This thesis investigates the performance of composite frame structures with smart
partially-restrained (PR) concrete filled tube (CFT) column connections through
simplified 2D and advanced 3D computational simulations. It also provides a design
methodology for new types of innovative connections based on achieving a beam hinging
mechanism. These types of connections intend to utilize the recentering properties of
super-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 were
designed based on a hierarchy of strength models for each connection component.
Numerical simulations with refined three dimensional (3D) solid elements were
conducted on full scale PR-CFT connection models in order to verify the strength models
and evaluate the system performance under static loading. Based on system information
obtained from these analyses, simplified connection models were formulated by replacing
the individual connection components with spring elements and condensing their
contributions. Connection behavior under cyclic loads was extrapolated and then
compared with the monotonic behavior.
In the second part of this study, the application of these connections to low-rise
composite frames was illustrated by designing both 2D and 3D, 4 and 6 story buildings
for the Los Angeles region. A total of 36 frames were studied. Pushover curves plotted
as the normalized shear force versus inter story drift ratio (ISDR) showed significant
transition points: elastic range or proportional limit, full yielding of the cross-section,
strength hardening, ultimate strength, and strength degradation or stability limit. Based
on the transition points in the monotonic pushover curves, three performance levels were
defined: Design Point, Yield Point, and Ultimate Point. All frames were stable up to the
yield point level. For all fames, after reaching the ultimate point, plastic rotation
increased significantly and concentrated on the lower levels. These observations were
quantified through the use of elastic strength ratios and inelastic curvature ductility ratios.
The composite frames showed superior performance over traditional welded ones in
terms of ductility and stability, and validated the premises of this research.
| Identifer | oai:union.ndltd.org:GATECH/oai:smartech.gatech.edu:1853/22655 |
| Date | 01 April 2008 |
| Creators | Hu, Jong Wan |
| Publisher | Georgia Institute of Technology |
| Source Sets | Georgia Tech Electronic Thesis and Dissertation Archive |
| Detected Language | English |
| Type | Dissertation |
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