Applied Studies 240: Introduction to Structures

Part II: The Flow of Forces

Project 4: Using Materials Wisely

Learning Plan

  1. Review the Learning Outcomes.
  2. Read the Introduction.
  3. Complete the Required Readings and explore the online resources.
  4. Answer the Focus Questions.
  5. Add materials as appropriate to your Personal Archive.
  6. Complete Project 4. (Revisit the marking matrix.)
  7. Submit Project 4 as part of Collection 2 when you have completed Projects 3, 4, 5, and 6.

Learning Outcomes

After successfully completing this project, you will acquire proficiency in the following areas:

  1. Understanding of the characteristics of concrete, wood, masonry, and steel that are relevant to their use as structural materials;
  2. Understanding of the characteristics of various materials in relation to sustainability;
  3. Ability to describe and explain elastic limit, yield point, ultimate stress, and rupture points of structural steel members;
  4. Ability to calculate axial deformation in structural members; and
  5. Ability to synthesize numerical calculation and illustrative sketches to describe the properties of structural materials and their response to tensile, compression, and shearing stresses.

Introduction

In this project, you will explore and apply the properties of common structural materials. You will also examine how the structural system impacts the sustainability of a building throughout all phases of its life cycle.

Required Reading

Supplemental Reading

If you found this project of interest, you may want to read the following:

  • King, B. (2017). The new carbon architecture: Building to cool the climate. Gabriola Island: New Society Publishers.

Focus Questions

  1. What do you think is the most important consideration when selecting a structural system?
  2. Should all building materials be subject to Canada’s carbon tax? Should some materials be exempt? Which ones and why?

Evaluation

Your work will be evaluated using the marking matrix outlined in the Evaluation and Grading section of the Course Orientation.

Project Description

In this series of projects, you will look at the materials of structural systems and the way they impact the sustainability of your designs. Your work here will consist of two small projects:

  1. Using locally available materials (through exercises at the end of Chapter 13)
  2. Designing a sustainable structural system for one of your own designs

Project 4a: Using Locally Available Materials

Complete Exercise 4 at the end of Chapter 13 in Form and Forces: Designing Efficient, Expressive Structures. Develop an answer to each component of the exercise and present your response as a collection.

Project 4b: Embodied Energy

One aspect of structures that your text does not address in detail is sustainability. The manufacturing, transportation, installation, operation, and demolition of structural materials do have an impact on the environment. This impact can include the emission of greenhouse gases, air pollution, water pollution, exposure to toxic chemicals, and waste. In this project, you will explore the sustainability of the structural system of your proposed design.

One measure of the sustainability of a material is embodied energy. This is the amount of energy required to make, transport, construct, and maintain a product. The required reading for this project, “Measures of Sustainability: Embodied Energy,” classifies different types of embodied energy in the following way:

  • initial embodied energy
    • direct energy – the energy needed for the transportation of the materials and their construction
    • indirect energy – the energy needed to “acquire, process, and manufacture the building materials, including any transportation related to these activities”
  • recurring embodied energy – the energy needed to “maintain, repair, restore, refurbish, or replace materials, components, or systems during the life of the building”

If renewable sources of energy are used, then embodied energy is not a threat to the environment, but if the source of energy emits greenhouse gases, then it may contribute to global warming. For example, because cement is made by applying intense heat to limestone and clay and fossil fuels are used in the process, the manufacture of concrete is estimated to constitute some 5% of the world’s total greenhouse gases.

As the chart in Figure 4.1 demonstrates, the structure of a building comprises a significant portion of a building’s embodied energy.

Figure 4.1

Figure 4.1. Breakdown of initial embodied energy by typical office building components averaged over wood, steel, and concrete structures (Cole & Kernan, 1996).

Not only is this significant, but as buildings become more energy efficient in their operations, the amount of embodied energy in a building is likely to increase as a percentage of a building’s total life-cycle energy consumption.

This quote explains the following about change:

According to the Sustainable Energy Agency of Ireland (SEAI), the embodied energy of a house is typically over five times that of its annual energy consumption. This means approximately 5–10% of the total energy consumption expended during the life of the house relates to its construction. But as we move towards passive housing standards (homes whose energy consumption is kept close to zero), this percentage is likely to increase considerably. Indeed, as we consume less during the lifetime of the house, the impact of construction on your build’s lifecycle emissions is likely to gain in stature.[3]

The point is, your choice of a structural system does have a profound impact on the environment. That impact, however, is complicated as shown in Figure 4.2 below.

