Handbook for Bridge Inspections - TSP2

The Development o f
Damage
It is important to fully realise the relationship between primary and
secondary damage when both evaluating the damage and decidi ng
the type ofrepair(s).ln most cases primary damage has to be
detennined before any remedial action can be taken. Repai rs deduced
from secondary damage are rarely successful.
5.4.2 The Extent to which Damage has
Developed
It is usually easy to come to a concl usion about serious damage
which has already reduced carrying capac ity or traffic safety when
remedial measures require to be speedil y set in motion.
Measu rements/Materials
Testing
The Co urse of Development
of Specific Damage
On the other hand it is more difficult to evaluate damage which is
sti ll developing. In such instances it is important to produce a
detailed overview of the following circumstances:
I. How long has it taken for the damage noted to develop?
2. How quick is the probability that it will continue developing in
the future?
Observations recorded during previous inspections wi ll be valuable
in connection with assessing how quickly an incidence of
damage has been developing.
In order to assist in assessing the development of damage measurements
and materials testing can additionally undertaken. As an
example, levelling can be employed in recording the development
of settlement, whilst measuring the depth of carbonisation and
chl oride content over a period can be used in evaluating the ri sk of
the re inforcement corroding in the fut ure.
In addition to practical experience theoretical models exist for
assessing the speed at which carbonisation and chlorides are spreading
when it comes to Slating how quick ly specific damage will
continue to develop.
When evaluating the speed of damage destruction one should particu
larly note that different kinds of damage take different courses:
• No development
• Decl ining course of development
• Steady pace of development
• Accelerating pace of development
No Development
Figure 5.4-1 ill ustrates these points. The following sub-secti ons
provide more detailed descriptions of the different courses of
development.
An exampl e could be spalling due to traffic impact. This can arise
quite suddenl y, yet does not develop any further. The damage is
either so immaterial that no action need be taken or so serious that
immediate measures are required. One should, however, real ise
that minor damage to concrete and steel due to traffic impact that
is not repaired in the long run can later lead to secondary damage
such as corrosion.