damage to a home from a sonic boom

[charliealphabravo]

i have circumstantial indications from speaking with a homeowner that her house was damaged by an overpressure from an aircraft, including her statement that she was awakened from her sleep at 2:30 in the morning by a tremendous explosion that shook the entire house. she initially reported the damage as the result of blasting from mining operations and i understand that she was told by the fire marshall that it was most likely a sonic boom as there is a nearby military base. again this is circumstantial, but she indicated that she had testified recently against a private military group that wanted to set up next to the military base in the county.

the stucco on the exterior of the frame wall structure is bowed inward approximately 1 inch between the framing members over an area that is approximately 8' wide and 8' high. i have not destructively examined the wall framing but it is an older house and it appears that there may not be any sheathing under the stucco. a nearby glazing is not fractured but there are separations around the window frame on the interior.

i will decline to express my own opinons on the matter here since i will be issuing a report but i would appreciate any armchair observations or sources of information that you might recommend.

thanks in advance
cb

 

[dik]

I'd have to do some research on effects of sonic booms, but I've done reports on the effects of vibration from blasting as well as propane tank explosions.

The vibration may cause damage and it would be a matter of examining any brittle surfaces for cracking and using a 'pocket microscope' to review the actual crack for pristine cracking and the lack of inclusions in the crack. Samples can be taken for laboratory examination of the cracked surface. It's sometimes difficult to determine the age of a crack.

As far as the overpressure from the shock wave, I've found that much of the damage is attributed to the reflected 'tension' wave or partial vacuum created from the reflected compression wave. It is possibly this that has caused the stucco to be 'pulled off' if this is the situation. It is fairly easy to determine if there is a void behind the stucco that shouldn't be. Stucco is also a brittle material and any cracking can be viewed for recent damage.

Was there damage done to similarly constructed homes in the area. I understand that there can be a fairly sharp focus to the effects of a sonic 'boom'.

Ron mentioned that he was involved with forensics as well as stucco... he may be able to shed some additional light on this.

 

[hokie66]

Afraid an armchair opinion is all I can give. In the absence of preexisting evidence, I am always sceptical of homeowner's reports of this type damage.

 

[GregLocock]

I got the vague impression that cb tended towards that opinion.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Ron]

Dik made an excellent point...check the other homes in the area for indicative damage.

If the stucco was placed on lath with no sheathing, some bowing is expected. What you described is excessive, but not unprecedented. Destructive observation is necessary before you render an appropriate opinion.

The pressure wave from a sonic boom is going to spread out rapidly. It would affect more than a single structure assuming the structures are not widely spaced. I doubt the affect would be limited to an 8x8 area, and the effect rapidly diminishes with distance.

I suspect that the sonic boom or blast, whichever it was, just caused the homeowner to start looking for damage that was perhaps already there. Unfortunately, she heard hoofbeats and started looking for zebras. Don't get sucked into that, as hokie66 noted.

 

[JStephen]

There was an informative Mythbusters on the topic, which you might see if you can hunt up. The plane on it had to fly awfully low to do anything.

 

[rb1957]

doesn't "smell" particularly legit to me either ... surely if a house experienced significant effects from a sonic boom there'd be others ?? presumably the USAF (or whoever flies in the region) would be able to shed some light on this.

btw, what the heck is a "private military group" ? Blackstock ??

 

[SlideRuleEra]

Sonic boom by USAF aircraft, over land, are extremely rare thes days:

...Air Force procedures require that, whenever possible, flights be over open water, above 10,000 feet and no closer than 15 miles from shore. Supersonic operations over land must be conducted above 30,000 feet or, when below 30,000 feet, in specially designated areas approved by Headquarters United States Air Force, Washington, D.C., and the Federal Aviation Administration.

http://www.af.mil/information/factsheets/factsheet.asp?id=184

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[JStephen]

On the Mythbusters, they had to fly at 200' or so to actually break glass and stuff like that.

Generally, the effect was like a gust of wind, not so much like an explosion.

 

[jhoulette]

HA! I ran into a very similar situation a few years back. An elderly woman was woken from her afternoon nap by what she described was an earthquake. I know the air force flies over this area a lot and figured she was startled by a jet.
For my situation, there was no evidence of damage.

I had to check with neighbors to verify. Oddest report I ever had the pleasure of writing.

You mentioned she was sleeping, my only advice is to keep in mind she may have been dreaming. Ron and dik provided what you need to do as an engineer.



Jim Houlette PE
Web:

http://www.evstudio.us

Online Magazine:

http://www.evstudio.info

 

[dik]

JStephen... I've done load tests on glass panels and it's surprising how strong they can be. Winnipeg, used to be the only city I was aware of that had an actual code requirement about testing glazing and I think they have dropped that over the last 3 decades. I've heard sonic booms and not paid any attention to pressures but, they do make quite a noise. It's not so much the pressure but the reflected wave that often causes the damage. I have no idea of the flight path or altitude of the jet. I will take a gander and see what I can find about sonic booms... just tweaked my curiosity a bit.

Dik

 

[Ron]

CB..separations around the window frame probably don't mean much, other than sealant, paint, and framing shrinkage. If displacement had occurred as a result of the sound pressure wave, it would likely be more prominent. Further, it would likely have pushed the window inward since it was implicit in your description that the stucco bowed inward. A separation on the inside would not be indicative of inward movement. Not sure of the window type, but if it is an older structure with older wood-framed windows, they were probably nailed in place. Older window installation tended to be more robust than present window installations; however, in current windows, you most often have "fins" that prevent inward movement anyway.

In short, I doubt there is any damage from the sonic boom. Having investigated lots of similar "occupant complaints" over the years having to do with trains, thunder, compactors, vehicle traffic, and air traffic, I've found the observations of the occupants to be generally unreliable from an evidentiary perspective. They can't be discounted entirely; however, they must be validated against engineering probability, not possibility.

Another point that dik made was one of looking at the age of the cracks that occur in the stucco. New cracks can be discerned from older cracks as he noted. In one recent evaluation we did, the occupant was convinced that a cracked window resulted from train vibrations. We were able to show that paint embedded in the edge of the crack was from painting that had been done prior to the construction of the nearby side track.

 

[conceng]

Sounds a bit like the homeowner who told me the motor grader banging against the curb and the asphalt roller rolling off the trailer before paving operations caused a crack in his driveway that ran from the curb, up the driveway, through the garage, dropped to the lower level of the split-level house and shot out the back side of the house. The crack i the garage followed a straight line, and a small section of "zip-strip" was exposed in the crack that reportedly wasn't there before the asphalt paving. It also caused his windows to jack themselves 3/8" out of square/plumb. Miraculously, there was no sign of sheetrock distress. I ran away as fast as I could.

Greg