Research On The Seismic Behaviors And Design Method Of Circular And Square H-CFST Column

Hollow-concrete-filled steel tubular structure(H-CFST) is mainly used for powersystem as wire poles. However, when H-CFST is applied to building structure asframe columns, compared with used as wire poles, it will be bearing larger axialcompression and the axial compression ratio is even higher. Therefore, this paperbased on the integrated theory of concrete filled in steel tube studies the seismicbehavior of H-CFST, which with circular and quadrate cross sections, under higheraxial compression ratio. The main research work are show as below:1)A correction coefficient(m) of confinement coefficient, which was a function ofhollow ratio, was proposed by derivation of calculus theory. And based on theinfluence of hollow ratio and steam maintenance to the core concrete strength, aenhancement coefficient of core concrete strength(k) was suggested. Then the axialcompression design calculation formula of concrete-filled steel tube in the DesignRegulation of Soild and Hollow Concrete-filled Steel Structure (CECS254-2011) hadbeen corrected by m and k. The thoeretical calculation was shown to be in goodagreement with the experimental data. The correction formula possessed of specificphysical meaning and concise expression so as to the application in engineering. Andthe stress-strain relationship expressions of core concrete filled in steel tube,whichwere suitable for both soild and hollow section, were proposed after correcting theexisting stress-strain relationship expressions of core Soild-concrete filled in steeltube by m and k.2)Horizontal low frequency cyclic loading tests were adopted to study the seismicbehaviors of H-CFST columns under diffierent design parameters(included axialcompression ratio, hollow ratio and section form). The seismic behaviors, such asfailure modes, hysteretic curves, energy dissipation, strength degradation, stiffnessdegradation, skeleton curves and ductility, were studied. And then, analysis thedesign parameter restriction of H-CFST applied in building frame column. The mainconclusions as below: a)square H-CFST was not suitable for applying to buildingframe column. Whan design parameters were restricted in some region, circularH-CFST members could meet the requirement that demanded in regulation ofCFST(CECS254-2011). b)The limit of axial compression ratio was too larger, in orderto achieve ductility target, the limit of axial compression ratio was suggested not exceeding0.6.3)Building the numerical models(distributed plastic fiber model and three-dimensional plastic finite element model) of H-CFST frame column. The numericalcalculation was good agreement with test result data. The influences of axialcompression ratio, hollow ratio, slendness ratio, concrete strength, steel ratio, steelstrength and section form to the skeleton curves of H-CFST were studied bynumerical calculation4)The three of the line restoring-force model for circular H-CFST column was wasproposed by regression analysis. The formular calculation was good agreement withtest result data, which indicate that the formula dependable and the proposed formulacould be used to design and analysis in practical engineering.