Monday, April 29, 2013

Q9: Environmental Impact of Disasters

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What is the environmental impact of natural and man-made disasters?   How can holistic life cycle thinking impact the way we design for disasters?

Author: Matthew Comber, Lionel Lemay ; Contributors: Frances Yang, Tonatiuh Rodriguez-Nikl

At the end of 2011, the National Oceanic and Atmospheric Administration (NOAA) said the U.S. had experienced 14 separate disasters, each with an economic loss of $1 billion or more, surpassing the record set in 2008 (NOAA 2011). Losses in 2011 amounted to $55 billion in the U.S. Globally, insurers lost at least $108 billion on disasters in 2011. Reinsurer Swiss Re Ltd. said that 2011 was the second-worst year in the industry's history. Only 2005, with Hurricane Katrina and other major storms, were more costly (Swiss Re 2011). In 2012, there have been 11 natural disasters costing $1 billion or more in damage, making 2012 the second highest year with billion-dollar disasters. Tornadoes in 2012, the widespread and intense drought that covered at least 60 percent of the contiguous U.S. and Hurricane Sandy are expected to be the most costly weather-related disasters in U.S. history.


Figure 9-1 Source: Billion-Dollar U.S. Weather/Climate Disasters 1980-2012 http://www.ncdc.noaa.gov/billions/events.pdf


Most of the increased disaster losses cannot be attributed to an increased occurrence of hazards but changes in population migration and wealth. In the last several decades, population in the United States has increased and migrated toward the coasts, concentrating along the earthquake-prone Pacific coast and the hurricane-prone Atlantic and Gulf coasts. Over 60% of the U.S. population lives within 50 miles of one of its coasts (including the Great Lakes) (CRSR 1997). At the same time, wealth and the value of their possessions have increased substantially. The high concentration of people in coastal regions has produced many economic benefits, but the combined effects of booming population growth and economic and technological development are threatening the ecosystems that provide these economic benefits. Moreover, many elements of these aged infrastructures are highly vulnerable to breakdowns that can be triggered by relatively minor events (Masters 2011).


Figure 9-2 Sources: GDP Data: MeasuringWorth.com; Storm Damage Data: Wunderground.com

As a society, we have placed a great deal of emphasis on recycling rates and reducing operational energy use in green building codes and rating systems.  However, standard building code requirements for seismic or wind loads that accept significant damage in a major event are not addressed.  For example, the latest version of LEED introduced special emphasis on LCA criteria, but does not recognize disaster resilience as one of its standard criteria.

There is a jurisdictional elective in the International Green Construction Code (IGCC) for performing LCA as a way to demonstrate that a proposed building has a lower environmental impact than a reference design, but there is no guidance on incorporating resilience into the analysis. ASHRAE 189.1, Standard for Design of High Performance, Green Buildings does have an option for evaluating the embodied emissions of all building materials in a building. Clause 9.5.1.2 Step 1-1.e does require that maintenance, repair, and replacement during the design life with or without operational energy consumption must be taken into account, but it is clear that this is referring to regular maintenance, repair and replacement and not damage caused by natural hazards.

For a building to be truly sustainable it should be resilient. It should consider potential for future use and re-use and have a long service life with low maintenance costs. (Kestner, Goupil & Lorenz, 2010) In addition, a sustainable building should be designed to sustain minimal damage due to natural disasters such as hurricanes, tornadoes, earthquakes, flooding and fire (Kneer & Maclise 2008). Otherwise, the environmental, economic and societal burden of our built environment could be overwhelming. A building that requires frequent repair and maintenance or complete replacement after disasters would result in unnecessary cost, from both private and public sources, and environmental burdens including the energy, waste and emissions due to disposal, repair and replacement.

Resilience and LCA

A few methodologies have been proposed (Court et al. 2012) and implemented (Comber et al. 2012 & 2013b, Comber & Poland 2013, Sarkisian et al. 2012) to assess the environmental impacts of seismic damage. At their core, these methodologies share a common approach: a pairing of a seismic loss assessment methodology with building component LCA data. The concept of using a seismic damage assessment to understand environmental impacts is very new- there is no standard method or procedure, however the methods proposed by these authors can be very useful depending upon the desired results and amount of detailed information damage an life cycle inventory data available.
 
