Introduction to Earthquake Resistant Design


The public has taken a greater interest in earthquake resistant design than ever. Several factors have contributed to this, including:


Damage to Teacher's Hostel, 1999 Taiwan EQ
[1]
  • Personal experiences with Loma Prieta, Northridge, Whittier, Landers, and other earthquakes
  • Tremendous economic impact of recent earthquakes
  • Evidence of potential for large loss of life provided by Turkey, Taiwan, Kobe and Mexico City

More concerns about seismic hazards are being shown by owners and public officials. Overall, there is a demand for a safer environment.

Engineering capabilities are advancing to meet the needs of the public and private sectors. Computers capable of advanced dynamic response simulations are available in most engineering offices, and advanced analyses are becoming more common in structural engineering practice. Most practicing engineers in California now have educational backgrounds including structural dynamics. Many high-tech products and devices available to improve seismic performance. Building codes now incorporate structural dynamics and other advanced concepts.

But the problems are becoming more complex. Expected ground motions more severe and complex than previously assumed. Near-source, soft soil, and long duration motions as well as "the big one" are cause for concern. The apparent increase in the frequency of damaging earthquakes has lessened public's tolerance for damage. Earthquakes are no longer considered a rare act of God, but as a recurrent natural phenomenon whose disastrous effects can and should be mitigated. Insurance companies have had to pay huge sums in claims after recent earthquakes such as Northridge and are concerned with probable maximum loss (PML).

Therefore, engineers must design accordingly. Owners want little disruption or damage, but they generally do not know how to explain what they want nor do they want to pay significantly more for improved performance.