Abstract
Bridges, overpasses, and other engineered structures in the Jackson Purchase region of Western Kentucky are, of necessity, built on a thick column of loose to semi-consolidated sediments. Because these sediments tend to amplify seismically induced ground motions at preferred periods, structures with natural periods close to the preferred periods of amplification of the ground motions are particularly vulnerable to damages during an earthquake because of in-phase resonance.
For this report, conventional seismic refraction and reflection techniques were used to determine the shearwave velocities of the more poorly consolidated, near-surface sediments for a matrix of sites in the region. Conventional seismic P-wave reflections along with existing drill hole and seismic reflection data in the region were then used to determine the depth to the top of the bedrock at the sites investigated. These data were used in SHAKE91 to calculate the fundamental period of the ground motion at the sites. This period, identified in the study as the dynamic site period, is the period at which ground motions in the sedimentary column are most apt to be amplified as a result of a seismic shear wave propagating from the top of the bedrock to the surface. Based on the results in this report, it is recommended that bridges, overpasses, and other engineered structures built in the region be designed so that their natural periods do not coincide with the fundamental period of the sedimentary column, thereby avoiding damage during an earthquake as a result of in-phase resonance.
Report Date
2-1997
Report Number
KTC-97-1
Digital Object Identifier
http://dx.doi.org/10.13023/KTC.RR.1997.01
Repository Citation
Street, Ron; Wang, Zhenming; Woolery, Edward W.; Harik, Issam E.; Allen, David L.; and Sutterer, Kevin G., "Dynamic Site Periods for the Jackson Purchase Region of Western Kentucky" (1997). Kentucky Transportation Center Research Report. 478.
https://uknowledge.uky.edu/ktc_researchreports/478
Notes
The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Kentucky, the Kentucky Transportation Cabinet, nor the Federal Highway Administration. This report does not constitute a standard, specification or regulation. The inclusion of manufacturer names or trade names are for identification purposes and are not to be considered an endorsement.