... if any of it is around in 10-15 years and hasn't all failed!
Jon had some pictures of failed columns from various parts of the world, and several things were of interest. All the examples he showed had suffered failure at or below ground level. In some cases the failure was corrosion, in others – an aluminium column – there was a fatigue crack around its circumference. An example from the UK had suffered a crack around 300mm below ground level which caused it to fail and fall across a busy road luckily causing no injuries – it was a 10m column. None of these columns appeared to be more than 20 years old. Perhaps it is modern columns which are designed to be more “crash friendly” compared to the over engineered columns of the 1950s which are the real issue?I have had an issue with making columns crash friendly - I fail to see the need when drunk drivers will find something to crash into: lamp post or not. What is the point in spending thousands of pounds designing (or for local authorities: installing) new crash safe columns that are designed to fail and have to be replaced (at more cost) when a vehicle crashes into them? and the most likely cause of these crashes will be people driving whilst intoxicated. Moving columns back from the road edge is fine, makes perfect sense. Installing ones designed to break? No, not in my book. Not when trees, street cabinets, buildings and telephone poles are dotted around and just as likely to be the target of a vehicle crash. And what about this: a car crashes into a crash-safe lamp post - the drunk driver is fine because the column and car absorbed the impact (and the alcohol has relaxed his body so it wasn't tense upon impact); but the column swings over in the opposite direction of the vehicle and lands on another car or a pedestrian... is that safe?
Unauthorised signage, hanging baskets and banners can all place additional loading on columns. Jon stated that banners are often the worst culprit with many banners generating more windage than the column and lantern combined. One council who wanted to put banners up on columns on a dual carriageway for the Olympics, were advised to have the columns tested for strength first. Several unsafe columns were found.I have actually heard about that one myself. Up here in York, lamp post banners are very rarely used... the most columns to have banners fitted were the Revo Festival columns which had double banners for Royal Ascot fitted (on the year the normal course was closed and the event moved here).
In another instance an electrician called to disconnect the service from an unsafe column found it was so structural weak that he refused to work under it. It was necessary to use a Hiab to support the column whilst the service was disconnected.I hope the HIAB removed the column immediately after it was disconnected!
The current trend for post top mounting of columns is also have an impact. In high winds, columns with post top mounted lanterns tend to oscillate with the movement being of small amplitude but high frequency. Columns with brackets tend to oscillate more slowly but with larger amplitudes. It is the frequency of oscillation that causes fatigue and it may require additional mass in the column or lantern to damp the oscillation.Ah, now we have a proper well-founded why boring-as-hell post top lantern/column combos should stop (other than looking incredibly boring and like massive golf clubs turned upside down and stuck into the ground!) - in that they can actually cause premature column failure. Since somebody from Amey was at the meeting, maybe he'll pass that info on and we'll see a return to proper streetlight installations!