Lightning damage to concrete foundation

[peterkosmoski]

Does anyone know of a case where a lightning strike caused cracking to form in a concrete structure?

I am evaluating a claim where there are extensive cracks in the slab of a house that was recently struck by lightning. The residence has only a few damages to the cosmetic finish materials outside of the localized blast area, indicating a relatively low level of shock vibration to the structure from the blast.

Does anyone know of any papers or publications that address lightning damage to concrete structures?

 

[jraef]

No specific information, but I have witnessed this on a remote pump station. The ground wire was connected to a re-bar grid in the concrete slab. When lightning struck the pole and raveled down to the re-bar grid it apparantly vaporized the water that had been absorbed by the concrete and caused it to expand so fast that it pulverized the areas immediately surrounding the re-bar. You could clearly make out the grid pattern from the topside by the broken concrete, but there were no burn marks other than where the ground wire connector had been.

"Venditori de oleum-vipera non vigere excordis populi"

 

[BJC]

jraef
I've seen the same thing.
The water in the concete will vaporize with high currents. If you have water in between the strands of the cable it will alos flash to steam. It's a good ideal to install the ground cable with a short stub of sch 80 PVC. If it's raised off the floor a little it keeps water on the floor from running down between the strands. Some RTV inside the PVC will help.

 

[peterkosmoski]

How did the damaged concrete appear from the top? Was it a single crack above the rebar, or something else?

 

[Skogsgurra]

I think that this group can have some interesting information for you:

http://groups.yahoo.com/group/LightningProtection/

There was a series of postings just before Christmas where damage to sidewalks and pavements were shown. I didn't save them but if you join the group and ask a question, I'm sure that you will get valuable information.

 

[busbar]

 
Longshot archived 1970 IEEE reference …

http://www.ieee-pcic.org/archive/Fagan_Lee_Paper.PDF

 

[jraef]

peterkosmoski,
The concrete appeared as though someone had beaten it with a hammer from the under side. It was somewhat pulverized in chunks maybe the size of pea gravel and a little dust, plus the damaged area was tapered in towards the re-bars. It was also cracked in some areas where the bars were closer together. Unfortunately that was in the days before digital cameras so I can't offer a photo without spending 3 hours going through my boxes. It was very similar to this, although it was horizontal so the debis remained in the damaged area.

http://www.nctimes.com/articles/2004/03/06/news/inland/3_5_0422_22_28.txt

"Venditori de oleum-vipera non vigere excordis populi"

 

[jraef]

This is another example of what I observed. If you click through this presentation it shows other images as well.

http://www.srh.noaa.gov/lch/severe/ltg/ltg3.htm

"Venditori de oleum-vipera non vigere excordis populi"

 

[SlideRuleEra]

peterkosmoski crossposted the question over in the Structural Forum, here is what I have found

ftp://imgs.ebuild.com/woc/C840413.pdf

ftp://imgs.ebuild.com/woc/C710218.pdf

 

[advidana]

Is the concrete below or below the frost line. Cracks could be caused by buckling because of ground freezing.

 

[peterkosmoski]

Thanks for the feedback guys. It has helped a lot.