Inspections, Repairs Lag for Steel-Frame Buildings : Safety: Many owners and managers say they await instructions from city. Engineering community is divided.
It is impossible to tell looking up from the street, but one of the twin Trillium office towers in Woodland Hills’ Warner Center leans about five inches to one side.
The Northridge earthquake shook the 17-story steel-frame building out of plumb, and several weeks of work last spring failed to straighten it.
“It won’t go back,” said manager Robert Benton.
Unnerved by the flaw, some tenants hired their own structural engineer and temporarily moved out. Ultimately, they returned, after the Los Angeles Building and Safety Department declared the building safe, if not as good as new.
The example of the Trillium only foreshadows the wrenching choices and immense capital outlays that lie ahead for the region’s commercial office marketplace as it slowly comes to grips with the unexpected vulnerability of steel-frame buildings. One of the most startling lessons of the earthquake was the extensive and, some think, potentially life-threatening damage to buildings made of steel, a construction material previously thought to be virtually immune to seismic forces.
Already, structural engineers have found cracks in the welded beam connections of at least 120 buildings, from high-rises to two-story office courts. Los Angeles officials expect damage to be found in many more, primarily in the San Fernando Valley and the Westside.
But a year after the earthquake, engineers and property managers say only a small percentage of suspect buildings have been thoroughly inspected, and the city of Los Angeles has not adopted an ordinance to require those inspections or set a standard for repairs.
Building owners--or in some cases their insurance carriers--must decide for themselves how thoroughly to inspect for damage, when to make repairs and whether to do the minimum restoration of pre-quake strength or add costly reinforcing designed to prevent future damage.
Many building managers have decided to wait until they get clear directions. “We’ve done only minor preliminary investigations,” said Ted Fisher, director of construction for the Voit Companies, manager of 11 steel-frame buildings in the San Fernando Valley.
Fisher said cracks have been found in several of them, but he worries that any repairs made now could later turn out to be inadequate.
“We’re waiting for the city ordinance to do complete inspection and then the repairs,” he said.
More than half of about 30 building owners and managers interviewed by The Times said they do not plan to do anything until instructed by the city.
Increasingly, it is evident that the guidance will be months or even years coming. The smaller cities hit by the Northridge earthquake--Santa Monica, Santa Clarita, Burbank and Glendale--have put off independent action, waiting for the Los Angeles City Building and Safety Department to take the lead.
But Los Angeles officials have made little progress even in defining the scope of the problem. Although the department has for months been seeking authority to order inspections, it has no efficient way to even identify which buildings need to be checked.
A working list of 755 steel-frame buildings was produced by an employee who spent months manually combing permits. A Times evaluation of a sample of the list has shown the method so flawed that dozens of buildings were missed.
The list includes, for example, 38 steel buildings on Ventura Boulevard. A Times survey of 10 blocks of the boulevard in Tarzana found six steel buildings, only two of which appeared on the city list. And the list included only 23 of the 77 steel buildings already reported to the city by their owners as damaged.
Acknowledging the shortcomings, building officials said they may have no choice but to assign a unit to perform a street-by-street survey, such as the one that catalogued the city’s unreinforced masonry buildings in the 1980s. The search could take years, said Luke Zamperini, who compiled the city list.
Meanwhile, the engineering community remains sharply divided over the degree of potential danger posed by both damaged and undamaged steel buildings which were constructed according to current standards. “There are wide differences of opinion,” said Ronald Hamburger of the San Francisco-based structural engineering firm EQE International.
Hamburger, spokesman for a statewide committee of structural engineers and academic researchers studying the problem, said one argument holds that the earthquake demonstrated the safety of steel buildings because none collapsed.
The opposing view is that the 6.7 temblor was of relatively short duration, and if it had gone on much longer, some steel buildings might have failed.
“The level of disagreement diminishes as the level of damage to the building increases,” Hamburger said.
Most experts agree that for those buildings actually damaged in the Northridge earthquake, their ability to withstand future quakes has been reduced.
The case of Holy Cross Hospital shows that engineers can look at the same building and reach opposite conclusions.
Last April, an engineer for the California Office of Statewide Health Planning and Development reported that the number of damaged connections discovered at the Mission Hills hospital made him “question allowing its continued occupancy.”
