Tuesday, August 14, 2007

Earthquake Standards & California Bridges

The mandate to meet earthquake standards give the bridges in California a higher level of safety in terms of routine issues that might impact their structural soundness.

228 bridges at top of state list for repairs
Among them are the Santa Monica Freeway viaduct, 5/10/101 split and 5/60 interchange. Caltrans says they pose no risk of collapse.
By Ari B. Bloomekatz
Los Angeles Times Staff Writer
August 13, 2007


Although Caltrans insists that the thousands of bridges it maintains are safe, the agency has identified 228 spans that officials say should be at the top of the list for repairs.

Officials said these bridges pose no danger of collapse but are considered top priorities for fixes based on such factors as structural problems and how much they are used by cars and trucks.

Those on the list received a "sufficiency rating" by inspectors of lower than 50 -- based on a possible top score of 100. Each bridge's score was calculated by weighing various factors such as structural adequacy and safety, which accounted for 55% of the rating. Other factors include how heavily traveled the spans are.

Of the 228 bridges listed on the "Priority Structurally Deficient Bridge List," 17 are in Los Angeles County. They include the interchange of the 5 and 60 freeways in Boyle Heights, the 5/10/101 split in downtown Los Angeles, the Commodore Schuyler F. Heim lift bridge near Terminal Island in Long Beach and the Santa Monica Freeway viaduct in downtown L.A.

The announcement comes in the wake of the collapse of the Interstate 35W bridge in Minneapolis that prompted transportation officials and engineers across the country to reinspect their own bridges and rush to guarantee their safety.

Mark DeSio, deputy director of external affairs for the California Department of Transportation, said the agency has reinspected all of the bridges similar to the Interstate 35W bridge, and engineering experts said the types of environmental and structural problems that faced the Minnesota bridge are starkly different from the problems facing spans in California.

Caltrans, which operates more than 2,000 bridges in Los Angeles County alone, said its bridges throughout the state are safe to drive on. The targeted bridges are those used the most and that need the most help, officials said.

"If a bridge was deemed not to be safe, it would be immediately closed until it was repaired," DeSio said.

Federal officials have classified thousands of bridges throughout California as being "structurally deficient" -- but local officials stressed that that did not mean the spans were in any danger of falling down like the one in Minneapolis.

In fact, California might be in better shape than other parts of the country because bridges here are already designed to withstand earthquakes.