Council Weighs Building Codes Drawn From Quake

With the Northridge earthquake fast receding from memory, the City Council is scheduled today to take up the last in a series of building code changes based on lessons learned from that quake.

The proposed building code changes apply to so-called “soft stories” in multistory apartment buildings that engineers say may be prone to collapse in a big earthquake.

While the plans call for voluntary standards for existing buildings, officials hope their adoption may prevent another calamity like the collapse of the Northridge Meadows Apartments. The changes would be mandatory for new buildings.

Sixteen people died when the Northridge apartment building pancaked in the early morning quake in 1994. Building officials believe that as many as 20,000 of the city’s 47,000 apartment buildings may be vulnerable to collapse during a large quake, such as an 8.0, due to soft, or weak, first and second stories.

The proposed amendments “address the stiffness and the strength of elements and connections” in buildings, said Nick Delli Quadri, senior structural engineer for the city Department of Building and Safety. “You can have all these structural elements right, but if they are not connected together well, they don’t work.”

The council voted two years ago to pursue voluntary rather than mandatory changes, in part because of the high cost of retrofitting existing buildings.

Retrofitting apartment buildings according to the proposed standards could cost anywhere from $15,000 to $200,000 depending on the size and problems of the building, officials said. Low-interest loans of up to $60,000 for retrofits will be made available through the city Housing Department.

That mandatory changes would be enforced only for future construction disappointed some engineers. But officials say recent years have shown that voluntary ordinances are somewhat effective because banks and insurance companies tend to require compliance as a condition for loans and policies.

For example, as many as 5,000 L.A. homes have been retrofitted voluntarily since the quake, said Tim McCormick, director of the city’s Anchor L.A. program.

Voluntary programs in which the cost of retrofits is high have been less successful, city officials concede.

In the case of apartment buildings with soft stories, “the greater cost could stall the program,” Delli Quadri said.

New buildings would be required to follow the new standards. Delli Quadri said a handful of emergency ordinances adopted immediately after the quake have already begun ensuring that new apartments will be safer.

The draft amendments stem from months of research and technical arguments over quake damage and how to prevent it. Much of the work was done by volunteers--structural engineers who took time to examine buildings and study old blueprints after the quake, McCormick said.

The engineers who sorted through the wreckage of Northridge Meadows reached chilling conclusions, finding that its overall design was not radically different from thousands of other apartment buildings in the city.

Moreover, some of the most accepted maxims about reinforcing buildings were shown to be untrue. For example, engineers concluded that widely used materials such as drywall and stucco were poor choices for providing reinforcement.

A key mistake that designers had made, the engineers concluded, was that one could use a variety of materials and that building strength could be measured by assessing the materials’ cumulative value.

“The old building codes used to think that everything worked together,” said McCormick. “What we found is that when the building starts to move, the stucco and drywall drop away and they just aren’t in the picture.”

In addition, tucked-under parking garages--where the second story is not adequately supported--not only look flimsy, they are, especially if there are wide stretches of open space between supports, Delli Quadri said. At Northridge Meadows, a weak parking garage, and combinations of brittle materials in the ground-floor units, all contributed to the deadly collapse, he said.

The proposed new standards call for steel frames for parking garages and plywood reinforcements for ground and second stories in multistory buildings. They also call for a variety of improvements to connections to ensure the stronger materials transmit force into the foundation rather than into weak points of the building itself, said Delli Quadri.

The council is scheduled to take only a preliminary action seeking legal approval for the changes, with final consideration of the code amendments a week or more away.

Building officials say they haven’t given up the idea of making the standards retroactive, and will continue to work to persuade policymakers to strengthen the codes.

“What the public doesn’t seem to be aware of is that this [Northridge] was not a big earthquake. it was a moderate earthquake,” said McCormick. “We expect to see a lot larger earthquakes than that. . . . We were very lucky.”