“Do the best you can do until you know better, when you know better, do better.”
This quote from Maya Angelou is a motto that we can apply to all aspects of our lives. As a society, we should learn from our mistakes, identify gaps, and work to rectify our lapses. In the field of design, we learned more a lot from the 1989 Loma Prieta earthquake and the work to make sure damage from future earthquakes is minimized goes on. Engineering weaknesses resulted in more damage than necessary and, moving forward, we must work together to ensure the integrity of buildings and infrastructure to safeguard real estate investments and to do our part to minimize loss of life.
Consulting Engineers Corp offers a full complement of services to help you protect your building. Whether you are the owner or facility manager, contact us for a building inspection. If you are a contractor planning a new structure, you can utilize our service to ensure code compliance and the structure’s ability to withstand the forces of the next big earthquake. For existing buildings, we offer design and required changes for equipment anchorage, design for equipment upgrades, such as strengthening a roof design for new HVAC or process equipment.
Our services include site inspection, retrofit design, and execution of the design of seismic retrofitting of soft stories. If you are unfamiliar with this field, that may sound like word salad to you: allow us to go over some of the aspects of this problem.
Loma Prieta Damages
One October 17th, 1989 at 5:04 pm local time, a 6.9 magnitude earthquake was felt in the San Francisco Bay area. This slip of the famous San Andreas fault took place. The epicenter was near Loma Prieta in the Santa Cruz mountains. The type of slip is known as an oblique slip where in one side of the fault slips down and to one direction, while the other side of the fault slips up and in the opposite direction. There were 63 deaths, 3,757 injuries and property damage was significant, estimated at $5 billion. The damage occurred, according to Wikipedia, in “ Santa Cruz County and less so to the south in Monterey County, but effects extended well to the north into the San Francisco Bay Area, both on the San Francisco Peninsula and across the Bay in Oakland.” The damage was caused in great part to Liquefaction, “especially in the heavily damaged Marina District of San Francisco, but its effects were also seen in the East Bay, and near the shore of Monterey Bay, where a non-destructive tsunami was also observed.” Especially in the marina district, the site of liquefaction, many apartment buildings collapsed, or partially collapsed, due to the weakness inherent in bottom story parking garages or retail spaces. These weak bottom floors are known as “soft stories,” and when this was combined with liquefaction, as it was in the Marina district, the damage was substantial. This area experienced a high rate of liquefaction because it was built on fill and so the soil more easily was shaken to the consistency of quicksand, exacerbating the quake.
The Lessons of the Loma Prieta Earthquake
Since 1989, the problem of soft stories has been examined in great depth by many institutions and the city of San Francisco has enacted codes to require the reinforcement of soft stories. One set of codes was passed in 2002 and more in 2013. Of great note is the San Francisco Soft Story Program 2013. This program is a mandatory retrofit program to strengthen structures with soft stories. This particular program applies to “ wood-frame buildings of three or more stories or two stories over a basement or underfloor area that have any portion extending above grade, and containing five or more residential dwelling units where the permit to construct was applied for prior to January 1, 1978, and where the building has not yet been seismically strengthened.” This program is a city-wide effort to seismically strengthen structures. This classification of building is common in Mission, Western Addition, Richmond, North Beach and the Marina District. In 2013, the number of buildings this code applied to was estimated to be nearly 3,000. Each of these buildings has to be inspected, a design created, and implementation execute. It was then optimistically estimated that it would take at least seven years to complete these retrofitting.
We are Consulting Engineers Corp., and we offer a full complement of services to inspect, design, and execute the retrofitting of soft stories. We have over 46 years of experience in engineering, have designed over 100,000,000 square feet of commercial and industrial buildings in the San Francisco Bay Area since 1970. We have a great working relationship with the local building officials and agencies. Our clients include some of the largest developers/building owners in California. Call us today for a free telephone consultation.