Static Performance Of Stainlesss Steel Uniplanar Welded Mixed Tubular Joints

Stainless steel is becoming more and more popular in modern building structures because of its elegant sculpt,better corrosion resistance,excellent durability,easy maintenance and cheap cost in full using life.In addition,due to the excellent corrosion resistance and durability stainless steel material overcomes the problems which carbon steel materials can not resolve.Steel tubular structures also have been widely used in actual projects with outstanding mechanical performance,beautiful appearance and less steel consumption.And square hollow section(SHS)joints and circular hollow section(CHS)joints are the most commonly used in actual projects.However,there are some advantages for CHS brace-to-SHS chord uniplanar welded mixed tubular joints.Compared with the CHS joints,they do not need more complex cutting technology of brace;Whlie compared with SHS joints,they have less stress concentration phenomenon and better fatigue performance.Moreover,the research of stainlesss steel uniplanar welded hybrid tubular joints is scarce in our country,which hinders the application of stainless steel structure in structure engineering to some extent.Based on the above information,this paper conducted the static performance of stainlesss steel uniplanar welded mixed tubular T-,Y-,and X-joints under axial compression.The followings are the main research works in this dissertation.(1)Standard specimen tensile test was conducted on the square and circular tubes of 304 stainless steel to study the mechanical properties,which provides material properties for the subsequent finite element analysis.(2)Experimental investigation was conducted to study the failure modes and the ultimate bearing capacities by 18 T-,Y-,and X-joints.(3)Compared the test results with the results calculated by current design specifications,it was showed that the results calculated by specifications have great discreteness and inaccuracy.(4)Finite element analysis software ABAQUS was used to conduct numerical simulation.The accuracy of the numerical model was verified by comparing the numerical simulation results with experimental results.The main parameters influencing ultimate bearing capacity-the ratio of brace diameter to chord width ?,the ratio of brace to chord thickness ?,the ratio of chord width to thickness 2?,and the angle ? between chord and brace-were studied by the verified numerical model.(5)Based on calculation formulae given in the Chinese specification,the modified calculation formulae were put forward.The modified formulae are applicable to the joints whose values of ? are between 0.25 to 0.8 and the joints without local buckling failure braces.It was showed that the modified calculation formulae have better accuracy than those given in specification.