I can clearly see your point, but is a pallet load of cobbles going to be that different a point load from a decent size planter? And even if the designed-in planters are small, surely you need to allow for some numpty coming along years later and replacing them?
If a single pallet or a change in planter made a difference, then there obviously would not be a large enough safety margin.
I was thinking along the lines that it is quite common to stack all deliveries in one spot, in order to leave the rest of the area clear for work. That could easily result in a temporary situation with many more tonnes of load in one spot than the roof truss under it was designed to take.
Colin Bignell
If you watch the video of the third collapse, a large area collapses at the same time for no apparent reason. There's nothing particularly heavy on to p. The trusses seem to have broken in the middle. The trusses rest on colum ns that are still in place. The bolts are missing but merely hold the truss es in place. During the collapse there are workers standing around who barely move.
It looks to me as though the trusses drop at the wall end first. My guess would be that the columns might have been pulled out of true by the earlier collapse and the trusses with them. Then, as everything cools at night, the trusses contracted and simply slipped off their supports at the wall end.
However, until somebody does an in depth investigation, it is all supposition and you can't really draw conclusions from the collapse of an already weakened structure.
That really is a rather important function. As already mentioned, it suggests that they were sheared off by the loads imposed.
Not much reason to if you know that nothing is coming your way.
Colin Bignell
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