Collapse Mechanism And Design Criterion Of Steel Beam-to-Column End-Plate Connections Under Cyclic Load

Steel moment-resisting frames with welded beam-to-column connections were traditionally regarded as having excellent performance, and widely adopted in steel constructions, but this opinion changed after the 1994 Northrige earthquake and the 1995 Hyogoken-Nanbu earthquake. These earthquakes also arouse engineers to resurvey the behavior of end-plate connections. It is well known that end-plate connections have definite flexibility, which can increase damp, prolong period, and decease swing of structure. So it can reduce the damage, and is one of the best choices for resisting earthquake. However, because studies on end-plate connections were very limited, cognition on the damage mechanism of this type of joints was rather inadequate. To avoid casualties and decrease the loss in the future, analyses and response the damage mechanism of end-plate connections under seismic load is significant for theory and practice.In order to study the hysteretic behavior of end-plate connections and verify the reliability of theoretical method, 8 end-plate species were tested under cyclic load. Tests consist of three parts: material property test of panel, slippage coefficient test of bolt connection and cyclic load test of end-plate connections. Effects of column axial force and rib stiffener on hysteretic behavior of connections were synthetically considered for the first time during cyclic-loading. Results of the experiment shows that end-plate connections have excellent hysteretic behaviors, and the determination factors, which have crucial influence on the behavior, are end-plate thickness, column web thickness, and the rib stiffeners.The main popular theoretical method adopted to study end-plate connection is finite element technique under monotonic loading at present. This paper applies nonlinear (material, geometry and contact) finite element method to analyze the behaviors of connections under cyclic load at fist time. Contact elements are set between end plate and column flange, screw cap and neighborhood plane, bolt bar and hole. After verification of FEM, more than 50 species of 10 series are computed. The major factors include dimensions of end-plate, column axial force, arrangement of bolts, and so on. Advices for seismic design based on tests and calculation are presented at last.The problem of connection seismic behaviors is of great importance for structure field, and the foreground of study and application is very wide. Experiments and theoretical analyses presented in this paper may well fit the realistic behavior of end-plate connections under seismic load. The conclusion can be useful for revising code, guiding design of engineering, and making a favorable base for analyzing the seismic behavior of whole structure.