URIEng
Structural
- Jan 23, 2014
- 2
Hi all,
I have been doing a bit of work on Utility pole foundations and done a fair bit of research into other experiments that have been done, and I am looking with particular interest at the difference between experimental and actual performance. As part of this investigation it is obvious that the testing that has been done in the past gives extremely conservative results compared to observed performance against high wind loads. There are a few hypothetical reasons as to why this is the case;
[ul]
[li]The conductors and the flexibility of the pole cause a dampening effect on the wind load (a dissipation of energy), even under relatively long duration laminar wind loads.[/li]
[li]The soil performs like a viscoelastic material (think silly putty) and under the short duration loads the soil has a higher resistance (maybe even related to inertia) than what it does when tested even over 1-2 minutes. This means that the centre of rotation remains close to the surface, the pole embedment acts more like a long pile rather than a short pile, and hence the pole can recover the deflections and remain vertical.[/li]
[/ul]
This would appear to be similar for both cohesive and non-cohesive soils, and for drained and undrained conditions.
My question is, does anyone know of any studies, text books, FE modelling, in-house testing, ANYTHING, that has looked at this problem? Even other opinions would be of value at this stage. This is one of those things where reality doesn't meet current theory, and current theory would add a significant $ value to future projects.
Thanks!
I have been doing a bit of work on Utility pole foundations and done a fair bit of research into other experiments that have been done, and I am looking with particular interest at the difference between experimental and actual performance. As part of this investigation it is obvious that the testing that has been done in the past gives extremely conservative results compared to observed performance against high wind loads. There are a few hypothetical reasons as to why this is the case;
[ul]
[li]The conductors and the flexibility of the pole cause a dampening effect on the wind load (a dissipation of energy), even under relatively long duration laminar wind loads.[/li]
[li]The soil performs like a viscoelastic material (think silly putty) and under the short duration loads the soil has a higher resistance (maybe even related to inertia) than what it does when tested even over 1-2 minutes. This means that the centre of rotation remains close to the surface, the pole embedment acts more like a long pile rather than a short pile, and hence the pole can recover the deflections and remain vertical.[/li]
[/ul]
This would appear to be similar for both cohesive and non-cohesive soils, and for drained and undrained conditions.
My question is, does anyone know of any studies, text books, FE modelling, in-house testing, ANYTHING, that has looked at this problem? Even other opinions would be of value at this stage. This is one of those things where reality doesn't meet current theory, and current theory would add a significant $ value to future projects.
Thanks!