This two-part series discusses resilience for design practice. Part 2 includes currently available guidance for resilience, example projects addressing resilience goals, and the next steps needed to advance resilience in design practice. Designing for Resilience Part 1 was presented in the December 2022 issue of STRUCTURE.
Resilience in Design Practice
According to the literature and policy statements, the common aspects of resilience are “the ability to prepare for and adapt to changing conditions and withstand and recover rapidly from disruptions” (Koliou et al., 2018). The performance of the built environment, and its support of social, economic, and public institutions, is essential for a community’s immediate response and long-term recovery after a disruptive natural hazard event.
How Is Beyond-Code Resilience Addressed?
A design team should consider the role of the building or facility within the community from a resilience perspective, drawing upon community resilience plans and knowledge of expected hazards. The design team should also become familiar with the existing conditions surrounding the site. This familiarity includes the quality of utilities and transportation services, natural infrastructure (or lack thereof), and other landscape conditions that can affect the severity of hazard events. For example, areas that are isolated or disconnected from transportation or utility services have additional challenges in restoring the intended community functions. Understanding these conditions can allow teams to recommend multi-tiered approaches to mitigate hazards (e.g., incorporating wetland features to reduce overtopping along a coastal levee).
With knowledge of community and site conditions, the design team can collaborate with clients to identify building functionality and services that may be needed during and after hazard events. The functionality requirements are then reframed as performance and acceptance criteria for design. For example, facilities that are needed immediately or shortly after a hazard event can be identified through coordination with the community resilience plans and team members. The timeframe for functional recovery may be addressed by considering approaches to reduce damage to structural and nonstructural systems, such as drift or deformation limits.
Current codes and standards are based on structural safety, a necessary condition but not adequate when considering functional recovery. A higher level of performance (reduced probability of damage and loss of function) may be required for the structural design, including coordination with other design team members about the building envelope, mechanical and electrical systems, and utility options.
Performance-based design (PBD) methods support the assessment of structural performance criteria that exceed code requirements. In such cases, buildings are often designed to meet applicable codes and standards to develop a baseline for PBD studies. Consideration should be given to whether the default Risk Category is appropriate for the baseline studies and any modifications. This approach is helpful when working with building officials and peer reviewers. PBD methods are also used to evaluate existing buildings for renovations or a proposed change in use.
What Guidance is Available?
The civil engineering profession is making advancements in several areas to incorporate resilience into design practice. Some of the documents that provide guidance and methodologies are briefly described here.
Research Needs to Support Immediate Occupancy Building Performance Objectives Following Natural Hazard Events (Sattar et al., 2018) identifies an extensive portfolio of research and implementation activities that target enhanced performance objectives for residential and commercial buildings to help reduce the likelihood of significant damage or structural collapse and provide some degree of property protection.
Prestandard for Performance-Based Wind Design (ASCE, 2019) enables the design of more efficient buildings that meet desired building functionality requirements and reduce property damage from wind events while meeting public safety and performance requirements. In addition, it clarifies design requirements for the design and review of buildings.
MOP 144 Hazard-Resilient Infrastructure: Analysis and Design (ASCE, 2021b) provides guidance and an underlying framework for creating consistency across hazards, systems, and sectors in the design of new infrastructure systems. It also discusses enhancing the resilience of existing systems and relates this framework to the economics associated with system lifecycle and socioeconomic considerations.
International Guidelines on Natural and Nature-Based Features for Flood Risk Management (Bridges et al., 2021) addresses the use of natural systems and functions to support flood risk management, including actions to reduce damage. The overarching objective is to produce sustainable outcomes that promote the resilience of communities and the environment.
FEMA P-58-6 Guidelines for Performance-Based Seismic Design of Buildings (FEMA 2018) provides guidelines and recommendations for specifying seismic performance objectives in terms of FEMA P-58 performance metrics and selecting appropriate structural and nonstructural systems, configurations, and characteristics necessary to achieve the desired performance in varying regions of seismicity.
Recommended Options for Improving the Built Environment for Post-Earthquake Reoccupancy and Functional Recovery Time (FEMA/NIST, 2021) provides a set of options for improving the built environment. It describes community resilience, re-occupancy and functional recovery, a target performance state, and identifies potential costs and benefits associated with enhanced seismic design.
