| Concrete-filled steel tube(CFST)members have the advantages of high bearing capacity,large stiffness,good ductility,seismic and fire resistance,fast construction speed.However,steel is vulnerable to corrosion during service.Corrosion can be divided into uniform corrosion and local corrosion.In practical engineering,the probability of local corrosion is greater than that of uniform corrosion,and the damage caused by local corrosion accounts for more than 80% of all corrosion accidents.When the local corrosion occurs in the outer steel tube of the CFST members,the performance of the CFST members will be seriously degraded.At present,the research on corrosion is mainly focused on steel members,and the research on the properties of corroded CFST members mainly focuses on uniform corrosion.However,the stress states of CFST members and steel members are different,and the degradation mechanisms of local corrosion and uniform corrosion on CFST are also different.It is necessary to conduct further research on the properties of CFST members with local corrosion.This paper investigates the local corrosion characteristics of steel plates,the mechanical properties of steel with local corrosion,the axial compressive performance of locally corroded circular CFST stub columns and the axial compressive performance of locally corroded circular CFST stub columns strengthened by CFRP cloth,and proposes a method for calculating the bearing capacity of locally corroded circular CFST stub columns and strengthening recommendations,which can be used as a reference for the evaluation and maintenance of corroded CFST in practical engineering.The main research content includes the following parts:(1)36 locally corroded steel plate specimens and 12 uniformly corroded steel plate specimens were obtained by artificially accelerated salt spray test.The threedimensional morphology of the corroded steel plate surface was extracted and analyzed to obtain the corresponding corrosion parameters.Monotonic tensile tests were carried out on the specimens to obtain the mechanical properties of uncorroded,locally corroded and uniformly corroded specimens,and the effect of corrosion on yielding stress,ultimate strength and elongation after fracture of steel plates was analyzed.The three-dimensional topography of corroded specimens was imported into ABAQUS software by the 3D reverse software Geomagic Studio to establish the finite element model of the locally corroded steel plate.Based on the finite element analysis,the stress distribution of the locally corroded steel plate was studied,and a simplified model of the locally corroded steel plate was proposed.(2)A total of seventy circular CFST stub columns subjected to axial compression were tested,the performance degradation of circular CFST stub columns subjected to axial compression caused by local corrosion was studied by simulating different forms of corrosion,such as groove corrosion,large-size corrosion and pitting corrosion by means of the mechanical defect.The effect of different local defect sizes on the performance of specimens was investigated in the test.Based on the test results such as failure phenomena and load-strain(stress)curve,the stress mechanism of locally corroded circular CFST stub columns subjected to axial compression was analyzed,and the degradation law of the properties such as bearing capacity and ductility of the specimens affected by various defect parameters was obtained.(3)The finite element model of locally corroded circular CFST stub columns subjected to axial compression was established by the ABAQUS software,and the correctness of the finite element model was verified by the test results.On the basis of finite element analysis,the stress mechanism of locally corroded CFST stub columns subjected to axial compression was studied.A systematic parametric analysis was carried out to study the influence of defect geometric parameters and material parameters such as the size,shape,depth and location of the local defect region,the steel ratio,the yielding stress of the steel and the concrete strength on the axial compressive performance of locally corroded circular CFST stub columns.Based on the experimental results,finite element analysis and theoretical analysis,a calculation method for the bearing capacity of locally corroded circular CFST stub columns subjected to axial compression was proposed.(4)The axial compression tests on thirty-four locally corroded circular CFST stub columns strengthened by CFRP were carried out,and the phenomenon,failure mode,bearing capacity and load-strain curve of the specimens were obtained.The strengthening effects of CFRP sheets wrapped members with different parameters were studied.The finite element model of locally corroded circular CFST stub columns strengthened by CFRP cloth subjected to axial compression was established and the accuracy of the model was verified by the test results.Based on the experimental results and finite element analysis,the strengthening and maintenance suggestions of locally corroded circular CFST stub columns subjected to axial compression were proposed. |
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