| The traditional steel frame system has been widely used in construction industry in China.In the traditional design concept,the steel frame has been regarded as one of structural systems with good seismic performance.But the Northern and Kobe earthquake toppled this idea.In these two earthquakes,a lot of beam-column connections of steel frame with node weld occurred brittle failure,ductile fracture did not appear expected.To appear in order to avoid brittle failure,many scholars suggest many types of ductile steel connections,whose basic principle is that steel plastic hinge will be moved away from the beam end,so that connections have better ductility and energy dissipation performance.For popularization and application of new ductile steel frame in our country,with expanded flanges are taken as the research object in this paper,connections with expanded flanges by using theoretical analysis are studied.The parameters of expanded zone are optimized by numerical simulation and experimental research,fracture index of steel enlarge.The results will provided the theoretical basis and data support for study of seismic performance of new ductile steel connection.There are mainly several research aspects:(1)Performance experimental study and analysis of steel beam-column connections with expanded flanges at beam end:using two sets of full scale expansion flanges specimens of steel beam-column connections and a set of full scale specimens of ordinary steel beam-column connections hysteretic performance experiment was carried out,analysis all specimens under low cycle loading hysteretic performance,such as hysteresis curves,skeleton curves,ductility coefficient,stiffness degradation,etc.,by analyzing these indexes enlarge wing in parameters affect the performance of steel node hysteresis and give reasonable Suggestions.(2)The expansion of flanges finite element analysis of steel beam-column connections:Based on the finite element theory,using ABAQUS finite element software to establish three-dimensional finite element nonlinear analysis of steel frame beam-column connection model,the modification of the results of finite element model related parameters,nonlinear analysis of steel frame beam-column connections node model,studies enlarge wing parameters(enlarge wing section straight line length la,concave segmental arc length lb,enlarge wing width c)on the properties of steel frame beam-column connections node hysteresis effect,enlarge flanges in parameters were optimized by the finite element analysis results.(3)The expansion of flanges steel beam-column connection fracture criterion analysis:from the perspective of the theory of damage mechanics,through the establishment of 18 expanded flanges in the variable set of 3 d expanded flanges steel beam-column node and ordinary node damage analysis model,based on the analysis of triaxial stress,crack index and the equivalent plastic strain index such as index to study the node ductility crack evolution process,crack growth length calculation,analysis of common nodes and airfoil node in the plastic fracture characteristics,and by comparative analysis with hysteretic performance results,based on former optimization to expanded flanges parameters are further optimized. |
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