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MHPCC Resources Utilized to Study Earthquake
Effects on Kealakaha Stream Bridge
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by Dr. Susan T. Brown

In the construction of bridges in the State of Hawaii, especially on the Big Island, the engineering design teams must examine the effects of ground vibration from earthquakes and volcanic activity on bridge structures. Seung Ha Lee, a graduate student in the Civil Engineering Department at UH Manoa, and his advisor, Professor Si-Hwan Park, utilized the supercomputing facility at Maui High Performance Computing Center (MHPCC) to study the interaction between the soil and the bridge structure for the proposed design of the Kealakaha Stream Bridge located 21 miles north of Hilo on the Big Island.

Map of the island of Hawaii Bridge Diagram
Location of bridge over Kealakaha stream
Layout of the Kealakaha Stream Bridge

The three-span prestressed concrete bridge would be located in a large soil region, and coupling this with the high seismic activity of the Big Island meant that a single-cpu system would not be adequate for the research; it was necessary to use a parallel model on a multi-cpu system. The MHPCC Squall system used was a 2-node 32-procesor Power3 (37h MHz) IBM SP system. This system is no longer in use at MHPCC; it has been replaced by a larger 256-processor system, Hurricane, which will itself retire at the end of June 2008. To find out more about the systems available at MHPCC, check out the News & Announcements section of the High Performance Computing at UH website at http://www.hawaii.edu/hpc or go directly to the MHPCC website at http://www.mhpcc.hpc.mil.

Seung Ha divided the total field into 3 layers with 2 scattered fields on the edges, as shown in the figure below.

Bedrock figure

Computations in the figure below showed the dispersion of the shocks in the soil in 0.03-second time intervals. This was from a simulated 30-second earthquake, like the one recently recorded at the Pahala station on Hawaii. The computations were performed on 16 processors.

Diagram of Amplitude Contours
Displacement Amplitude Contours in 0.03 sec Intervals

Seung Ha's work was funded by a 2004-05 UH/MHPCC Engagement Grant. The results have since been incorporated into a larger project funded by Hawaii Department of Transportation (HDOT), concerned with seismic instrumentation and monitoring of the bridge, and will provide useful information in understanding the actual seismic response of the bridge when an earthquake occurs. The full Lee and Park findings can be reviewed in their Engagement Grant report. This work was also presented at the Joint American Society of Mechanical Engineers/American Society of Civil Engineers/Standards Engineering Society conference (PDF) in Baton Rouge, LA, and published in the 2007 edition of MHPCC’s Applications Briefs (PDF).

Since completing his UH studies Seung Ha is now working for NAN, Inc., the largest locally-based military contractor whose main office is in Honolulu. Professor Park continues his work in Civil and Environmental Engineering at UH Manoa. You can read more about his work on his webpage at http://www.cee.hawaii.edu/persons/park/park.htm.

 
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