Study On The Preliminary Theory Of Direct Displacement-Based Seismic Design Approach Based On Relative Reliability Concept

Direct displacement-based design （DDBD） had been put forward for decade as anadvanced design approach, the relative research has made great progress. However, theconfused reliability made DDBD approach can not promote to application.Base on the work of the research group, and pushover analog computation byOpensees, put forward the preliminary theory of DDBD approach based on relativereliability concept, analysis the error of base shear between DDBD under frequentearthquake and force-based method and correction it, preliminary determinedisplacement target of performance target and section bearing capacity expression inDDBD approach based on relative reliability concept, proof the effectivenesspreliminary of DDBD approach through comparative analysis, provides theoreticalreference for establish effective reliability theory system in DDBD.The chiefconclusions of the paper are as follows:①Establish reliability theory system in DDBD method based on average reliabilitylevel of structure designed by the current standard, and put forward two specific ways.②The first method. For any performance target, the expected level of seismic riskare transformed into frequent earthquake to calculate reliability, and made thedisplacement demand （interstory drift ratio） under frequent earthquake as effect, thedisplacement （interstory drift ratio） corresponding to performance level as resistance.Corresponding expression of bearing capacity is:S=γ_GS_GE+γ_Ehη₁S₍Ehk≤R/γ_RE。.③The second method. For every performance target, the expected level of seismicrisk was directly used to calculate reliability, and made the displacement demand（interstory drift ratio） under the expected earthquake as effect, the displacement（interstory drift ratio） corresponding to performance level as resistance. Correspondingexpression of bearing capacity is:S=γ_GS_GE+γ_Ehη₂S₍Ehk≤R/γ_RE。④Preliminary determine the factor of section bearing capacity expression inDDBD. The first method：η₁=1.25; The second method, under frequent earthquake,η₂=1.25, under medium earthquake, η₂=0.59, under infrequent earthquake, η₂=0.33.⑤Completed comparative analysis between DDBD and force-based designmethod. The results show that DDBD approach based on relative reliability concept cancontrol the target displacement effectively, and the reliability of the performance targetis closer to the existing average reliability level, proof the effectiveness preliminary of DDBD approach based on relative reliability concept.