Effects of Beam-column Joint Stiffness on Seismic Behavior of SteelFrames Based on Multiple Point Constraints

The behavior of beam-to-column connections with angles falls between fully rigid and ideal pin connections and belongs to the category of semi-rigid connections.In this paper,a series of steel plan frames with different degrees of connection stiffness are established in ABAQUS by modeling the beam-to-column connections with the SPRING2element and using different moment-rotation curves as the node constraint.Using multiple point constraints,the lateral force distribution is maintained and displacement-controlled pushover analysis is achieved.The model is verified by comparing the simulated curve with the experimental curve of the load displacement of a two-floor-span semi-rigid frame.Based on the verification,a six-floor-two-span plane frame is modeled with different joint stiffness influence factorsα.In the finite element analysis procedure,connective,geometric,and material nonlinearities are considered.The effect under differentαfactors on the seismic performance is discussed,such as frame bearing capacity,lateral stiffness,ductility,energy dissipation,and stiffness deterioration.Analytic results show that frame bearing capacity,lateral stiffness,ductility,and energy dissipation increase gradually with the reduction of theαfactor,but the increase in amplitude slows down.The curve of stiffness degradation show that the degeneration of rigidity is obvious as theαfactor reduces.In conclusion,when the joint stiffness influence factorαis between 1/15and 1/20,the joint has higher bearing capacity and better ductility performance to meet the requirement of earthquake resistance.The above-mentioned conclusion can serve as guidance for engineering.