Around the world, a major tenet of building is to use solid, heavy materials, the kinds that anchor a building to the ground. After all, the thicker and heavier the stronger, right?
Not so fast. When it comes to earthquakes, the lighter the better. Witness the immeasurably disastrous effect of a magnitude 6.6 earthquake in 2003 in the ancient city of Bam in southeast Iran. Several hundred years of construction and indigenous history were destroyed in the blink of an eye, including 60% of the city’s residential area and major historical and religious structures.
A 2003 BBC News report stated “the collapse of so many modern buildings revealed that building regulations have simply been ignored in the rush to industrialize the mud plains east of Istanbul, despite warnings that this was earthquake territory of the most vulnerable kind.”
It has been suggested that corrupt local building officials with lax or non-compliant codes for proper seismic construction may have contributed to the magnitude of the deaths in that disaster. (Estimates tally the loss of life at more than 26,000 with countless more injured.) But the results had much to do with the method of construction. Built largely of mud-bricks, these structures were ill equipped to resist the lateral forces from such a powerful quake.
As all architects know, the amount of damage a building sustains in an earthquake is largely a function of mass and lateral forces, and proper connection details. The greater the mass the more likely it is to respond to violent swings and the more likely it will incur damage.
Instead, if the exteriors of skyscrapers and other bulky buildings could be clad with lightweight fabrics or foils, the mass of the building would be reduced and the structure that supports it could be lightened as well. Likewise, structural armatures could be knitted or made from lightweight composites with flexibility built in.
In contrast, ancient island cultures located in earthquake-prone zones the record of destruction is virtually nil. With indigent structures mostly constructed of bamboo or highly flexible timbers with thatching for protection, if an earthquake hit buildings simply swayed and shook with the tremors, leaving minor but easy repairs in its wake.
Only since modern times, with steel and concrete buildings, do we find an increase in major disasters after earthquakes. Engineers have been challenged to design ever-higher skyscrapers and to make them earthquake proof, a significant obstacle with increasing weights of building materials.
The fabric-clad skyscraper is an innovative concept first posited by fabric structures architect Todd Dalland in 1993 and subsequently refined to suggest that these towers could be temporary and transportable when their initial purpose has expired.
The irony of the Bam disaster is that historically, the Iranian culture grew out of the nomadic tribes of the Middle East, and their tents — lightweight structures with the ability to bend with the forces — would have minimized the risk to people’s safety.
[Adapted from my editorial initially published in 2004]
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Bruce N Wright
Editor | Writer | Wordsmith