Stricter Rules Asked for Steel Frame Buildings

Alarmed by widespread cracking of steel frame buildings in the Northridge earthquake, the California Seismic Safety Commission took the unprecedented step Thursday of urging building officials throughout the western United States to suspend a construction code and require proof that new mid- to high-rise buildings can withstand major earthquakes.

The unanimous recommendation, already adopted in modified form by the city and county of Los Angeles, is expected to boost the cost of constructing office buildings, hospitals and other steel-frame structures, in some cases by millions of dollars.

The commission said the change was necessary because some new steel structures continue to be built using the same methods that allowed steel frames to crack during the Northridge quake. Although the commission is an advisory body, members said they are optimistic that their recommendation will be followed by the International Conference of Building Officials and California’s Building Standards Commission.

“The commission is taking a leadership role--all the other entities have a vested interest in this,” said Paul Fratessa, chairman of the Seismic Safety Commission. “It’s very difficult for a (local) building department to charge ahead and change something that will cost (developers) money.”

Steel frame buildings, designed to bend with enormous forces without breaking, were long considered among the safest to ride out an earthquake.

None of these modern buildings came close to collapse in the Jan. 17 quake, engineers said. But cracks have been discovered in the welded connections of at least 110 buildings, more than a quarter of all steel frame buildings in quake-affected areas in the San Fernando Valley and on the Westside. Up to 90% of the connections in some buildings cracked. Cracks were detected in buildings constructed since 1966; the tallest was 23 stories.

“What we saw from the Northridge earthquake were things we just didn’t expect. We are all in a quandary,” Arthur E. Ross, president of the Structural Engineers Assn. of California, testified Thursday.

Although the seismic commission urged building officials to set aside the old code governing the connections, the body said it would be unable to offer even interim construction alternatives until mid-September when a research consortium meets. It added that there is no consensus on how to prevent supporting beams and columns from snapping in an earthquake.

Developers and engineers will have to substantiate building designs on a case-by-case basis by providing “additional calculations, testing, improvements in design, inspection and construction practices.”

Los Angeles engineers must now try to satisfy safety concerns without clear-cut standards, and some building officials said the commission’s recommendation will have a chilling effect on the construction of steel frame buildings while researchers continue their struggle to find a solution.

“Effectively, this puts (some) projects on hold,” said Tom Kinsman, principal engineer for Seattle’s department of construction and land use. “There are big liability issues for engineers if there are known questions about a design.”

But engineers and steel industry officials agreed that the lessons of the Northridge quake could not be ignored and supported the seismic commission’s recommendations. Some privately said they were relieved because they feared that the commission might push for a total ban on the construction of steel frame buildings.

Engineers acknowledged that some new buildings were being constructed using the old design, but they said the vast majority were incorporating strengthened connections.

“Any engineer practicing in a seismic zone has already mentally suspended this code section,” said steel fabricator Roger Ferch, vice president of Herrick Corp., among the largest steel fabricators in the West.

Only one engineer formally opposed the suspension, calling it alarmist. “At this stage . . . there is no clear indication of why the joints failed,” wrote Rick Ranous, a senior structural engineer with the state Office of Emergency Services, urging that the commission issue another warning about the problem instead.

Building officials in several western cities, including Seattle, San Francisco and Reno, said they would probably change their requirements for steel frame buildings if the two groups petitioned by the seismic commission follow its recommendation.

Members of both groups said approval was likely. “I think they have to do it. I don’t see how they can say no,” said Fred Herman, an International Conference of Building Officials board member.

In San Francisco and Seattle, building officials said they are more closely scrutinizing blueprints for steel frame buildings.

The city of Los Angeles on Aug. 1 made a policy change requiring that engineers present proof on a case-by-case basis that connections in proposed steel-frame buildings have been sufficiently strengthened. The action is being felt, although the impact has been softened by the dearth of construction.

In Los Angeles County, building officials are closely scrutinizing building plans and requiring similar evidence that connections are safe, but have not formally suspended the building code.

County building officials said they are requiring the firm constructing the Downtown Walt Disney Concert Hall--which is being built to a standard far above code requirements--to submit an additional written plan outlining how welding inspections will be conducted and the frequency of those checks.

Engineers for the massive County-USC Medical Center, which includes a 15-story hospital and will replace existing facilities, say reinforcing the steel frames could tack on as much as $10 million to the $740-million tab.

Adding reinforcement plates to the connections in a 10-story, $44-million county courthouse that will be built next year near Los Angeles International Airport will probably cost an extra $500,000, engineers said.

Experts estimated that strengthening steel connections would generally increase construction costs about 2%.

“This makes a building harder to pencil out,” said Los Angeles structural engineer Thomas Sabol. “It will be a big hurdle.”

“This is just another degree of uncertainty in a very tight market,” said one steel fabricator.

Building owners in Los Angeles also expressed mounting frustration with the lack of definitive building regulations. “We’re not in favor of government abdicating its role, and it appears to me . . . they’re doing that,” said Geoffrey Ely, spokesman for the Greater Los Angeles Building Owners and Managers Assn., which represents 30% of the area’s commercial buildings. “We’ve got owners about to spend millions of dollars and there’s no standard methodology yet.”

Researchers at the University of Texas at Austin are showing more promising results than previously reported in their effort to develop welding methods and design changes that will reduce damage to steel frame buildings in earthquakes. Previous tests found that methods recommended by Los Angeles city officials to repair broken welds and beams failed when subjected to simulated magnitude 7.0 earthquakes.

Although a second round of tests has produced more positive results, professor Michael D. Engelhardt, a leading steel expert who is conducting the study for the American Institute of Steel Construction, cautioned that further research will be necessary to solve the problem.

A recently formed consortium of scientists, structural engineers and others in the steel industry is seeking government funding for an $18.5-million, three-year research project. With an initial grant of less than $2 million, the group hopes to come up with interim construction guidelines by the end of the year, a spokesman said.