Cheng, Chan, and Chung 2007

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This research investigates the seismic performance of four steel beam to concrete filled steel tube column connection with floor slabs. Two interior and two exterior joints were tested. The development and validation of analytical models for the assessment of the force-deformation behavior of the joint components are also conducted. The slab effect on the shear transfer panel zone is investigated as well.

Experimental Study, Results, and Discussion

Four CFT connections with floor slabs were constructed under the assumption that the mid-span of the composite beams and mid-height of the CFT columns are all hinges based on the deformation shape. Columns were held still to avoid the interfering of the P-delta effect in the subassembly tests. Story drift was represented in the form of beam tip rotation in this research. Two specimens represent interior column joints in cruciform shape, the other two represent exterior column joints in cruciform shape. Steel beams, slabs, and columns were identical for all specimens. CFT columns were square cross section and were 0.354 in. thick and had a section length of 13.8 in. Composite beams consisted of a H450 x 200 x 9 x14 mm steel beam and a two meter wide 5.91 in. thick slab with 6.89 in. concrete topping on the metal deck. Shear studs for the composite beam were prohibited in the region of 19.7 in. from the column face. The concrete strength for the columns and floor was 3.55 and 2.2 ksi. Steel tubes had yield strength of 67 ksi.

Several types of connection details were tested. A web-through design of a continuous shear tab passing through the panel zone of the connection and applied shear studs on the inner tube wall with two shear-tabs on the outer tube wall to sandwich the beam web were compared. Different lap lengths of the shear tabs and beam web were also tested. Tapered beam flanges were applied for all specimens save one; one specimen had only the bottom flange tapered. Tests were conducted with the column under constant axial load. A hydraulic actuator at each beam tip applied the cyclic load with displacement control in the form of triangular waves in a manner which was modified from FEMA suggestions.

The paper builds on a connection model proposed by the authors in 2003 and incorporates the effects of floor slabs on force-deformation behavior. This model was used in analytical analysis of the tests done and the analytical results were compared with the test results. The study found that the composite effect of the floor slab and steel beam is significant under the sagging moment but is only slightly effective under hogging moment. Tapered beam flanges and lengthened shear tabs stiffened at the beam-ends and effectively moved the plastic hinges away from the column face, resulting in ductile performance of the connections. Shear tab passing through the panel zone has only a marginal effect on the shear transfer in the panel zone. Analytical models validate the strong-column-weak-beam performance of the connections in the tests and found that the slab effect on the shear transfer in the panel zone may be neglected. The proposed model simulated the envelope of force-deformation behavior for the entire connection, including flexural deformation in the beams and columns as well as shear distortions in the panel zone.

References

  • Cheng, C.-T., Chan, C.-F., and Chung, L.-L. (2007). "Seismic behavior of steel beams and CFT column moment-resisting connections with floor slabs," Journal of Constructional Steel Research, 63(11), p. 1479-1493. doi:10.1016/j.jcsr.2007.01.014