Seismic Performance Of Earthquake Resilient Steel Frame Joints With Buckling-Restrained Flange Cover Plates

The construction of seismic resilient steel frame beam-column joints with additional replaceable energy dissipation members can effectively improve the seismic performance and post-earthquake functional recoverability of traditional steel structures,which has become a research hotspot in the field of earthquake engineering.However,the engineering practicability and mechanical performance of replaceable energy dissipation members need to be further improved.The study shows that the joint with cantilever beam splicing recommended by codes has good engineering practicality,and the buckling-restrained brace(BRB)is a metal damper with dual functions of load-bearing at small earthquake and high ductility energy dissipation at severe earthquake.Based on the above researches,this paper draws on the design concept and construction of all-steel BRB,modifies the traditional flange cover plate used in joint with cantilever beam splicing,weakens the flange cover plate to form a load-bearing-energy dissipation core plate.The filling plates and restraint plates are set outside the core plate,and assembled with the beam flange through high-strength bolts to form a buckling-restrained system of the core plate.In this paper,a new earthquake resilient steel frame beam-column joint with buckling-restrained flange cover plate(BRFCP)was proposed.Nine full-scale beam-column joint specimens were designed and processed.The effects of core plate thickness,restraint plate form,restraining range,filling plate form and restraining gap on the hysteretic behavior of the joint were studied through quasi-static loading test.The phenomena observed in the test were analyzed,and the damage and energy dissipation modes of the joints were summarized;The seismic performance indexes such as hysteretic and skeleton curves,stiffness degradation characteristics and energy dissipation capacity of test joint specimens collected in the test were compared and analyzed,and the influence of research parameters on joint performance was obtained.The test results show that the joint proposed in this paper has good load-bearing and energy dissipation capacity,and the design concept of buckling-restrained has been well realized,and the joint has good seismic resilience.The restraint plate form and restraining range is the main parameters affecting the deformation of core plate,and the integral restraint plate has better restraining effect compared with the separated restraint plate.The refined finite element models of the test joints were established by ABAQUS.The numerical results were compared with the test results,and the phenomena that were difficult to observe and the data obtained in the test were supplemented and analyzed.Besides,the effects of the test boundary condition,the plate friction coefficient and the initial geometric imperfections of the core plate on the numerical simulation results were analyzed.The comparisons show that the numerical model established in this paper can well reflect the hysteretic characteristics of the joint under cyclic loading.On this basis,the parametric numerical analysis of the joint with integral restraint plate was carried out,and the influence law of parameters such as core plate,restraint plate and its high-strength bolts and restraining gap on the joint performance was obtained.A simplified calculation model of the joint with integral restraint plate was established,the formulae for calculating the bearing capacity and initial stiffness of the joint were derived,and the theoretical calculation formulae for the skeleton curve of the joint were given.Through parametric theoretical analysis,the influence law of parameters such as core plate and restraint plate and their high-strength bolts on the initial stiffness and yield bearing capacity of the joint was obtained.The design process of the joint was proposed,and the design equations of key components such as core plate,restraint plate and web connection plate were given.The correctness of the theoretical calculation equations and design methods of the joints were verified through comparison of tests,numerical simulations and theoretical skeleton curves,and comparison of numerical simulation results with the results of design equations,respectively.Relevant design suggestions were given in combination with the numerical simulation results.