What Is Resiliency?



Defining a Critical Term

Not until terms and concepts have been clearly defined can one hope to make any progress in examining the question clearly and simply and expect the reader to share one’s views.
—Carl von Clausewitz

The term “resiliency” is coming up in discussions at standards development meetings, in the design and construction community, and at every level of government, especially within the context of sustainability. But what exactly is resiliency?  

A brief internet survey reveals the complexity of the term and its various forms. The website of the U.S. Federal Emergency Management Agency, for example, shows a document with no fewer than 25 definitions of resiliency, gleaned from a variety of standards-setting bodies and professional and trade organizations. Even more definitions for specific types of resiliency, such as coastal resiliency, also are included.

Why Define Resiliency?

A plethora of definitions — some similar, none identical — fail to create the clarity demanded in the von Clausewitz quote above. Resiliency must be defined generically in order to be useful within a standards development context. Only a universal definition will allow us to assess the resiliency of the many materials we standardize and use.

In the Merriam-Webster Dictionary, resilience is defined simply:

the capability of a strained body to recover its size and shape after deformation caused especially by compressive stress
an ability to recover from or adjust easily to misfortune or change

The first of these definitions is deeply rooted in and consistent with definitions of the physical properties of plastics, rubber, and many other materials in ASTM terminology. The second definition is more pertinent to the broader term we are trying to establish here.

Objects and Events

To define any word, we must look at its context. In the context of products, “resiliency” refers to an object and its ability or inability to withstand events over time. Thus a bridge and a cellphone are objects that we expect to be able to endure certain events over the course of their service lives.

Often, a successful convergence between an object and an event — like a bridge withstanding a storm or a cellphone falling off your desk — depends upon how well the parts of the object have been designed to tolerate various impacts. In the case of building construction, the materials that make up a particular object — like structural beams, concrete, wallboard, fasteners, etc. — are also objects that can be assessed for resiliency as well.  

So resiliency can be understood at both the micro and the macro level. We expect systems and objects to encounter a variety of events over the course of their service lives, but ultimately the resilience of a system is measured by how well the objects that comprise them perform together, over time and, particularly, under duress. The system breaks down when one or more of its component parts fails, and the system cannot be easily repaired or a component replaced in the aftermath of an event.

Humans can anticipate, with greater or lesser degrees of accuracy, the types of events that may occur over a given period of time, in a given place. There are daily events (like a dolly hitting a mailroom wall), once-in-a-lifetime events (like Category 4 hurricanes) and those that are expected to occur once every few centuries (a major earthquake).

Daily events are easy to anticipate. More intense and less common occurrences can be predicted, to some extent, based on past experience in a given place. But what about occurrences that are difficult to anticipate, such as a car bomb or an earthquake?

Risk assessment is inherent to resiliency. The odds of something happening can be both a time-dependent variable and a situational variable. For example, consider the risk of a Category 4 hurricane happening in North Dakota versus Florida.  

Defining the Term

The reality is resilience is complex. But perhaps it can be defined in a way that takes time and risk into consideration. ASTM's sustainability committee (E60) is working on doing just this in a proposed standard on resiliency.

Earlier, we stated there are two time categories associated with resiliency­ — the “everyday events” and those that most people would agree are “extreme events,” such as hurricanes, that occur less frequently. Many products and buildings are resilient on a day-to-day basis.

We can use special wallboards, for example, to handle that collision between the dolly and the wall in the mailroom. The use of those products makes sense in that setting because of the obvious risk of collision. An event that rarely occurs would require something different.

If the post office hallway is expected to withstand an explosion and protect those within it, something such as steel-reinforced concrete might be used (though it could be covered in something such as wallboard to provide additional everyday functionality). If we outfit a cellphone with a waterproof case, we expect it to work in the event we drop it in a puddle. If it isn’t protected we might place it in a bag of rice and hope it recovers its previous functionality.

But this raises another question: What is meant by “recover”? Resilience is not simply the ability to endure but also to be repaired. In theory, and given the right materials, repair after everyday events would be unnecessary or simply rare. Repairing the drywall in the post office hallway every month or even year is not practical, so you might select impact-resistant drywall.

But if something can be fixed without being totally replaced after a more intense event, it is also resilient. A hurricane flooding that same mailroom may damage the lower couple of feet of drywall, but it can be cut out and replaced. In this case, the impact-resistant drywall offers resilience on a day-to day basis and under more extreme circumstances.  

So we now have a working definition for resiliency that accounts for the different occurrences or events we have discussed:

Resiliency (or resilience), n. — The ability of an object or material to endure daily wear in the intended and expected service circumstances and/or be easily repaired after a more catastrophic occurrence without the need for complete replacement.

This definition also relates to my note that resiliency is being discussed in the context of sustainability. Clearly, resilient products save resources, and that is integral to sustainability.

While this definition is likely not entirely complete and certainly is up for debate, we have used a logical discussion to get to a place where fine-tuning can begin. And once this is finely tuned, we can really begin talking about resiliency, to the satisfaction of Carl von Clausewitz.

 

Michael Schmeida is director of technical services at the Gypsum Association.

Issue Month: 
September/October
Issue Year: 
2016
Industry Sectors: 
Construction
Metals & Materials
Safety
Quality