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Bridges & Special Structures Design

Underbridge inspection units (UBIUs) that reach from above deck to below.
Department of Transportation

Bridges & Special Structures Design

Repair of Bridge Deck Fascias


Project Number: SPR-1730

Contract Number: 2019-0314 Z3

Status: Complete

Start Date: 10/01/2021

End Date 09/30/2023

Summary:

The relatively high supply of moisture in bridge deck fascias often causes them to deteriorate more quickly than other portions of the bridge. This causes the fascia concrete to become debonded from the reinforcement and fall, posing a safety hazard to traffic or pedestrians beneath the bridge. A related concern is that the deterioration of the connection between the barrier and deck may significantly degrade the crashworthiness of the barrier, thus undermining its main function. A literature review, nationwide survey, and several examinations of bridges in Michigan that exhibit bridge deck fascia deterioration were conducted with the goal of determining the cause of the deterioration. Alternative repair details were developed. The repair details were divided into two categories: 1) restoration of original geometry and strength, and 2) maintain current geometry and prevent further deterioration. The restoration of original geometry and strength requires drilling and epoxying dowels and using a repair cementitious material. Small-scale and large-scale testing was conducted with the goal of evaluating the proposed repair detail for restoring the original geometry and strength. A computer program called MDOT Barrier was developed to evaluate the crashworthiness of bridge barriers that feature deck fascia deterioration and to determine whether intervention is required. Guidelines for designing and detailing future repair details and new barrier to deck overhang connections were developed. A special provision for the repair of bridge deck fascia and an implementation plan was prepared. It was determined that the main cause of deck fascia deterioration was the excessive amount of moisture which led to reinforcement corrosion and freeze-thaw deterioration. Several alternative details aimed at reducing the moisture content in the deck fascia were developed for new bridges. For cases, when a repair is required, two repair concrete materials combined with epoxy coated dowels, which are drilled and epoxied into the existing deck were proposed: 1) a self-consolidating concrete mix, and 2) a fiber reinforced self-consolidating concrete mix. The proposed repair details were proved viable through small-scale and large-scale testing. Small-scale testing included tests for: 1) material characterization; 2) relative material durability; and 3) strength of the repair concrete host concrete interface to direct shear. The FRSCC was deemed as the most appropriate mixture as it possesses self-consolidating properties, and good initial and sustained tensile strength. The proposed repair detail was evaluated at full scale using barrier deck subassemblies. A total of three tests were conducted. Both selected repair concrete materials were able to provide the equivalent of TL-4 level crashworthiness. It was demonstrated that both hooked and straight rebars in the deck overhang were able to transfer forces form the barrier to the deck during vehicle impact.

 

Publications:

  • Final Report
  •