Impact Shock Waves (by Explosion) on Building Structures

[shakeelahsan]

Dear All,

There was an explosion in Lahore this morning and we were called in to evaluate structural strength of one of our client's Building (RCC structure)amid the situation. The building was within 2 Km from explosion site and has observed minute cracks in architectural finishes, building being an old RCC Structure, however did not face any structural cracks. What is an overall impact of such shock waves on building structures?

Engr. Shakeel Ahsan
Director Engineering
CMEC - Pakistan

 

[dik]

It can vary greatly depending on the explosion and proximity. You should also be concerned about the reflected shock wave.

I did a report in Winnipeg many years ago about a propane tank explosion on a multistorey curtain wall. The suction from the reflected force did greater damage. Anchorages were pulled out of the aluminum extrusions for the curtain wall.

Dik

 

[JStructsteel]

I wouldnt think that the shockwave is similar to an earthquake. I wouldnt think you would see any blast pressure at 2K, but maybe I am wrong. How big was the explosion?

 

[shakeelahsan]

Some 500 Kg exploded in a vehicle.

Dik, can I get your report?

Engr. Shakeel Ahsan
Director Engineering
CMEC - Pakistan

 

[cvg]

As reported by AP - "An area nearly the size of a city block was destroyed, with cars on the street left mangled and bricks strewn dozens of yards (meters) in all directions. A crater several (yards) meters in diameter, several feet deep and fringed by the cracked roadway marked the exact spot of the blast, which Bhutta said was caused by 220 pounds (100 kilograms) of explosive."

http://news.yahoo.com/s/ap/20090527/ap_on_re_as/as_pakistan

 

[IRstuff]

You appear tobe saying that the windows were intact, so it's unlikely that the damage was caused by the acoustic shockwave. More likely, it's due to your building foundations and the material it sits on, and the Earth's crust between you and the blast. Soil composition can result in magnification of the ground shock wave.

The US FEMA has a bunch of handbooks regarding terrorist attacks and resistant building design:

http://www.fema.gov/plan/prevent/rms/

TTFN

FAQ731-376

 

[dik]

I'll check with my client, but it's very unlikely.

Dik

 

[Lutfi]

Shakeel,

I did a quick pressure and impulse calculation using a charge of very close to your quoted weight (however, since I do not know what type of explosive it was) therefore, I assumed it to be TNT. Based on my output, here is what you will get at 90 degrees:

Range Shock-Velocity Time of arrival Pressure Impulse Load Duration
Feet FPMsec Msec PSI PSI-msec Msec
1.7 23.06 0.08 8037.28 3298.82 0.82

1000 1.12 819.17 0.34 8.9 51.34





Regards,
Lutfi