Civil Engineering Reference
In-Depth Information
7
Instrumentation and monitoring
of structures
John P. Broomfield
Chapter 1
dealt with the different test methods available for assessing
corrosion-related properties of reinforced concrete. Many of the techniques
are applied with hand-held battery-operated equipment and a 'one off '
reading is taken. In some cases such as cover meter measurements, that
reading will not change. In others, such as concrete resistivity, corrosion
rate or corrosion potential (reference electrode potential) it will change as
aggressive agents in the environment move into the concrete and lead to or
accelerate corrosion.
We can define corrosion monitoring as collecting corrosion-related data on
a regular basis. In this chapter we will exclude strain gauge monitoring which
is adequately covered elsewhere in the literature, and cathodic protection
monitoring which is discussed in
Chapter 4
and its references.
Corrosion monitoring can be done on new or existing structures. Its
application to new structures requires forethought on the part of the designer,
a clear understanding of what is required, what sensors and monitoring
equipment is available and where to site sensors. Probe installation is relatively
straightforward and can be integrated with the construction process along with
power, signal and monitoring systems.
In existing structures corrosion monitoring may be by regular inspection
using the techniques described in
Chapter 1,
or by probes installed in the
concrete or on its surface. These will have wired or wireless connections to
monitoring equipment.
There are two major issues with corrosion monitoring:
1
What can be monitored?
2
What are the merits of monitoring?
We can monitor with a limited number of techniques. The main techniques
for structural monitoring are:
• Strain
• Crack/displacement
• Stress
