3 ms·

I am no expert in this field, so: why are you so sure this is impossible? If I understand it correctly, a lightning strike to the (already slightly damaged) cab

by lqet 8y ago

I am no expert in this field, so: why are you so sure this is impossible? If I understand it correctly, a lightning strike to the (already slightly damaged) cable stays will seek its way through the steel cables, heating them up. If there is water between the cables and the concrete, a small steam explosion will occur. If the cables are already corroded (which they were, according to the article) and thus brittle, this may cause heavy damage to them. As the mentioned corrosion is indicative of water present, and since the cable stays are a single point of failure (also explained in the article), I personally find this a quite likely chain of events.

megous 8y ago
Presumably the bridge had a lightning protection system installed.
jaclaz 8y ago
Check a representation of one of the stays, here: https://static01.nyt.com/newsgraphics/2018/08/27/italy-bridge/0b40f75c7cf935f2ee7d76ff188d2d3a92f8c15f/cutaway-diagram-600.jpg https://static01.nyt.com/newsgraphics/2018/08/27/italy-bridg... Basically the concrete around the steel cables is nothing but a "protection box". From the little I know about explosions, the idea is that there is a sudden expansion from the inside to the outside. For having any damage to parts near the "core" there must be sufficient "containment", that the concrete simply cannot represent IMHO. The actual steel used for cables is high tensile and - believe me - extremely resistant besides rather hard while concrete (particularly concrete so ammalorated to let the water creep in) has very little tensile strength. So, IF actually there was a steam explosion, the result/effect would have been much more likely (besides "nothing") unscathed cables and ruined concrete around them (with no structural failure of the bridge) As an alternative to explosives it is common to use expanding cement grout in actual concrete demolition, which essentially is explosive on slow motion. When dealing with reinforced concrete you normally need to cut the rebars with a torch (or other means) after the concrete has cracked. Check (just an example this kind of cement originated in Japan in the '70's and now there are more similar products than stars in the sky): https://www.youtube.com/watch?v=7cvcnkzK8Jk https://www.youtube.com/watch?v=7cvcnkzK8Jk

by lqet 8y ago

megous 8y ago

Presumably the bridge had a lightning protection system installed.

jaclaz 8y ago

Check a representation of one of the stays, here: https://static01.nyt.com/newsgraphics/2018/08/27/italy-bridge/0b40f75c7cf935f2ee7d76ff188d2d3a92f8c15f/cutaway-diagram-600.jpg https://static01.nyt.com/newsgraphics/2018/08/27/italy-bridg... Basically the concrete around the steel cables is nothing but a "protection box". From the little I know about explosions, the idea is that there is a sudden expansion from the inside to the outside. For having any damage to parts near the "core" there must be sufficient "containment", that the concrete simply cannot represent IMHO. The actual steel used for cables is high tensile and - believe me - extremely resistant besides rather hard while concrete (particularly concrete so ammalorated to let the water creep in) has very little tensile strength. So, IF actually there was a steam explosion, the result/effect would have been much more likely (besides "nothing") unscathed cables and ruined concrete around them (with no structural failure of the bridge) As an alternative to explosives it is common to use expanding cement grout in actual concrete demolition, which essentially is explosive on slow motion. When dealing with reinforced concrete you normally need to cut the rebars with a torch (or other means) after the concrete has cracked. Check (just an example this kind of cement originated in Japan in the '70's and now there are more similar products than stars in the sky): https://www.youtube.com/watch?v=7cvcnkzK8Jk https://www.youtube.com/watch?v=7cvcnkzK8Jk