The photographs opposite show an example of a non destructive test being set up on a concrete beam supporting a motorway using electro-levels (ELs) precise tilt sensors.

In essence the ELs are fitted to various elements of a structure to monitor rotations during the application of known loads, bending moments calculated from the data allowed the integrity of the beam to be assessed.

The CMCS instrumentation systems including loggers and software are based on extensive testing carried out by G Price and I F Wardle while at the Building Research Establishment.

The top photograph shows a modern CMCS electro-level system being fitted on the under-side of concrete beams supporting the elevated section of Harrow Road (Paddington), before the spalling concrete was removed and later replaced.

The plot opposite shows the deflected profile of the beam under the known axial weight of a lorry, albeit only 0.06 mm at the centre.

Similarly rotations on elements on offshore structures have been monitored by electro-levels to determine bending moments in the piles and the degree of fixity between the piles and the deck and between the piles and the soil. The latter involved divers to fit the Els below the water line.

After extensive testing the systems have been used successfully on a number of 'off shore' and 'on shore' structures over the past 20 years, allowing certificates of safe loading to be issued, by comparing the monitored performance to theoretical performance based on .