Numerical study on seismic behaviors of steel frame end-plate connections

• A finite element method of end-plate connection under cyclic loading was proposed.
• The connection methods could significantly affect the cyclic behaviors.
• A suggestion was given to choose proper connection methods for various situations.

In order to study the seismic behaviors of steel frame end-plate connections, an efficient and accurate finite element model of ABAQUS was established subjected to cyclic loadings. Element types, material cyclic constitutive models and contact models for bolts, end plate and members were described. Geometry and material nonlinearity were adequately considered. The simulated results of numerical models were verified by typical quasi-static tests of end-plate connections, including both hysteretic curves and failure modes. It provided a strong tool for investigating the performances of this kind of connection. Based on the verified models, connections with different connection methods were established to investigate the effect of connection methods on behaviors of connections, including fully welded connection, extended end-plate connection and flush end-plate connection. The carrying capacity, initial stiffness, hysteretic behaviors, degraded characteristics, fracture tendency index, failure modes and energy dissipation capacity were compared and discussed in depth. The results showed that: If the beam and column are reliably connected, the extended end-plate connection can obtain the same ultimate carrying capacity and initial stiffness (monotonic behaviors) as the welded connection, however, their hysteretic curves, degradation developing curves, and fracture tendency were quite different. It indicated that the connection methods could significantly affect the cyclic behaviors. The stiffeners of end-plate connection could be treated as the first defense of connection, effectively changing the failure mode and avoiding brittle fracture. Therefore, in the high seismic zones, hysteretic behaviors, failure modes and seismic ductility should be taken into account comprehensively to choose the appropriate connection methods.