Carbon Group Post 1: Why Climate Change Matters

Structural Materials and Global Climate: Why Climate Change Matters

The Carbon Task Group of the Structural Engineering Institute’s Sustainability Committee has spent years studying the ways structural materials and systems affect climate change. This is the first of a planned series of blog posts on topics discussed in depth in our forthcoming technical report.

Why should we care about climate change? How bad could it be? Warmer winters will be nice, right?

We all know what’s happening. Among other things, people are burning a lot of fossil fuels—coal, oil, gas—sending unprecedented quantities of carbon dioxide and other greenhouse gases into the atmosphere. These heat-trapping gases are raising the temperature of our air and oceans, and increasing the ocean’s acidity. Polar ice is melting, contributing to sea level rise. Some regions are experiencing more intense storms and more frequent droughts. Coral reefs are dying. But so what, we can adapt, you might think. Well, maybe, but it would not be easy and the risks are great.

Even if you don’t live by the ocean or in a place where water shortages may become commonplace, there’s a lot to worry about. Climate change promises to be politically destabilizing, as millions of people find their homes inundated or food supplies threatened. They will need to resettle, increasing the flow of refugees. Political instability will lead to conflict, and yet more refugees. The Pentagon considers climate change a major risk, an “accelerant of instability” and a “threat multiplier.” We will all be affected.

And changes are coming fast. A recent study found that the United States is likely to reach an average temperature increase of at least 2°C by 2035, nearly 15 years earlier than the prediction for the globe as a whole, and that there’s at least a 50-50 chance that the northeast could reach this dubious milestone in only 10 years (Figure 1). Coastal cities such as Boston are talking about taking extreme measures to control advancing seas, such as constructing a four-mile-long, 20-foot high, barrier wall around the harbor to protect the low-lying areas of the city (Figure 2).

But the most unsettling changes are not inevitable. We still have a short amount of time to mitigate such worst-case outcomes, and structural engineers have a key role to play. We will explore what we can do in coming blog posts, so stay tuned.

Figure 1 shows the range of climate model predictions for the timing of temperature increases in the northeastern United States, the United States as a whole, and the world as a whole. The vertical axis represents the percentage of climate models that predict a given temperature will be reached by a given year.

Figure 2 shows a proposed 4-mile-long barrier wall to protect the city of Boston (Boston Globe, 17 February 2017).

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2016 Geo-Structures Presentations

The ASCE-SEI Sustainability Committee and the ASCE Geo-Institute Sustainability in Geotechnical Engineering Committee had a very successful 2016 Geo-Structures Congress. We are happy to report that the two committees had representation at five sessions; they presented on various aspects of sustainable design. Since one of our main committee goals is to spread the word on sustainable design aspects that the practicing structural engineer can put to use, we’re posting the presentations here on our website. Have any questions on these presentations or on how to make your designs more sustainable, please comment below or contact Dave DeLong. Online copies of all of the following presentations are available here.

Track: The SEI Climate Action Initiative

‘Introduction/The Role of the Structural Engineer’ by Jim D’Aloisio

Raise awareness of the importance of climate change mitigation and adaptation by structural engineers, and share mitigation and adaptation ideas and strategies with the structural engineering community

’Mitigation of Emissions During Construction’ by Megan Stringer

My presentation discussed how engineers can quantify and reduce the embodied energy and emissions from buildings. 

‘Rationale for Concern’ byMark Webster

'Mitigation of Emissions During Building Operation'  by Dave DeLong

'The decisions that structural engineers make in detailing the building envelope can influence the building's R-value by a great degree. By detailing to increase this R-value, structural engineers can reduce the heating and cooling loads - and, as a result, the carbon impact - of the building over its service life

Track: Disaster Resilience – Indispensable for Sustainable Design

‘Introduction / Incorporating Life Cycle Assessment with Disaster Resilience’ by Tona Rodriguez-Nikl

An introduction to the session, putting forward the argument that disaster resilience must be considered as part of sustainable design. / A summary of recent efforts to integrate life cycle assessment with disaster risk methodologies. The goal of these studies is to quantify how different levels of disaster resistance affect environmental life cycle impacts.

‘Resilient Design Strategies for Structural Engineers

My presentation discussed resiliency, why it matters to structural engineers and how engineers can design resiliently. The presentation also reviewed current legislation, organizations, and rating systems that deal with resiliency. 

