Handbook for Bridge Inspections - TSP2

Purpose
Procedures
7.3.7 Inspection of Prestressed Tendons
To conduct an inspection of the condition of pre-tensioned and
post-tensioned cabl es anchored in concrete. Checking pre-tensioned
cables may be worthwhile if defective injection is suspected,
as this can have very serious consequences for the bridge's load
bearing capacity.
Checking post-tensioned cables is difficu lt and should only be carried
out by a specialist company using special equipment, and then
only after consulting the bridge's designers.
Ultrasound, X-rays or a fibre optic endoscope can be used to locate
damage. The use of a fibre optic endoscope requires holes to be
drilled in the cable tubes. One should, therefore, have a clear
understanding of where the cavities and the damage arc located, as
drilling incorrectly and damaging a tension cabl e can have serious
consequences.
Scope
Acceptance Inspections and Major Inspections
Tension cables are not normally checked.
Special Inspections
A tension cable check wi ll be undertaken as required, fo r example
when badly executed injection of the cable tubes is suspected.
Fig1lrc 7.3-/1
Fib.·c Optic Testiflg
of a Tel/siollcd Cable
Advantages and
Disadvantages
Equipment
Purpose
A good overview can be obtained of the conditions inside a cable
tube, but the method is destructive and it is all too easy to hit the
cable tube or the cavit ies. In addition there is a risk of damaging
the cable itself.
To be decided for each specific occasion.
7.3.8 Cutting open the Concrete to Assess the
Corrosion level
To carry out a visual check of the level of corrosion in the reinforcement
and to record the type of reinforcement and its diameter.
Additional ly, the cover should be measured.