Experimental Study On Axial Compression Of Circular Steel Tube Considering Local Corrosion

With the development of society and economy,steel structures have been widely used for their superior performance,and the design method of steel structures has gradually matured.However,people have relatively low awareness of the durability of steel structures.With more and more steel structures entering the later years of service life,the study of the durability of steel structures is becoming increasingly urgent.Therefore,the mechanical properties of corroded steel structures need to be studied.At present,the research on corrosion steel mainly includes two aspects,one is the research on the law of corrosion development,and the other one is the study of the mechanical properties of the corrosion steel.The circular steel tube is used as a common component in the spatial structures.The related research is rare,and many coastal structures or swimming pools are affected by the damp environment.The corrosion usually develops inhomogeneous,so it is necessary to study the mechanical properties of the circular steel tubes which is subjected to local corrosion.This thesis has carried out the following research work:In order to get a variety of local corrosion steel tubes,this thesis designed the indoor accelerated corrosion test.The accelerated corrosion method is the constant current accelerated corrosion method.The specimen is placed into the Sodium Chloride Solution for electrolysis,and it is connected to the anode.The corrosion amount is calculated by Faraday's law,and the measured value of the loss weight is compared with the theoretical value.Because the bearing capacity of the circular steel tube is mainly the stability of the compressive bar,the ultimate bearing capacity of the specimen is obtained from the axial compression loading test.Three kinds of circumferential corrosion dimensions including 1/4 ring direction,1/2 ring direction and full ring direction are designed.Three kinds of lengths of test piece are set up to study the size and slenderness ratio of the ring to the ultimate bearing capacity of the sample.Impact.As a result,it was found that the size of the circumferential corrosion changes the local instability mode,and there are different variations in the critical stress of the two local failures,and the local instability will have a profound effect on the overall stability of the test piece.Three longitudinal corrosion sizes including 225 mm,450mm and 900 mm are designed.Each type of circumferential corrosion size is set up with 3 tubes in different lengths,and three longitudinal corrosion sizes are the length of 1/4,1/2 and 1 times the shortest specimen length,in order to observe the influence of the circumferential corrosion size and the length ratio on the ultimate bearing capacity of the specimen.As a result,it was found that the size of the circumferential corrosion changes the local instability mode,and there are different variations in the critical stress of the two local failures,and the local instability will have a profound effect on the overall stability of the test piece.In this paper,7.5% depth,15% depth and 30% depth are designed as three kinds of corrosion depth.Each corrosion depth is set upwith 3 tubes in sifferent lengths to observe the effect of corrosion depth and length ratio on the degradation of ultimate bearing capacity.The results show that the depth of corrosion has a significant effect on the ultimate bearing capacity,and the increase in the depth of corrosion will lead to local destabilization.