| Concrete Filled Steel Tube (CFT) composite shear wall is a new type ofcomposite structure elements with CFTs embedded. It has good load restistingcapacity and seismic behavior, which is suitable for vertical and lateral resistingelements in high-rise buildings or skyscrapers. CFT composite shear wall has awide application prospect.7CFT composite shear wall specimens with4types of CFT layouts and3reinforced concrete (RC) shear wall specimens with different detailing methodswere designed and tested under high axial compression ratio and cyclic lateralloading. The shear span depth ratio of all specimens is2.08and the axialcompression ratio ranges from0.44to0.73. The test results indicate that most ofthe specimens failed in flexural failure mode and the crush area was focusednear the bottom of each specimen with a width of the whole specimen crosssection height and a height of300~400mm. No obvious slip was observedbetween the steel tubes and the surrounding concrete. Compared with the RCshear wall specimens, the flexural bearing capacity of the CFT shear wallspecimens increased by about23%~35%, its drift angles at the yield load, thepeak load and the ultimate stage were about1/300, more than1/100and1/75respectively. Some specimens’ drift angles at the ultimate stage reached1/40.The hysteretic behavior of the CFT shear wall specimens was improvedsignificantly. It can be concluded the the CFT composite shear walls designedhere have an excellent seismic performance and collapse prevention capacity.Due to the application of steel tubes, the failure ductility and anti-collapseability of shear wall are obviously promoted, Mearsured vertical straindistributions along the specimen cross section height prove that the verticalstrain distributions along the wall section height basically satisfied theplane-section assumption before the peak load. The steel tubes and the stirrupsin the boundary elements have yielded at peak load while the tubes near thecenter of each wall section didn’t yield during the test. A method to predict theflexural bearing capacity of a CFT composite shear wall has been proposed, which agrees well with the experiment results. A modified prediction methodwhich partly considering the CFT confinement was suggested. The distributionsof the axial load among the concrete outside the CFTS and the CFTs of thespecimens agreed well with the results predicted following CECS188-2005specification. Using spiral confined embedded emelents rather than normalstirrups confinement in a RC shear wall can obviously improve its seismicbehavior, but CFT shear walls behave much better under same conditions.The nonlinear analysis of the CFT shear wall specimens were carried outusing MSC.Marc and the FE models were calibrated using test data. Parameterstudy was conducted on behavior of CFT shear walls. The simulation resultsindicate that when the steel tubes are set in the boundary elements and middlesection, the CFT shear wall has a higher bearing capacity, higher lateralstiffness and deformation ability under high axial compression ratio. Its axialcompression bearing capacity and its shear resisting capacity increase as well.While its ductility and energy dissipation capacity decrease with the axialcompression ratio increases. Increasing the steel tube ratio can effectivelyimprove the bearing capacity and lateral stiffness of a CFT shear wall, but itsdeformation capacity improves slightly. As the strength grade of the steel tubeor the concrete is increased, the bearing capacity and lateral stiffness of a CFTshear wall will be improved effectively while the deformation capacity andductility are not significantly changed. Based on the experiement and analyticalresults, some suggestions on how to design and detail a CFT composite shearwall have been proposed. |
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