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Did I Uncover a $100M Mistake with the Millennium Tower “Fix”?
- db48x 4y agoI’m surprised that there are no prediction markets going on the Millennium Tower.
- rationalist 4y agoLong video, but I watched it until the advertisement at the end. I don't live anywhere near S.F. and my engineering background is limited (undergraduate degree, nothing professional), but I agree that the video author does have a valid and very important concern. It would've been a lot nicer if he shortened the video and if he showed his calculations for the steel bar that the all-thread is transferring the load to.
- ww520 4y agoWatched the video. It's very interesting. It has the background information on the sinking Millennium Tower and the pending remedy for it. It describes and analyzes the pending remedy in detail. It's worrying that the downward force is hinging on such a small steel plate. It looks like a disaster waiting to happen. It's also surprising very little calculation has been submitted by the engineering firm for the proposed remedy. The people involved seem amateur.
- hn_throwaway_99 4y agoInteresting to me is that the potential failure mode this engineer thinks is possible is actually very similar to what caused the Hyatt Regency walkway collapse, https://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse https://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse.
- dogsgobork 4y agoInterestingly it looks like the engineering firm that later identified the issue with the walkway is the engineering firm that designed the Millennium tower fix.
- ww520 4y agoThe same engineering firm that did the original design leading to the sinking.
- Georgelemental 4y agoTLDR (IANA engineer): The project to prevent the tower from sinking further, relies on four small steel plates that are supposed to bear a large amount of load. These plates are encased in concrete and therefore cannot be checked or maintained after installation. The video creator can't find any evidence that the project engineers calculated whether the plates can bear this load, and his own calculations suggests that they cannot.
- ww520 4y agoAlso the steel cable strength calculated in the submitted proposal exceeds the safety margin of the cable’s yield strength.
- imtringued 4y agoIt's not a steel cable. The idea is that the bolts are sacrificial components that stretch when the building sinks further and can be jacked back up to correct the sinking and these bolts need to be inspected and possibly replaced routinely. That in itself is not damning. The real question is how do they intend to inspect the threaded connection to the concrete? To avoid frequent inspections you would want to over engineer it so it lasts for hundreds of years even if the building will be torn down in 15 years but the steel bar is ridiculously undersized and should be considered sacrificial as well but it cannot be replaced nor inspected. What is really disappointing about this whole project is that nobody stopped and thought about building a model for dynamic and static load tests to prove that it works in reality. After all, this has never been done before on a building of this scale.
- YeBanKo 4y agoIirc steel rust was one of the factors contributing to the collapse of the Morandi Bridge in Italy. And because corroded elements were covered in concrete, could not be inspected with naked eye until concrete started cracking, which was too late.
- peterfarkas 4y agoI've read about this and it surprised me that concrete-encased steel could not be inspected in the case of the Morandi bridge. X-ray, or measuring how conductive it is should work.