Seismic Performance Assessment of Buildings Volume 8 – Methodology for Assessment of Functional Recovery Time: Preliminary Report (FEMA, 2021) describes a preliminary methodology to assess seismic performance in terms of the probable functional recovery time of individual buildings subject to a damaging earthquake based on their unique site, structural, nonstructural, and occupancy characteristics. The methodology and procedures apply to new or existing buildings.
Addressing Resilience Today
Functionality is directly influenced by nonstructural system operations, such as architectural, landscape, mechanical, electrical, or plumbing systems. While structural performance in a major earthquake can range from undamaged to collapse, much of our modern building stock can survive a moderate earthquake with little to no structural damage. However, nonstructural systems, glazing, and fragile architectural element damage can impede egress, use, or functionality. Building codes focus on increasing the mitigation of damage to nonstructural elements to combat this deficiency, including design and inspection requirements that were nonexistent 20 years ago.
These efforts may be deferred or diluted when applied to hardening and improving nonstructural elements. Building trades are specialists in constructing systems but need engineers to specify requirements for structural, bracing, or anchor elements for nonstructural elements. Building codes and inspection requirements have advanced to raise awareness and improve processes, enabling these systems to provide their intended functions. However, structural engineers can further improve the results by providing clear direction and consistent observation of complete and appropriate construction.
Most projects considering resilience are currently Risk Category III and IV buildings and infrastructure. The following examples demonstrate some resilience mitigation options.
Improving Hospital Performance for Earthquake Events
In several small to moderate earthquakes, existing hospital buildings were no longer occupiable or serving their function due to nonstructural failures, such as flooding from a water line break. Water line breaks do not pose immediate life-safety issues. Still, the resultant flooding needs to be remediated, including sanitizing the affected areas before the hospital can be used for healthcare services. These processes significantly delay the occupation and use of these critical spaces, rendering the high-performance facility to a non-functional status. In most cases, project documents must clearly identify the stringent recovery criteria so that the design and construction teams recognize its importance and bid the work accordingly.
Improving Hospital Performance for Wind Events
The St. John’s Regional Medical Center in Joplin, Missouri, provides a good example of items to consider during design to improve a facility’s resilience following a major wind event. On May 22, 2011, an EF5-rated tornado struck Joplin leaving a ¾-mile-wide, 22-mile-long path of destruction. The St. John’s Medical Center was severely damaged during the event (see Figure 3) and had to be demolished and replaced. While the structural system for the building was intact and received only minor, repairable damage, most of the windows in the building were broken by wind-borne debris, including roof gravel from the building roof. The one location where the windows remained intact was the Behavioral Health area of the building since these windows were installed with impact-resistant glazing. The building envelope was also severely damaged by rooftop mechanical units that were not sufficiently anchored to their base. If the design of the building had considered eliminating gravel from the roofing system, installing impact-resistant glazing in all the windows, and designing and inspecting the rooftop mechanical unit anchorage, the destruction that occurred might have been prevented and allowed the Medical Center to support emergency response and rebuilding of the community following the event.
Improving Hospital Performance for Flood Events
The Veterans Administration Hospital in New Orleans, LA, was closed following Hurricane Katrina. It only took two feet of flood water at the site to completely shut down the hospital because the major utilities and Emergency Room services were located in the basement and on the ground floor levels, respectively. As the flood water filled the basement and damaged the first floor, the hospital had to be closed because of the lack of power and ability to deal with the flooding. As a result, the new facility was designed with electrical generators located on the upper levels. The Emergency Room was relocated to the 2nd-floor level, with a ramp designed to also serve as a boat ramp to allow patients to be brought to the hospital in future flooding events (USCRT 2021).
Rebuilding at TAFB after Hurricane Michael
Tyndall Air Force Base (TAFB) experienced catastrophic damage during Hurricane Michael in 2018. The Category 5 storm generated wind gusts up to 172 mph, and the storm surge generated flooding of 9 to 14 feet with waves. No one was hurt on the base, but every building sustained damage, including the air hangars (see Figure 4). After the storm, TAFB collaborated with the U.S. Army Corps of Engineers, U.S. Fish and Wildlife Survey, and Jacobs Engineering Group on a rebuild program that emphasized a system-of-systems approach combining structural, nonstructural, and natural solutions. The solutions considered economic impacts on the local community, including employment and businesses (Achenbach et al. 2018). Pilot projects leveraging natural infrastructure were established around the base to strengthen dunes and enhance the back bay area marshes. At the same time, structures are being rebuilt following performance standards for design wind speeds and flood elevations and leveraging technology to enhance infrastructure-system efficiency and sustainability.
