Failure Mechanism And Design Criteria Of Steel Beam-to-column Double-angle Shear Connections Under Cyclic Load

Double-angle Connections are considered as PR (Partially restrained) typed connections or more specially are simple shear connections in practical structural design. This means that they are idealized as pinned and are assumed to transfer only shear loads to the supporting members. However, it has been found that they have some rotational stiffness and may transfer some moments to the supporting members. Development of moment in the connections can have positive as well as negative effects on the performance of structures. The positive effect of moment is to contribute to lateral strength and stiffness of the frames. The negative effect of connection moment is to subject columns to extra moments that they are not considered in their design. Especially during earthquake, it is expected that relatively large rotation can occur in the connections. Hysteretic behavior of connections will have pronounced effects on the overall behavior and dynamic response of the structures, so study on failure mechanism analysis and design criteria of steel beam-to-column double-angle shear connections under cyclic load is significant for theory and practice.In order to study the hysteretic behavior of double-angle connections and verify the reliability of theoretical method, 4 double-angle connections specimens were tested under cyclic load. Tests consist of three parts: martial property test, slippage coefficient test of bolt connection and double-angle connections test under cyclic load. Effects of length of angle, diameter and gage of bolts on hysteretic behavior of connections were synthetically considered under cyclic load. The results indicate that specimens exhibit good ductile behavior. The length of angle, diameter and gage of bolts significantly affect the strength and ductility of connections.This paper applies nonlinear (material, geometry and contact) finite element method to analyze the behaviors of connections under cyclic load for fist time. Contact problem between angle and column flange surface, bolt nut and neighborhood plate, bolt shank and bolt hole are simulated really. After verification of FEM, 45 species of 15 series are computed. The major parameters including slippage coefficients, pretensions forces, dimensions of angles, arrangement of bolts, connection method among angle, beam web, column flange, and so on are studied. Some important conclusions are drawn.At last, Advices for seismic design based on tests and FEM analysis are presented at last. The study is rather comprehensive and systematic, and the conclusions can be useful for revising design code, guiding design of engineering, and provide good basis for further to study behavior of shearbeam-to-column connections.