As the toll of earthquake damage to steel-frame buildings mounts, the state has issued an unprecedented advisory urging owners of buildings that suffered cosmetic damage to conduct thorough inspections to check for cracks in supporting columns.
Steel-frame office buildings have long been considered invulnerable to collapse, but the California Seismic Safety Commission issued its advisory this week because engineers have uncovered widespread evidence that steel beams and welds cracked in the Jan. 17 Northridge quake.
Los Angeles city officials said that cracking has been found in the steel frames of at least 50 buildings, constituting at least 10% of the low- to mid-rise structures built in the area since 1970.
Most of the failures occurred in mid-rise buildings of less than 10 stories, but an 18-story twin tower in Warner Center and an unidentified 23-story high-rise elsewhere in the San Fernando Valley also had structural problems.
The failures already have prompted city officials to require more rigorous welding procedures in new steel-frame buildings.
Although Orange County did not suffer much damage in the quake, the Sony Jumbotron at Anaheim Stadium collapsed because the two main steel support beams were thinner than designers specified, an engineer said. As a result, the city reinforced steel beams throughout the stadium to bring them up to current earthquake standards.
In January, the state Seismic Safety Commission said that 57 structures in Orange County and three of its cities missed a state deadline for coming up with plans to reduce the risk to unreinforced buildings in an earthquake. The governments said they had either complied with the law or were scrambing to comply.
On Thursday, officials said they plan to announce within two weeks that owners of all steel-frame buildings near the quake's epicenter will be required to conduct inspections for hidden structural damage.
Richard Holguin, assistant chief of the building bureau of the city's Building and Safety Department, said officials are also considering whether to require citywide inspections of such buildings, which made up half of all buildings constructed last year in Los Angeles.
Meanwhile, the mounting damage tally has sparked concerns about the safety of the cloud-piercing towers in Downtown, Century City and elsewhere, even though engineers emphasize that no steel-frame buildings came close to collapsing during the temblor.
