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A bridge is one of the worst places to be when a quake strikes. Mark DeSio, Deputy Director for External Affairs at Caltrans, explains how seismic techniques are employed to keep transportation flowing when the whole state is moving.

What techniques is Caltrans employing to protect transportation infrastructure from the effect of earthquakes?

Mark DeSio. Caltrans utilizes tightly spaced rebar wrapped around the column to increase confinement to make them more ductile. Bridges are designed so that damage occurs in components that can continue to support the bridge after an earthquake. Selected bridges, particularly long span bridges crossing the San Francisco Bay such as the new San Francisco-Oakland Bay Bridge, Benicia-Martinez and Carquinez, have been designed to provide for a higher level of post-earthquake functionality. Bridges are made continuous or enlarged bearing areas are provided to prevent loss of vertical support

In addition, the Caltrans Seismic Retrofit Program has retrofitted older bridges to improve their seismic performance. This is achieved by placing steel casings around columns to increase their ductility while pipe seat extenders or cable restrainers are used to keep bridge joints tied together.

Caltrans also utilizes an independent Seismic Advisory Board to advise the Department on seismic policy and technical practices. Following the Loma Prieta Earthquake we established a seismic research program to improve the performance of bridges in a major seismic event. The results of this program are used to update Caltrans seismic design standards.

What role does innovative ‘smart’ infrastructure technology have to play in protecting California’s transportation systems and their users?

MD. Caltrans has instrumented approximately 70 bridges in locations throughout the state to measure their response in an earthquake in order to improve seismic performance.
In collaboration with the US Geological Survey and the California Geological Survey we uses earthquake sensors located around the state to collect earthquake strong motion data to automatically send out email notifications including a map showing the level of ground shaking.

New infrastructure items can obviously be built with the latest technologies but what of older existing structures? Can they be effectively retrofitted to bring them up to 21st century standards?
   
MD. Seismic retrofit techniques such as the use of steel casings, pipe seat extenders, cable hinge restrainers, and other measures have been shown to significantly improve the seismic performance older bridges. These techniques have been validated through research performed at many universities. We’ve had some positive real-world validation too as retrofitted bridges in the areas of strongest shaking in the Northridge Earthquake performed well.

What emergency response plans does California DOT have in place to cope in the immediate wake of a major quake?

MD. When an earthquake hits a portion of the state with a certain magnitude, it triggers the Caltrans Shakecast system. ShakeCast is a web-based application that automatically retrieves measured earthquake shaking data from the US Geological Survey, analyzes it against individual bridge performance characteristics, and generates inspection prioritization emails and other web-based products for emergency responders within minutes of an event.

Maintenance field personnel and engineers are deployed for the initial response and conduct preliminary surveys, while bridge engineers assess whether they should deploy, or not, based on the event’s magnitude and assessments conducted in the impacted areas.
   
If necessary, Caltrans will deploy teams of bridge engineers to the affected area. These engineers check bridges in the area for damage that could compromise the structural integrity of the bridge. If significant damage is found, the bridge is temporarily closed while the damaged structure is evaluated. Following the evaluation, a decision is made whether to re-open the bridge. If the bridge is to remain closed, repair or shoring options are then considered.

In addition we exercise on a continuous basis, both internal and externally, with the different hazard types that may impact the transportation system. Best management practices are developed based on after action reports from exercises and actual events, and incorporated into our emergency operations plans. We also coordinate our response efforts with the California Emergency Management Agency, Federal Agencies, such as the Federal Emergency Management Agency, and our local partners.

Aging transportation infrastructure is a problem for many states. How does the frequent seismic activity create additional difficulties for California in terms of allocating resources?

MD. Caltrans has provided the resources necessary for the Seismic Retrofit Program, which is nearly complete. There is an ongoing need to provide funds for the needs of our existing bridges, including for their seismic needs. This could include bearings and dampers that wear out, bridges that are modified requiring new seismic retrofit measures or new findings require bridge seismic needs to be assessed.

Associated Press reports suggest that the recent quake on the Mexico-California border caused as much as $100 million in damage. What are the likely impacts in terms of transportation infrastructure of an inevitably far bigger far bigger quake that is widely expected to strike in the not too distant future?

As reported by the Seismic Advisory Board in the report Race to Seismic
Safety in a major earthquake “standard bridges near the epicenter will be sufficiently damaged as to be out of service for a period of time, and some may require replacement.” Bridges further from the fault will have lesser damage and are expected to remain open or be returned to service soon after the event.