Performance of Existing ABC Projects: Inspection Case Studies

Link to Latest Report: September 2019 Progress Report

Background:

Accelerated Bridge Construction (ABC) employs prefabricated bridge elements moved to the bridge location and installed in place. Accordingly, ABC reduces many uncertainties associated with construction processes and performance during service life. It also improves the life cycle cost by reducing construction time and traffic interruptions, better control over schedule, and normally by the higher quality of elements resulting in better life-cycle performance. Nevertheless, prefabricated elements need to be made continuous using cast-in-place joints. ABC “closure joints” connecting deck elements to each other and to the bridge girders have greater exposure to degrading environmental effects, and often there is more focus on their evaluation. These joints, expected to become serviceable quickly can therefore be viewed as critical elements of the ABC bridges. Instances of defective (leaky) joints have been reported, and concerns have been raised about the long-term durability of the joints. The long-term deflections and environmental loading can only exacerbate this situation. These may overshadow the many advantages of ABC specifically as life-cycle performance and costs are concerned. Hence, there have been questions on the long-term performance of ABC bridges. There have been limited investigations by some states to monitor the ABC bridges for determining their performance. ABC-UTC, through a collaborative effort by partner universities, is planning to embark on a coordinated and extensive inspection program to inspect several bridges in various states.  The inspection protocol will be prepared by ISU, and all five partner universities will inspect a minimum of two bridges in their respective state.  The results will be compiled and published on ABC-UTC website and will become available to outside users and researchers.

Objective:

The primary objective of this project is to collect much needed information on performance of two in-service ABC bridges. This will help the designers and owners to avoid problematic details or seek means to improve the performance.  The inspection protocol will be developed by ISU to facilitate for a consistent data collection among all partner universities.  However, it is envisioned that inspection will include routine visual inspection, special inspection of certain details, and application off NDT methods wherever needed.  The results will be compiled in a format for effective recording and will be reported accordingly.

Scope:
An overview of the study tasks is given below.

  • Task 1 –   Communicate with other Universities for establishment of test protocol
    • The research team will communicate and exchange information for development of an effective inspection protocol by the lead university. This tasks should also generate the inspection forms to be used during site inspection activity.
  • Task 2 – Identify the bridges to be inspected
    • Through communication and coordination with the State DOT officials, two ABC bridges will be selected that are more representative of typical state ABC bridges in regards with age, type, geometry, and traffic and environmental factors.
  • Task 3 – Perform inspection
    • A team consisting of PI, Co-PI and research assistance will travel to bridge location to perform the inspection.
  • Task 4 – Compilation of results and reporting
    • The results and findings of the inspection will be reported in a manner consistent with testing protocol agreed with other partner universities.

Research Team:
Principal Investigator:  Dr. Armin Mehrabi
Co-Principal Investigator: Dr. David Garber
Research Assistant:  To be determined