fib BULLETIN NO. 110

Title:Management of post-tensioned bridges

State-of-the-art-report

Year: 2023

Pages: 129

Format approx. DIN A4 (210x297 mm)

ISBN: 978-2-88394-173-1

Abstract:

One of the big issues worrying the entire modern world is the increasing number of bridges in a bad or disrepair condition, which is arising the questions about the safety and reliability of our infrastructure in the upcoming years. Within the entire stock of bridges, the post-tensioned concrete bridges are a specific group, which require special attention. During their first, but at the same time numerous applications in the post-war period, the post-tensioning technology was only in a developing stage. Deficiencies of the technology of prestressing and grouting led to shortened service life of these bridges and in some cases even to their sudden collapses. Nowadays, many post-tensioned bridges built in the 1950s, 1960s, and 1970s are reaching the end of their service life, that is reflected in their reduced load-bearing capacity and necessity of adequate measures to be taken for their further safe operation. Massive reconstruction or complete rebuilding is unavoidable in many cases. 

Special problems also arise during inspection of post-tensioned bridges. If the tendons are not grouted, the corrosion occurring even at a small location along the tendon leads to a loss of prestressing force on the entire un-grouted section. Corrosion of un-grouted tendon is often invisible at first glance. The reason is, that there is enough space for corrosion products in the duct and thus the concrete cover layer, , being the most unmissable indicator of steel corrosion, does not fall off. Another reason is the fact, that the decrease in the prestressing force is not followed by significant deformations of the structure, even in advanced stages. For example, in the case of segmental precast girder bridges, which had some pre-camber at the time of assembly, small deflections will mean only the loss of the camber and the girders would seem to be straight even after significant loss of prestressing force. Cracks, that indicate a serious problem of deteriorating prestressing tendons, are often just of hairline width and visible only from a close distance. From all these points of view mentioned above, it is clear, that an extra attention should be paid to the post-tensioned bridges and especially to the segmental structures, during their inspection, diagnostics, and reconstruction.

This bulletin is expected to cover the current practices, risk assessments, inspections, investigations, and interventions in managing new and existing post-tensioned bridges to address their durability issues. If a problem is detected at an earlier stage, repairs can be made to maintain the intended service life of the structure.

Figuratively speaking, knowing your specific "patients" based on their "predisposition to their most common serious diseases", the possibilities and limits of their "diagnosis" and "treatment" is a basic prerequisite for being good "bridge doctors".

This bulletin should serve to bridge managers, designers, and contractors, as an overview of the current state-of-the-art in the field of post-tensioned concrete bridge management. To serve as a guide, when dealing with this type of deteriorated bridges.

Peter Paulík
Convener of fib Working Party 1.1.5 "Management of of prestressed concrete bridges"

Download the copyright page (= list of authors) as a PDF file. 

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