structural RESILIENCE A Call to Action Part 2 By SEI Board of Governors Resilience Committee
T
his 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
STRUCTURE magazine
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