Incorporating Nature-Based Infrastructure for Transportation Resilience to Flood Events
The Delaware Department of Transportation partnered with the Delaware Center for the Inland Bays, the Delaware Department of Natural Resources and Environment Control, and the U.S. Environmental Protection Agency to examine the vulnerability and develop conceptual designs for enhancing the resilience of the Delaware State Route 1 (SR1) corridor between Rehoboth Beach and Fenwick Island. The corridor is vulnerable to flooding due to relative sea level rise and storm surges, damage and erosion due to wave action, and impacts of urban stormwater runoff. Various datasets and tools were synthesized to assess coastal vulnerability for various design scenarios and conceptual designs for adaptation alternatives. At Dewey Beach, a project was implemented at Read Avenue that included sand dune levees, tidal marsh plantings, rock sill retrofitting, a braided oyster reef for shoreline stabilization, and a storm drain outfall replacement. The projects are expected to provide several benefits, including coastal flood protection, safety, reduced inland flooding, ecosystem enhancement, and increased resilience to future coastal changes (Brown et al., 2018; Collins et al., 2021).
Improving High-Voltage Electrical Substation Equipment Earthquake Performance
Within a substation, the high-voltage electrical equipment is interconnected with a bus to allow current to flow through the substation. Electrical equipment can move dynamically during an earthquake in response to ground motion. Past earthquake performance of high-voltage equipment has demonstrated failures caused by the bus connections. The connecting bus must have adequate slack or flexible end connections to accommodate equipment movement, as indicated in Figure 5. New substations in earthquake regions with high-voltage equipment interconnecting buses can be designed for a flexible bus according to IEEE Standard 1527, which was first published in 2006. Before this standard was published, substations were built with equipment interconnected by rigid buses or flexible buses with inadequate slack that did not account for the equipment movement. These installations can be mitigated with a flexible bus or flexible end connections, with adequate slack to account for equipment earthquake response to improve resilience.
Base Isolation of High-Voltage Electrical Power Transformers
The high-voltage transformer is the most critical component for power delivery for electric power distribution systems. The high-voltage transformer has several components that are seismically vulnerable. These components include the internal coil/core, bushings, radiators, lightning arresters, and oil conservators. Transformers are expensive (millions of dollars) and have long replacement times (one to two years). From a seismic qualification perspective, testing a high-voltage power transformer with a shake table is not practical. Therefore, analytical seismic qualification methods (IEEE 693 Standard) are used. Power transformer base isolation technology, as shown in Figure 6, has been implemented to reduce the seismic vulnerability of this critical component (Kempner et al. 2015). In recent years, there have been many high-voltage transformers base isolated in the Pacific Northwest, USA, to improve the resilience of the power delivery infrastructure.
High-Voltage Transmission Line Vulnerability Assessment
Utilities perform vulnerability assessments to improve the seismic resilience of high voltage transmission line infrastructure for liquefaction and landslide hazards relative to a Pacific Northwest subduction zone event. The system’s vulnerability to liquefaction and lateral spreading is focused on major river crossings. Mitigation options include construction in wetlands and into major rivers. Additional solutions include seismically hardened crossings for new transmission line projects or preconstruction staging for temporary submerged high-voltage cables.
High-voltage transmission lines are also vulnerable to earthquake-generated landslides. The assessment determines vulnerability levels and potential mitigation options for landslides. For example, if hardening the transmission lines is not practical, the information could be used by customers at the delivery points to implement alternate resilience options.
A Call to Action
Structural engineers have a critical role in improving the built environment’s ability to contribute to resilience in our communities. Engineers can educate stakeholders about the benefits of resilience in designing new buildings and infrastructure systems and monitoring, maintaining, and upgrading existing infrastructure. With knowledge of community and site conditions, engineers can collaborate with clients and the design team to deliver value-added services that identify building and infrastructure performance and functionality needed during and after hazard events.
Guidance is needed for engineers to enable resilience in design practice that includes consideration of ethics, resilience concepts and best practices, and design criteria for building performance beyond that specified by codes and standards.
