I-10 Is Reopened--but Spans Need Retrofitting : Roads: Newly rebuilt freeway bridges have seismic weaknesses. Repairs are not expected to require closure.

By VIRGINIA ELLIS

April 12, 1994 12 AM PT

TIMES STAFF WRITER

SACRAMENTO — In its haste to reopen the Santa Monica Freeway after the Northridge earthquake, Caltrans allowed two replacement bridges to be built with seismic weaknesses that must be corrected to prevent significant damage in a future temblor, according to records and interviews.

The bridges, which reopened at 11 p.m. Monday, are believed to be safe from collapse. But a committee of internationally prominent engineers has advised Caltrans that seismic weaknesses in the abutments--the concrete structures connecting the bridges to land--would leave them vulnerable to earthquake damage.

“If we have a big earthquake, then yes, there can be serious damage to the extent where the bridge structure would have to be closed temporarily for that damage to be repaired,” said Frieder Seible, the chairman of an advisory committee of outside experts hired by Caltrans to scrutinize designs of replacement bridges.

Seible said the damage he anticipates, while significant, would not cause injury or loss of life.

The freeway bridges, which collapsed at La Cienega Boulevard and at Washington Boulevard in the Jan. 17 quake, were rebuilt at a cost of $29.4 million in less than three months, according to an accelerated construction schedule ordered by Gov. Pete Wilson. Officials said recently that the closure of the Santa Monica Freeway, the world’s busiest with 341,000 vehicles a day, was costing the local economy $1 million a day.

Now, as a result of Seible’s findings, Caltrans officials said that several weeks after the Interstate 10 bridges open to traffic, a construction team will have to go back at additional cost and retrofit the structures to strengthen the abutments.

Officials said the effort, involving the drilling for eight pilings four feet in diameter, is not expected to require closure of the freeway. They said they do not expect to have to relocate residents or businesses, although the annoying pounding of pile drivers will return to the area.

The job, expected to cost less than $300,000, will be put out to bid.

Caltrans officials acknowledged that if it had not been for the accelerated design and construction schedule, they probably would have pinpointed the seismic weaknesses early enough to correct them before the bridges were completed.

“We were going awfully fast and the abutment reinforcement simply didn’t get done because we knew it could be done later,” said Secretary of Business, Transportation and Housing Dean Dunphy.

Chief Caltrans bridge engineer James E. Roberts said that normally the advisory panels, known as peer review committees, examine the design before bridges go out for contract. But in the case of the Santa Monica Freeway, he said, the time schedule was so short that the bridges were already under construction when the committee got its first look at the plans.

By then, Roberts said, the concrete for the abutments had been poured and it was too late to alter that part of the structures.

“We’ll go back essentially and add on (pilings) to a new bridge,” he said. “It may not look pretty . . . (but) the important thing is getting the safety feature in there.”

Under an emergency proclamation signed by the governor on the day of the earthquake, Caltrans was given extraordinary authority to shorten normal contracting procedures. Wilson directed that replacements for collapsed bridges be built “as soon as possible.”

The bridges on the Santa Monica were the first of six collapsed structures to be scheduled for construction. Their speedy completion has been touted as an example of how quickly Caltrans and the Wilson Administration could react to a disaster.

Last week, the governor jubilantly announced that the bridges would open substantially ahead of schedule, winning widespread praise for both Caltrans and C.C. Myers Inc., the construction company that built the new structures.

Their design was finished in record time. Then contracting procedures, which usually take months, were completed in less than three weeks, allowing construction to begin Feb. 5.

Enticed by a $200,000-per-day bonus for every day the bridges were completed before a June 24 deadline, the C. C. Myers company finished the structures 74 days early, earning a $14.5-million bonus.

While the rapid reopening of the freeway and the relief it provides for delay-weary commuters is expected to help boost the Republican governor’s reelection campaign, at least one prominent Democrat now questions whether the bridges were constructed too hastily.

“It seems to me that the peer review committee is designed to make sure that the public’s getting its money worth and that these bridges are safe and that they don’t damage and don’t collapse,” said Assembly Transportation Chairman Richard Katz (D-Sylmar). “To go ahead and start building something before the peer review committee has a chance to do its work is playing Russian roulette with people who drive and depend upon that freeway.”

But Caltrans officials and others in the Business, Transportation and Housing Agency, which oversees the department for Wilson, said they believed that as long as public safety was not jeopardized, it was essential to the Los Angeles economy to open the freeway as soon as possible.

“If there had been some question about the structural integrity of the bridges which could affect public safety, then the project would have been halted,” said Caltrans spokesman Jim Drago.

The news, meanwhile, that Caltrans now plans to retrofit the new bridges came as a surprise to engineer Wei Koo, who heads the Orange County firm Koo & Associates, which designed the new bridges.

When he was given the job, Koo said he was advised that the two bridges had not been rated “important,” meaning they did not require the highest level of reinforcement.

