Toshiyuki, Noguchi, and Mori 1996

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In this paper, equations were proposed to calculate the rotation capacity of circular and square CFT beam-columns. For this purpose, regression analysis was performed based upon test results from the Japanese literature.

Analytical Study

The test data included 165 rectangular and 47 circular beam-columns. For the rectangular sections, the ranges for the yield strength of the steel and the compressive strength of the concrete were 28 to 120 ksi and 2.61 to 14.8 ksi, respectively. The D/t ratio varied between 14 and 95 and the range of axial load ratio was 0 to 0.9. For circular sections, the steel strength ranged from 41 ksi to 119 ksi and the concrete strength ranged from 2.32 to 17.7 ksi. The D/t ratio varied between 18 and 67. The lower and upper limits of axial load ratios were 0.1 and 0.7, respectively.

The rotation capacity was determined based upon the limit rotation when the post-peak strength of the beam-column decreased to 95% of its peak value. The rotation capacity was found to decrease with an increase in the D/t ratio due to the reduction of confinement. A sharper decrease in strength was also observed after peak strength when the axial load ratio got larger. This was attributed to the occurrence of local buckling.

By fitting a line to the test data, the following equation was proposed for the limit rotation of rectangular beam-columns:


An average value of 1.17 was obtained for the ratio between experimental and analytical rotation capacities.

The same technique was used to derive the equation for the rotation capacity of circular beam-columns and the following equation was proposed:


The average value of the ratio between the experimental and analytical results was found to be 0.99.

References

Toshiyuki, F., Noguchi, T., and Mori, O. (1996). “Evaluation of Deformation Capacity of Concrete-Filled Steel Tubular (CFT) Beam-Columns,” Proceedings of the Third Joint Technical Coordinating Committee Meeting, U.S.-Japan Cooperative Research Program, Phase 5: Composite and Hybrid Structures, Hong Kong, December 12-14, 1996, National Science Foundation, Arlington, Virginia.