiber Reinforced Polymer Pier

Basalt fiber composite pipe confined concrete structure is suitable for bridge construction because of its excellent mechanical properties and environmental protection.Owing to the limitation of transportation and overall structural design,the FRP tube cannot be designed into full length and there must be some joints in the FRP tube.The industry also lacks a full understanding of the weakening of the axial compression performance of segmental basalt fiber composite pipe confined concrete piers due to the existence of joints.It is essential to investigate the influence of different stirrup connection methods on segmental specimens.In this thesis,seven segmental specimens with different number,diameter and spacing of stirrups and one integral specimen as the control group were set up,and the specimens were subjected to axial compression test.The classical formula was modified by the method of theoretical analysis.The finite element model of basalt fiber tube was established by using ABAQUS software,and the distribution mode of constraint stress was analyzed.The main conclusions drawn from this study are as follows:(1)All specimens failed owing to the rupture of basalt fiber tube,but the failure modes of integral specimens and segmental specimen were different,and the failure modes of all segmental specimens were similar.(2)The test results show that the segmental specimens with the maximum number and diameter of stirrups can achieve the same bearing capacity as the integral specimen.The deformation capacity of all segmental specimens was better than that of the integral specimens.The ultimate bearing capacity and ultimate deformation of the specimen increased with the increase of the number and diameter of stirrups,and showed a trend of first increasing and then decreasing with the increase of stirrup spacing.In this thesis,the stirrup with 40 mm spacing was reasonable.(3)The strain distribution on the tube of the integral specimen was uniform.The maximum and fastest developing strain occurs near the joint interface on the tube and stirrups of the segmental specimen,which corresponds to the failure mode of the segmental specimen.All strain–stress curves exhibited approximately bilinear shapes.All segmental specimens have very close initial stiffness,post-yield stiffness and yield strength,but they are smaller than those of integral specimens.(4)The ultimate strength calculation formula of core concrete considering the joint restraint of stirrup and basalt fiber tube obtained by theoretical analysis was greater than the measured value,and the reduction coefficient was established to describe the influence of unconstrained area caused by joint interface gap.(5)The finite element model of the basalt fiber tube was established by ABAQUS software to investigate the effect of free joint interface on segmental specimens.Then proposed a reduction coefficient to quantify the influence of this factor on the restraint stress of basalt fiber tube.