Seismic shifts: 10 years of learning
By Charles Clifton
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Where, then, has a decade of analysis and rebuilding brought us to? Here is what we’ve found:
Our steel buildings performed astonishingly well. In fact, analysis after the February 2011 earthquake showed the Christchurch buildings with standard construction of concrete floors on steel decks supported on steel beams were about 2.5x more resilient than industry-led design had calculated.
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Modern buildings are designed for “controlled damage”. If we think of buildings like a car, in the worst-case scenario like a head-on collision at high speed, we want the car to take the brunt of the force and the people inside it to survive unscathed – then we figure out whether the car can be repaired or must be replaced.
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This resilience doesn’t need to cost more. Advancing the strong-column-weak-beam model to a no-damage model has historically been a question of how you design economically for a low-probability event, as earthquake previously was in the Canterbury region.
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There is room for improving the efficiency of steel construction. In-situ concrete, where concrete is poured around a steel framework, is highly earthquake-resilient; pre-cast concrete is not.
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