Selection Process

Associated Learning Outcomes:

At the end of this module, learners will be able to:

• Recommend a building be built with either concrete, steel, timber, or a combination given the GHG emission target, size and occupancy of the building, and purpose.
• Understand the material selection process for building construction.

Why a Selection Process is Important

A selection process is an important step in the very early design stages of a building because each material serves a different purpose, has different properties such as strength and flexibility, and it is important that the selected material aligns with the project’s specific requirements, goals, and constraints. A systematic analysis of such factors will present the most suitable material for the building when considering the structural requirements, budget, aesthetic appeal, sustainability goals, lifetime expectancy of the building, ease of construction, and maintenance requirements. A good material selection process will optimize the overall performance, longevity, and sustainability of the building.

Factors That Affect Material Choice

When it comes to building construction, several factors influence the choice of materials, including concrete, timber, and steel. Each material possesses unique characteristics that make them suitable for different applications. Let’s explore the key factors that affect material choice in construction:

1. Structural Requirements: The structural demands of a building play a crucial role in material selection. Concrete and steel are known for their strength and load-bearing capabilities, making them ideal for large-scale structures that require significant structural support. Timber, on the other hand, is commonly used in residential or light commercial buildings where lighter loads are involved.
2. Cost: Cost considerations are essential in construction projects. The cost of materials, installation, and maintenance should be carefully evaluated. Concrete and steel often have higher upfront costs but may offer long-term durability and reduced maintenance requirements. Timber can be a cost-effective option for certain applications due to its lower material cost and ease of construction.
3. Construction Time: The speed of construction can significantly impact material choice. Prefabricated steel components can be quickly assembled, reducing construction time and labour costs. Concrete construction may take longer due to curing time, while timber construction can be relatively fast, especially when using pre-cut or engineered timber products.
4. Durability and Longevity: The durability and lifespan of the materials are crucial factors in determining the overall cost-effectiveness of a building. Steel and concrete are known for their durability and resistance to fire, pests, and weathering. Properly treated and maintained timber can also exhibit excellent durability, but it may require periodic maintenance and protection against moisture and insects.
5. Design Flexibility: The design possibilities and flexibility offered by different materials can influence the material choice. Concrete and steel allow for complex architectural designs and can support large spans and heights. Timber offers a cozy and natural aesthetic, making it suitable for various architectural styles and interior finishes.
6. Environmental Impact: The environmental impact of materials is gaining increasing attention in construction. Concrete and steel production has a higher carbon footprint compared to timber. However, sustainable practices, such as using recycled materials and responsibly sourced timber, can mitigate the environmental impact of all materials.
7. Local Availability: The availability of materials in a specific region can influence material selection. Timber may be readily available in areas with abundant forests, while steel and concrete may be more accessible in urban centers with well-established supply chains.
8. Regulatory Compliance: Building codes and regulations often dictate the types of materials that can be used in construction. Compliance with safety, fire, and structural regulations is essential, and certain materials may be required or recommended based on specific building codes.

When selecting construction materials, it is crucial to consider these factors holistically, weighing the advantages and disadvantages of each material against the project’s requirements and constraints. A comprehensive evaluation, such as utilizing a weighted objectives chart, will help ensure the appropriate material choice for a successful and sustainable construction project.

For a refresher on creating a weighted objectives chart, see the video below.

Test your Knowledge – Case Study

A hypothetical project is being constructed in the desert where there is minimal access to supply chains and factories that manufacture timber, steel, and concrete. This project is a warehouse building that will be used to store large equipment and materials that are being used at a nearby mine. Aesthetics are not of concern because the warehouse is far away from any local town. The structure needs a long-span, sturdy truss system that can hold the weight of the roof. The climate is dry and arid and temperatures go below freezing at night and get up to 35C during the day. There is a large temperature differential and long exposure to the sun. The selected material needs to be strong, corrosive resistant, long-lasting and able to handle temperature changes.

To answer this problem, consider asking yourself the following questions:

1. How do the project requirements relate to the pros and cons offered by steel, concrete, and timber?
2. There is a large temperature change, how will this be accounted for?
3. Can this be accomplished with one main structural material? Or will different materials be required to work together?
4. How does ignoring aesthetics affect your decision?

