Experimental Study On Ultimate Bearing Capacity Of Circular Carbon Steel Concrete-filled Steel Tube Short Column After Corrosion In Acid Environment

Worldwide interest in the use of concrete-filled steel tubular(CFST)columns in civil engineering applications has increased significantly in recent years due to its advantages,such as high strength,good ductility,fast construction and good economical benefit.With the increasing application of concrete-filled steel tubular(CFST)columns in the field of structural engineering,there are more and more opportunities for them to be exposed to acidic corrosive environments during service.Based on previous researches on concrete-filled steel tubular concrete,this paper uses the axial static load test method to calculate the ultimate bearing capacity,initial stiffness,ductility and other mechanical properties and bearing capacity of circular carbon steel concrete filled steel tubular short columns after acid corrosion environment.This paper mainly completed the following:(1)Pouring and curing of 117 round carbon steel concrete-filled steel tube columns were completed,and 108 concrete-filled steel tube columns were subjected to acidic environment corrosion treatment,and the test phenomena after the acidic environment corrosion treatment were analyzed.Then all the specimens were subjected to the axial static load test.Based on the observed test phenomena,three failure modes of the specimens were summarized.(2)Based on the test,the initial stiffness,ductility coefficient,ultimate bearing capacity and other test data of specimens are obtained based on the load-displacement curve.The effects of the wall thickness(T),concrete strength(C),acidic corrosion environment p H(p H)and erosion time(D)on the test results were studied.The thickness of the steel pipe and the strength of the concrete have a positive effect on the ultimate bearing capacity of specimens.The p H value(p H)and etching time(D)of the acidic corrosive environment have an adverse effect on the ultimate bearing capacity of specimens.The lower the p H value of the acidic corrosive environment,that is,the stronger the acidity,the smaller the ultimate bearing capacity of specimens,and the maximum average reduction of the ultimate bearing capacity of the specimen is 21%.The maximum difference in the initial stiffness of the specimen is 65%.When the p H value is 6 and 7,the initial stiffness of specimens are relatively close,indicating that when the acidity of the acidic corrosive environment is weak,the stiffness of specimens has little effect.When the thickness of the steel pipe is small,the stiffness of the specimen gradually decreases with the increase of the etching time in the acidic corrosive environment.(3)Based on the parameter analysis,design formulae were obtained through regression analysis to estimate the ultimate bearing capacity of specimens after corrosion in an acidic environment.The calculation results are compared with the experimental results.The results show that the calculation formulae are accurate and have sufficient safety reserves.The research results can provide reference for subsequent related research.