Resilience: What Does it Mean for Engineering Practice?

Welcome to the first of a new series of columns in Engineered Systems on the broad topics of resilience and security. Let’s start with a brief introduction. I am currently senior vice president for structures and codes at the National Ready Mixed Concrete Association. Prior to that, I was an academic and owned a small consulting firm. As a structural engineer, much of my research and consulting is involved with advanced analysis and problems in acoustic and vibration.
How does that relate to the Engineered Systems' audience? In addition to structural engineering, I have been an active member of ASHRAE for nearly 20 years. Starting with the Seismic and Wind Design and Acoustics Technical Committees, I have been a member of the technical committee on HVAC Security (now Security and Resilience) from its beginning and was chair of the committee for six years. In addition to still being an active member of the committee, I have recently agreed to lead a subcommittee on resilience that will help to develop the overall ASHRAE approach to resilient design.

What is Resilience?

Resilience, per the industry statement, is defined as “the ability to prepare and plan for, absorb, recover from, and more successfully adapt to adverse events.”
This explanation seems direct, but what does it really mean to a practicing engineer? We will look at each aspect of the resilience definition in turn and discuss the practical applications. Planning for and absorbing the effects of adverse events is typically what we have always thought of as standard engineering design. Whether defined by the building code or through the general standard of practice, we identify design conditions that are appropriate for our project and develop our design to ensure proper functionality during normal conditions and, at a minimum, life safety, in the worst case. The question about how much damage is acceptable during an extreme event is a hot topic in many organizations with a recognition that no damage is an unrealistic goal for all but a few extremely critical facilities.
The ideas of recovery and adaptation are really the portions of the resilience definition that engineers might not be as familiar with in terms of day-to-day design. Conceptually, they are not difficult. When an adverse event occurs, we want our buildings to recover to a prescribed level of functionality within a reasonable time. In addition, creating designs that can adapt over time to varying conditions, such as climate change, further adds to the life cycle functionality of buildings. At some level, this is just what we used to call “good design practice.” You wanted to design an HVAC system that was easy to repair and that, when the time came, could be replaced by a system more suitable to the current needs of the building owner and occupants.
Coming out of the ideas of resistance and recovery is the concept of functional recovery. That is, what level of functionality is required within a given time after an event? This is the concept of resilience that has gained acceptance in many standards developing organizations, and it has the advantage of being both measurable, to some extent, and understandable to the people making decisions about facility requirements — owners and jurisdictions. This definition does have important implications for the HVAC industry as we decide what it means for a system to be functional and what levels of functionality are truly needed for a building to operate after an event.
Future columns will address these concepts in detail, including discussing ongoing efforts in different codes and standards organizations to come to grips with the questions about how to achieve resilient designs. In addition, we will be exploring some of the same issues regarding security issues. In each column, I hope to bring forward the current academic and practical thinking on topics related to security and resilience and to address how those issues may affect building systems design.
I am glad you are coming on this journey with me through the evolving world of resilience and security, and please send me any comments or suggestions for topics you would like to see addressed.