Seismic design lateral force distribution based on inelastic state of K-eccentric brace frames combined with high strength steel

Abstract

The HSS-EBFs refer to the eccentrically braced frames combined with high strength steel, the ordinary steel (namely the nominal yield strength is lower than 345 MPa, such as Q345) is utilized for links, however the high strength steel is used for columns and beams. The columns and beams are kept in elastic under major earthquake and the plastic deformation is isolated to the links. Therefore the using of high strength steel brings many benefits, such as reduces the member sections with reducing the use of painting and welding, and increases indoor usable floor area, however it weakens the lateral stiffness of the structure. The lateral force distribution of HSS-EBFs is differing with the traditional EBFs, and the story stiffness of structure is changed from elastic to inelastic state. In this paper, four groups of K-eccentric brace frames combined with high strength steel with different story are designed to study the lateral force distribution under major earthquakes. The HSS-EBFs are conducted by nonlinear dynamic analysis using near-fault ground motions and far-fault ground motions, and the velocity pulse effect and the acceleration cumulative cyclic effect are considered. The lateral force distribution of the HSS-EBFs in inelastic state are proposed based on the mean values of the elastic–plastic story shear force, which is consistent with the code representation. The raised elastic to plastic lateral force distribution has a better accuracy than other existing distribution forms. The results of the study can provide reference for performance-based seismic design of HSS-EBFs.