Carbon Group Post 7: Fiber Reinforced Polymers (FRP)

Fiber reinforced polymers (FRPs) are often used for retrofit and specialized applications even though they are not common for primary structural systems. For those unfamiliar with FRPs, carbon fiber and glass fiber sporting equipment such as surfboards, bicycles, and golf clubs may provide the best example of the material. FRPs are applied by impregnating a fiber such as carbon or glass with a polymer such as epoxy. Once the polymer hardens, the fibers provide the bulk of the structural strength and stiffness while the polymer maintains the shape and protects the fibers. FRPs are convenient in that their properties are customizable by varying the size and orientation of the fibers.

Application of near surface mounted FRP strips for supplemental strengthening (courtesy of  Simpson Gumpertz & Heger Inc.)

This blog post is concerned with the climate impact of FRPs. How high are their greenhouse gas (GHG) emissions? What place do FRPs have in minimizing climate impact of structures?
The greenhouse gas (GHG) impact of FRPs has been summarized in a chapter of a recent ASCE publication, Structural Materials and GlobalClimate: A Primer on Carbon Emissions for Structural Engineers.  This post presents the main conclusions of the FRP portion of that publication.

By weight, the GHG emissions from FRPs are relatively high when compared to materials such as steel or concrete. However, FRPs can be competitive with other materials on a GHG-basis due to their high strength-to-weight ratios and their potential for use in retrofit applications that greatly extend the life of structures.

The high strength-to-weight ratios of FRPs makes them competitive with other materials despite their high emissions per unit weight. Sufficient strength can be achieved with a relatively low amount of material. For example, the strength of a carbon-epoxy FRP is around 220 ksi, while most steel is well below 100 ksi. A comparison of GHG emissions based on the amount of material required to resist the same force at ultimate stress suggests that FRPs emit between 18% and 29% of the GHGs emitted by steel. Details of this comparison can be reviewed in Structural Materials and GlobalClimate: A Primer on Carbon Emissions for Structural Engineers.

A second reason that FRPs are competitive with other materials is their utility in retrofit applications that can greatly increase the service life of a structure. If the judicious use of FRPs can avoid the need to demolish and reconstruct, then all of the GHG emissions associated with those operations can be saved. The net impact, even if GHG emissions from FRPs are relatively high, can be much lower in the retrofit case.

Each situation is different and it is impossible to make general conclusions about the overall GHG emissions from any given project and no material is hands down better than any other. Rather, the GHG impacts of each material are one of the many factors for their selection in a structural system. There are many other aspects of the behavior of FRPs that influence its use as a structural material (e.g, cost, environmental resistance, and brittle behavior of FRPs requiring higher safety factors) but there is no doubt that FRPs have a place in environmentally-responsible construction.

FRP column test specimen with longitudinal strips and wraps in the transverse direction

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A Personal History of Sustainability for Structures

How does one become interested in sustainability for structures? Over the course of a series of interviews with members of the ASCE-SEI Sustainability Committee, we hope to provide the answers. This blog and other frequently describe why sustainability is important, but the path taken by sustainability champions is seldom considered. Diverse experiences are to be expected. Understanding the reason for one’s passion for structural sustainability might help us grow the movement.

Ken Maschke, P.E., S.E., LEED A.P. is the first to be profiled in this series. Ken has served on the committee for three years and now leads the Communications Working Group. With about 10 years experience in structural engineering, he represents the crest of the wave of Generation-Y engineers now coming into their own in the profession. Sustainability was not a focus of his college education, but shortly before Ken graduated the U.S. Green Building Council unveiled the first LEED green building certification system.

How did your education prepare you for sustainable design?

Like many structural engineers, my undergraduate degree at the University of Michigan was actually in civil and environmental engineering. I fretted the hydrology and water treatment classes that were a part of the standard curriculum. At the time, I thought that the information was only useful to environmental engineers seeking to clean up superfund sites or support litigation, à la Erin Brockovich. Now I can appreciate how this basic background can be applied to aspects of sustainable design.

Photovoltaic panel located on 13th century castle in South of France. Mt. Ventoux and Rhône River in Background

Why did you decide to become LEED certified?

I was bribed. My company, Thornton Tomasetti, recognized the value of workforce versed in sustainable design before I did. They provided LEED AP training seminars, sponsored my test registration, and offered a bonus upon becoming certified. The company continues to help staff maintain their credentials.

What opened your eyes to sustainable structures?

Grain silo repurposed as condos in Denmark

In 2007, I had the opportunity to participate in an externship program with a firm in Copenhagen, Denmark. While LEED certification was still catching on domestically, sustainable features were de facto in Danish construction. I was almost laughed out of the office when I asked what a thermal break was. Fortunately, the team was patient with me and provided my first education in designing for true sustainability, as opposed to angling for LEED credits.

A couple years later I took leave from my job to live in France for six months. My wife had received a contract for on-site French to English translation for an energy company. Again, I was impressed by the attention that the French paid to energy and resource efficiency. Since, I wasn’t working, I had plenty of time to do some online research and review my own design practices.

Shortly after returning from France, I had the opportunity to assist a local artist with a large-scale park concept making extensive use of solar panels. Around the same time, I toured a solar energy harvesting power plant in Nevada, as part of the 2010 ASCE Annual Conference. From that time on, I knew that sustainability would have to be an integral part of my career.

How do you employ sustainable strategies at work?

I work in our Building Performance Practice Area. Our multidisciplinary team provides technical support to building owners, managers, and designers throughout a building’s lifecycle. We specify maintenance regimens, design repairs, and help realize building renovations. By definition, I feel that our practice is sustainable. We strive to keep existing buildings operational and improve their performance. Doing this hopefully lessens the need for new building construction.

My favorite projects could be characterized as adaptive reuse. We give new life to existing buildings by changing their occupancy or providing significant performance upgrades. I’m currently overseeing the structural transformation of an old seminary into an institute for economic education and research. Another current project repurposes an old lumberyard as a gymnasium for a charter school. We try to preserve as much of the existing structures as possible while also giving consideration to thermal performance upgrades.

The New Harmony Solar Park was estimated to have the potential of creating 3.69 Gwh per year

How has membership on the ASCE-SEI Sustainability Committee enhanced your work?

Being part of the committee provides access to the latest information on sustainable structures and great peer group. It is empowering to know that there are such motivated individuals devoting their careers (and loads of personal time) to advancing sustainability in the structural engineering profession. I look forward to learning more about their history with sustainable structures and future aspirations.

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