Experimental Study And Numerical Analysis Of Joints With Outer Stiffening Ring Of Square Steel Tubular Column–H Shaped Steel Beam

Beam-column joints are playing an important role in the structural seismicperformance. Its design of seismic performance is the key of the steel frame structuredesign.Through studying the destructional form of steel frame in Northridge and Kobeearthquake, many joints occurred brittle failure in the earthquake. In view of the brittlefailure of joints, various types of improved steel structure joints were successively putforward. However, these joints have some limitations, so that discussion of the newsteel joints is essential.Combined with external reinforcement ring plate joints, flange-plate andcover-plate joints which can make the plastic hinge remove out recommended byFEMA-350, three different types of joints of cold-formed square steel tubular column–H shaped beam with reinforcement rings are designed which includes the newimproved flange-plate joint, the new cover-plate joint and the traditional reinforcedring type joint. Based on the pseudo static test research and theory of nonlinearanalysis, the comparison analysis of the mechanical properties between new joints andtraditional joint is carried out. The major research are as follows:(1)Three different new joint specimens of cold-formed square steel tubularcolumn to H-shaped beam with external rings are designed. Through low-cyclicloading test, the ultimate bearing capacity, ductility, stiffness and strength degradation,dissipation and failure mode of the specimens are researched.(2) Through the analysis of the failure process and failure phenomenon of everyjoint, the new flange-plate reinforced joint with external stiffening ring and the newcover-plate reinforced joint with external stiffening ring whose beam flanges stretchinto the bottom of external stiffening ring both shift plastic hinge from the end of ringplate about1/3depth of beam. So that the beam-column joints effectively are protected.The traditional joint with external stiffening ring that the beam flanges and ring plate through the butt weld connection don’t form plastic hinge on the beam, finally it occurto tearing failure on the weld of beam flanges between outer stiffening ring plate, beamweb appear larger crack through almost the entire web.(3) Using the test data to draw P hysteresis curves, M hysteresis curves,skeleton curves, the strength degradation curve and stiffness degradation curve,analyzing micro-strain of each part of joints. The mechanical property of Two typesnew steel joints with outer stiffening ring reinforced are better than the traditional jointwith outer stiffening ring.(4) ABAQUS，a software of finite-element analysis, is selected to simulate theexperiment of three joints test specimen, compared with the results of macro bearingcapacity and micro strain contrast, further study on the mechanical property of the newreinforced joints, in addition to verify the reliability of the finite-element calculation.(5) Furthermore, the influence on seismic performance of joints with differentthickness of stiffening ring is analyzed through finite-element software ABAQUS. Theresults show that the thickness of reinforcement ring plate which equals the beamflange is the critical thickness of plastic hinge removed or not, the critical thickness canbe used as optimum economic thickness in practical engineering.