Conclusions

This thesis has combined the concepts of deformation monitoring with the survey techniques used for measuring high buildings and towers. By studying the structural engineering theory and external forces, the movement of towers can be determined with a greater certainty and accuracy.


I believe there is lot of scope for further research in this area that deals with measuring movements, minimising deformations and predicting the future behaviour of tower structures.

Typical magnitudes

The results from the study and experiments indicated the typical magnitudes of movements for towers and pole structures.

 

For a 3m high metal pole
Deflections and bending under wind loads can reach as high as 9mm.
Diurnal, seasonal and differential heating changes are around 1-3mm.

 

For a 50m tall tower
Wind deflections are about 100-300mm (from Light tower experiment).
Thermal expansion is 50mm but can reach up to 150-200mm for large temperature variations. (Johnston, 1964)
Building movements less than 25mm. (Arnold & Reitherman, 1982)

 

Recommendations

For the efficient monitoring of towers, the wind force acting on the structure must be calculated. This can be done by measuring wind deflections at different points along the length of the pole, or by performing wind tunnel tests for tall towers.

 

Also, the wind speed at the tower can greatly vary depending on topography i.e. in urban canyons surrounded by buildings. Therefore, the local wind speed must be determined using a precise wind gauge or weather station.

 

It is important to measure the ambient temperature as well as the surface temperature of the towers when determining the heat induced deformations. Since volumetric thermal expansion can be complex, it might be better to perform theoretical calculations and consult with material manufactures when selecting poles or masts for mounting antennas. Also, sensor based systems such as tiltmeters and inclinometers can be deployed in combination with other survey instruments to determine the critical structural deformations to a high degree of accuracy.