Performance Evaluation of Recent Improvements of Bridge Abutments and Approach Backfill

The main objective of this study is to evaluate the performance of modifications that have been made in the design and construction of approach slabs in Iowa since 2005. This will aid in verifying the adequacy of the new design and construction procedures for approach slabs. Three sub-objectives have been identified to aid in the achievement of the overall objective as follows: (1) Assess the overall of performance of approach slabs constructed during the 2005 field trials along with other structures built to the current design under subsequent contracts. (2) Determine if settlement at the approach slabs selected for evaluation exists using nondestructive evaluation techniques including boroscope (cable snake camera) inspection, surveying, and ground penetrating radar (GPR) assessment. (3) Evaluate the condition of the approach slab, joint, and the end of the bridge structure for cracking and related distress, including evaluation of the bridge paving notch, approach pavement, roadway shoulder, abutment wings, abutment footing face under the bridge, sub-drain outlets for the abutment backfill drainage, berm slope erosion conditions, and joint type and condition. The following tasks have been identified to accomplish the objectives of this project: Task 1: Document and construction drawings review; Task 2: Field inspection of approach slabs and the end of bridge; and Task 3: Performance assessment and final report. In Task 1, Wiss, Janney, Elstner Associates, Incorporated (WJE) will review design and construction documents of the approach slabs of the bridges selected for field evaluation and compare them to the current design and construction practices. WJE will also conduct a limited review of other state departments of transportation (DOTs) practices for design and construction of approach slabs. WJE will utilize its internal library resources to identify pertinent technical papers, DOT-sponsored research reports, and National Cooperative Highway Research Program (NCHRP) projects for successful completion of this task. WJE maintains a current technical reference library, which includes two dedicated staff librarians and over 24,000 reference books, journals, and WJE report files to aid in the engineering practices of the company. The Library maintains contact with other specialized libraries (such as the Portland Cement Association Library) and academic libraries (such as Northwestern University Library) and is a participant in the worldwide inter-library loan system. WJE Librarians have access to online abstract services and engineering citation databases to thoroughly identify current articles related to transportation research. Task 2 will include field inspection and select testing of existing Iowa bridges with focus on the condition and performance of the approach slabs and the end of the bridge. The proposed scope for this work includes visual inspection, measuring approach slabs elevation with respect to bridge, nondestructive evaluation (boroscope and GPR assessment), and documentation of the condition of bridge paving notch, surfaces of the bridge approach pavement, roadway shoulder, abutment wings, abutment footing face under the bridge, sub-drain outlets for the abutment backfill drainage, berm slope erosion, and joint type and condition. The purpose of the inspections is to determine whether settlement of the approach slabs has occurred, inspect for evidence of the cause for the settlement, and determine the overall performance of the design and construction practices implemented for constructing approach slabs. WJE will use collected elevation measurements to determine the Bridge Approach Performance Index (BI). This will require the knowledge of the original profile of the selected approach slabs. The BI index can be used in conjunction with International Roughness Index (IRI) to assess the condition of the bridge approaches based on the rating system developed in the study sponsored by Iowa DOT between 2002 and 2005. WJE will not measure IRI but can include IRI results in the assessment if the results are available and provided by Iowa DOT. GPR testing will be conducted on each approach slab to assess abutment backfill settlement resulting in the presence of voiding beneath the approach. WJE has used this technique to identify voids under approach slabs during a previous project with Iowa DOT in western Iowa in 2011. The results of this project were reported to Iowa DOT in a report titled “Approach Slab Assessment - Full Testing Program Report” and dated November 2, 2011. For field documentation, WJE will utilize an in-house annotation program (Plannotate 2) that was developed specifically to annotate digital inspection data and photographs onto PDF’s using tablet computers. Inspection data may include the location of potential voids and settlement, observed distress conditions, dimensional information of distress, and photographs of inspected elements and observed conditions. The scope of work and associated budget assumes that inspections will be performed on each approach slab for up to four bridges. WJE assumes that any required traffic control will be provided by Iowa DOT. Task 3 will include synthesis of the results from the field inspection and document review tasks to evaluate the overall performance of approach slabs of the selected bridges. The findings of the study will help Iowa DOT to determine the adequacy of current design and construction practices of approach slabs or if further improvements could be made.


    • English


    • Status: Active
    • Contract Numbers:


    • Sponsor Organizations:

      Iowa Department of Transportation

      800 Lincoln Way
      Ames, IA  United States  50010
    • Managing Organizations:

      Wiss, Janney, Elstner Associates, Incorporated

      330 Pfingsten Road
      Northbrook, IL  United States  60062
    • Project Managers:

      Goetz, Vanessa

    • Performing Organizations:

      Wiss, Janney, Elstner Associates, Incorporated

      330 Pfingsten Road
      Northbrook, IL  United States  60062
    • Start Date: 20171201
    • Expected Completion Date: 20190228
    • Actual Completion Date: 0

    Subject/Index Terms

    Filing Info

    • Accession Number: 01652791
    • Record Type: Research project
    • Source Agency: Iowa Department of Transportation
    • Contract Numbers: TR-736
    • Files: RiP, STATEDOT
    • Created Date: Dec 1 2017 9:29AM