By Jacob Silverman, HowStuffWorks.com
Calling a building "blastproof" can be misleading. Some bomb blasts could take out even the most secured structure, but it is possible to make buildings highly resistant to conventional bomb attacks. Frequently these same security measures increase a building's chances of getting through a hurricane or other natural disaster unscathed. And since the 1995 bombing of the Alfred P. Murrah Federal Building and the 9/11 attacks, engineers and public safety officials have come a long way in the science of blastproofing, employing remarkable designs that make buildings safer without sacrificing comfort or aesthetics.
Superstrong Wallpaper and Other Innovations
While blastproofing a building depends largely on safety features engineered into a building's designs, some new innovations in the field can be added later to help retrofit a building. Look no farther than superstrong wallpaper — we're not kidding. The X-Flex Blast Protection System, developed in part by the U.S. Army Corps of Engineers and the Berry Plastics Corporation, is a strong, highly flexible wallpaper that you can adhesively apply to walls. In tests, brick and stone walls stood up well to the impact of a wrecking ball. The wallpaper soon may find a home in some U.S. military bases overseas.
In a bombing attack, shrapnel and flying glass are major causes of injury. In response, some researchers have turned their attention to developing blastproof curtains that hang over windows and prevent glass from being blown into a building during an attack. One such curtain uses a fabric only a few millimeters thick, known as an auxetic material, that actually gets thicker when stretched. That unique ability allows the fabric to better absorb the impact of a blast and even to push back against incoming debris.
In some buildings, such as the tower at 7 World Trade Center (WTC), which was the first building to be rebuilt after 9/11, engineers have focused on the glass itself. Tower 7 uses incredibly strong glass that's been laminated, meaning that, should it break, it won't shatter. Instead, it'll stay in place, with the familiar spiderweb cracking pattern you might've seen in shatterproof glass.
Protecting One World Trade Center
The new One World Trade Center, or Tower 1, will be a model of blastproofing, learning from the past by way of both the devastating attacks of 9/11 and the 1993 bombing that failed to topple the towers, as well as absorbing the newer design features of Tower 7. A few of the new building's features are elegantly simple, like redesigning the building's base as a square (rather than the proposed parallelogram shape) in order to move it farther away from the nearby roadway. A large plaza was also added for the same reason. And whereas the original towers' structural backbones were their steel shells, the new tower will use a tremendous amount of concrete to create core walls that make for an overall stronger building, particularly at its center.
The first 20 stories of Tower 1 will be a concrete bunker — a section also referred to as the podium — supported by 20 massive steel columns, the heaviest of which weigh 78 tons. Concrete also will reinforce the elevator shafts on all sides and levels of the tower. The concrete in the building's foundation will be able to withstand pressures of up to 14,000 pounds per square inch — more than three times the strength of that found in many New York skyscrapers.
Walking into the lobby of Tower 1, visitors won't notice some of the new blastproofing measures. For example, the glass may appear normal, but it'll actually be the strongest glass available, tempered and laminated, and it'll also be flexible, capable of fending off flying debris. Similarly, the lobby's faÃ§ade will be designed, in the event of a blast, to bow in, making it capable of absorbing more energy. Finally, a blast wall behind the front desk will be disguised as a work of art. (Another blast wall outside the building will also be adorned with art.)
Besides increasing the building's strength, designers and security experts paid particular attention to making the building highly resistant to fire. The air filtration system will include special filters in case of biological or chemical attack. And finally, the evacuation system — from the width of stairwells, to the speed of elevators, to access points for emergency personnel — has been tremendously improved, ensuring that, in the event of the worst, people and personnel get where they need to go quickly and safely.
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