eprintid: 37840
rev_number: 6
userid: 9229
dir: disk0/00/03/78/40
datestamp: 2020-01-28 17:01:27
lastmod: 2020-01-28 17:01:27
status_changed: 2020-01-28 17:01:27
type: thesis_degree
metadata_visibility: show
contact_email: jrb193@pitt.edu
eprint_status: archive
creators_name: Bumstead, James
creators_email: jrb193@pitt.edu
title: Numerical Study of Repair Strategies for Earthquake-Damaged CFST Bridge Columns
ispublished: unpub
divisions: sch_eng_civilenvironmental
full_text_status: public
keywords: concrete filled steel tubes, plastic hinge relocation repair, external energy dissipators
abstract: 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.
date: 2020-01-28
date_type: published
pages: 148
institution: University of Pittsburgh
refereed: TRUE
etdcommittee_type: committee_member
etdcommittee_type: committee_member
etdcommittee_type: committee_chair
etdcommittee_name: Vandenbossche, Julie
etdcommittee_name: Khazanovich, Lev
etdcommittee_name: Stephens, Max
etd_defense_date: 2019-11-15
etd_approval_date: 2020-01-28
etd_submission_date: 2019-11-20
etd_release_date: 2020-01-28
etd_access_restriction: immediate
etd_patent_pending: FALSE
thesis_type: thesis
degree: MS
citation:   Bumstead, James  (2020) Numerical Study of Repair Strategies for Earthquake-Damaged CFST Bridge Columns.  Master's Thesis, University of Pittsburgh.    (Unpublished)  
document_url: http://d-scholarship-dev.library.pitt.edu/37840/1/Bumstead_Thesis_11.20.19.pdf