‘Learning to Survive: A global comparison of recovery from disasters’ by Erica Fischer and Sal Gimbert-Carter

Disasters have catastrophic impacts on countries economically, socially, culturally, and politically. This presentation compares how three different countries responded to three different disasters: 2004 Summatra Earthquake and Tsunami in Indonesia, 2005 Hurricane Katrina in New Orleans, and 2010-2011 Christchurch Earthquake Sequence in New Zealand.

 

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How do United States design codes incorporate disaster resilience and adaptation to climate change?

In the United States, building codes govern the planning, design, construction and often operation of our buildings. Codes encompass sets of regulatory data that specify the minimum standards by which we must construct our building and non-building structures. The International Building Code (IBC) is widely used in the United States. It reflects a set of rules on how we should build and what type of techniques, materials and processes we should follow. The result is a safe and permitted structure. The IBC, however, does little to regulate building behavior with regard to disaster resilience and climate change adaption.


Disaster Resilience and climate change adaptation strategies are often implemented by choice from available disaster mitigation programs. These programs are categorically divided into voluntary and mandatory programs. Most, however, are voluntary. Elective programs encourage owners and communities to implement design choice that can reduce the risk of damage from natural disasters while mandatory programs seek to enforce and enhance standards through law. In the same way that governments adopt model codes as law (e.g. the IBC), mandatory mitigation programs provide language for state and local government and Federal Agencies to adopt as law with the objective of reducing losses from natural hazards. HPBRS (High Performance Building Requirements for Sustainability) is a mandatory program ready for adoption. Often such requirements are formatted to facilitate adoption as amendments to the current IBC. Still, such mandatory amendments need to be adopted by local and state officials for progress to be made. And even when done so, the increased disaster resistance and improved durability are considered enhanced sustainability requirements within such amendments.

 

Disaster mitigation programs for adoption are technically either prescriptive-based or performance-based. The simplest approach is prescriptive, where one specifies how to build using rules that engage the engineer with what the design must achieve, avoid and/or eliminate. Prescriptive guidelines are built upon assumptions about the nature of the hazard, the structural response, and the design objectives. Design professionals must carefully evaluate these assumptions again the objectives of the project before proceeding. Performance-based approaches state what the final results need to be and how it will be measured. It does not specify how those results are to be achieved. Such approaches can be achieved through probabilistic assessments of hazards and consequential damage whereby a cost-benefit analysis to balance increased costs with improved structural resistance is provided. The probabilistic process can be repeated to achieve varying levels of robustness. This can help optimize the balance between additional materials required for construction and probable savings from repairs during the facility’s lifetime. Despite superiority of the performance-based approaches, many of the programs discussed are prescriptive. They are relatively simple and therefore have greater likelihood of being adopted by owners and government agencies.

 

Much is happening to incorporate disaster resilience design strategies into standards and codes. Engineers continue to encourage the use of LEED and life-cycle assessment. A performance-based design standard for fire protection is to be published as a joint venture through the Fire Protection Committee of ASCE/SEI and NFPA. The AISC Design Guide 19 for fire design is also available. Other developments in FP can be found in ASCE/SEI/SFPE 29-05 Standard Calculation Methods for Structural Fire Protection 2005 and ACI 216.1-07 Code Requirements for Determining Fire Resistance of Concrete and Masonry Construction Assemblies, July 2007.

 

Established in 1969, the National Institute of Standards and Technology (NIST) Engineering Laboratory has for many years supported numerous national programs with the ultimate aim of identifying improvements in codes, standards, and practices. NIST supports the adoption of disaster risk management in the code and is currently funding researching in following topics:

 

• Application of Database-assisted Design within the framework of the wind tunnel methods.
• Risk Targeted Earthquake to replace the Maximum Considered Earthquake in an effort to make risk the common denominator in design, instead of hazard.
• Structural load improvements.
• Methods for estimating wind speeds based on the logarithmic law long.
• Use of Saffir-Simpson hurricane scale for design wind speeds; database assisted design; and wind directionality effects.
• In conjunction with NRC, criteria on hurricane-borne missile speeds.
• Guidelines for including manufacturing into LCA.

