Connections for Concrete-Filled Steel Tubes in Bridge Applications

April 30, 2021 1:00 pm

In this quarterly Research Seminar, Dawn E. Lehman, Ph.D. and Charles W. Roeder, Ph.D., Principal Investigators, will present work under the ABC-UTC research project entitled New Seismic-Resisting Connections for Concrete-Filled Tube Components In High-Speed Rail Systems, now completed, and the ongoing ABC-UTC research project entitled Economic Pier-to-Pile Connections for Permanently Cased Shaft (CFST) Piles, both conducted at the University of Washington.

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Concrete-filled steel tubes (CFST) are suitable for deep pile and shaft foundations due to their great ductility and large flexural, axial and shear strengths, but direct pier-to-foundation connections are needed to facilitate accelerated bridge construction. The LSDyna computer program is used to perform a nonlinear analytical study of direct connections between a reinforced concrete (RC) pier and CFST foundation. The model includes advanced constitutive modeling of the concrete and the bond between the steel tube and concrete fill, and was validated by comparison to large-scale RC and CFST test results. Different force and moment transfer mechanisms were investigated. Supplemental ribs inside the tube were evaluated for enhanced load transfer with minimal embedment length. The effects of rib location, tube diameter, reinforcing bar diameter, and embedment depth on connection performance were investigated. Initial design recommendations are provided, and experimental validation is in progress.

This project is being conducted using joint funding. The ABC-UTC/UW funding is supporting the nonlinear computer analysis of the performance of the connections for accelerated bridge construction.  Experimental work is being done at the UW in support of the analytical research with funding provided by the Pacific Earthquake Engineering Research (PEER) Center. The ABC-UTC/UW research is supporting the analytical research and that will be the focus of this presentation, although some references may be made to the experimental work since comparison of this work speaks to accuracy and reliability of the analytical results.



Dawn E. Lehman, Ph.D.
Civil & Environmental Engineering Department
University of Washington


Charles W. Roeder, Ph.D.
Civil & Environmental Engineering Department
University of Washington

Presentation Graphics:

Figure 1. General connection to be evaluated

Figure 2. Nonlinear finite element modeling

Figure 3. Parameter study performed

Figure 4. Typical result

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