| Circular tubular structures are widely used in long span and space structures due to goodmechanical properties, artistic styling and easy fabrication and construction. As is the critical part ofcircular tubular structure, tubular joint usually fails ahead of component due to weaker stiffness ofchord in radial direction compared with the one of brace in axial direction. Hence, it becomes a weakposition of the whole tubular structure. Up to now, welding internal stiffened-ring is the most popularreinforcing method at ambient temperature. Additionally, the mechanical properties of steel degradewith the increase of temperature, which greatly affects safety performance of steel tubular structure.Therefore, the fire resistance of circular hollow section (CHS) T-joint and internal ring stiffened CHST-joint is investigated by experimental study and finite element analysis in this paper.Main research contents are listed as follows,(1) The fire resistant experimental study of CHS T-joints is carried out in the condition ofconstraint applied load and heating environment. And the failure mode, temperature-timecurves and displacement-temperature curves of CHS T-joint are obtained. Additionally, thereasons for failure of CHS T-joint in heating environment are analyzed deeply.(2) The fire resistant experimental study of internal ring stiffened CHS T-joints is conducted inthe condition of constraint applied load and heating environment. And the failure mode,temperature-time curves and displacement-temperature curves of CHS T-joint are gained.It is found that the internal stiffened-ring can extend fire resistance time and increase thecritical temperature of joint by comparing the test data of CHS T-joint and internal ringstiffened CHS T-joint, which means it greatly enhance the fire resistance of tubular joint.(3) Corresponding fire resistant finite element verification models of CHS T-joints are buildaccording to experimental conditions by using general finite element software ABAQUS.The results obtained from finite element (FE) models agree well with test data, whichproves the reliability and accuracy of FE models. Based on this, parameters analysis iscarried out to investigate the influence of geometric parameters on fire resistance of CHST-joint. The parameters include the ratio of length to diameter α, the ratio of diameter γ, theratio of thickness γ and load ration n. (4) Corresponding fire resistant finite element verification models of internal ring stiffenedCHS T-joints are established according to experimental condition. The verification modelsare confirmed to be reliable and reasonable though comparison between FE results and testdata. Based on the verification model, sensitive and parameters analysis are implementedto study the fire resistance of internal ring stiffened CHS T-joint. Sensitive analysis aims toinvestigate the influence of position and deflection angle of stiffened-rings on fire resistantperformance of tubular joint, and the parameters analysis focuses on the impact ofparameters, such as thickness of stiffened-ring/thickness of chord wall, width ofstiffened-ring/diameter of chord, ratio of length to diameter α, the ratio of diameter β, theratio of thickness γ, on fire resistance of stiffened joints. |
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