Resisting pressure to close down, however, hospital officials shored up the weakened joints following the recommendations of their structural engineer, Taylor & Gaines. They have since begun a $10-million program to repair 44 damaged joints and examine and re-weld as necessary all 283 connections in the six-story building, said Clayton W. Harvey, director of facility services for Holy Cross.
So far, at least 50 such projects have been undertaken around the city, according to the structural engineers who designed the repairs.
The more resolute owners simply clear out their tenants before starting, both to eliminate liability for injury and to facilitate the construction. Based on the advice of its structural engineers, TCW Realty Advisors, which manages property for pension funds, has vacated four buildings, two in the Westside and two in the Valley, said its president, Richard Grantham.
More often, though, the owners elect not to sacrifice the rent from tenants or the productivity of workers.
Then the repair of broken girders goes on in a strange environment melding the dirt and heavy machinery of outdoor construction with the pastel decor of the 9-to-5 office.
Each damaged joint must be exposed by cutting through walls, typically both from inside and out. Small rooms are built around the openings and complicated venting systems set up to keep the sparks and odors of welding from corrupting office spaces. Working at night to avoid disturbing the white-collar shift, welders cut out the damaged chunks with arc torches and weld new metal into place.
Sometimes whole sections of beam or column up to 42 inches in width come out, with braces and shoring set up to carry the building’s weight. Full-time deputy inspectors and ultrasound technicians go over each weld.
In larger buildings, the work can go on for months.
Structural engineer David L. Houghton of Meyers, Nelson, Houghton has designed about 15 repair jobs and said the average cost has been between $15,000 and $22,000 per joint, and can go as high as $60,000.
Those who have plunged ahead before being ordered to accept both the costs and headaches of being pioneers.
“We are developing new methods that have not been developed before,” said Robert A. Mabry, who is overseeing more than $20 million in repairs to nearly 300 cracked joints in the two main buildings of Great Western Bank’s Chatsworth headquarters.
One problem Great Western faced was how to get access to weld the outward facing surfaces without removing the precast concrete that forms the skin of its 11-story office tower. Contractor Matt Construction ran its own laboratory tests to devise the solution--cutting a large window in the beam itself for the welder to work through, then welding the window shut.
There are myriad debates along the way. Should welds be preheated the old way, by propane torch, or should the more controlled, and greatly more expensive, electric heating be used? Should backup bars--plates used by welders to make their first pass--be removed or left in place? Some engineers say yes, others no.
The question that looms over all others is whether to restore the building to its original condition--and consequently settle for the possibility that the next earthquake will break it again--or add reinforcing to make the building stronger.
Most owners making repairs now are choosing the less costly approach, which they also regard as more reliable given the current lack of technical standards for reinforcing. “If you stiffen the . . . joints, we don’t know what problems we are going to introduce,” said Harvey of Holy Cross Hospital.
Harvey is confident that tight adherence to construction specifications will improve the building. He has concluded that poor workmanship contributed to its joint failures.
Some engineers aren’t satisfied that simple repairs will suffice.
“I don’t have any confidence that the connections are adequate if they are damaged,” said Thomas A. Sabol, president of Englekirk & Sabol, a Los Angeles structural engineering firm. He strongly believes in reinforcing connections with a brace, such as the one he developed for repairs at the new Getty Center rising in the Sepulveda Pass.
Discovering that about 10% of the welded connections failed in one of its unfinished buildings, the Getty Trust helped fund testing at the University of Texas at Austin to find a solution.
After several highly publicized tests ended in weld failure, Sabol said, he came up with better results by welding a reinforcing cover plate over the beam flange.
The tests “suggest that even well-executed connections of the type some people, unfortunately, are doing today don’t perform well,” Sabol said.
After a year in which it has been befuddled by such doubts, the engineering community is at last regaining its confidence in steel.
This week, a special state committee called SAC (representing the Structural Engineers Assn. of California, the Applied Technology Council and California Universities for Research in Earthquake Engineering) plans to release preliminary guidelines covering the design and execution of connections in repairs, retrofits and new construction.
Speaking for the committee, Hamburger of EQE International said tests will continue for two or three years to refine techniques, but that the basics are falling into place.
