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Title:Mechanically Spliced Precast Bridge Columns
Authors:Theodore Sjurseth, Evan Greeneway, Kallan Hart, Mathew LaVoy, Mostafa Tazarv, and Nadim Wehbe
University:South Dakota State University
Publication Date:Mar 2022
Report #:MPC-22-451
Project #:MPC-595
TRID #:01845107
Keywords:bridge construction, columns, earthquake resistant design, precast concrete, splicing, structural connection


A mechanical bar splice, also known as bar coupler, is an alternative to the traditional lap splicing to connect bars in reinforced concrete (RC) structures. Even though mechanical bar splices can be used as new precast column connections to accelerate bridge construction (ABC), the use of bar couplers in the plastic hinge region of bridge columns is prohibited in current U.S. codes. This is mainly because the coupler performance and the effects of couplers on the seismic behavior of columns have not been fully investigated. A recent study at South Dakota State University (SDSU) attacked the first problem by testing more than 160 bar couplers, established a comprehensive database of the coupler behavior, and proposed standard test methods and acceptance criteria for seismic couplers. Nevertheless, test data regarding the performance of mechanically spliced bridge columns is scarce, and the available data is for columns with different geometries, confinement levels, and testing procedures. The literature lacks a systematic performance database on mechanically spliced bridge columns. An experimental investigation was performed at the SDSU Lohr Structures Laboratory to determine the seismic performance of mechanically spliced bridge columns and to develop the first-of-its-kind mechanically spliced column performance database. Eight half-scale bridge columns were constructed and tested. One column was cast-in-place (CIP) to serve as the reference model and seven were precast, incorporating different coupler products at the column base. One of the precast columns included a repairable detailing that allowed replacement of steel bars through detachable couplers. All columns were tested under the same slow cyclic displacement-controlled lateral loading. The test results showed that seismic couplers can reduce the precast column displacement capacities from 3% to 45% compared with CIP. Nevertheless, all precast columns tested in this project met the current code seismic requirements, thus they are recommended for use in all 50 U.S. states. The drift capacity of the repairable column was 9.8%, which was higher than the CIP drift capacity of 8.96%. The stiffness of the repairable column was lower than that for CIP due to the nature of the new connection and the damage of concrete at the rocking face. The repair through replacement of BRR was feasible but difficult at 5% drift ratio due to a Z-shape buckling of the exposed bars. Furthermore, a post-test analytical study was performed to evaluate current modeling methods for bridge columns, specifically mechanically spliced columns, followed by a parametric study including 400 pushover and 540 nonlinear dynamic analyses. The models were able to successfully reproduce the force-displacement relationship of the test columns. The results from the pushover analyses showed that columns with couplers may reduce the displacement ductility capacity up to 45% when compared with conventional CIP columns, which agreed well with the new column experimental data. Furthermore, the results from the nonlinear dynamic analyses, the first of its kind on mechanically spliced columns, showed that couplers have minimal effect on the precast column seismic drift demands. A maximum of 7% deviation was found when spliced column dynamic response was compared with that of the CIP column. Three design methods for mechanically spliced bridge columns were evaluated and found viable for practice.

How to Cite

Sjurseth, Theodore, Evan Greeneway, Kallan Hart, Mathew LaVoy, Mostafa Tazarv, and Nadim Wehbe. Mechanically Spliced Precast Bridge Columns, MPC-22-451. North Dakota State University - Upper Great Plains Transportation Institute, Fargo: Mountain-Plains Consortium, 2022.

NDSU Dept 2880P.O. Box 6050Fargo, ND 58108-6050