Where were you on 9/11?

Sunday, September 11th, 2011, marks the 10th anniversary of 9/11, one of the darkest days in American history. In respect of the occasion, the major comic syndicates have rallied their cartoonists to dedicate their strips on that Sunday to pay homage to those who lost their lives or were injured in the 9/11 terrorist attacks. All of the nearly 100 participating strips, many of which appear on Sunday newspaper editions in color in their own special pullout section, will have an overarching September 11th remembrance theme.

Local_Historian wrote: Husband's seminar ended a day early, but he was stuck, so we started making plans to go get him, when his best friend came to the house, asked for the keys, and drove out to get him. They were home in a bit over 30 hours - literally a non stop drive out, time for a shower and food, and they got in the car and came back. Here's how the friend put it - he had a serious craving for a realy Philly cheese steak sandwich, so he was of a mind to go get one - could he borrow the car for a couple days? They still call it the Philly Cheese Steak Run.

Even veteran disaster investigators were stunned by the fall of the Twin Towers on September 11, 2001. The next thoughts of the researchers who probed the calamity, aside from outrage, were how and why it happened from an engineering perspective. Why did WTC 1 stand nearly twice as long as WTC 2 after the impact of the aircraft? How could World Trade Center Building 7, which a plane did not hit, stand for seven hours and then collapse? And could such building failures occur elsewhere? Answers to all these questions have not only solved mysteries but also have led to changes in international building codes that may help prevent future tragedies.

the team of more than 200 investigators gathered all the evidence they could to reconstruct the situation the buildings faced before and after the catastrophe. They analyzed 236 pieces of steel obtained from the wreckage, representing all grades of steel used in the buildings and including several pieces impacted by the aircraft or affected by fire. They obtained some 7,000 photographs and roughly 7,000 video segments totaling in excess of 150 hours from the media, public agencies and individual photographers. They compiled and reviewed tens of thousands of pages of documents and interviewed more than 1,000 people who had been on the scene or had been involved with the design, construction and maintenance of the buildings. They conducted lab tests involving large fires and the heating of structural components.

The investigators then developed computer models of how each tower was damaged upon impact, how the jet fuel dispersed, how the fires evolved across each floor, how the structures heated and how they ultimately failed. These simulations of the structures and the physical properties of their materials were extraordinarily complex, with the aircraft impact analysis requiring computations "that were accurate over microseconds," Sunder recalls. At times, researchers had to invent new modeling capabilities to get the simulations to work, such as mapping of fire-generated environmental temperatures onto the structural components of the buildings.

It turns out that even a combination of high-speed collisions by two airliners and fires across multiple floors would not have destroyed the Twin Towers, according to NIST's final 2005 report on their collapse. The robustness and size of the structures helped them withstand the hits, and in the absence of damage, fires as intense as the ones the towers faced would likely not have led to collapse.

Unfortunately, the impacts dislodged fireproofing insulation that coated steel in the floors and columns, leaving the metal vulnerable to weakening under fire. The ceiling sprinklers also did not work, because the water supplying them was cut off by the collisions. Ultimately, WTC 2 collapsed more quickly than WTC 1 because it had more aircraft damage to the building core. Given how little time each tower had to evacuate, if both towers had been fully occupied with 40,000 people total instead of the estimated 17,400 present, about 14,000 occupants might have died instead of the 2,749 who did perish in the attacks.

As to what happened with NIST's recommendations, "23 changes to the 2009 editions of the International Codes and another 17 changes to the 2012 editions, responsive to the recommendations, have been adopted," Sunder says. For instance, buildings taller than 420 feet are now required to include an extra exit stairwell or a specially designed elevator that occupants can use for evacuations. Also, stairwells in buildings more than 75 feet high must now have glow-in-the-dark markings that show the exit path even when lighting is out or dim.

They only aired it once so as not to benefit financially from it - they just wanted to acknowledge the tragic event ......