The damage occurs in a matter of moments, but the recovery can take months, even years. This is the signature of most natural disasters. And, as structures succumb to the power of Mother Nature, the struggle ensues to restore safety and normalcy to our communities.
Obviously, these kinds of disasters are something we can’t control, but our community resiliency afterwards – the speed and efficiency with which we recover – is something we can. Safety and preservation of property are the key elements to the restoration of housing and business functions and the limitation of displacement and economic loss.
The Earthquake Reality
In California, earthquakes pose the greatest natural threat. A forecast made in 2008 by the United States Geological Society predicts a 63 percent chance of a 6.7-magnitude earthquake in the San Francisco Bay Area by 2038. Many California businesses have experienced earthquake events, but a region-affecting catastrophic event such as the 1906 San Francisco Quake has not been experienced in this generation. Structural engineers are propelled by these forecasts to provide structures with the stamina to resist nature’s forces and keep people safe, returning communities to normal as soon as possible.
Developing better codes and standards for design
For decades, structural engineers have been improving seismic safety by designing structures and their contents to better withstand the demands of seismic events. They also perform construction reviews and inspections to ensure that buildings are being built to new higher performance levels. In addition, engineers routinely engage in bringing seismic safety awareness to the public. Volunteer organizations such as the Structural Engineers Association of California (SEAOC) and the American Society of Civil Engineers (ASCE) have provided resources and guidance on how to better prepare California for the next major earthquake. In 1973, soon after the 1971 San Fernando Earthquake caused a surprising amount of damage, SEAOC was instrumental in setting up ATC (The Applied Technology Council) to perform funded research and develop tools and guidelines to improve California’s seismic safety.
After an earthquake, one of the first objectives is to assess the damage and the level of instability of buildings to determine if they are safe from collapse and hazards to the public. Local building officials perform these post-earthquake evaluations based on a publication called “ATC-20, Procedures for Post-Earthquake Safety Evaluation of Buildings.” In the event that local building inspectors become overwhelmed, volunteer engineers who have been approved by the California Emergency Management Agency – Safety Assessment Program can perform these evaluations. The post-event schedule of building review is prioritized by lifeline buildings, utilities, and schools; then businesses; and finally residential structures.
Buildings are tagged after inspection with one of three placards that indicate the level of safety – green for no apparent significant structural damage, yellow for restricted use, and red for buildings that are unsafe and cannot be entered.
The yellow and red tags cannot be removed without permission from the appropriate building department, which will require that further evaluation be conducted and/or building repairs be designed and fully constructed. In some cases, original assessments may be modified during subsequent, more-detailed reviews, which are a lower priority while building reviewers continue completing their first round of inspections.
Understanding this process and requirements and working with local jurisdictions will help contribute to the overall recovery and return businesses to operation as quickly as possible.
To better prepare for a seismic event and increase the speed of recovery, some companies are choosing to be pro-active. A seismic evaluation based on current earthquake engineering knowledge and analytical technology will provide insight as to the strength and deformation capacities of an existing building’s fiscal and life safety risks. If needed, a program can be set up to address issues within an appropriate time schedule. A pre-event evaluation can also speed up the post-event assessment process by identifying buildings and parts of buildings which may be vulnerable, improving structure familiarity, and knowing which buildings are much less likely to be affected dramatically.
Another option available to businesses is to engage a qualified structural engineering firm as a part of an earthquake preparedness program such as San Francisco’s Building Occupancy Resumption Program (BORP). Private structural engineering firms can work with local jurisdictions and come to the aid of a business immediately after an earthquake. If required, design of repairs, construction support, and assistance in having the building reassessed can also be provided. As an example, several structural firms currently have on-call arrangements like this with PG&E in which they will respond to PG&E’s facilities immediately after an earthquake with the goal of returning power to the community more quickly.
The Association of Bay Area Governments (ABAG) and the San Francisco Planning and Urban Research Association (SPUR), both committed to reducing community hazards due to earthquakes, are additional references available to the public.
Preparing in advance to limit the damage to structures through stricter codes and better designs is the first and best response to an earthquake. For damages that do occur after a seismic event, having a plan in place for repairs and reassessment will provide the means for regaining safe structures and getting communities up and functioning again in as short a time as possible. ZFA encourages you to create an earthquake preparedness plan for your business and home and discuss the plan with your local building department and a structural engineer. Included in this newsletter is a basic outline to aid in starting the process of developing this plan, along with some useful links to additional information.