WASHINGTON WAS rocked on Tuesday morning after a third hijacked aircraft crashed into the Pentagon building, heart of the US Defense Department.
The aircraft smashed into the side of the reinforced concrete building at 9.43am and exploded, causing massive structural damage. Half an hour later part of the structure collapsed. The building was evacuated and as NCE went to press a team was preparing to enter to search for survivors.
When constructed in 1942, the five storey reinforced concrete Pentagon building was thought to be the largest building in the world.
Each of the building's five sides is 281m long on the outer face and 110m on the inner. It has a 2.4ha central court and a total floor area of over 371,000m 2.Main corridors surround the inner court with smaller corridors branching out like the spokes of a wheel. The famous five sided shape was chosen to achieve the shortest pedestrian travel times within the building.
A beam and slab reinforced concrete frame was selected to save thousands of tons of steel needed for the Second World War. Columns are at 6m centres, with 355mm by 510mm beams. Floors are typically 135mm thick.
Wall construction consists of two 100mm thick brick inner leafs with a 150mm thick limestone facing, in keeping with similar buildings in the region. Over 41,000 piles were used for the foundations with an average length of 27m.