Going Beyond Building Codes to Design for Structural Resiliency
Claire Moore, regional engineering practice leader at HOK’s San Francisco office, describes her team’s approach to designing buildings that will survive earthquakes and more.
How can we design buildings and infrastructure that provide resiliency against many types of hazards? Earthquakes, hurricanes, floods and wildfires become natural disasters when they significantly affect people, property and communities. Because most of the areas in the world in which our clients are developing projects are at risk of some type of natural disaster—or even an intentional attack—HOK integrates resilient design strategies into all our projects. We plan for and attempt to mitigate the damage, repair costs and time required to return a building and its community to functionality after an adverse event.
Beyond Building Codes
Here in California, where we’re always at risk for a major earthquake, many believe that a building designed to meet building codes is “earthquake proof.” Architects and engineers need to make sure clients understand that these codes actually just define a baseline focused on the life safety of occupants.
After an earthquake, a building designed to code may keep occupants safe despite sustaining significant damage to its interior, cladding and systems. This would make it costly to bring back to a functional state and not economically viable to repair. As we saw in New Orleans in the aftermath of Hurricane Katrina, this level of physical damage—along with the impact on residents, communities and businesses—could cripple a region.
If designers can help building owners and stakeholders understand that codes don’t take into account recovery times and repair costs, they likely would begin mandating more resilient design and construction strategies that contribute to higher performance after emergencies and disasters.
Next-Generation, Performance-Based Design
To improve resilience to earthquake hazards, HOK’s structural engineering team uses performance-based design. We can offer clients a wide range of building design options based on their defined performance objectives.
One tool we use is the Federal Emergency Management Association’s (FEMA) P-58 next-generation building seismic performance assessment methodology. This software demonstrates to stakeholders the probable consequences of each design decision in terms of occupant safety, damage, repair costs and recovery times. The entire team can examine the expected performance of a design for a specific earthquake intensity or scenario over an interval of time. We can run statistical models showing the probability distributions and impact predictions and then customize the design to meet a client’s resiliency objectives.
Salt Lake City Airport Structures
HOK’s engineering group is working with our planners, architects and interior designers on the Salt Lake City International Airport Terminal Redevelopment Program. The 2.6-million-sq.-ft. project scope includes a new 78-gate terminal, concourses, a parking garage, a central utility plant and a rental car facility, as well as runway updates to the existing airport. As master engineer, HOK’s team is providing mechanical, electrical, plumbing, structural, IT and security services.
Because Salt Lake City’s airport is near the Wasatch Fault, the buildings need to meet rigorous earthquake safety standards. The airport’s leaders worked with our design team to develop structural seismic performance objectives tailored for each building. The integrated design of each program element responds to regional resilience and economic considerations.
Resilience Rating Systems
As a founding member of the U.S. Resiliency Council (USRC), HOK is familiar with several new rating systems that can identify expected impacts of an earthquake or other adverse event on a building. The information in these rating systems helps owners make educated decisions about designing, purchasing, leasing, refinancing and insuring buildings. In addition to supporting the development of long-term strategic risk management solutions, clients can use the rating system metrics to demonstrate their commitment to their stakeholders and the community.
The USRC’s Building Rating System takes into account the performance of a building’s structure, MEP systems, cladding, windows, partitions and ceilings. The system goes beyond building codes, looking at the performance of a building in three dimensions: safety, damage and recovery. This tool enables clients to document the specific contributions of their projects to developing more resilient communities.
Each building forms a piece of its community. The USRC’s goal is to better educate building owners about the threats and opportunities. As owners incorporate more resiliency into their building projects, these improvements will help save lives and create long-lasting buildings that elevate the entire community.