Thousands of California Buildings Need Earthquake Upgrades

By John D. Lesak

Recent construction projects focused on seismic performance improvements are making headlines. Many of them are for buildings generally considered recent, such as modernist architectural works from the middle of the last century — the 1960s and 1970s, for example, which produced many beautiful buildings with structures made of reinforced concrete. Many of them perform poorly, however, with brittleness in their columns and joints.

Called “non-ductile reinforced concrete,” these structures face requirements for professional review and possible minimum retrofitting within a specific, mandated timeframe. These rules are on the books in Los Angeles as well as surrounding jurisdictions including Long Beach, Santa Monica and West Hollywood. They are valuable, too, reflecting critical safety concerns learned from hard lessons after the 1989 Loma Prieta and 1994 Northridge earthquakes.

Other municipalities are requiring reviews and retrofits of low-rise, wood frame buildings with open, poorly braced ground floors designed to accommodate parking, retail storefronts, or retracting overhead doors. In San Francisco and San Jose, and in surrounding cities from Alameda to Richmond, seismic ordinances are swiftly addressing these “soft story” structures. Expect more mandates, too. New ordinances have been enacted outside of California in far-flung states or localities from Oregon to South Carolina to New York.

For the buildings with non-ductile concrete, new California rules include the Non-ductile Concrete Retrofit Program in Los Angeles. Property owners have three years to respond with a checklist showing whether they have a non-ductile concrete building, and 10 years to “submit proof of previous retrofit, or plans to retrofit or plans to

(Continued on the next page) demolish building.” The construction itself could run up to 25 years — not exactly a fire drill.

Construction teams and their clients are learning a lot from these projects. Most important is the lesson that it’s better to undertake a voluntary seismic retrofit, as soon as possible, rather than awaiting a mandatory cure from authorities having jurisdiction.

Put another way: It’s better to act now, and act fast, than to wait for building officials to show up at your door.

In fact, savvy building owners are racing to upgrade and preserve some of the country’s most iconic modernist buildings by bracing them with inconspicuous, thoughtfully designed seismic strengthening. Many of these concrete buildings were completed prior to the mid-1970s, and their beams and columns are inadequate to ensure public safety during and after tremors. These include historically important midcentury buildings of considerable size in city centers and on college campuses.

Examples include two UCLA buildings, the 1929 Powell Library and the recently renovated Pritzker Hall, where clever and unobtrusive retrofits help stabilize and preserve these iconic buildings. The latter modernist structure, completed in 1967 and designed by celebrated architect Paul Revere Williams, achieves the seismic performance required by the University of California system by adding viscous dampers in key locations. Conceived by KPFF with the lead architect CO Architects — Page & Turnbull served as preservation architect — the project cleverly reduces seismic demand by means of a phased and unobtrusive approach.

Construction crews on an iconic, 13-story midcentury landmark in Hollywood, which opened in 1956, have taken advantage of reduced occupancy during the Covid pandemic to jump-start their successful seismic retrofit. In another example in nearby Riverside, Calif., Page & Turnbull designed a new second-floor opening in a vacant 1964 library to create The Cheech Marin Center for Chicano Art & Culture. The second-floor slab opening is sized specifically to creatively address seismic performance and enhance safety at a reasonable cost.

As we proceed, we’re learning more about seismic retrofits for modern concrete structures. The Non-Ductile Reinforced Concrete Ordinance in Los Angeles, passed in October 2015, has been written so that building owners are allowed to avoid other code-mandated upgrades to prioritize public safety through seismic performance. Project teams are finding that the seismic retrofits can be highly intrusive, however, affecting many other building systems including electrical and plumbing, for example. In the end, work scopes are growing to address more needed improvements simultaneously.

Seismic upgrades are essential, no doubt. And this is one of the rare cases where the government is asking building owners to bring their properties in line with codes written long after these structures were originally approved. Moving quickly to get an engineering study and to plot out a long-term approach for a smart retrofit is more important than ever.

For those who are wondering, there are lots of non-ductile concrete out there in our existing building stock. Anything built through 1979 should be reviewed for potential inadequacies. In the end, the goal of the construction community is collapse-prevention during future tremors. In many buildings, the reinforced concrete may be beautifully designed and historic, but it simply isn’t adequate to resist catastrophic failure.

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