|
|
Although often overshadowed by the seismicity of the American west coast, the New Madrid, Missouri region is a very real and significant seismic threat to the Midwest. The general public, even if aware that earthquakes often occur in the central United States, does not readily admit the potential destruction that would follow a major event. Fortunately, state departments of transportation, the Federal Highway Administration, and many local building code officials are acutely aware of the risk and the damage - in terms of loss of life as well as economic losses - which would follow even a moderate event in the New Madrid region.
New structures are now designed in accordance with current seismic guidelines developed from observation of structural behavior during earthquakes and millions of dollars worth of research. However, both the research funding and empirical evaluations focus on conventional structures. In this paper, we will look at a bridge structure which is somewhat outside the norm for earthquake design and the methods used to ensure the structure is as capable of resisting seismic loading as our current state of knowledge will permit.
This bridge, comprised of a 3-span, 1150-foot main span, symmetrical cable-stayed unit and 1870 feet of conventional approach structure is currently under construction within 50 miles of New Madrid, Missouri. Because of its proximity to the New Madrid Seismic Zone, it is highly probable that this bridge will experience a significant seismic event within its design life.1
1Project Manager, HNTB Corporation, Kansas City, Missouri 64106