Damage Assessment

Consideration of isolated disastrous events can be a useful approach for clients who are looking at potentially large capital losses associated with direct damage or downtime during the repair process.  Care should be taken, however, to communicate to the client that these events have a somewhat small probability of occurrence during any building’s lifespan.  A more holistic understanding of a building’s probable lifetime environmental impacts may be gained by conducting a probabilistic seismic hazard assessment and examining the potential impacts across a range of risk levels. Comber et al. (2013a) propose a method for conducting such an assessment and note the importance of including a consideration of small- to moderate-sized seismic events in such an assessment.

The method proposed by Court et al. has yet to be explicitly defined; rather the authors are currently making recommendations to FEMA for various approaches that may be feasible.  Regardless of the final version of their approach, it stands to provide a useful method to gaining a detailed understanding of the building’s impacts and their distributions throughout the structure.  Sarkisian et al. propose a method and associated software tool that allows a general understanding of total impacts best used when comparing one structural seismic system to another.  The methodology proposed by Comber et al. is a more detailed approach that is designed to target key “environmentally sensitive” components so that the structural and/or nonstructural seismic design strategy can be adjusted at the project outset to best protect those components from damage.  A common theme can be found throughout these authors’ approaches: the role of the structure (and thus the structural engineer) must often be heightened to one of protecting nonstructural components in order to effectively minimize impacts of seismic damage.

Environmental Impact Data

Sarkisian et al. propose a process-based LCA that is defined in terms of material quantities, whereas Comber et al. use an Economic Input-Output LCA that is based on a building cost estimate (more detail on their EIO procedure is presented by Comber et al. 2013a).

Sustainable Building Standards

For green building standards to truly address sustainable construction, the concept of disaster resilience must be addressed. State-of-the-art modern buildings are no doubt currently in construction that are designed to meet LEED or other green building requirements that could be easily destroyed as a result of a hurricane, earthquake or other force of nature.  There is a high risk that the monetary & environmental investment made to create high-efficiency systems in these buildings will not generate a return if the building undergoes damage due to a natural hazard event.  A consideration of the risks and benefits associated with resilient design strategies would ensure that the statistical minimum lifetime environmental impacts are realized in these designs.

References

Comber M.V., Poland C., Sinclair M. (2012).  “Environmental impact seismic assessment: application of performance-based earthquake engineering methodologies to optimize environmental performance.”  Proceedings, American Society of Civil Engineers/ Structural Engineering Institute (ASCE-SEI) Structures Congress, Chicago, IL.

Comber, M.V., Erickson, C., & Poland, C. (2013a). “Quantifying and Minimizing the Environmental Impacts of Seismic Damage to Buildings: A Procedure and Case Study.” Journal of Structural Engineering, in review.

Comber, M.V., Poland, C., & Sinclair, K.M. (2013b). “Sustainable Concrete Structures through Seismic Resilience: A Case Study.” Proceedings, International Concrete Sustainability Conference, San Francisco, CA.

Comber, M.V. & Poland, C. (2013). “Disaster Resilience and Sustainable Design: Quantifying the Benefits of a Holistic Design Approach.” Proceedings, American Society of Civil Engineers- Structural Engineering Institute (ASCE-SEI) Structures Congress, Pittsburgh, PA.

Congressional Research Service Report (CRSR). (1997). Oceans & Coastal Resources: A Briefing Book, Congressional Research Service Report 97-588 ENR.

http://www.cnie.org/NLE/CRSreports/BriefingBooks/Oceans. Accessed November 13, 2012.
Court A., Simonen K., Webster M., Trusty W., Morris P. (2012).  “Linking next-generation performance-based seismic design criteria to environmental performance (ATC-86 and ATC-58).”  Proceedings, American Society of Civil Engineers/ Structural Engineering Institute (ASCE-SEI) Structures Congress, Chicago, IL.

