AASHTO Journal

Oklahoma DOT Uses USGS-Developed Earthquake Software to Refines Bridge Inspections

State bridge inspectors working for the Oklahoma Department of Transportation "will be able to provide a faster, more targeted response in ensuring public safety the next time an earthquake rolls across Oklahoma," the agency said, because of a new technology program ODOT will use.

The state DOT said it is adopting "ShakeCast," a computer software analytical and mapping program created by the U.S. Geological Survey that is in the final stage of a two-year, nearly $650,000 contract to help ODOT develop an earthquake response protocol.

Formalizing the plan, providing final training and an additional four years of system maintenance will conclude the contract, ODOT said.

Using ShakeCast, the state agency said the nearly 300 trained ODOT employees who assess bridge conditions will be able to quickly determine which structures they should first inspect after an earthquake. And "if conditions warrant, key ODOT employees will receive a software-generated inspection priority order based on several factors including ODOT bridge data such as bridge condition, age and proximity to an earthquake's epicenter, combined with USGS seismic movement data and magnitude rating."

capitol0816.jpgUntil now, the department's protocol called for visually inspecting all roadway bridges within five miles of any earthquake epicenter following a temblor of 4.4 to 4.7 magnitude, and the inspection radius increased with the earthquake magnitudes.

Generally, with a 4- to 5-magnitude earthquake the department has found no damage, in a period when tremors have been more frequent along with drilling and hydraulic fracturing activity.

The department said it has taken a lead role in developing response protocols to Oklahoma's increased earthquake activity by working closely with other agencies such as the U.S. Army Corps of Engineers, which has 23 bridges on the state highway system.

"ODOT also shared its recently developed bridge inspection manual with other state agencies as well as local governments and will assist with local bridge inspections during earthquake response events as resources allow," it said.

Going forward with ShakeCast, ODOT said the inspections will identify only specific bridges susceptible to damage, a process that allows faster and more pinpointed response.

"This technology is one of the biggest advances in ensuring public safety that I've seen in my 30-year career at the department," said Casey Shell, ODOT chief engineer. "By comparing state bridge data with the severity of an earthquake's ground motions, ShakeCast will allow us to inspect fewer bridges but with a much greater degree of confidence that we could quickly find any potential damage."

ODOT Bridge Engineer Steve Jacobi said: "Bridges are designed to national standards, which includes the ability to withstand vibration. Oklahoma's bridges have weathered the increased seismicity very well, and our data shows that even our oldest state highway bridge designs are safe at the earthquake levels experienced to date. However, the department is committed to visual inspections to ensure public safety after larger magnitude earthquakes. If there is ever even the slightest question about a bridge's safety, it would be immediately closed until more thorough inspections could be completed."

ODOT also said the state's chances of suffering earthquake-related bridge damage have lessened because the department has replaced more than 900 structurally deficient bridges statewide since 2004. Another 251 structurally deficient bridges remain on the state highway system, it added, and most of those are scheduled for replacement by the end of this decade.

ODOT said it has joined nine other earthquake-prone states in a pooled-fund study with the USGS to help further enhance ShakeCast, and develop future versions of the software. ODOT is contributing an additional $45,000 to the USGS in a three-year period to the study.

Questions regarding this article may be directed to editor@aashtojournal.org.

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