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Numerical Study of Repair Strategies for Earthquake-Damaged CFST Bridge Columns

Bumstead, James (2020) Numerical Study of Repair Strategies for Earthquake-Damaged CFST Bridge Columns. Master's Thesis, University of Pittsburgh. (Unpublished)

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Concrete filled steel tubes (CFSTs) provide a unique, economical alternative to traditional reinforced concrete (RC) columns in highway bridges for their ease of construction and efficient structural properties. The steel tube provides optimal flexural resistance and continuous confinement to the infill concrete, while the concrete fill improves stiffness and strength of the column, and prevents inward local tube buckling of the steel tube. Recent research has developed a practical and structurally robust, column-to-foundation/cap-beam connection for use in mid-to-high seismic regions. This connection, referred to as the embedded ring (ER) connection, is a full-strength connection, where well-detailed, ER CFST columns exhibit local, outward tube buckling directly above the foundation/cap-beam when subjected to reverse-cyclic, lateral loadings. This typical ductile failure mode is readily identifiable post-earthquake events, and is uniquely advantageous compared to typical RC columns due to limited concrete spalling and the availability of the steel tube for welded connections.
The main objective of this research was to develop practical repair strategies for ER CFST columns which exhibit this ductile failure progression, with the goal of reestablishing the original column strength and stiffness. Two strategies were developed: (1) a traditional plastic hinge relocation method that utilizes an enlarged, CFST pedestal that surrounds the damaged region, and (2) a performance-based repair that implements external energy dissipators and column-rocking to limit damage. A non-linear, numerical analysis approach was adopted to assess the hysteretic response of these repair methods in comparison to that of an undamaged, CFST column. Results indicated that both repair strategies successfully restored lost stiffness and strength, specifically peak strength values of 1.26Mp and 1.02Mp for the traditional and performance-based methods were observed, respectively, where Mp represents the plastic moment of the original column. Additionally, a limited experimental study was carried out on the proposed, bucking restrained, energy dissipator where, under cyclic-compressive loadings, compressive yielding (1.12Fy) and inelastic strains (9.0εy) were measured within the laterally-restrained, structural fuse of the dissipator.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee MemberVandenbossche, Julie
Committee MemberKhazanovich, Lev
Committee ChairStephens, Max
Date: 28 January 2020
Date Type: Publication
Defense Date: 15 November 2019
Approval Date: 28 January 2020
Submission Date: 20 November 2019
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 148
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Civil and Environmental Engineering
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: concrete filled steel tubes, plastic hinge relocation repair, external energy dissipators
Date Deposited: 28 Jan 2020 17:01
Last Modified: 28 Jan 2020 17:01


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