Study On The Seismic Performance Of K-type Eccentrically Braced Steel Frames Composited With High Strength Steel Designed By Direct Displacement-based Design Method

In recent years the tenets of Performance-Based Seismic Engineering(PBSE)have been introduced for design of earthquake resistant structures.Thus,it is necessary that a design methodology be capable of producing a system that can achieve a performance target.Research has identified limitations in conventional force-based design practices in meeting the needs of PBSE.In response,a significant movement has been made towards displacement-based design in an attempt to bypass these limitations.This paper proposes a Direct Displacement-Based Design(DDBD)methodology for design of new seismic resistant eccentrically braced steel frames(EBFs).Two crucial issues in earlier DDBD methods that need resolution are(1)assumption of frame yield displacements and(2)determination of system equivalent damping.To resolve the first,a procedure using EBFs’ mechanism is proposed to construct a yield displacement profile.The procedure illustrates that displacement ductility demand can be controlled via design.Secondly,the total energy dissipated by the frame from components yielding is commonly estimated by evaluating the base shear-roof displacement hysteresis..Estimation of equivalent viscous damping factor used to characterize the substitute structure for different structural systems is a dominant parameter in this design methodology,but the equivalent linear method has been validated with larger error.This paper will raise a rational method to calculate the quivalent viscous damping of EBFs in DDBD.In this paper,results of experimental and numerical investigations performed for estimating the equivalent viscous damping in DDBD procedure of eccentrically braced steel frames.First,finite element model of test specimen is created by ABAQUS software to verify the precision of the finite element software.Second a numericalinvestigation is conducted on a set of analytical EBFs.The equivalent viscous damping and ductility of each analytical model are calculated from hysteretic responses.On the basis of analytical results,new equations are proposed for equivalent viscous damping as a function of ductility for EBFs.As a result,the new equation is used in direct displacement-based design of EBFs.Lastly,three K-type eccentrically braced steel frames composited with high strength steel(HSS-EBFs)are designed using the proposed DDBD,including 5-story,8-story and 12-story,and subjected to nine earthquakes.The results indicate that HSS-EBFs thus designed have a much greater potential in meeting a performance target.