It's incredible how well documented and rich of information is the article. I'm Italian and I could not find in any Italian newspapers all the information that I needed! It makes me aware of how poor is the information in my country!
https://www.ingenio-web.it/20966-il-crollo-del-ponte-morandi...
https://www.ingenio-web.it/20925-il-viadotto-sul-polcevera-e...
https://www.ingenio-web.it/20939-ing-camomilla-come-e-perche...
It's not a "straw", it is a "stay" in English.
Strallo is a term mutuated from boats, a sail boat has a mast (albero) that is kept vertical and strong by one or more sets of "stays" (stralli):
https://en.wikipedia.org/wiki/Stays_(nautical)
https://it.wikipedia.org/wiki/Strallo_(vela)
On the sail boat the function of the stay is "opposite" to that of a bridge stay, it is used to keep the mast pressed to the base and more rigid, on a bridge they are simply "suspension supports" allowing to carry the weight of the viaduct deck and transferring the vertical load to the tower or pylon (torre o antenna).
The best piece I've read about the disaster