Bridges that have this rating have to be designed to withstand a major earthquake without collapse or any damage that would require them to be closed for any period of time. That designation, created at the suggestion of a board of inquiry appointed to investigate bridge damage in the 1989 Loma Prieta earthquake, is reserved for those structures which either would carry emergency traffic or were located in areas where there were no alternative routes.

Bridges not designated as “important,” such as those on the Santa Monica, have to be designed so there would be no collapse but some damage, with temporary closure of the roadways allowed.

Koo said that even though the bridges were designed under this rating, he believes damage to the bridges in a major quake would be minor.

He said, and Roberts confirmed, that the design met all of the codes and specifications for bridge design in effect at the time.

However, Koo noted that before the designs were completed, there were some changes in the code which required better reinforcement, but they came too late to be incorporated into the plans.

When the peer review committee met in mid-February to review the plans, it advised Caltrans that the specifications did not provide sufficient strength for the abutments. In a major temblor, it said, the abutments could move laterally, causing the bridge deck to slip to one side.

“The expected lateral movement at the abutment will lead to abutment damage,” the committee wrote on Feb. 22. “ . . . A redesign to allow for controlled movements with associated energy absorption is not feasible due to time constraints.”

The committee also noted that since the Santa Monica Freeway replacement structures had not been rated “essential” or “important” under Caltrans requirements, damage to the abutments could be “tolerated.”

But in an interview, Seible a structural engineering professor at UC San Diego, said the committee “expressed a very strong sentiment” to Caltrans that all the replacement bridges in the Los Angeles area should have an “important” rating. He said the panel felt that the rating could be justified for bridges on the Santa Monica, because it is the world’s busiest freeway.

Besides Seible, the committee included Nigel Priestley, another UC San Diego structural engineering professor and a leader in seismic bridge research; Ron Scott, a Caltech engineering professor and expert in soils; Al Ely, an Orange County structural engineer, and Robert Cassano, former director of Caltrans’ structures division.

Roberts said he agreed with the committee’s findings, and directed that the bridges be retrofitted with steel-reinforced pilings that will contain the structure and prevent slippage in a major quake.

He said that he wants the other bridges on the Santa Monica, even those that have been retrofitted in recent years, to be re-evaluated.

While the peer review findings came too late to affect the abutments on the Santa Monica, he said they did come in time to prevent similar problems on other bridges that are being rebuilt. He said the plans for those structures were being changed to provide for stronger abutments, allowing them to ride out a major quake without serious damage.

The freeway project continued to set off political aftershocks Monday.

Democratic officials in Washington are still stewing over Wilson’s surprise announcement last week of the sooner-than-expected freeway opening, and they have accused him of trying to steal the credit for the project that was financed entirely by federal tax revenues.

Rep. Bill Baker (R-Danville) noted tongue in cheek, “There is no shortage of politicians, both Republicans and Democrats, who are hovering around the area waiting to take credit.”

U.S. Secretary of Transportation Federico Pena, who testified at a House Public Works and Transportation Committee hearing in Los Angeles, said Monday that he has asked for a “thorough review of the recovery effort,”’ including exploring how states estimate their cost and timetables for reconstruction after a disaster.

California officials originally put the cost of repairing the area’s freeways at $1 billion, but recently reduced that to $500 million, saying that they could repair some of the bridges that they originally thought needed rebuilding.

Times staff writer Richard Simon contributed to this article.

The Road Back

Repair work on the Santa Monica Freeway began the day after the Jan. 17 Northridge earthquake. Crews--as many as 400 workers on peak days--worked 24 hours a day, seven days a week to reopen the freeway. Here is a look at the rebuilding sequence.

FIXING THE FREEWAY

1) Damaged structure was torn down, roadways cleared and the rubble hauled away.

2) Shafts up to 50 feet deep are drilled for piles, concrete was poured for columns and piles. This took about three weeks.

3) Ironworkers created a frame of steel that later covered with concrete. Because the structures are 600 to 700 feet long, construction of the bottom slab and vertical wall supports can began on one end as the structures were erected at the other end.

4) Once formed, the top deck is surfaced.

5) After waiting five days for the concrete to cure, tension was applied to metal strands, called tendons, which were placed in the concrete to add strength to the structure.

6) Although the freeway was deemed safe from collapse, experts have said the bridge abutments need to be strengthened to avoid damage in a quake. Caltrans officials plan to start the work, involving the installation of pilings, in about a month. The work is expected to take about three weeks.

Steel rings were placed around the columns during construction to further strengthen them. The rings were inserted around the rebar before concrete was poured.

On each of the two bridges, four pilings four feet in diameter and as mush as 80 feet deep will be attached to the sides of each abutment.

Repair cost: Project was bid for $14.9 million. Contractor C.C. Myers Inc. receives a $200,000 bonus for each day the freeway was completed before the June 24 deadline.

Damage: The earthquake knocked out two bridges, at La Cienega and Washington boulevards.

Researched by NONA YATES / Los Angeles Times

Source: Caltrans