The word resiliency in its definition means to withstand negative forces… being able to overcome that which is “bringing you down.” You could say structural engineers are in that battle on a regular basis, designing buildings to withstand the forces—gravity, wind, seismic—that could bring them down.
Every structure must meet minimum building code requirements that address life safety. Specifically, the Federal Emergency Management Agency (FEMA) has outlined four seismic structural performance levels for buildings.
In all building performance scenarios, a code-designed structure is required to achieve a Life Safety level of performance after a “typical” earthquake. Damage may still be significant, but the structure remains stable.
Even moderate quakes with minimal damage can be significant for the affected region – for example, the 2001 Nisqually quake that shook up $2 billion worth of damage in Seattle.
“The fact that a relatively mild earthquake can yield such significant losses may be the most important lesson Nisqually has to offer,” notes a U.S. Department of Commerce report, which concluded indirect costs to businesses was among the most common disruptions. Building damage was the most common direct cost.
Structural engineers have the ability to think beyond the minimum and engineer to Operational levels that provide full functionality following an earthquake like Nisqually. While life safety is addressed and damage is repairable in baseline building codes, a higher performing structure has the capability to not only withstand seismic forces, but can potentially avoid damage and loss of services by remaining operational immediately after a quake. Think Mission Critical Buildings like hospitals, data centers, emergency response centers, or even logistic or manufacturing centers that may be processing a significant portion of a company’s revenue stream on any given day.
Protecting Lives & Investments through Performance Based Design
Imagine not just a city that remains standing, but an economy that keeps humming after a disaster – that is resiliency and that is the vision many property/business owners and jurisdictions are starting to consider. In the midst of threats from natural disasters, changing environments and man-made influences, the value of communities that can remain stable and operational is becoming more apparent.
Enter Performance Based Design (PBD).
Building performances serve as an indicator of how well a structure supports the defined needs of its users, particularly after environmental influences such as earthquakes.
DCI Principal Greg Gilda says many savvy business are looking to Performance Based Design as a way to mitigate the business risks in their facilities that are caused by natural or man-made disasters. He likens PBD to daily life management.
“We decide what time we need to be at work and then set our alarm clocks accordingly. We even choose our daily clothing based on the performance we need for our daily activities; for example, going for a run and it’s raining, we will—at least most of us—choose a different outfit for that versus if we were going to DCI’s 30th Anniversary party.
“Businesses follow a similar approach with their daily operations,” he goes on to explain, “key business equipment may be chosen based on reliability and operational costs and facility locations may be chosen based on ease of access. Critical data centers, logistics hubs, and corporate headquarters are examples of buildings that are increasingly being designed to remain operational during these events,” he explains. “These efforts include a performance based approach not only for the primary structure, but also the secondary structure, architectural features, mechanical, and electrical systems, to name a few.”
Greg notes that as more businesses start to assess the potential savings and profit achieved from PBD and the resiliency that results from it, we will see this approach become more prevalent.
“Resiliency is beyond designing good buildings, it’s about looking at what it takes to get a building back up and operational,” says Harry Jones, DCI Principal and member of Stanford University’s Seismic Advisory Committee.
As outlined in Stanford’s Seismic Engineering Guidelines, to which Harry contributed, Stanford’s overall seismic performance goal is to “improve the seismic resiliency of the campus,” which is defined as, “the capability to sustain functionality and recover from losses generated by seismic events.”
While hospitals and other critical facilities have long been designed to “bounce back” from an earthquake, Harry confirms these performance standards are now being implemented by cities and the private sector to either stay fully operational or experience just a hiccup in interruptions post-earthquake.
“This can be as simple as making a structural system that’s easy to inspect; for example: complicated braces behind walls. After a seismic event, you’ll need to tear off and inspect,” Harry says, “which is added time and lost functionality.”
Stanford also prioritizes seismic resiliency with the understanding that an earthquake could shut down campus, which means potentially displacing their student population to other universities while the campus recovers.
“Housing, dining… those are important things,” Harry says. “You start to think about what the building’s critical functions are and how quickly they are needed after an earthquake event; and then (you) design buildings to meet that requirement using Performance Based Design tools. We tend to think of PBD as mainly for very tall, concrete towers, but it can also be used for ‘ordinary’ buildings and looking at the performance of that building, the mechanical systems, the non-structural systems. Seismic resiliency evolved from that – it’s just a different terminology.”
…and Striving to Avoid the Worst
Mexican government officials are still tallying up the economic loss from Mexico City’s magnitude 7.1 earthquake that happened in September and killed at least 326 people.
According to a CNBC article, Mexico City’s mayor has said 360 buildings will also be demolished or would need to receive major structural reinforcement, further adding to costs, and echoing a similar story that continues to make headlines today.
Locals of Christchurch, New Zealand are still feeling the aftershock of the 6.3 magnitude earthquake that struck in 2011. That quake killed 185 people and created more than $33 billion in damage. Most deaths were caused by collapsed buildings, which were designed during lax building codes of the early 1960s. Although most buildings didn’t collapse, many were torn down because of damage—a life safety issue that Mexico City now faces—digging the region into an economic hole.
The loss of life, property and livelihood is what drives structural engineers to find answers. Through Performance Based Design and innovative solutions, they are working to bring resiliency to clients and their communities.
While we cannot stop earthquakes from happening, we have the power to prevent them from becoming disasters.
About the Author
Erin Spaulding, Communications Coordinator / Erin comes from a journalism background with an emphasis in feature writing. She enjoys capturing the unique details of a story and is a firm believer that every person (and every project, for that matter) has a story to tell. Erin loves running, fly fishing and learning about unique spaces. Back in Michigan, she owns a little studio condo readapted from an asylum into a mixed-use residential building.