References
Achenbach, J., K. Begos, and D. Lamothe, 2018. Hurricane Michael: Tyndall Air Force Base was in the eye of the storm, and almost every structure was damaged, Washington Post, www.washingtonpost.com/national/hurricane-michael-tyndall-air-force-base-was-in-the-eye-of-the-storm-and-almost-every-structure-was-damaged/2018/10/23/26eca0b0-d6cb-11e8-aeb7-ddcad4a0a54e_story.html
ASCE (2021b) Hazard-Resilient Infrastructure: Analysis and Design, MOP 144, American Society of Civil Engineers, Reston, VA. https://ascelibrary.org/doi/book/10.1061/9780784415757
Bridges, T. S., J. K. King, J. D. Simm, M. W. Beck, G. Collins, Q. Lodder, and R. K. Mohan, eds. (2021) International Guidelines on Natural and Nature‑Based Features for Flood Risk Management. U.S. Army Engineer Research and Development Center, Vicksburg, MS.
Brown, S.P., Gilliam, L., and Nicol, D. (2018) Coastal Green Infrastructure to Enhance Resilience of State Route 1, Delaware, FHWA-HEP-18-062, Alexandria, VA. file:///F:/USNA/ASCE_Resilience_Committee/dot_58164_DS1.pdf
Collins, B., Trout, L., and Janiec, D. (2021) Integrated Shoreline Resilience: Living Shoreline Retrofits Combined with Stormwater Management, Concept through Delivery Case Study. 2021 RAE Living Shoreline Workshop. https://estuaries.org/wp-content/uploads/2021/11/Read-Ave-Presentation_2021-RAE-Living-Shoreline-Workshop_2021-10-18_Final.pdf
FEMA (2018) Guidelines for Performance-Based Seismic Design of Buildings, FEMA P-58-6, Federal Emergency Management Agency, Washington D.C. https://femap58.atcouncil.org/documents/fema-p-58/28-fema-p-58-6-guidelines-for-design/file
FEMA (2021) Seismic Performance Assessment of Buildings Volume 8 – Methodology for Assessment of Functional Recovery Time Preliminary Report, ATC 138-3, Prepared by the Applied Technology Council, Prepared for the Federal Emergency Management Agency, Washington DC https://femap58.atcouncil.org/documents/fema-p-58/34-atc-138-3-volume-8-methodology-for-assessment-of-functional-recovery-time/file
FEMA/NIST (2021) Recommended Options for Improving the Built Environment for Post-Earthquake Reoccupancy and Functional Recovery Time, FEMA P-2090 /NIST SP-1254, National Institute of Standards and Technology, Gaithersburg, MD. https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.1254.pdf
IEEE 1527 Recommended Practice for the Design of Flexible Buswork Located in Seismic Active Area, 2018, IEEE Power Engineering Society, The Institute of Electrical and Electronic Engineers, Inc., 3 Park Avenue, New York, NY 10016-5997, USA.
IEEE 693 Recommended Practice for Seismic Design of Substations Active Area, 2018, IEEE Power Engineering Society, The Institute of Electrical and Electronic Engineers, Inc., 3 Park Avenue, New York, NY 10016-5997, USA.
Kempner, L. and M. Riley, 2015. High Voltage Transformer Base Isolation, Bonneville Power Administration, US Department of Energy. www.caee.ca/pdf/Paper_94291.pdf
Koliou M, van de Lindt JW, McAllister TP, Ellingwood BR, Dillard M, Cutler H. 2018. State of the research in community resilience: Progress and challenges, Sustainable and Resilient Infrastructure, January. https://pubmed.ncbi.nlm.nih.gov/31080883
NIST, 2014. Technical Investigation of the May 22, 2011, Tornado in Joplin, Missouri, NCSTAR 3, Final Report, National Institute of Standards and Technology, Gaithersburg, MD. https://doi.org/10.6028/NIST.NCSTAR.3
Sattar, S. et al., 2018. Research Needs to Support Immediate Occupancy Building Performance Objective Following Natural Hazard Events, NIST SP-1224, National Institute of Standards and Technology, Gaithersburg, MD. https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.1224.pdf
USCRT, 2021. After Katrina, Health Care Facility’s Infrastructure Planned to Withstand Future Flooding, US Climate Resilience Toolkit, https://toolkit.climate.gov/case-studies/after-katrina-health-care-facilitys-infrastructure-planned-withstand-future-flooding