Elremaily and Azizinamini 2001

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This paper presents the experimental portion of a research program aimed at understanding the behavior of steel beam to CFT through beam connection details and developing accompanying design provisions. The experimental results provide the basis for the development of a design model presented in another paper.

Experimental Study, Results, and Discussion

Seven two-thirds scale through beam connection specimens representing an interior joint in a building were tested. Each specimen consisted of a CFT column with an I-beam girder. A full cross section of the girder was continued through the column core. The main test variables were the beam-to-column flexural capacity ratio, the type of weld used to attach the beam to the tube, and the presence or absence of some connection elements within the panel zone. CFT and girder dimensions varied by specimen. Specimens were divided into three groups with specified experimental purposes. The first group was designed to study the behavior of the connection when failure takes places in the column. In these specimens a fillet weld was used to attach the beam to the tube and one specimen in this group did not have concrete in the panel zone (the panel zone was filled with Styrofoam). The second group was designed to study the inelastic behavior of the connection as it would behave in a real structure. Full penetration and fillet welds were tested in this group, as well as the effect of the presence of rebar within the joint. The third group was design to determine the shear capacity of the joint. The beam and column outside the joint area were strengthened and the effect of a web plate in the joint zone on strength and stiffness was tested. During testing, the column was subjected to a constant axial load. Equal and opposite vertical loads were applied at the beam ends to simulate the deformed shape of an interior joint in a building subjected to lateral loads. Column ends were restrained from horizontal movement but allowed to rotate in the plane of loading.

The failure of specimens in group one was due to fracture of the fillet weld that attached the beam flanges to the tube followed by tearing of the tube wall at the flange tips. Despite weld fracture, the connection did not show sudden drop of stiffness or strength and was able to sustain more load. All specimens in the second group were able to develop the full plastic capacity of the beam and joint failure was prevented. Failure of these specimens was due to plastic hinge formation in the beam outside the joint. This behavior is very favorable in an actual design situation where column and joint failures should be avoided. Comparison between specimen in this group with and without rebar shows that when the column is stronger than the beam rebar are not required within the joint. Failure of specimen in the third group was due to excessive shear deformation in the panel zone. The specimen in this group with beam web present in the panel zone was able to carry a higher load than the specimen without beam web present.

References

  • Elremaily, A. and Azizinamini, A. (2001). "Experimental behavior of steel beam to CFT column connections," Journal of Constructional Steel Research, 57(10), p. 1099-1119. doi:10.1016/S0143-974X(01)00025-6