Yes, there was. Why did building seven come down? It was not struck by either of the planes.
About building 7
When a bat hits a ball it is called impulse, no high rise building is designed to take an impulse like a jumbo jet flying smack dab into it. If you look at the photos of the building being hit by the jet you can actually see the building bend at the impact.
The impact damaged some of the major load bearing members, and the fire did the rest. Jet fuel is not gasoline at the pump. Standard jet fuel has an octane rating of 100, and can burn at up to 1500 degrees Fahrenheit. Steel loses about 50% of its strength at just 550 degrees Fahrenheit.
The combination of the impulse, and the fire caused a load failure and the floors began to pancake.
Building 7, being much smaller and more frail, was more sensitive to the above. It also had no central steel core and not constructed as a high rise would be for such tremendous impact. The shock and the destruction caused the damage. You need not be hit by the cannonball to be blown to smithreens. Close counts in handgrenades.
In your experience, when explosions like this have occurred, have other buildings fallen?
Here is a comprehensive explanation by people I think would have a definitive answer:
http://www.popularmechanics.com/technology/design/a3524/4278874/
GAITHERSBURG, Maryland — The National Institute of Standards and Technology (NIST) has released its long-awaited report on the collapse of World Trade 7 following the attacks of Sept. 11, 2001. “Our take-home message today is that the reason for the collapse of World Trade Center 7 is no longer a mystery,” NIST lead investigator Shyam Sunder told journalists at this morning’s press conference in Gaithersburg, Md. “WTC 7 collapsed because of fires fueled by office furnishings. It did not collapse from explosives or from diesel fuel fires.”
Conspiracy theorists have long pointed to the collapse of the 47-story structure as key evidence that the U.S. government orchestrated or abetted the 9/11 attacks. No planes struck the building, and the commonly available views of the exterior didn’t show significant damage. Yet, at 5:20 pm, 7 hours after the collapse of the Twin Towers (WTC 1 and 2), WTC 7 rapidly fell in on itself. Since WTC 7 housed Secret Service and CIA offices, conspiracy theorists claimed that the building was destroyed in a controlled demolition in order to obliterate evidence of the U.S. government’s complicity in the terrorist attacks. “It is impossible for a building to fall the way it fell without explosives being involved,” stated actress and TV personality Rosie O’Donnell of ABC’s The View in March 2007. “For the first time in history, steel was melted by fire. It is physically impossible,” she said.
Today’s report confirms that a fire was, indeed, the cause. “This is the first time that we are aware of, that a building taller than about 15 stories has collapsed primarily due to fires,” Sunder told reporters at the press conference. “What we found was that uncontrolled building fires—similar to fires experienced in other tall buildings—caused an extraordinary event, the collapse of WTC7.” The unprecedented nature of the event means that understanding the precise mechanism of the collapse is important not just to answer conspiracy theorists’ questions, but to improve safety standards in the engineering of large buildings.
The final report describes how debris from the collapse of WTC 1 ignited fires on at least 10 floors of WTC 7 at the western half of the south face. Fires on Floors 7 through 9 and 11 through 13 burned out of control, because the water supply to the automatic sprinkler system had failed. The primary and backup water supply to the sprinkler systems for the lower floors relied on the city’s water supply. Those water lines were damaged by the collapse of WTC 1 and 2. These uncontrolled fires in WTC 7 eventually spread to the northeast part of the building, where the collapse began.