Seismic events and weather-related disasters effect developed and developing countries, with much devastation faced by the rapidly growing low-income and lower middle-income countries (WBG, 2014). A lack of code compliancy along with failure to address issue of building and land-use regulatory policy in developing countries has lead to rapid urbanization without regard to disaster risk. The Global Facility for Disaster Reduction and Recovery (GFDRR), a World Bank-managed fund supported by 21 donor partners, the European Union, the World Bank, and the United Nations, is aiding in the provision of advanced knowledge and advice on disaster risk management. During the 2012-2013 fiscal year, GFDRR helped over 80 developing countries to better identify, prepare for, and recover from natural disasters (WBG, 2015). Assistance is provided across five areas: 1) risk identification; 2) risk reduction; 3) disaster preparedness; 4) financial protection for countries and people; and 5) resilient recovery when disaster does strike. The GFDRR aims to conventionalize disaster risk management and recovery into all country development polices and plans. A huge step towards this goal is the commitment of the International Development Association (IDA) to review all country strategies and operations for climate and disaster risks. (WBG, 2015).

 

Spending time and money up front to reduce the likelihood of loss during a natural disaster can bring significant benefits to owners and communities. These benefits are many and include lowering insurance costs, raising property values, providing security to residents, maintaining a consistent tax base, and minimizing the cost of disaster response and recovery. No community can ever be completely safe from all hazards, but resiliency planning gives communities the knowledge and abilities to protect themselves before and mend themselves after a disaster. Structural engineers and our supporting organizations play a vital role in resilient communities. As the nation moves forward to incorporate disaster resiliency as a national priority, standards organizations will be expected to play a critical and complementary role in achieving that goal.

References

Rodriguez-Nikl, T., Comber, M., Foo, S., Gimbert-Carter, S., Koklanos, P., Lemay, L., Maclise, L., VanGeem, M., and Webster, M. (2015). “Disaster Resilience and Sustainability”, SEI Sustainability Committee, Disaster Resilience Working Group, http://tiny.cc/DisResSust.

"Standards and Codes: Disaster-Resilient Structures and Communities." NIST. NIST Engineering Laboratory, 11 Jan. 2011. Web. 20 Oct. 2015.

“Improving Building Code Implementation and Compliance for More Resilient Buildings in Developing Coutnries: Considerations for Policy Makers.” The World Bank, October, 2014. Web. 21 Sept. 2015.

"Helping Countries Better Prepare for and Manage Disaster Risks, Climate Change." The World Bank, 30 January 2014. Web. 17 Sept. 2015.

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Hold Your Buildings to Higher Standards... of Resilient Design

Building codes are modeled to safeguard public health and safety, not necessarily to limit damage or maintain a building’s function after a natural or man-made disaster. As a result, performance based design guidelines have been developed allowing structural engineers to design structures to a certain structural performance objective. This can include reductions in damage, repair costs and/or recovery time. Structures designed to perform to higher than code standards will typically require more materials and incur greater costs associated with design and construction resources (i.e. design time, construction time, and cost associated with both). These structures, however, have the potential to be more resilient during a disaster. The upfront costs associated with these structures can result in large monetary savings in the future. The project team should consider all of the benefits associated with a more resilient structure and decide if those benefits outweigh the upfront costs.

Monetary damages from natural disasters have seen significant increases over the last 5 years (Source: SEI Committee Report). Structural engineers should consider this when making the choice to design to higher standards. There is a vital need for resilient design with more people migrating to the coasts (where natural disaster hazards are greatest), and the economic value of possessions increasing substantially (Source: SEI Committee Report). Spending time and money up front to reduce the likelihood of loss during a natural or man-made disaster can bring significant benefits to owners and communities. These benefits include lowering insurance costs, raising property values, providing security to residents, maintaining a consistent tax base, and minimizing the cost of disaster response and recovery. 

Structural engineers must also take holistic design approaches because the interaction between structural and non-structural systems varies greatly. A system may require larger initial investments in materials and resources, but could have significant savings due to reduced damage of non-structural building components during a natural or man-made disaster, implying lower expected lifetime costs of the building.  

Designing structures for higher standards will typically result in additional upfront costs: both monetary and environmental. These costs should be considered throughout the life cycle of a building, especially for those structures at risk of natural and man-made disasters.  Hazard mitigation techniques typically come with significant benefits, and. implementing resiliency strategies will allow for better protection before and better recovery after an event.    

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What Do Structural Engineers Have to Do with Disaster Resilience and Climate Change Adaptation?

Structural Engineers have the most direct impact on the disaster resilience of new and existing buildings and their ability to adapt with ever-changing climate. Although we typically cannot impact the location of a new structure, we can often impact its orientation, shape and exposure to various risks. The orientation and shape of the structure and the location of movement joints may significantly impact how much force is transferred to the building cladding, framing and lateral system during a severe wind event, earthquake, extreme temperature event, tidal event or terrorist attack. The first step in the process is to identify which risk factors pose a significant risk to the structure.

