note to anyone trying to learn English as a second language - do NOT try to talk like this guy!

(he's great though, and the explanation is logical. we'll see what extra details come from it)

I'm a structural enginerd...I have years of prestressed concrete experience. I agree with this video. Post tension failure hit my brain as soon as I saw the video. Sudden loss of strength. PT concrete without PT = unreinforced concrete = sudden loss of strength = brittle failure. However, the PT cable could have been made of subpar materials. I once broke a #6 rebar with one hand in front of the Owner, inspector, and Contractor! Regardless, the PT rod was likely at yield when it was being tightened. As soon as it reached Fu...boom. What goes through the brains of the guys tightening a PT rod and notices the cable doesn't take load!

Last night they mentioned on the news that the plans were changed last minute, with the support columns moved an extra 12 ft apart. This should have triggered a full reexamination of the plans, but inexplicably they just went ahead without doing the math to see if it was safe.