Cyclic behaviour of Y-shaped eccentrically braced frames fabricated with high-strength steel composite

Abstract Eccentrically braced frames fabricated with high-strength steel (HSS-EBFs) are a new type of seismic structural system. HSS-EBF systems can incorporate Q345 steel (nominal yield strength: 345 MPa) for links, high-strength steel (HSS) (nominal yield strength not less than 460 MPa) for beams and columns, and HSS or Q345 steel for braces. This configuration not only reduces the amount of steel consumed but also increases the usage of HSS in seismic areas. This paper describes an experimental study on HSS-EBFs with vertical links. One half-scale three-storey one-bay by one-bay building with Y-shaped HSS-EBFs (Y-HSS-EBFs) was subjected to a constant vertical linear dead load and cyclic lateral load to examine the seismic performance. The structural failure process, ductility, stiffness, deformation capacity, and energy dissipation capacity of the Y-HSS-EBFs were investigated. The analysis confirmed that the cyclic behaviour of the Y-HSS-EBFs showed good performance for plastic deformation. The force–displacement hysteretic curves of the Y-HSS-EBFs exhibited good plastic deformation behaviour and did not generate the pinching phenomenon. The maximum storey drift ratio and maximum ductility factor on the first storey reached 1/40 and 2.5, respectively. However, severe instability and damage were observed up to the maximum storey drift angle. Plastic deformation is mainly due to the shear deformation of the link web and bending deflection of the link flange at the link-to-beam connection in the first storey. This paper presents an analysis of the experimental investigation and test results can be referred to for the seismic design of this new type of structure.