The accident involving a bridge under construction happened several days ago and I found a video of the actual collapse.

It also looks like this prestressed concrete bridge had no torsional strength and it was supported only at the ends at the time it fell. Also, it weighed over 900 tons which seems awfully heavy for just a pedestrian bridge. Seems the whole project was a catastrophe in the making -and it finally happened.

https://www.ntsb.gov/investigations/AccidentReports/Reports/HWY18MH009-investigative-update2.pdf

Although the evaluation is ongoing, the assessment has determined that errors were made in design of the northernmost nodal region of the 174-foot-long span, where two truss members were connected to the bridge deck. These design errors resulted in (1) overestimation of the capacity (resistance) of a critical section through the node comprised of diagonal member 11 and vertical member 12; and (2) apparent underestimation of the demand (load) on that same critical section. Additionally, the FHWA evaluation determined that the cracking observed in the node prior to the collapse is consistent with the identified errors. The investigation continues to examine the design, review, and construction processes as well as the actions taken once the cracking was observed

https://www.miamiherald.com/news/local/community/miami-dade/article221706575.html

 

I would love to see the failure analysis on this. Heads are going to roll.

 

Yep - Another structural failure (with injuries or fatalities) in a high rise building under construction.

That'll get the lawyers swarming like sharks.

 

Now that's what i call structural integrity
(for a garbage dump that is)

 

From the photos, it doesn't look like there's any diagonal bracing or shear wall to counteract horizontal forces such as earthquakes or a severe ind storm. .

 

How does a crane takes out the structure of a building, to begin with? I'm puzzled.

It is as if the entire structure is made out of toothpicks. For a concrete structure, the columns are too thin. The beams also seem to be nonexistent. The slabs are like paper.

Here is a good example how a concrete structure should be, and that is only for a three store building:
http://www.understandconstruction.com/uploads/1/7/0/2/17029032/9886678_orig.jpg

That means, a building that high should have 1m x 1m columns at its base, and beams with a depth of at least 60cm. The slab should be thicker than 20cm, with reinforcement where the columns and beams meet with it. Also, there should be cross-members present at the corners, besides the elevators and stair shafts serving as structural elements for horizontal forces. That is the way to do it!

Unfortunately, in the USA there isn't much experience with concrete building construction, and the builders are used to the lighter steel frame construction.

Kind regards, Samuel Lourenço

 

Actually, the U.S. has a lot of experience with reinforced concrete construction and here in San Francisco, I would estimate that about 70% of the buildings are concrete frame.

 

Actually, the U.S. has a lot of experience with reinforced concrete construction and here in San Francisco, I would estimate that about 70% of the buildings are concrete frame.

Hence the poor quality of that building. That project should have not been approved.

Unfortunately, the cancer of bad construction is spreading. I was astonished to see a steel frame building being constructed in Lisbon. That construction should be embargoed, demolished, and a solid concrete frame building with decent columns should be built there.

I don't like toothpick construction. Steel frame construction, as well as wood framed construction, doesn't have a place in Portugal. Only concrete frame should be allowed for houses and offices, and pre-fab should be only for warehouses and factories.

Kind regards, Samuel Lourenço