Seismic Performance And Force Reduction Factor Spectra Of Fused Diagrid Structure

The high-rise diagrid structure makes full use of structural components,reduces material usage and construction costs,and thus becomes one of the most popular high-rise structural systems.The research on high-rise diagrid structure mainly focuses on the elastic mechanical property,related design parameter,structural layout,diagonal angle and complicated nodes,while the performance under earthquake loads has not been comprehensively studied.The energy dissipation capacity and ductility of conventional diagrid structure are so limited that the structure tends to suffer extensive damage when the structural demand exceeds elastic resistance,which will cause hefty financial loss.The R factor of bending-type structure including diagrid also has not been comprehensively investigated.Therefore it is necessary to improve the seismic performance of high-rise diagrid structure and study the R factor of bending-type structure.The dissertation aims to improve the seismic performance and safety of high-rise diagrid structure,propose effective energy dissipation mechanism and performance-based seismic design procedure for earthquake-resilient high-rise diagrid structure,investigate the rotation ductility and curvature ductility based R factor spectrum for bending-type structure,and finally make high-rise diagrid structure eligible to be implemented in highly seismic zones.Main contents of the dissertation are summarized as follows:(1)A 30-storey conventional diagrid structure,located at Los Angeles,is designed and numerically modeled in OpenSees to simulate inelastic diagonal buckling and post-buckling structural behavior.Nonlinear pushover analysis and dynamic analysis are performed to evaluate the energy dissipation capacity and seismic performance of diagrid structure.The FEMA P695 methodology is adopted to assess the collapse risk of diagrid structure.(2)A new earthquake-resilient high-rise diagrid structure fused with shear links(DSSL)is proposed.A performance-based plastic design procedure is proposed for DSSL.A prototype DSSL,located at Los Angeles,is designed using the proposed design procedure.Nonlinear pushover analysis and dynamic analysis are performed to confirm the validity of the new energy dissipation mechanism and design method.The FEMA P695 methodology is used to evaluate the collapse risk of the prototype DSSL.(3)A new double fused high-rise diagrid structure(DFDS)with tri-linear force-displacement relation is proposed.High-mode energy modification factor is proposed to modify the equivalent energy design procedure(EEDP)and used to establish the EEDP-based plastic design procedure for DFDS.A prototype DFDS,located at Los Angeles,is designed using the proposed design procedure and utilized to confirm double-fuse energy dissipation mechanism and performance targets.The FEMA P695 methodology is used to evaluate the collapse risk of DFDS.(4)Three 24-storey DFDSs with diagonal angle of 54,64 and 70 degree respectively are designed using the proposed EEDP-based plastic design procedure.Nonlinear pushover and dynamic analyses are performed to investigate the effect of diagonal angle on the seismic performance of DFDS.The FEMA P695 methodology is adopted to study the effect of diagonal angle on the collapse prevention capacity of DFDS.(5)A rotation-ductility-based nonlinear analysis approach is proposed to investigate the R factor spectra of bending-type structure such as diagrid structure.The seismic nominal height and concentrated plasticity numerical model using zero-length spring element are introduced.The double characteristic period normalization method is adopted to remain the peak feature of individual R factor spectrum.The effects of structural fundamental period,rotation ductility,fault distance,post-yield stiffness ratio and second vibration mode on the R factor spectra of bending-type structure are investigated.The relation between rotation ductility and displacement ductility is established.The formula to compute rotation-ductility-based R factor and the corresponding second-vibration-mode modification factor are proposed.The rotation-ductility-based R factor is then implemented in the seismic design of high-rise diagrid structure.(6)A curvature-ductility-based nonlinear analysis approach is proposed to investigate the effects of structural fundamental period,curvature ductility,storey stiffness distribution,weak storey and second vibration mode on the R factor spectra of bending-type structure.The relation between curvature ductility and displacement ductility is established.The formula to compute curvature-ductility-based R factor and the corresponding second-vibration-mode modification factor are proposed.The R factor obtained from the rotation-ductility-based analysis and the curvature-ductility-based analysis are compared to reveal the effect of energy dissipation mechanism on the R factor.(7)As an important part of the gravity system in the diagrid building,a new-type steel-concrete composite floor beam with diamond plate top flange is proposed to increase building space and can be used in fast construction with the perimeter diagrid system.11 specimens are tested to explore the shear resistance of the diamond plate-concrete interface and the bending resistance of the new composite beam.The failure mode,force-displacement relation and strain distribution of the specimens are analyzed and the bearing capacity computation method is finally proposed for the new steel-concrete composite beam.