Economic Policy Institute (EPI). (2012). State of Working America, http://stateofworkingamerica.org/chart/swa-wealth-figure-6a-average-household-net. Accessed November 13, 2012.

Kestner, D, Goupil, J. & Lorenz, E. ed. (2010).  Sustainability Guidelines for the Structural Engineer.  American Society of Civil Engineers Structural Engineering Institute, Reston Virginia.

Kneer, E., & Maclise, L. (2008). “Consideration of Building Performance in Sustainable Design: A Structural Engineer’s Role.” Proceedings, Structural Engineers Association of California (SEAOC) Annual Convention.

Masters, J. (2011). 2011’s Billion-Dollar Disasters: Is climate Change to Blame?, Weaterwise, March-April 2012, http://www.weatherwise.org/Archives/Back%20Issues/2012/March-April%202012/dollar-disasters-full.html. Accessed November 13, 2012.

National Climate Data Center (NOAA). (2011). http://www.ncdc.noaa.gov/billions. Accessed November 13, 2012.

Sarkisian M., Hu L., Shook D. (2012).  “Mapping a structure’s impact on the environment.”  Proceedings, American Society of Civil Engineers/ Structural Engineering Institute (ASCE-SEI) Structures Congress, Chicago, IL.

Swiss Re Estimates 2011 Economic Cat Loss at $350 Bn; Insured Loss $108 Bn. (2011) http://www.insurancejournal.com/news/international/2011/12/15/227534.htm, accessed November 13, 2012.

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Saturday, April 27, 2013

Q2: Most Effective Strategies

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What are some of the most effective design strategies that I can put into practice as a structural engineer?
Author: Frances Yang; Contributors: Steve Buonopane, Lionel Lemay, Kate Simonen, Dirk Kestner

Design for material efficiency

  • Design that maximizes efficient use of materials by not oversizing simply for ease and speed of construction can reduce an estimated 5% to 7.4% of embodied carbon, excluding operational energy. (Anderson 2009)
  • On the other hand, designs with unconventionally long spans tend to incur a 20% increase in embodied carbon to the structure, or 10% to the whole building.(Arup 2010)

Design for adaptability and deconstruction to enable future change in function

  • This is highly dependent on the assumptions of future use, but a simple estimate performed by Anderson and Silman indicates that a 43% embodied carbon savings can be achieved if the design doubles the structure’s lifespan. (Anderson 2009)
  • The Deconstructable and Reusable Composite Slab invented by a team of structural engineers enables reusability of nearly all components.  A precast system set on reusable steel beams loses the efficiency of composite action, and therefore demands approx. 30% more material.  This new system retains composite action while allowing for disassembly and reuse.   This concept won an award in the 2007 Lifecycle Building Challenge. (Webster 2007)



Figure 1: Deconstructable and Reusable Composite Slab. Image © Simpson Gumpertz & Heger Inc.

Use salvaged materials

  • A design that uses 50% salvaged steel sections showed a 34% decrease in embodied carbon. (Anderson 2009)
  • NREL’s building in Colorado used 124 salvaged pipe columns for 88% of the columns on the project.  A cradle-to-gate LCA on the columns found that when compared to equivalent manufactured pipe columns, the use of salvaged columns reduced CO2 emissions by 65%. Total energy was reduced by over 76 %. (Guggemos 2010)

Minimize cement in the concrete

  • Use of slag, a waste material, to replace, 50% of conventional cement in the concrete alone resulted in a 38% carbon savings for a concrete framed structure, and a 22% savings for the same structure with a steel frame.  (Anderson 2009)
  • Another study for the Concrete Centre confirms the previous findings by Anderson and states that specification of cement content in concrete mixes can affect the embodied carbon of the structure by +/-33%. (Arup 2010)  Read more on sources of variability in Q5.
  • The lowest reduction cited was in a study by MIT that found that increasing supplementary cementitious material (SCM) substitution in a concrete building from 10% to 25% decreased pre-use GWP by only 4.3%. The same study also found that Increasing SCM substitution from 10% to 50% in ICF walls can reduce the pre-use GWP by 12% to 14%. (Ocshendorf 2010)
  • Furthermore, Anderson found that a design using both concrete containing 50% slag and 30% recycled aggregate, in combination with 50% salvaged steel, can reduce embodied carbon by an estimated 41% to 45% of embodied carbon. (Anderson 2009)

It should be noted that these were based on a direct replacement of cement with SCM’s, such as slag or fly ash, meaning the reduction in cement was equally the percent recycled content.  Structural engineers should be careful when reviewing concrete mix submittals that the supplier has effectively reduced the quantity of cement, not merely added SCMs to increase recycled content.

