Skalomenos, Hayashi, Nishi, Inamasu, Nakashima 2016
CFT’s have significant advantages such as increased strength and stiffness, and larger energy dissipation over plain concrete or steel columns.
Experimental Study, Results & Discussion
CFT’s have significant advantages such as increased strength and stiffness, and larger energy dissipation over plain concrete or steel columns. They have excellent structural properties for seismic resistance and have been researched intensively to examine their behavior under seismic loads as they are used in structures and bridges. This paper investigated the nature of ultra high strength steel compared to conventional steel in CFT’s to further improve the seismic performance of the columns. For the testing, there were seven curricular and square specimens. They underwent constant compressive axial and cyclic flexural loading protocols with two and 20 cycles exacted at each drift level. The analytical model created to emulate the planned superposed strength method confirmed its precision with results from the experiment. From these test results, the axial load, cross-sectional shape, number of cycles in the lateral loading history, and the influence on the CFT’s cyclical behavior of the high strength steel, were studied. The high-strength steel had a larger elastic deformation and a greater maximum strength. Local buckling was delayed in the CFT’s with high-strength steel, thus having a lower axial shortening. Square high strength steel specimens endured larger drift angles with fewer deformations due to the development of the local buckling. After the buckling, repeated loading cycles likened the possibility of fracture and increased axial shortening. Loading history with a large number of repeated cycles shows high strength specimens underwent much less deterioration, maintaining a more satisfactory long-duration performance.
Analytical Study
The analytical model was developed based on the method from Nakamura and Wakabayashi that determines the moment capacity of a member while employing the superposition concept. An inelastic trilinear moment-deformation model was created to characterize the high-strength steel CFT column’s behavior. The model and design equations predicted, with credible accuracy, the possible scope of strength and deformation, and the inelastic and elastic stiffness, for the high-strength steel in the CFT columns.
Reference
Skalomenos, K., Hayashi, K., Nishi, R., Inamasu, H., Nakashima, M. (2016) “Experimental Behavior of Concrete-Filled Steel Tube Columns Using Ultrahigh-Strength Steel” Journal of Structural Engineering Vol. 142, Issue 9 doi:10.1061/(ASCE)ST.1943-541X.0001513.