| dc.description.abstract | In the interest of public safety, building designs and construction in Canada are regulated by local legislation which is typically a provincial, or as appropriate municipal, building code based on the National Building Code of Canada (NBCC). The current version of NBCC is an objective-based building code which allow code users to substitute prescribed building designs with a solution achieving the same level of performance defined by intent statements. These intent statements provide rationale behind prescriptive solutions including some degree of baseline as well as factors of safety for building design. However, due to its structure and for practical reasons, it does not and cannot envision every single design possibility in practice. In addition, its slow update cycle cannot keep up with technology advancements currently driven by concerns around energy efficiency, sustainability and development of new materials, and construction methods and climate change. These contribute to some of the challenges that may be faced in application of the NBCC which are investigated through the following five parameters: ‘History and Scientific Background’, ‘Reliability’, ‘Economic Impact’, ‘Design Practicality’ and ‘Guidance for Compliance’.
In order to identify and assess the potential issues, three case studies involving atrium design, design for spatial separation of buildings, and finally, design of a building with exposed mass timber elements are presented. Through these three case studies, this thesis investigates technical challenges that exist in executing different design scenarios under the current NBCC. Further, the case studies identify several important factors that designers should be aware of to avoid inappropriate application of the prescriptive solutions specified by the code or, equally, inappropriate evaluations during assessment of an alternative solution through the performance-based approach to building design in the Canadian context.
Results lead to identification of challenges encountered in utilizing the current NBCC, not only in terms of achieving the intended level of performance of a design, but also, if desired, in pursuing appropriate alternative design solutions. One of the reasons is that the appropriate level of performance for building design is found challenging to establish, as the intent prescribed in the building code is qualitative while the potential catastrophic events considered could have a low probability but a significant consequence. In addition, these prescribed building code provisions may have limited background information or scientific gaps, as well as outdated technology based on the state of art knowledge available at the time of establishment, some may be from as early as 1960s, leading to overly conservative or even inappropriate design decisions in the present building environment. Inconsistencies in recognizing the relative performance of modern technologies in these provisions are also identified, such as the approximately 90% effectiveness of sprinkler performance, which increases the complexity and uncertainty in building design and review, as they significantly impact the establishment of the baseline for compliant design as well.
Further, some important considerations are not appropriately addressed in the current NBCC. In some designs, costs of the acceptable solutions are demonstrated to be 44 times more than alternative solutions. Similarly, building design performance in natural disasters such as earthquakes is not accounted for. This could result in potentially high consequences. Finally, the current NBCC does not recognize social implications, sustainability, and environmental costs that have become contributing factors to building design, material selections, and construction practices towards a cleaner environment.
Lastly, limitations found in key aspects of design guidance can lead to inappropriate design when following prescriptive solutions specified by the code or, equally important, can lead to inappropriate evaluation during assessment of an alternative solution. Limited guidance and lack of quantitative assessment thresholds on how either the design team should generate, or how a local officer of the Authority Having Jurisdiction (AHJ) should review and evaluate these building design proposals in terms of their level of performance is provided in current building code. As a result, complex and sophisticated designs may require stakeholders to not only possess experience in industry, but also knowledge of modern research, technology, and fire and life safety risks and trade-offs. Such knowledge can only really be obtained through enhanced education which is limited in Canada currently. The existing level of the competence of both designers and reviewers may lead to inappropriate application of a code compliant fire safety solution, let alone an alternative solution to compliant design.
Based on the foregoing, a new paradigm of building design and evaluation in Canada is required. However, with the current Canadian building code environment and challenges identified in this thesis, a long path lies ahead waiting for exploration. | en |
