Mechanical Bar Splices for Accelerated Bridge Construction of Columns

Accelerated bridge construction (ABC) is a new paradigm in the USA mainly to expedite construction using new techniques, advanced planning, and novel detailing. ABC heavily relies on prefabricated bridge elements and systems. Pilot studies indicated that the application of precast columns in the USA is limited due to uncertainties related to the performance of precast column connections (Marsh et al., 2011; Kapur et al., 2013). One method to connect precast columns to adjoining members is through the use of mechanical bar splices commonly referred to as couplers. Even though current codes prohibit the application of couplers in the critical area of columns (e.g. American Association of State Highway and Transportation Officials (AASHTO) Guide Specifications, Article 8.8.3), recent studies have revealed the feasibility of precast columns utilizing couplers in the plastic hinge regions helping expanding ABC in high seismic zones. The seismic performance is not a concern for none- or low-seismic states. Nevertheless, the application of bar couplers in precast bridge columns located in these states is also scarce probably because of the uncertainty pertaining to the coupler performance, column connection performance, and an engineering precaution. Utah, Florida, Colorado, and Washington have incorporated grouted sleeve bar couplers for bridge columns. There are several types of couplers in the market and new coupler types are emerging. Their prime role is to shorten the splice length and to reduce bar congestion in connections. Since 2 bridge columns are the focus of the present study, couplers that transfer both tensile and compressive forces are investigated. Five suitable coupler types are (Fig. 1): shear screw couplers, (2) headed bar couplers, (3) grouted sleeve couplers, (4) threaded couplers, and (5) swaged couplers. The principle investigator (PI) recently conducted a research funded by the US Depart of Transportation through the University Transportation Center - Accelerated Bridge Construction (ABC-UTC). A state-of-the-art literature review was conducted in this study to investigate the coupler performance as well as the performance of mechanically spliced columns. It was found that the available test data is not sufficient to conclusively comment on the suitability of couplers for precast column construction. A comprehensive testing schedule was recommended to investigate the coupler performance for ABC applications (Tazarv and Saiidi, 2015). (a) Shear Screw Coupler [ancon.co.uk] (b) Headed Bar Coupler [hrc-usa.com] (c) Grouted Sleeve Couplers [splicesleeve.com] [erico.com] [armaturis.com] (d) Threaded Coupler (e) Swaged Coupler [ancon.com.au] Figure 1. Mechanical Reinforcing Bar Splices Due to a lack of test data, the PI developed an analytical method to include the effect of mechanical bar couplers on the performance of precast bridge columns. A generic material model was proposed (Fig. 2) for all coupler types assuming that a portion of the coupler is rigid and does not contribute to the splice overall elongation is defined as the coupler rigid length factor. Therefore, for the same tensile force, the coupler region axial deformation will be lower resulting in a lower strain in the coupler region compared to the strain of the connecting reinforcing bar (Eq. 1) where Lcr is the length of the coupler region and Lsp is the coupler length. Overall, the stressstrain relationship for any type of mechanical bar splices can be determined by knowing only the coupler rigid length factor (). 3 (a) Coupler Region (b) Stress-Strain Model for Couplers Figure 2. Stress-Strain Model for Mechanical Bar Splices A comprehensive parametric study was carried out to investigate the coupler effect on the mechanically spliced bridge column displacement capacity. It was found that stiffer couplers closer to the column ends can reduce the column displacement capacity by 40% compared to the non-spliced conventional columns. Subsequently, a simple design equation was proposed to further aid the designers. Even though the study by Tazarv and Saiidi (2015) provided a better understanding of the coupler behavior and their effects on column performance, a comprehensive testing schedule is needed to establish the coupler behavior and to develop design guidelines for the field deployment of mechanically spliced precast bridge columns.

Language

  • English

Project

  • Status: Active
  • Funding: $285146
  • Contract Numbers:

    DTRT13-G-UTC38

  • Sponsor Organizations:

    Research and Innovative Technology Administration

    University Transportation Centers Program
    1200 New Jersey Avenue
    Washington, DC  United States  20590
  • Project Managers:

    Kline, Robin

  • Performing Organizations:

    South Dakota State University, Brookings

    Department of Civil and Environmental Engineering
    P.O. Box 2219
    Brookings, SD  United States  57007
  • Principal Investigators:

    Tazarv, Mostafa

    Wehbe, Nadim

  • Start Date: 20160505
  • Expected Completion Date: 20180731
  • Actual Completion Date: 0
  • Source Data: MPC-511

Subject/Index Terms

Filing Info

  • Accession Number: 01601169
  • Record Type: Research project
  • Source Agency: Mountain-Plains Consortium
  • Contract Numbers: DTRT13-G-UTC38
  • Files: UTC, RiP
  • Created Date: May 31 2016 11:10AM