| The superiority of the concrete-filled rectangular steel tube structure has gradually been recognized by engineers, This kind of structure has been increasing used to actual projects. Now one of important factors restricting the development of this kind of structure is that perfect and mature calculation theory aiming at various joint connection form has not been formed. So the beam-to-column joint is one of the pivotal technique problems concrete-filled rectangular steel tube (CFRST) structure study and popularize.Based on the investigation of research and application of concrete-filled rectangular steel tube frame joint in China and abroad, The paper has conducted quasi-static test on four concrete-filled rectangular steel tube frame joint (exterior stiffened ring) model. The parameter includes the axial compression ratio and beam column linear stiffness ratio, Through quasti-static test the hysteretic behavior, ductility, degradation of strength and stiffness, ability of energy dissipation, failure mechanism and characteristics has been researched.The experimental results indicate that the CFRST frame joint has plump hysteretic loops; good ductility and evening deformation ability after the joints reach ultimate load; The deformation ductility coefficient is between 3.5 and 4.48, which shows that this kind of CFRST frame joint can meet the requirement of ductile joint; has superior seismic behavior and energy dissipation ability.Based on the analysis of mechanism of frame joint, utilizing the forth strength theory and concrete compression strut mechanical model, This paper has given the shear load-carrying capacity formulas for panel zone and compared with experimental results and the correlative formulas given by specification. We can know via comparison, the formulas calculating result recommended by specification is bigger than experimental results, can not reflect the influence of axial compression ratio. The formulas calculating result of shear capacity of panel zone proposed in this paper agrees approximately with the experimental values and can reflect the influence of axial compression ratio, Theory is perfect relatively, mechanics concept is clear, So they can provide the reference to the engineering practice. |
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