INSIDE THE DOT
South Dakota Department of Transportation
Tolerances for Placement of Tie Bars in Portland Cement Concrete Pavements
12/2/2013 - 11/30/2015
Tie bars are used in jointed portland cement concrete pavements to provide load transfer between longitudinal slabs and to prevent lane separation. Tie bars are located within the middle third of the pavement and span the longitudinal joint of two slabs. Tie bars are placed by staking or baskets prior to the placement of the concrete or during paving via automatic inserters. Inspection of South Dakota pavements after construction using ground penetrating radar (GPR) has revealed that many bars were misaligned or missing. More bars were reported missing or misaligned when automatic inserters were used. Many states, including South Dakota, have banned the use of automatic inserters based on a lack of confidence regarding the placement of tie bars. The long-term effect on the pavement from misaligned or missing bars is unknown, but it can be assumed that additional maintenance costs and reduced pavement life are both possible. While tie bars are considered necessary for long-lasting pavements, only a few states have set tolerances for placement. Specifications that have been established may lack engineering or economic basis, making it is impossible to know whether they are too lax or too stringent. Specifications may be unrealistically difficult to construct or verify. In the absence of an engineering or economic basis for the specifications, it is difficult to judge what corrective actions are warranted when they are not met.
1 Characterize specifications currently used regarding tie bar placement tolerances in PCCP.
2 Develop structural analysis of tie bars that provides a basis for design and placement tolerances.
3 Develop recommendations for tie bar placement tolerances based on current specifications.
1 Meet with the technical panel to review project scope and work plan.
2 Review literature regarding tie bar placement specifications.
3 Based on literature review develop a load testing test matrix and procedure for individual or group tie bar configurations.
4 Meet with technical panel to review test matrix and testing procedure.
5 With technical panel approval of the test matrix and testing procedure, construct appropriate specimens.
6 Perform structural load testing as described in the testing procedure approved by the technical panel.
7 Meet with technical panel to discuss load testing results and decide if any additional testing is needed.
8 Prepare a final report and executive summary of the research methodology, findings, conclusions, and recommendations.
9 Make an executive presentation to the SDDOT Research Review Board at the completion of the project.
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