Structural Engineers must determine the potential risks for a given location over the service life of the structure even if this risk is not addressed by the governing code. For instance, current FEMA flood elevations do not directly factor in the impacts of future sea-level rise; depending on the service life of the structure, this may have a significant impact on the building’s exposure risk. We must first determine what code-prescribed requirements apply for addressing these various disaster risks, based on the occupancy type and importance of the structure. Some questions that need to be addressed are as follows:

• What design codes are currently available for addressing that specific risk?
• Do these codes specify loading and serviceability requirements?
• Where codes or design aides are not yet available, what design practices can be implemented to help address this risk?
• Building codes represent minimum/baseline requirements. Are these sufficient for the structure given its location?

After the various risk factors have been identified and the magnitudes of forces to be applied to the structure are understood, the Structural Engineer must then select the proper structural system and determine how the exterior cladding is anchored and transfers forces back to the structure. Below are some items to consider in this exercise:

• Building Material Type: Structural steel, reinforced concrete, wood, masonry, light gage, etc.
• Lateral System Type: Load-bearing or non-load bearing shear walls, moment frames, braced frames, dual systems, etc.
• Level of Ductility: Response Modification Coefficient (R-value) of lateral system, provision of alternative load paths (to address progressive collapse), decoupling of lateral system from gravity system, system redundancies (e.g. use of full depth shear connections that can transmit diaphragm shear in addition to vertical shear), etc.
• Structural Movement Joints: Are structural movement joints required? Where and how often are structural movement joints to be placed? Where are the lateral system frames located relative to these joints? For instance, locating lateral frames further away from the center of the diaphragm will increase member forces during an extreme temperature event.
• Cladding Anchorage: How and where is the cladding anchored to structure? It’s generally best to apply any lateral forces directly to floor diaphragms. Does the superstructure support the weight of the cladding? How can cladding spans be configured to absorb the most energy and to minimize the forces transferred to the building frame during a disaster?

Once the risks have been determined and the building frame system has been chosen, the Structural Engineer must determine the required level of performance during a design event based on the client’s objectives, the acceptable amount of damage after one of these events, and the client’s budget. For example, ASCE 41 categorizes the performance of a structure during a seismic event in three levels: Immediate Occupancy, Life Safety and Collapse Prevention. Similar performance levels can be established and specifically tailored for different types of disasters. The goal is to determine how quickly after an event the building must be operational. In addition, the Structural Engineer must determine how, where and what level of ductility and redundancy must be provided to avoid a disproportionate level of damage or progressive collapse of the structure.

There are many ways Structural Engineers can be proactive about disaster preparedness, providing the best possible service to their client, serving their local community as well the overall engineering community. A Structural Engineer must effectively communicate with the design team and owner on what potential disasters must be considered, identifying what the code requirements are, and what the most efficient tools and methods for addressing those risks are. Structural Engineers can serve on code committees to advance current literature on addressing the risks posed by various disasters. It’s also important to be prepared for disasters by undergoing training on performing structural assessments of existing buildings post-disaster (e.g. ATC-20-1: Postearthquake Safety Evaluation of Buildings, ATC-45: Safety Evaluation of Buildings After Wind-Storms and Floods). Our ability to quickly assess the condition and level of damage of a structure after such an event is critical to the local government’s ability to assess the overall impact to a geographic area and the resources that will be required to reconstruct or remediate the area, as appropriate.

Structural Engineers play a critical role in impacting the disaster resilience of new and existing buildings and it is incumbent on all of us to be mindful of these risk factors in our day to day work. As climate change, sea level rise, and the frequency of extreme weather events continues to escalate, our ability to address these risks on a variety of fronts will be critical to the long term sustainability of our communities.

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Disaster Resilience and Sustainability White Paper

Structural engineers can make a significant contribution to the sustainability of the built environment by considering disaster resilience in their designs. Download the SEI Sustainability Committee Disaster Resilience Working Group's definitive guide and learn how to design more resilient structures. Click here and look for the link to download at the bottom of the page.

Executive Summary

The importance of sustainability within structural engineering has become more widely accepted in recent decades. When structural engineers think of sustainability, they often limit their scope to material selection and recycling. Few structural engineers recognize the relationship between sustainability and disaster resilience, an area in which they can make significant contributions. Consequently, the aims of this report are to

1. Raise awareness of the relationship between disaster resilience and sustainability by discussing how a holistic view of sustainability must recognize the need for disaster resilience, and to
2. Provide a critical review of resilience-related efforts and resources available to practicing structural engineers and related professionals.

