Council to Consider Code Changes Stemming From ’94 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 the quake.

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

While the plans call for voluntary standards rather than mandatory rules for existing buildings, officials hope their adoption may prevent another calamity like the collapse of the Northridge Meadows apartments.

Sixteen people died when the apartments collapsed 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, because of 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 old apartment buildings according to the proposed new standards could cost anywhere from $15,000 to $200,000 depending on the size of the building and the depth of its problems, building officials said. Low-interest loans of up to $60,000 for retrofitting will be made available through the city Housing Department.

Enforcing mandatory changes only in new construction disappointed some engineers, but officials say voluntary ordinances are at least somewhat effective. That’s because banks and insurance companies tend to require compliance as a condition for loans and policies.

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

But 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 will be required to follow the new standards, although a handful of emergency ordinances adopted immediately after the quake dealing with improved construction materials have already begun ensuring that new apartments will be safer, Delli Quadri said.

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 examined buildings and studied old blueprints after the quake, McCormick said.

The engineers who sorted through the wreckage of Northridge Meadows after the quake reached especially chilling conclusions, finding that the overall design of Northridge Meadows 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 a variety of materials could be used and that building strength could be measured by assessing the materials’ cumulative value.

“The old building codes use to think that everything worked together,” McCormick said. “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 in which the second story is not adequately supported not only look flimsy--they are, especially if there are wide stretches of 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, Delli Quadri said.