Integrate the structural system for optimal operational energy performance

See Q3 for these.

Design and promote resilient structures

Traditional LCA methodologies do not consider the risk of building life and life of building components to catastrophic hazards. Some methods of integrating LCA and damage assessment are under development. A broader need is for resilience-based design to make its way into standard practice. See Q9 for more on this topic.

Specify more environmentally responsible sourcing

The issues around biogeniccarbon are complex.  Life cycle assessment does not currently capture all the metrics relevant to healthy forests yet importance of responsibly managed forests is undeniable.  See Q5 for more on biogenic carbon and support behind responsible forest management.

In summary, there are numerous design and specification strategies structural engineers can implement to improve the environmental performance of buildings both upstream and downstream of construction.  See our Bibliography, and particularly TheSustainable Design Guide for Structural Engineers, for more detail on how to implement all of these.

References

Anderson, J., Silman, R. (2009) “A Life Cycle Inventory of Structural Engineering Design Strategies for Greenhouse Gas Reduction,” Structural Engineering International, March 2009 Issue.

Arup (2010) “Embodied Carbon Study: Study of Commercial Office, Hospital and School buildings,” The Concrete Centre, United Kingdom.

Guggemos, A.A., Plaut, M.; Bergstrom, E.; Gotthelf, H.; and Haney, J. (2010) “Greening the Structural Steel Process: A Case Study of the National Renewable Energy Laboratory,” Proceedings of the 2010 Structures Congress, ASCE, Reston, Virginia.

Kestner, D., Goupil, J., and Lorenz, E. (2010) Sustainability Guidelines for the Structural Engineer, Sponsored by Sustainability Committee of the Structural Engineering Institute of ASCE, Reston, VA: ASCE, 978-0-7844-1119-3.

Marceau, M., and VanGeem, M. (2008) Comparison of the Life Cycle Assessments of an Insulating Concrete Form House and a Wood Frame House, SN3041, Portland Cement Association, Skokie, Illinois.

Masanet, E., Stadel, A., and Gursel, P. (2012)  Life-Cycle Evaluation of Concrete Building Construction as a Strategy for Sustainable Cities, SN3119, Portland Cement Association, Skokie, Illinois.

Ochsendorf, J. et al. (2010) “Life Cycle Assessment (LCA) of Buildings Interim Report,” Concrete Sustainability Hub, Massachusetts Institute of Technology, Cambridge, Massachusetts.

Webster, M., Kestner, D., Parker, J., Waltham, M.. (2007)  “Deconstructalbe and Reusable Composite Slab,” Winners in the Building Category: Component – Professional Unbuilt, Lifecycle Building Challenge <http://www.lifecyclebuilding.org/2007.php>

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Thursday, April 25, 2013

Q1:Which is better, steel or concrete?

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Which is better, steel or concrete?

Author: Frances Yang; Contributors: Steve Buonopane, Kate Simonen, Adam Slivers

Although many trade-sponsored studies promote one type of structural material as more sustainable than the other, the results across all concrete vs. steel studies we have seen reinforce the conclusion that the likely variation within each material is greater than the difference between materials (Weisenberger 2010, Masanet 2012, Arup 2010).


Figure 1-1: Results from literature review of 13 embodied carbon studies

This conclusion is influenced by two primary factors. First, all structures are truly composite systems of steel and concrete, with significant amounts of both concrete (foundations, fill in deck) and steel (rebar).   Second, differences in the goal, scope and functional units of various LCAs leads to greater differences in results than the difference between the concrete and steel figures of each study (Hsu 2010).  Variability across material types within a single LCA study are often less than 5%, yet variability of the same material types across multiple LCA studies are on the order of 25% to 35% (Ramesh 2010).



