Cracked!

Sitting in his custom cubicle in a prestigious West Los Angeles engineering firm, Anders Carlson adjusts his glasses and scrolls through the different programs of his laptop. He double-clicks an icon, and a schematic of a large building appears. ”So the subtitle of this is ‘Whacking Steel Buildings,’“ he says as the program begins. Then Carlson sits back, proudly watching what started as his doctoral thesis at Caltech -- a sophisticated computer simulation that demonstrates with remarkable accuracy what happens to steel-frame buildings during an earthquake.

More specifically, Carlson‘s design extrapolates on what did happen during the Northridge quake of 1994. He obtained ground-movement data for a particular building, correlated the structural damage it sustained, and then increased the volume -- from the 6.7 Richter-scale rating that Northridge generated, to the 7.0 that experts are predicting -- to see what would happen.

The results unfold on Carlson’s laptop screen. A 17-story edifice wobbles back and forth like a crude video game. One after another, the joints turn bright red to indicate areas of high stress. Eventually the welded connections crack, the integrity of the structure is compromised, and the top of the building begins to lean, failing to return to center. Carlson breaks into a grin that‘s almost an apology and explains his research in simple layman terms. In a moderately strong earthquake, he says, ”These buildings will probably collapse.“

Across town on the Caltech campus, Professor John Hall, who has spent the past decade studying the motion of steel-frame buildings in earthquakes, affirms the work of Carlson, his former student. ”In a magnitude-7 earthquake, the ground can move back and forth on the order of a meter or more. Those kinds of motion could possibly collapse a good-size steel building.“

Here’s why this should matter to you. There are 10 known fault lines in the L.A. area capable of generating a magnitude-7 quake. There are over 1,500 steel-frame buildings sitting along these lines -- basically every glass-covered high-rise you lay eyes on -- each one crafted with what is now known to be a flawed engineering technique. Specifically, the weld metal holding the structures together is too brittle to bend under seismic pressure -- it cracks instead, often leaving the beam-to-column connections severed.

Damage inflicted by previous quakes has finally persuaded engineering officials to require a more durable weld metal in seismically sensitive zones, but an ominous question remains unanswered: What about the hundreds of fully occupied steel buildings that have already been constructed, looming over Los Angeles like a collective time bomb? What about the welds?

City officials were aware of the inadequate welds within months after the Northridge shaker in early 1994, but their reaction was delayed, halting and piecemeal. Early on, political considerations caused the tower-filled districts of Century City and Bunker Hill to be exempted from the city‘s inspections. The cluster of high-rises in Universal City, which falls under county jurisdiction, somehow managed to escape what is supposed to be a mandatory post-quake inspection for the past three and a half years. And, in a clear indication of the priority of this issue among the people it affects the most, condominium groups from the Wilshire Corridor hired lobbyists to ensure that their buildings would not be subjected to a city inspection. It worked. Which illustrates the point perfectly: Even the people who cook and sleep in these buildings don’t want them fixed.

To date, the sole initiative taken by the city to address this issue has been to require that 250 of the affected area‘s 1,500 steel towers go through a mandatory process of having their welded connections inspected and repaired. But even this emergency ordinance required only that the buildings be restored to their pre-Northridge condition; upgrading the buildings with stronger connections was never even considered. For that matter, the other 1,250 steel-frame buildings throughout the city were never inspected -- even though virtually all were constructed with the same faulty beam-to-column connections.

Why have Los Angeles officials been so reluctant to defuse this catastrophe-in-waiting? Because no one close to the problem can stand the heat it generates. The cost of repairing or retrofitting a single steel-frame building can easily run into the tens of millions of dollars. Meanwhile, the welds in these buildings are so well hidden that a fractured frame can go undetected for years unless and until it is subjected to rigorous inspection -- or rigorous shaking, whichever happens to come first. The cost of a remedy is awesome, the problem is concealed, and the next earthquake is intangible. So the preferred fix has been quite manageable across the board: out of sight, out of mind.

While much time and money has been spent researching the fractured joints of steel-frame buildings, the most difficult aspect of this issue has proved to be the mechanics of human nature. Can local government find a way to effectively balance its concern for public safety with its concern for fiscal stability? A five-story steel-frame building may contain 300 welds -- each weld hidden behind walls, ceilings and in many cases asbestos; each weld costing anywhere from $10,000 to $50,000 to inspect and repair. Can politicos force building owners to inspect their property at this cost? What is the price tag on public safety?