| Concrete-filled steel tube structures were widely used in various building structures for its excellent mechanical properties and construction properties.However,because of the easy corrosion disadvantage of steel,the existing structure of concrete-filled steel tube must be treated with anti-corrosion treatment.Nevertheless,corrosion of steel seems to happen all the time,especially when it is localized.The local corrosion of concrete-filled steel tubes will lead to the degradation of its mechanical properties and harm the safety of the structure.In order to make good use of the advantages of concrete-filled steel tubes and overcome its disadvantages,it is necessary to study the mechanical properties of concrete-filled steel tubes after local corrosion,and to study more effective reinforcement methods for concrete-filled steel tubes with local corrosion.In this thesis,the axial compression test of 122 circular concrete-filled steel tubular stub columns were completed by taking the circular concrete-filled steel tubes with localized corrosion as the research object.Local corrosion was simulated by artificial notching.Taking corrosion type,corrosion length and corrosion angle as the main parameters,the mechanical properties of circular concrete-filled steel tube with local corrosion axial compression stub columns were experimentally studied.At the same time,FRP cloth was used to strengthen circular concrete-filled steel tubular stub columns with localized corrosion.Taking the type of FRP and the number of wrapping layers as the main parameters,the influence of FRP cloth on the strengthening effect of circular concrete-filled steel tubular stub columns with localized corrosion was studied.The results indicate that,(1)The failure mode of the specimen is mainly shear-type failure accompanied by local buckling.Local buckling of the specimen is located in the corrosion area,while the horizontal corrosion orientation will increase the buckling degree of the specimen.Unreinforced horizontal corrosion-notched specimens show ring-drum type failure in the corrosion area,and FRP-reinforced horizontal and vertical cracked specimens show ring-drum type failure near the upper-end plate.The local drum buckling area is generally located in the end area of the specimen and the two sides of the corrosion notch surface.The fracture of FRP sheets with vertical corrosion notches generally starts at the middle of the corrosion site,and the fracture of FRP sheets with oblique and horizontal corrosion notches generally starts at the end area of the corrosion site.(2)The existence of corrosion notch will reduce the ductility of the specimen.With the increase of corrosion angle,the ductility of the specimen decreases gradually.Decreasing the corrosion angle will increase the compressive properties of the specimen,and the hole-type notch is more conducive to the compressive properties of the specimen than the crack-type notch.Among the three corrosion angles,the horizontal direction is the most favorable corrosion orientation,while the vertical orientation is the most unfavorable.For specimens with 45-mm holes,90-mm holes,45-mm cracks and 90-mm crack notches,the variation of compressive properties of horizontal and vertical corrosion-oriented specimens is 4.5%,3.1%,1.5%,0.9% and 4.4%,-0.2%,-6.2%-14.7%,respectively.(3)The reinforcement effect of CFRP sheet is better than that of GFRP sheet.Under the two corrosion types,the compressive properties of the locally corroded specimens with vertical corrosion orientation are improved the most.Among the vertical corrosion specimens with crack-type and hole-type corrosion notches,the compressive properties of the specimens with corrosion lengths of 90-mm CFRP double-layer reinforcement,45-mm CFRP double-layer reinforcement,90-mm GFRP double-layer reinforcement,and 45-mm GFRP double-layer reinforcement are 26.8%,22.2%,5.4%,6.6%,and 32.8%,27.3%,13.8%,12.7%,respectively.(4)Based on the results of each parameter analysis,a simplified formula for calculating the peak bearing capacity of FRP-reinforced circular concrete-filled steel tubular stub columns with local corrosion is proposed.The calculated value is compared with the test value,and they are basically identical. |
