Title: Seismic Behavior of Hollow-Core Composite Bridge Columns Having Slender Inner Steel Tubes
Author(s): Mohanad M. Abdulazeez and Mohamed A. ElGawady
Publication: Structural Journal
Appears on pages(s): 143-158
Keywords: buckling instabilities; composite bridge column; hollow-core; reparability; seismic behavior; sustainability
This paper experimentally investigates the seismic behavior of two as-built and one repaired large-scale hollow-core fiber-reinforced polymer-concrete-steel (HC-FCS) columns. Each HC-FCS column consisted of a concrete shell sandwiched between an outer glass fiber-reinforced polymer (GFRP) tube and an inner steel tube. Both tubes provided continuous confinement for the concrete shell along with the height of the column. The columns had two different steel tube diameter-to-thickness ratios (Ds/ts) of 85 and 254. Each steel tube was embedded into the footing, with an embedded length of 1.25 to 1.6 times its diameter, while the GFRP tube was not embedded into the footing. Two columns were tested as as-built specimens. Then, one of these columns was repaired and retested. This study revealed that HC-FCS columns having a high Ds/ts of 254 and short embedded length (1.25Ds) do not dissipate high levels of energy and display nonlinear elastic performance due to severe steel tube buckling and slippage. However, the column with a Ds/ts of 85 combined with substantial embedment length (1.6Ds) results in a nonlinear inelastic behavior, high energy dissipation, and ductile behavior. A repair technique for a high Ds/ts HC-FCS column precluding buckling of the inner steel tube was proposed and examined. The repair method was characterized by use of an anchorage system with steel tube concrete filling at the joint interface region. The repaired column achieved the ductile behavior and performed well under seismic loading with flexural strength increased by 22%. However, the lateral displacement capacity decreased by 26% compared to the virgin column due to the residual deformations and stresses exhibited during the previous test.