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A Year to Rebuild LA
Construction News 27 January 1994

Mark Smulian reports from Los Angeles on the huge operation to put the city back together after last week's earthquake

The Los Angeles earthquake was not the long-feared "big one", but at 6.6 on the Richter Scale it was large enough to throw the local construction industry into frenzied activity.

Last week teams from both the city council and private firms were surveying damage to more than 10,000 buildings. Surveyors from Caltrans, California's highway authority, inspected 500 road bridges, 19 of which collapsed entirely or were badly damaged. This week contractors will start on what will be at least 12 months' work rebuilding the city and trying to upgrade the seismic protection.

But as work progresses all of LA is waiting, disturbed that the disaster may be compounded by heavy rains causing mud slides as Pacific storms head for the city and threaten the makeshift homes of 15,000 people. Most surveyors and engineers involved have been working 18-hour days since the quake.

Elwood Smeitana, vice president of earthquake engineering specialist EQE, felt tremors in his home 45 km from the epicentre. He rushed to his office to set up a command centre, just as he did for the Wittier and Loma Prieta quakes in the 1980s.He said: "The rule is, as soon as everyone feels the ground shaking, they get into the office. Within one hour we get the command centre set up, then we will be fielding non-stop phone calls 18 hours a day for at least 10 days."

For up to two weeks, EQE's other work grinds to a halt. California has seen many more powerful quakes, but these have had their epicentre in the desert and so have been relatively harmless. This time the quake's epicentre was in Northridge, an LA suburb in the San Fernando Valley which sits astride a previously unknown fault line.

Mr Smeitana said: "We were just so lucky it happened at 4.30 in the morning on a public holiday. It is sickening to think what the loss of life would have been if it had struck in the rush hour."

Even so, the death toll has risen to nearly 60, including Kevin Maher, an electrician from Carrick-on-Shannon, Ireland. He died trying to remove a live power line from a car in which a child was trapped.

In Northridge, kilometres of walls lie broken and most homes have lost their chimneys. In many the damage appears superficial, but even then some have the city's ominous red 'condemned' stickers on them. More have the yellow 'enter at your risk' signs. Green means no immediate danger, but the homes still need full surveys.

This house-to-house surveying was supervised by the city council. Its chief deputy engineer Ralph Kennedy said: "We got to all the private homes where people wanted us through our people working all day for seven days. We also estimate there is $100 million damage to public buildings alone, and we haven't even had time to start looking at the sewers and storm drains."

He said the disaster would force a major change to the building code - the US building regulations - "to put right things we have not treated with enough care".

The most serious damage was to a student hostel in Northridge, where one floor plunged to ground level, killing 12 people. Next door, a hostel partly collapsed, but an identical building across the street survived unscathed.

Such is the random nature of the damage. According to Mr Smeitana, there are three reasons for this. First is simply luck. Second is the way the earthquake occurred in a vertical thrust up through the ground, rather than the more usual horizontal cracking. And third is that LA's building codes have tried to accommodate earthquake protection. The last major revision was in the early 1970s and buildings dating from then in general resisted the quake well.

He said: "Buildings older than the early 1970s are most vulnerable because, when the building code changed, the changes were significant and good seismic systems were then used."

The worst affected buildings were unreinforced brick structures, about the commonest type of pre-1970s building. Concrete tilt-up - a technique common in California, where walls are laid flat on the building's floor and then hauled upright - also offered little resistance. The best performers were wooden and newer steel buildings.

But EQE's teams learned two new lessons from this quake. One being that, even in buildings which otherwise suffered little damage, services fell from walls because their anchorages were inadequate. Mr Smeitana thinks the building code will certainly need to be tightened.

Estimates for the total cost of the damage are so far guesses. The city council provisionally puts the figure at US$15 billion. Mr Smeitana said: "If that is even remotely right, it will be like building a new Suez Canal. No $15 billion project gets finished in under a year and work will continue a long time."

But job hungry British workers turning up on spec may be disappointed. Mike Merrick - a British engineer working for MTA, the bus and subway authority - explained that a contractor needs a state licence to get insurance to cover his work. Private clients might still hire a black market contractor, but anyone tempted would be competing with cheap labour from Mexico.

Metro Comes Through Unscathed

One structure which came through the earthquake with flying colours was the LA metro underground railway, still under construction. And managers of MTA, the metro and bus authority, hope the quake which devastated the freeway network will break the city's obsession with cars.

The lines are designed to withstand a quake of up to seven on the Richter Scale, so the Northridge quake was very nearly a full test for it.Ed McSpedon, president of rail construction for MTA, said: "It surprised a lot of people that the tunnels withstood the quake, but it did not surprise us."

The MTA team quickly found there was no distress to the road surfaces above the metro tunnelling and the elevated line near LA Airport was also unscathed. But the tunnels had to be inspected.

Mr McSpedon said: "We had no idea what we would find down there. But by noon we established there was no damage and the tunnellers went back to work."

Charles Stark, project manager for the metro's new phase, said the tunnels were designed to be thick enough to withstand high earth pressure, but flexible enough to stay usable. Reinforcing steel is used to help earthquake-proof the tunnels, so that they move with the earth and do not collapse. He said: "Tunnels are the place to be in a quake."

Rather less successful were the city's underground services. Gas mains and water mains ruptured, often with spectacular results, in the early days of the disaster.

Ralph Kennedy, chief deputy city engineer, said that 300 breaks in the city's sewers posed a major problem. "Sewage is corrosive of steel, which is what best withstands an earthquake, while clay pipes last indefinitely but break in a quake."

A further problem is that buildings moved in a quake may be detached from their gas supply.

Retrofitting Proves Its Worth

The 650 million retrofitting programme for California's freeways which started after the Loma Prieta earthquake in 1989 proved its worth.

All retrofitted bridges withstood the quake.But it was a different story for bridges strengthened under the 1971 retrofitting scheme. John Scales, structures supervising engineer with Parsons Brinckerhoff, said he was unaware of any damage to the 114 bridges retrofitted after Loma Prieta. But he said 400 bridges still needed strengthening.

He said: "Caltrans is estimating publicly that they will have the damaged freeways open again by the end of the year, but internally they think they may get the job done more quickly."

There are 19 bridges which have either collapsed or suffered severe damage. Those have been divided into 10 contracts. One will be designed by a consultant, the others in-house by Caltrans, and building contractors have already been appointed.

Paul Askelson, Caltrans' structural maintenance engineer for southern California, said his crews and 36 civil engineers had visited 400 bridges within two days of the quake.

He said: "We found a lot of shear keys failed, a lot of movement was transmitted through them. Hinge restrainers put in the 1971 retrofitting caused problems and in some cases columns failed." Elwood Smeitana of EQE worked on the retrofitting programme before the quake.

He said: "The quake has taught us that we had better refocus our financial priorities on to retrofitting."