Are cranes designed to be operated like that? I really have no idea. But my mental image of a wrecking ball is the crane being fixed and the ball being drawn backwards and then released to swing in an arc... picking up a lot more velocity in the progress.
We had a similar structure at our old facility; a rock-solid RC core with a building built around it. The rest of the building was a breeze, but the core took weeks of bashing with a wrecking ball before it came down. We were testing our infrared imager, and we could see bright flashes in the midwave infrared when the ball hit the concrete.
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!
Yes, cranes (especially the old crawlers) are made to do that. I'm guessing that there must be some kind of site constraint, as that's an odd motion for a wrecking ball. If not using the secondary hoist to pull the wrecking ball back (as you described), I would have envisioned rotating the crane "side to side" to get the ball moving, instead of "boom up, boom down".
And having read thebard3's post (nothing else in the area), I have no idea why they are tap-tap-tapping the ball like that. Must really be fans of Happy Gilmore...
Looks like they’ve seen our feedback and have switched to side to side. Though it seems like they are hoping to shake it enough that the whole thing just tips over.
Any idea what the solid jet of black liquid that spewed from the top of the core for a good 10-15 seconds after the collapse was?
It looks like they're still only moving the boom up and down, almost as if they're trying to use the wreaking ball to snag a member of the structural framework and somehow pull it over.
The use of the crane in that way requires only a single crane operator to manage the wrecking ball, and only requires a relatively standard crane.
Note that reinforced concrete is strongest in compression, which will be most of the impacts. They have to plan out the impacts to force the concrete into tension.
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!
Long ago, my employer had a crane with wrecking ball.
Mostly, they used that wrecking ball with trackhoes, busting up ground-level concrete.
Swinging side to side with the crane is fine, unless you miss the target, as that wrecking ball swings out but also swings back. (Loads swinging too far from a crane is not good, wrecking balls hitting the boom is not good!)
Dropping the wrecking ball sounds good. But the way it worked, if you just dropped it and that's all you did, it would spool out a bunch of cable that would then get tangled. So you had to engage a brake immediately after it hit to keep that from happening. And if you engaged that brake a 1/10 of a second too soon, you snagged yourself a wrecking ball prior to hitting the target, which was hard on both crane and operator.
Anyway, the whole premise sounds simple and looks simple in the cartoons but wasn't that easy to do in practice.
I expect most crane operators have never used a wrecking ball to any extent, either.
I have absolutely no knowledge of demo operations. That being said;
After 7 days, why are they not placing more blasting charges at the base? What is hitting the top of it, with an apparent undersized ball, supposed to accomplish? Are they just trying to "shave" off layers until it's gone?
SuperSalad
I'm sure it's not safe to be working in or near the building until it's on the ground. The crane/ball allows them to demolish it from a distance.