Sustainability encompasses three spheres: economic, environmental, and social. Within each of these spheres, sustainability requires providing for the needs of the present while allowing future generations to meet their own needs. Disaster resilience pertains to the ability to suffer less damage and recover more quickly from adverse events such as hurricanes and earthquakes. A resilient structure provides socially valuable services such as shelter and safety, even in the face of disaster, and it should do so while minimizing economic and environmental costs. Ignoring resilience during design can lead to structures that may seem green but that cannot reliably provide the services that we expect from them. Sustainability and disaster resilience are related in complex ways. Often times striving for one will help achieve the other as when a more robust structure reduces the environmental and economic cost of repairing extensive damage. Sometimes the two are at cross-purposes. For example, striving for material efficiency may render a structure less redundant, and hence less safe in a disaster.



The main section of this report discusses a variety of efforts to promote resilience and resources for resilient design. Some of these are prescriptive, offering a set of design rules more stringent than existing building codes. Others are performance-based, offering performance criteria and methods for predicting the performance. Prescriptive criteria are simpler, but do not explicitly assure better performance. Performance-based approaches allow the designer to provide specified improvements in performance, but this requires much more effort to achieve. Some of the efforts are voluntary and others are intended to become model codes. Voluntary efforts depend on the desire of the owner or developer to enforce the guidelines. Model codes aim to become law that all designers and builders must follow. Voluntary initiatives may become accepted more quickly and be more adaptable to changing times, but efforts to change model codes have the potential to effect change more broadly.

The report also discusses current efforts to quantify the connection between disaster resilience and sustainability through life cycle methods. There is no current agreement as to the best way of achieving this, nor are there standard tools for the structural engineer to use in everyday practice. However, it is important to remain aware of developments in this area, as it will likely become a common consideration in structural design. The structural engineer who stays abreast of developments, and even better, who contributes to them ñ will be at an advantage when these methods mature.



In the interest of encouraging positive and meaningful action, the report provides the following suggestions for structural engineers who are interested in supporting disaster resilience and sustainability:

1. Becoming better informed by using the references and links in this document.
2. Participating in the code adoption process to encourage resilient design standards.
3. Supporting legislation that requires or provides incentives for resilient construction.
4. Educating owners regarding the importance and value of resilient construction.
5. advocating with insurance companies and portfolio managers to offer decreased costs for better performing facilities.
6. Advocate with ASCE, SEI and other professional organizations to raise the profile of structural engineers.

Concluding the report is a thoughtful afterword on resilience and sustainability in developing countries. The afterword suggests considerations for those interested in projects in these countries and provides potential solutions to common challenges, some of which can inform design practices in developed countries such as the United States.

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How are disaster resilience, climate change, and sustainability related?

Sustainability has many definitions and applications. A long view of the future is one important aspect of sustainability. The Brundtland definition of sustainable development supports this by stating, “sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” The application of sustainable development pertains to three different spheres of life: economic, environmental, and social. These are sometimes called the three pillars of sustainability. To be sustainable, a project must respect the three pillars over a long time span.

Disaster resilience refers to the ability to suffer less damage and recover quickly from adverse events. Both man-made and natural disasters occur quickly and can have significant consequences on portions of the built environment. There are many definitions of resilience, but most of them identify two key aspects: robustness and rapidity. Robustness is the ability to limit damage. Ductility, redundancy and integrity are important characteristics that help limit damage in structures. Rapidity is the ability to restore service to pre-disaster conditions quickly after the disaster. Disaster resilience is necessary for sustainability. A facility with many features that would otherwise render it sustainable will be of no use if it is heavily damaged in a disaster. Reconstruction would incur significant financial, social, and environmental impacts. These impacts must be considered in sustainability assessments. A resilient design ensures the usefulness and longevity of other sustainability features.

Climate change refers to any significant difference in the measures of climate that lasts for a significant period of time. These changes include those related to an increase in greenhouse gasses in the atmosphere, which contribute to global warming. The scientific community is in near unanimous agreement that global warming is anthropogenic, i.e., caused by humans. Some segments of the population dispute the cause, but few dispute that climate change is occurring. Whatever the cause, weather-related disasters are expected to increase in severity and magnitude in many parts of the world. Weather events of increased severity underscore the need for a resilient built environment. In more hostile climates, resilience must be a more important component of sustainability. Moreover, construction and maintenance activities generate greenhouse gasses that can accelerate climate change. Meaningful reductions of such impacts can have positive effects in mitigating the severity of climate change.

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