DMRB CS 465 – Management of post-tensioned concrete bridges

Access free from the DMRB website. Also available from CIS.

Generally post-tensioned concrete bridges have given good service and few have had significant problems. However, tendons can be vulnerable to corrosion and severe deterioration where internal grouting of tendon ducts is incomplete and moist air, water and contaminants can enter the ducting system.

Experience has shown that construction practices and a lack of maintenance are of the greatest significance in affecting deterioration of post-tensioned concrete bridges. For most forms of concrete bridge construction, defects tend to be relatively easy to interpret and result in ductile modes of failure. Safety critical defects in post-tensioned concrete are typically hidden, very difficult to detect and may result in a brittle mode of failure. The primary problem with post-tensioned bridges which sets them apart from other types, is the difficulty in establishing the internal condition of the tendons because external signs of distress are not generally expected to occur.

For this reason the most vulnerable bridges need monitoring and reinspection after an appropriate interval, since the level of uncertainty about the condition of the post-tensioning system increases with time. Visual inspections alone may not give warning of imminent collapse; on the other hand, intrusive investigations can be expensive and potentially damaging for the structure and should only be carried out if there is a clear need.

This document details a process of risk review, risk assessment and risk management for post-tensioned concrete bridges to provide assurance on the safety of the stock of those bridges