Mechanical Properties Of Concrete Filled Double Skin Steel Tubular Members After Exposed To High Temperature

Concrete-filled double skin steel tubular(CFDST), not only inherits theadvantages of concrete-filled steel tube, but also has much good performance, such asunfolding cross-section, high flexural stiffness, light weight, and good fire resistance.At present, most researches on the concrete filled double skin steel tubular focused onthe room temperature phase, and experimental studies after fire is still small, so in thispaper, the mechanical properties of CFDST members were studied after hightemperature, which have practical significance to this new type of compositecomponent in the practical engineering application.The paper experimentally and theoretically investigates the behavior (axialcompression and pure bending) of CFDST members after exposure high temperature,the main work of study can be summarized as follows:(1)The tests were designed22Stub Columns7pure bending specimens, the axialcompression specimens were divided into circle round and square cover two forms,each11.All of pure bending specimens were square hollow section. With temperatureand hollow ratio as main parameters, the test study were carried on systematically ofaxial compression and pure bending specimen after high temperature, analyze thefailure mode and load-deformation curve about the inner steel tube、outer steel tubeand the core concrete, the influence of temperature and hollow ratio were consideredto the ultimate bearing capacity of high temperature specimen.(2) The constitutive model of CFDST was determined after high temperature,then use the finite element software ABAQUS to made model, calculated the wholeprocess of axial compression curve of CFDST members after high temperature, thecalculation results with the test results verify good. Base on the above, through thetypical example, in-depth analysis the work mechanism of CFDST axial compressionspecimen after exposure high temperature. Through establishment the differentparameters model, analyzed the influence of hollow ratio, inner and outer steel yield strength, nominal steel ratio, concrete strength on the ultimate bearing capacity ofaxial compression members after high temperature, proposes a simplified formula ofaxial compression bearing capacity after high temperature.(3) Through finite element software to verify the moment–deflectionrelationship which of pure bending members after exposure high temperature. Bytypical examples, discusses the mechanism of the inner steel tube、outer steel tube andthe core concrete which of pure bending specimen after high temperature. Throughanalysis of the influence of various parameters on the pure bending bending strength,the parameters are hollow ratio, nominal steel ratio, internal and external steel yieldstrength, and the strength of concrete, deduced the simplified calculation formula offlexural bearing capacity of the pure bending specimen after exposure hightemperature.