Hamburger said he still would not recommend rushing into repair work until the next series of tests scheduled this spring. In those tests, various repair methods will be simulated by intentionally breaking welded mock-ups and re-welding them.
“Hopefully by the time we’ve tested the repaired connections, I think owners can proceed with good confidence,” Hamburger said.
Last spring, with memories of the Northridge earthquake still fresh, Los Angeles building officials contemplated tough new laws to require steel building inspections, repairs and retrofitting.
Since then, political obstacles have considerably blunted their ambitions. All residential buildings have been exempted and, in place of a prescribed standard for repairs, the city now plans to let building owners and their engineers make all the critical decisions, including whether to repair or retrofit.
Even in watered-down form, the proposal has languished after being approved by the Los Angeles City Council’s Ad Hoc Committee on Earthquake Recovery last November. Lee Hintlian, deputy for the committee chairman, Los Angeles City Councilman Hal Bernson, said building officials still have not sold council members on the proposal.
“There is some hesitancy, Hintlian said. “You’ve got to consider the entire scope of the impact, including the financial impact.
Times researcher Stephanie Stassel and data analyst Sandra Poindexter contributed to this story.
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L.A. After the Quake
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Broken Steel / RE-WELDING DAMAGED BUILDINGS
After the Northridge earthquake, cracks were found in the beams and columns of at least 120 welded steel buildings in Los Angeles, and city officials expect to uncover damage in many more. Although structural engineers and building officials still have not set standards for repairing the damage, many building owners are going ahead with the work. These are the steps they typically take:
1) Preliminary Inspection: Cracked walls, ceiling tiles and damaged windows are all indications that a building may have serious structural damage. But damage to welded joints can be hidden. To find out, a sampling of beam connections must be exposed and tested.
2) Getting to the Beams: Joints to be inspected are identified by reviewing building plans and sometimes by computer modeling. The walls are opened and fireproofing is scraped off of beams around the joints.
3) Second Inspection: A visual inspection of beams and welds is performed, checking for cracks, deformations or other damage to the steel.
4) Ultrasound Testing: An ultrasound or magnetic device is used to find hidden cracks in beams and welds. Those exceeding specified tolerances are marked for repair.
5) Applying for Work Permits: The plans are submitted to the city, which issues a building permit and work begins.
6) Welding and Repair: In damaged areas, old weld material is removed, broken areas are cut out, and the edges are cleaned in preparation for re-welding. In some cases, new steel sections are cut and welded into a damaged area.
7) A Final Test: When the weld has cooled (about 24 hours), ultrasound testing may be done again. About two weeks after completion or repairs, final testing is performed. An inspector hired by the contractor must be present to certify that the work is performed as specified.
8) City Approval: The inspector notifies the city of the completion of repairs. The city signs off on the permit.
Looking for Trouble
Ultrasound devices work by measuring the length of time a sound wave travels before it is deflected.
Gum mixture: Painted on beam to conduct sound.
Ultrasound measuring device: High-frequency sound waves bump into hidden cracks and flaws.
Ceramic electric blankets are wrapped around beams, tacked in place and covered with insulation. Beams are heated to prepare for welding then cooled slowly after.
Making Ends Meet
Arc welding joins metals with the heat produced by an electric arc. An arc forms as the electrode nears the metal’s surface.
Interior Columns: A protective wall is built around the column. Welders work inside the enclosure.
Fire Watch: A person is stationed outside the work area, alert for smoke or fire.
Fireproof Walls: A wall is built to keep sparks, dust and fumes contained. Welders take frequent breaks from the heat.
Outside access: If windows or panels can be removed, repairs can be made from the outside. Scaffolding is erected.
Reaching a Repair
Cutouts: Beams are cut to allow room to weld where space is limited, such as when beams are against walls.
“Rat hold”: Opening provides access to joint.
Backup bar: Keeps weld in place. Sometimes removed after welding.
Replacing: A section of steel may be cut out and replaced with new steel.
Shoring: A brace holds the building’s weight during the process.
Joint and Beam Failures
Cracks near welded points
Bolts sheared off
Steel bent or buckled
Weld pulled loose, tearing a hole in supporting beam
Sources: Matt Construction Corp.; TriTech Asset Services Group Inc., World Book Encyclopedia.