Estimating residual tension in PC steel using the surface strain methodDeterioration Diagnosis Technology
for PC Road Bridges

  • Infrastructure
  • Maintenance & Management

By measuring the surface strain and crack widths of PC (Prestressed Concrete) girders, it is possible to detect the behavior of cracks running perpendicular to the bridge axis when vehicles are driving over it and estimate the residual tension of the PC steel to determine the degree of deterioration and need for repairs.


*In October 2022, this service was featured in a performance catalogue of the Ministry of Land, Infrastructure, Transport, and Tourism.
Here is the website of MLIT.


*The catalogue is available from here.

Point

  • Compressive stress can be estimated without damaging the structure.
  • It is possible to check for aging deterioration of PC steel.
  • Cost is low due to the use of general-purpose measuring instruments and optical fiber.

Overview of Deterioration Diagnosis Technology
for PC Road Bridges

For prestressed concrete girders with cracks perpendicular to the bridge axis

Assuming that there are cracks running perpendicular to the length of the main girder (perpendicular to the bridge axis), these cracks are used to estimate the tensile force of the PC steel that is responsible for the compressive stress in the concrete.

The tensile force of the PC steel is estimated by measuring the movement of cracks that are normally closed when a relatively light-weight vehicle passes over the girder, but open when a heavier-weight vehicle such as a dump truck passes over it due to the tensile stress being greater than the remaining compressive stress.

With this method, compressive stress can be estimated repeatedly using the same crack without damaging the structure anew, and it is also possible to track the decrease in tensile force of PC steel over time, or in other words, to check for aging deterioration.

  • Measurement using strain gauge and pi-shaped displacement gauge

  • Measurement using optical fiber and strain gauge

Features of Deterioration Diagnosis Technology for PC Road Bridges

  • Low cost (using general-purpose measuring instruments)
    *Actual cost varies depending on conditions.
  • Proven high accuracy
  • Nondestructive testing method
    *Using cracks at right angles to the bridge
  • Possible to repeat measurements at the same location
  • Possible to monitor changes in tension over time