Figures 1-2, 1-3: Courtesy of S. Hsu at MIT

Another very important consideration in LCA is the full life-cycle.  Most studies only include cradle-to-gate or cradle-to-site impacts, meaning from extraction of the raw materials to leaving the product factory gate or completion of construction on site.  Truly holistic evaluation should include the full life-cycle.  A recent MIT study compared steel, concrete and wood frame commercial and residential structures, and quantified the carbon emission impact of building systems over their complete life cycle. This study found that the greatest differences in impact were in the operation phase of the life-cycle (Ochsendorf 2011). See Q2 and Q3 for ideas on how structural design and specifications can affect operational impacts.

So a more effective question the SE should ask is, “What can a structural engineer do, to lower the environmental footprint of the building within the structural system and material(s) selected?”  LCA can help you identify the material or system which has the most potential for effective sustainability improvements within your specific project constraints. Most often, the selection of the main structural system is based on traditional performance criteria—strength, fire resistance, durability, constructability, low vibration, noise control, aesthetics and cost—just to name a few. Sustainability criteria, including environmental impacts, are additional performance criteria that should be considered in the design process on all projects.

Material efficiency, designing for adaptability and deconstruction to enable reuse, using salvaged materials, integration of structural system with building systems to optimize energy use such as design to utilize thermal mass or to optimize daylighting potential, reducing cement where appropriate in concrete mixtures, and specifying more environmentally responsible sourcing -- structural engineers can implement all of these measures to some degree all buildings.  (See Q2 for more detail.)  As every building project has unique criteria and available resources, the best approach for SEs is to maximize these opportunities, and use them to inform materials selection, rather than the other way around.

At the same time, variability in accounting is a current problem in arriving at truly comparable results, and structural engineers need to do the following things to address this problem:

  1. Be clear on the boundaries and accounting method used in LCA studies to insure final comparisons consider the full life-cycle impacts.  This first requires an understanding of the methodological differences that can impact LCA results.  See Q5 for the various accounting methods seen in life-cycle inventories and tools.
  2. Focus on reducing impacts that are within their control through design and specification.  See Q2, plus Q3 for examples specific to operational energy performance, and Q9 for resilience.
  3. Engage in creation of product category rules (PCRs) and environmental product declarations (EPDs).  See Q6 for more on PCRs, EPDs, and whole building LCA standardization
  4. Recognize the broad range of environmental impacts related to material extraction, manufacturing, use and end of life.  See Q7 and Q8 for more information on LCA metrics.

References

Arup (2010) “Embodied Carbon Study: Study of Commercial Office, Hospital and School buildings,” The Concrete Centre, United Kingdom. 

Hsu, S. (2010) “Life Cycle Assessment of Materials and Construction in Commercial Structures: Variability and Limitations,” Massachusetts Institute of Technology, Cambridge, Massachusetts. 

Masanet, E., Stadel, A., and Gursel, P. (2012) Life-Cycle Evaluation of Concrete Building Construction as a Strategy for Sustainable Cities, SN3119, Portland Cement Association, Skokie, Illinois. 

Ochsendorf, J., et al. (2011) “Methods, Impacts, and Opportunities in the Concrete Building Life Cycle,” Massachusetts Institute of Technology, Cambridge, Massachusetts. 

Ramesh, T., Prakash, R., Shukla, K.K. (2010) “Life cycle energy analysis of buildings: An overview,” Energy and Buildings, 42 1592-1600. 

Seppo, J.; Horvath, A., and Guggemos, A. (2006) “Life-Cycle Assessment of Office Buildings in Europe and the United States,” Journal of Infrastructure Systems, March 2006 Issue. 

Weisenberger, G. (2010) “And the Winner is... A framing system’s environmental impact depends on more than just the choice of materials,” Modern Steel Construction, Aug 2010 Issue.

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