by Bohdan Rewko (Bo of T.O.)

Created on: October 13, 2007   Last Updated: October 14, 2007

Tall buildings, for the most part are designed for a shelf life of about a hundred years. Why? Is it because that way the builders will not be around to see them come down? I'm not sure. A hundred years seems reasonable from the point of view of return on original investment, but who decides when they actually come down? Some tall buildings have come down long before their expiration date, while others such as the Eiffel Tower, continue to proudly scrape the sky many years after their scheduled date of dismantling. What about the Empire State Building or the Sears Tower? How long will, or should they be with us? Should society treat them with more dignity than automobiles or razor blades that are here today and gone tomorrow?

These are all reasonable questions given that tall buildings have only been with us for about a hundred years, since the the electric age gave us motorized elevators and high pressure pumps. But what gives buildings structural integrity and stability, and should there be greater scrutiny and demands on their design? Should they be designed to stand for a hundred years, or two, or perhaps even three hundred or more years? One of the factors in the decision making process is the cost benefit of maintaining an outdated structure technologically, but what about structural integrity?

This brings us to general safety of building types. There are two so-called forms of non-combustible construction (so-called because we all saw what can happen to two non-combustible buildings in New York City on 9-11) which is mandatory for all high-rise buildings. There is reinforced concrete, and there is structural steel. Most high-rise buildings are one or the other, or a combination of the two. The higher the building, the greater the likelihood that structural steel will be used for the construction of floors, beams and columns, because steel offers a greater strength to weight ratio than does reinforced concrete. In high-rise commercial buildings there is usually a central elevator core with beams radiating out and supported by perimeter columns. The whole is laterally braced to withstand earthquakes and wind loads.

Most buildings are built quite solid. The taller they are, the more solid they tend to be. Structural engineers are often under pressure from developers not to "overbuild", but on the other hand, they do not as a rule want their buildings to topple on their watch. However, some problems with tall buildings arise over time and relate not to original

• 1
• 2
• 3
• Next Page >>