Title: Explosion Proofing

(SFX: explosions)

     UNTIL THE OKLAHOMA BOMBING, AMERICANS WERE LUCKY NOT TO HAVE TO
WORRY ABOUT EXPLOSIONS IN THEIR OWN COUNTRY.  SCIENTISTS, ON THE OTHER HAND,
HAVE BEEN THINKING ABOUT IT FOR YEARS.  THE US ARMY, FOR EXAMPLE, HAS A WHOLE
BRANCH OF CIVIL ENGINEERING DEDICATED TO MAKING BUILDINGS EXPLOSIVE SAFE. 
ONE SCIENTIST WHO'S STUDIED EVERYTHING FROM DAMS TO HELICOPTERS,  IS ENGINEER
AVI SINGHAL AT ARIZONA STATE UNIVERSITY. 

     Singhal: "The destruction of the building is very much a phenomena of how the
buildings is constructed, what is the shape of the buildings, . . .and also how the
individual parts of the building are put together." 

     UNLIKE A HURRICANE WHICH DOES DAMAGE SINCE IT BLOWS SO HARD ON A
BUILDING, A BOMB BOTH BLOWS AND SUCKS.  AS THE FORCE OF THE BOMB WHISTLES PAST
A WALL IT LEAVES A VACUUM THAT SUCKS AIR BACK IN.  SO A WALL EXPERIENCES TWO
EXTREMES OF PRESSURE WITHIN MILLISECONDS. SO THE FIRST STEP IN BUILDING A BOMB-PROOF BUILDING IS TO FIND A MATERIAL THAT CAN WITHSTAND BOTH BEING
COMPRESSED AND BEING STRETCHED.  MOST MATERIALS CAN'T DO BOTH, SAYS SINGHAL,
SO YOU HAVE TO COMBINE THEM. 

     Singhal: "Concrete is very weak in tension, steel is very good in tension, concrete is
very good in compression and by marrying concrete and steel you make the reinforced
concrete strong both in compression and in tension. "

     SIMPLY REINFORCING CONCRETE IS  NOT GOING TO SAVE A WHOLE BUILDING, BUT
IT WILL HELP KEEP SOME OF THE WALLS STANDING WHICH PROTECTS PEOPLE, AND MAKES
FOR EASIER RECONSTRUCTION.  SINGHAL IS NOW WORKING ON A VARIETY OF OTHER
TECHNIQUES TO KEEP OUR BUILDING'S SAFE.