Wang, Han, and Uy 2007

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Five specimens of connections of reduced beam section (RBS) steel beam to concrete-filled steel tubular (CFT) circular hollow section column using an external ring were tested. The experiments considered the hysteretic behavior under combined constant axial load and cyclic lateral load. For comparison, three specimens of a weak-column without an RBS configuration steel beam to CFT column connection were tested under the same conditions.

Experimental Study, Results, and Discussion

Eight connection specimens of steel beam to CFT column using an external ring with circular cross-section were tested under an axial load and a cyclically increasing lateral load. The column height was 41.3 in. and the steel beam span was 59 in. Steel tubes on the columns had a diameter of 5.5 in. and thickness of 0.084 in. The steel tube and beam/ring had measured yield strength of 39.5 ksi and 41.9 ksi. The steel tube was filled with self consolidating concrete which had measured cube strength of 8.7 ksi.

Five RBS specimens were designed with strong-column-weak beam behavior and three specimens without an RBS section were designed with strong-beam-weak column behavior. Three parameters were tested. The width of the external ring was varied; three sizes of two thirds, one third, and equal to the ring width specified by Japanese Code AIJ. The axial load level of the CFT column was varied. RBS beam connections were compared to normal beam connections. During testing, the lateral load was applied at the top of the CFT column. A very rigid stub of high strength steel was connected at one end to the top part of the column and at the other to a high powered hydraulic ram. The lateral loading history of the connection was generally based on the ATC-24 guidelines for cyclic testing of structural steel components.

All the RBS connections observed a failure mode of beam failure in general. In contrast, the weak-column connections failed in a brittle mode. The RBS connections exhibited good seismic performance and ductility while the ultimate load may be reduced slightly. At a higher axial load level in the column, the column lateral load carrying capacity is slightly reduced, but its ductility suffered a large reduction. As a result, the energy dissipation was also greatly reduced. The damping coefficient was only slightly increased. Initially, there was a slight increase in the column lateral rigidity at low deflections, but the degradation in column lateral rigidity was much greater at large lateral deflections. The ultimate load of the connections was decreased with a decreasing width of the ring of the connections; the ring failure mode occurred under the same axial level and beam configuration.

References

  • Wang, W.-D., Han, L.-H., and Uy, B. (2008). “Experimental Behaviour of Steel Reduced Beam Section to Concrete-Filled Circular Hollow Section Column Connections.” Journal of Constructional Steel Research, 64(5), 493–504. doi:10.1016/j.jcsr.2007.10.005