After considering these questions, develop a rough sketch and design of your building with the chosen material. Be sure to justify your material choice and how you would optimize the design if you were the project manager.

Material Trends in Modern Construction

Modern construction practices are constantly evolving, driven by advancements in technology, sustainability concerns, and the need for efficient and cost-effective building solutions. Several material trends have emerged in recent years that are shaping the landscape of modern construction. Let’s explore some of these trends:

1. Sustainable and Eco-Friendly Materials: With a growing emphasis on environmental consciousness, there is a significant shift towards sustainable and eco-friendly materials in modern construction. This includes the use of recycled and reclaimed materials, such as recycled steel, reclaimed wood, and repurposed concrete. Additionally, there is increasing use of renewable materials like bamboo, hemp, and straw as viable alternatives to traditional construction materials.
2. High-Performance Insulation: Energy efficiency is a top priority in modern construction, leading to a focus on high-performance insulation materials. Innovative insulation options, such as spray foam insulation, aerogel insulation, and vacuum insulation panels, provide excellent thermal resistance, moisture control, and sound insulation properties. These materials help reduce energy consumption, enhance indoor comfort, and minimize the carbon footprint of buildings.
3. Advanced Composite Materials: Composite materials are gaining popularity due to their high strength, lightweight, and versatility. Fibre-reinforced polymers (FRPs), including carbon fibre and fibreglass, offer exceptional durability, corrosion resistance, and design flexibility. They are used in various applications, such as structural elements, façade panels, and reinforcement for concrete and steel structures, enabling efficient and sustainable construction.
4. Smart Materials and Systems: The integration of smart materials and systems has revolutionized modern construction. Self-healing concrete incorporates microcapsules that release healing agents when cracks occur, prolonging the lifespan of structures. Additionally, sensor-based systems and smart building management technologies optimize energy usage and enhance occupant comfort and safety.
5. Modular and Prefabricated Construction: The adoption of modular and prefabricated construction methods is growing rapidly. Modular construction involves fabricating building components off-site and assembling them on-site, resulting in reduced construction time, cost savings, and minimize material waste. Prefabricated building systems, including prefabricated walls, floors, and façade panels, offer improved precision, quality control, and construction efficiency.
6. 3D Printing: 3D printing technology has made significant strides in construction. It enables the fabrication of complex and customized building components with reduced material waste and construction time. Large-scale 3D printers can create structures using various materials, such as concrete, clay, and even recycled plastics. This technology has the potential to revolutionize construction by streamlining the building process and enabling architectural freedom.

These material trends in modern construction reflect a shift towards sustainability, efficiency, and innovation. By embracing these advancements, the construction industry can create more resilient, energy-efficient, and environmentally friendly buildings for a sustainable future.

Lab Report

Part 1

Laboratory tests in bending and buckling are to be conducted on eight specimens (steel rectangular bar, steel hollow square tube, wet timber with a square cross-section, dry timber with a square cross-section, dry timber with I-beam cross-section, wet timber with I-beam cross-section (in 3rd point bending set-up, i.e. four-point bending), rectangular hollow steel tube (in buckling setup)), and a concrete column.

After observing the loading scenarios conducted by the TA’s in the lab, answer the following questions in a report style:

Part 2

Similarly to part 1, this lab will focus on the strength of various concrete beams by loading and breaking the beams. There will be a total of 6 beams made, with their differences being how little or how much steel rebar reinforcement is in each, and the amounts of admixtures. Additionally when the beams are cast a slump and air content test will be conducted for each concrete mixture. Cylinders for a compressive strength test will also be cast and tested 28 days later. The beams will be broken using a 3rd point-bending set-up.

After observing the loading scenarios conducted in the lab, answer the following questions in a report style:

1. Compare the setup of each beam and determine the ratio of concrete to steel, from this predict how each beam will fail – steel or concrete controlled. [10 Marks]
2. List and compare then calculate the average result for the slump, air content and compressive strength for each beam. [30 Marks]
3. Describe with words/pictures/equations how each beam was tested and your observations during each test. [25 Marks]
4. Show graphically each test and what the loading profile looks like and indicate at what load the beam was determined to be broken. [25 Marks]
5. Compare the finding of each beam and how they related to each other and the failure mode predictions, including any sources of error or improvements to the testing that could be made. [10 Marks]

Final Exam