Study of Seismic Behavior of a Tall Eccentrically Braced Frame Dual System Based on ASCE 7-05

One of the common structural systems in mid to high rise buildings is defmed as moment frame (MF)plus shear truss that is named dual system in ASCE 7-05. MFs in dual systems which are designed according to the current code must be able to resist at least 25% of seismic forces. This paper discusses nonlinear behaviour of a sample case of 20-story eccentrically braced frame (EBF) dual system which its MFs resist more than 25% of seismic forces. Six structural configurations were designed and examined with nonlinear static and nonlinear dynamic procedures. Results indicate that the bestcombination occurs when 45% of lateral load is absorbed by the MFs. Also the results show that dual systems have better seismic behaviour than MFs or EBFs, separately