A typical temporary installation is shown here. Transducers in place monitoring strain during a load test on a section of crosshead removed from a concrete flyover. The crack formed as a result of loading may be seen running left to right.

When the integrity of a structure is in doubt, instrumentation offers the opportunity to understand its behaviour and clarify the need for strengthening/repair or whether the structure is indeed perfectly competent. Compared to the high cost and disruption caused by repair, structural monitoring can result in large savings to building/structure owners. Instrumentation can be applied to monitor most parameters, including the following:-

1. Linear Displacement/strain - A variety of transducers are used, with a resolution as fine as 1 micron (A human hair is typically 70 microns thick). Non contact methods are also available.
2. Angular displacement - The use of electrolevels is particularly recommended, as currently installed in the leaning tower of Pisa. These instruments are sensitive enough to detect changes in gravitational pull from the moon.
3. Vibration/Acceleration - Piezoelectric and strain gauge accelerometers for monitoring vibration in structures/mechanisms.
4. Level - Water levels used for simplicity in monitoring sag, subsidence etc.
5. Stress/Load/pressure - Load cells and pressure transducers using strain gauge and vibrating wire technology.
6. Bend sensors - Using fibre optic technology.
7. Other - A large range of transducers are available, please ask for details.

For new build projects, instrumentation may be embedded into the structure, enabling theoretical values to be confirmed with real values.
Having decided upon the parameters to measure, a choice of monitoring techniques is available:-

A choice of format for results enables clear understanding of patterns of measurement changes and hence possible causes. Examples of graphical and animated formats are shown below;