Figure 4.2

Figure 4.2. Comparison of embodied carbon between timber and concrete structures for a 12-storey structure (adapted from Arup/Bruce King, 2017).

What this shows is that wood structures can cause almost as many emissions as a concrete structure if poorly sourced and transported. It also illustrates that carbon counting is a very inexact science. Notice that there are no numbers on the vertical scale which makes it difficult to really assess the impact of either material on the environment. Notice too that in the previous quote, it states that “approximately 5–10% of the total energy consumption expended during the life of the house relates to its construction.” Ten percent is, of course, double the amount of five percent, which is a very wide spread.

The fact of the matter is that we lack good, consistent, accurate data on how buildings and building materials behave. This is not to say that buildings do not have a profound impact on climate change but rather that to effectively combat that change, we need to know what works and what doesn’t.

Dr. Ted Kesik’s website on this topic (which is one of the required readings for this project) provides a good assessment of the relative importance of embodied energy:

Embodied energy can be a very useful measure provided it is not viewed in absolute terms. The initial embodied energy of various materials, components and systems can vary between projects, depending on suppliers, construction methods, site location and the seasonality of the work (e.g., winter heating). The recurring embodied energy is difficult to estimate over the long term since the non-renewable energy contents of replacement materials, components or systems are difficult to predict. For example, how energy intensive will glass be 100 years from now? However, as buildings become more energy efficient and the amount of operating energy decreases, embodied energy becomes a more important consideration. There also exist strong correlations between embodied energy and environmental impacts. But it is widely acknowledged today that embodied energy represents one of many measures and should not be used as the sole basis of material, component or system selection.[4]

Using the design you identified earlier (see Identifying a Suitable Project), investigate it in terms of its embodied energy. Your job is to create a structural system for your design that incorporates the least amount of embodied energy while still fulfilling its other requirements. You can consider systems ranging from green concrete to masonry vaulting to cross-laminated timber to straw bales to bioplastics.

You will have to do some exploration to find sources for the system you choose. No matter what system you choose, however, consider it in terms of all the phases of a building project:

  • growth and sourcing (Where do the materials come from? Is it a sustainable approach?)
  • manufacture (How much energy is needed for processing the material? Is there air or water pollution associated with the process? Are there toxic chemicals involved?)
  • transportation (What will be involved in getting the materials to your site?)
  • construction (How and when are the materials assembled? How much waste is generated?)
  • operations (What is needed to maintain the system? Do the materials “off gas?” Do they pose any health risks to the inhabitants?)
  • end of life (Can the materials be recycled? How much waste will be sent to landfill?)
  • cost (Is this system economically sustainable? Does it encourage local labour?)

Make sure you consider all the materials used in the system. A lot of wood products, for example, use chemicals such as formaldehyde as a resin or bonding agent. In this respect, check out the International Living Future Institute’s Red List.

Are any of these chemicals present in the system you are proposing? If so, how will you mitigate their environmental impact?

Assemble your findings in the form of a collection.

Going Further

If this is a topic that interests you, you may want to explore the use of these two software packages:

  • The Impact Estimator for Buildings – Athena Sustainable Materials Institute. This free software provides a life cycle analysis of the materials in your design. See http://www.athenasmi.org/our-software-data/impact-estimator/
  • Tally® Environmental Impact Tool – Kieran Timberlake and Thinkstep can produce a life cycle analysis from a Revit model. You can download a free trial version. See http://choosetally.com/

Feel free to use either tool in Project 4b.

Review Terms

You should be familiar with and able to define the following terms and concepts:

direct energy
elastic limit
indirect energy
initial embodied energy
recurring embodied energy
rupture points of structural steel members
ultimate stress
yield point

Submission Requirements

For Collection 2, include the following items from Project 4:

  • Project 4a – Exercise 4 from Chapter 13 of Form and Forces
  • Project 4b – your investigation of a sustainable structural system submitted as a collection

Note: Do not submit Collection 2 until you have completed the requirements for Projects 3, 4, 5, and 6.

Footnotes

[3] (n.d.) Your carbon budget – Understanding embodied energy. Retrieved from https://www.pmcarchitects.com/sustainability-content-paul-mcalister-architects/your-carbon-budget-understanding-embodied-energy

[4] Kesik, T. (2002). Measures of sustainability: Embodied energy. Canadian Architect. Retrieved from https://www.canadianarchitect.com/asf/perspectives_sustainibility/measures_of_sustainablity/measures_of_sustainablity_embodied.htm)

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