Seismic performance evaluations and analyses for composite moment frames with smart SMA PR-CFT connections

PR-CFT connections;Seismic performance;Nonlinear frame analysis;Composite frames;Smart materials;SMA;Damage evaluations;FE analysis

Hu, Jong Wan ; Civil and Environmental Engineering

University:Georgia Institute of Technology

Department:Civil and Environmental Engineering

关键词: PR-CFT connections;    Seismic performance;    Nonlinear frame analysis;    Composite frames;    Smart materials;    SMA;    Damage evaluations;    FE analysis;   

Others  :  https://smartech.gatech.edu/bitstream/1853/22655/1/Hu_JongWan_200805.pdf

美国|英语

来源: SMARTech Repository

【 摘 要 】

This thesis investigates the performance of composite frame structures with smartpartially-restrained (PR) concrete filled tube (CFT) column connections throughsimplified 2D and advanced 3D computational simulations. It also provides a designmethodology for new types of innovative connections based on achieving a beam hingingmechanism. These types of connections intend to utilize the recentering properties ofsuper-elastic SMA tension bars, the energy dissipation capacity of low-carbon steel bars,and the robustness of CFT columns.In the first part of this study, three different PR-CFT connection prototypes weredesigned based on a hierarchy of strength models for each connection component.Numerical simulations with refined three dimensional (3D) solid elements wereconducted on full scale PR-CFT connection models in order to verify the strength modelsand evaluate the system performance under static loading. Based on system informationobtained from these analyses, simplified connection models were formulated by replacingthe individual connection components with spring elements and condensing theircontributions. Connection behavior under cyclic loads was extrapolated and thencompared with the monotonic behavior.In the second part of this study, the application of these connections to low-risecomposite frames was illustrated by designing both 2D and 3D, 4 and 6 story buildingsfor the Los Angeles region. A total of 36 frames were studied. Pushover curves plottedas the normalized shear force versus inter story drift ratio (ISDR) showed significanttransition points: elastic range or proportional limit, full yielding of the cross-section,strength hardening, ultimate strength, and strength degradation or stability limit. Basedon the transition points in the monotonic pushover curves, three performance levels weredefined: Design Point, Yield Point, and Ultimate Point. All frames were stable up to theyield point level. For all fames, after reaching the ultimate point, plastic rotationincreased significantly and concentrated on the lower levels. These observations werequantified through the use of elastic strength ratios and inelastic curvature ductility ratios.The composite frames showed superior performance over traditional welded ones interms of ductility and stability, and validated the premises of this research.