Another crane collapse

I think another article said it was due to high winds.

https://www.constructionenquirer.com/2020/07/08/man-seriously-injured-in-london-crane-collapse/

Damn

What is strange to me is that it tipped off the base concrete as if it was free standing on them without either being bolted down or base counterweight added. All four pads are setting there in place. Only 22 meters high so a little fellow compared to most. I'm sure the jib was the same length as the tower so in set on the ground when folded. Only made it a day since erection.

All the base ballast fell off. There’s one photo where you can see the base ballast laying on the ground. They had it sitting on poured pads. The rear pad sunk and it went over.

Still sad, would think more considerations for safety would rule these days, nothing left to chance.

This guy does a pretty good explanation of what happened with this crane.

Cannot imagine NOT anchoring these to a footing or hard mounts, the base pad at the ballast pile is shattered as if had NO substantial support under it.

Around here they all go on piers. Even self erecting. That being said we’ve have to go back and drill a new set of crane piers after the mud failed at 500 psi!!! No excuse for that failure. Even a 1/2” of settling in one corner translates to a serious list that high up.

Have dug a lot of crane pads and lately the small foot print low impact style based seems to be more popular mainly cause it's cheap

The last one I dug had 2 4 foot by 6 foot by 3 feet thick base footings witch I thought was way under what should be but what really surprised me was the amount of ballast blocks they stacked on the bottom that were not doweled together just sitting there the kicker was I hammered the footings out twice to re dig because of one bad plans from engineers and 2 wrong batch was poured anything can happen these days

The crane had a max of 4500 lbs it couldn't even pick a bundle of rebar off a trailer in the street

The only reason to bolt one down if it’s free is to keep the pads from sliding. The are supposed to have something against the feet to keep the whole crane from twisting. But it’s not to hold the crane down.

A tower crane with an empty hook is pretty back heavy. The crane is designed to always have the counterweights facing the wind, if the mast goes out of level at all the crane won’t weathervane properly.(Counterweight are always gonna be on the low side) So instead of the wind pushing the mast the opposite direction of the Weights, the weights are pulling and the wind can be pushing in the same direction. At the point your ground-bearing pressure is way more then it was ever meant to be. So even if the pad was sufficient it’s now overloaded.

Just to clarify counterweights go on the counterJib up top. The weights on the bottom are ballast. Most cranes don’t require the ballast be fixed to the base. A lot of them are just free standing. The ballast is meant to hold the base down instead of the traditional method Of anchoring the base in 8ft of cement. It’s a cheaper method. Now instead of pouring all the ballast into the ground and anchoring The mast, we can pour a pad to support the weight of the crane and use the same ballast multiple times.

From the final resting position, it definitely look like it fell backward over and not forward...

Here's another guy theorizing:
I am actually surprised to also learn that this crane does not use extensive deep foundation attachment but rather just a lot more depending on balance.

kinda sad to see another failed deadly crane accident.