April 16, 2019 9:00 AM - 10:00 AM
Credits: 1 OAQ Credit; 1 BOMI CPD Point, 1 RCI CEH

Now that CSA A123.21 is referenced in the National Building Code of Canada, what has changed? NBCC provides means of calculating the loads acting on the roof assembly due to wind uplift. Selection of roof assemblies suitable for use on any given building has been simplified with the development of the CSA standard. It is now possible to identify which roof assemblies have sufficient resistance to wind uplift so the code requirement can be satisfied. The challenge that lies ahead in our industry is now to make this a habit and to ensure that the right individual does the right action. Designers are expected to perform the calculations leading to the determination of the required wind loads and include this information in their specifications. On the other hand, bidders are expected to look for published test reports showing roof assemblies that offer greater resistance than calculated loads. These test reports exist because manufacturers tested their roof assemblies to the CSA standard. And as we thought we had it all figured out, NBCC moves to ultimate limit states design, imposing a 40% increase to calculated wind loads ... What is the impact of this modification to the roof assembly selection process? Are safety factors still required? What is the impact of this modification to the roof assembly selection process? Are safety factors still required? What is the impact of this modification to the roof assembly selection process? Are safety factors still required?

Learning objectives:

Understand how to use the requirements the National Building Code 2015 for wind loads along with reports from roofing assemblies tested as per CSA A123.21 dynamic wind uplift standard.
Recognize the importance of providing a clear language for required wind loads in specifications to ensure that the right party (designer of record) holds the liability for the selection of the roof assembly.
Understand the change in NBCC 2015 from serviceability limit state design to ultimate limit state design and the impact of this change on the resistance and safety factors.

What changes have we seen since CSA A123.21 appeared in the 2015 edition of the National Building Code of Canada? The CNB makes it possible to define the loads relating to the tearing of the roof assemblies from the wind. Thanks to the CSA standard, it is now possible to determine the level of resistance to wind pulling of roof assemblies. This greatly simplifies the selection of the appropriate assemblies for any building and meeting the requirements of the CNB. The challenge our industry now faces is to create a habit out of this process and have each stakeholder contribute in the right way. Designers are expected to perform calculations to define building-specific wind pull loads and enter them into specifications. On the other hand, the bidding contractors are responsible for proposing roof assemblies whose resistance to wind tearing is greater than the loads listed in the estimate. This selection is made on the basis of test reports from manufacturers who have previously submitted their assemblies to the tests defined in the CSA standard. Pretty simple, right? But while everything was in place, the CNB moved towards calculations of loads at ultimate limit states, imposing a 40% increase in calculated wind loads… What is the impact of this change on the assembly selection process? Do safety factors still have their place? This selection is made on the basis of test reports from manufacturers who have previously submitted their assemblies to the tests defined in the CSA standard. Pretty simple, right? But while everything was in place, the CNB moved towards calculations of loads at ultimate limit states, imposing a 40% increase in calculated wind loads… What is the impact of this change on the assembly selection process? Do safety factors still have their place? This selection is made on the basis of test reports from manufacturers who have previously submitted their assemblies to the tests defined in the CSA standard. Pretty simple, right? But while everything was in place, the CNB moved towards calculations of loads at ultimate limit states, imposing a 40% increase in calculated wind loads… What is the impact of this change on the assembly selection process? Do safety factors still have their place? imposing a 40% increase in calculated wind loads… What is the impact of this change on the assembly selection process? Do safety factors still have their place? imposing a 40% increase in calculated wind loads… What is the impact of this change on the assembly selection process? Do safety factors still have their place?

Learning objectives:

Understand how to use the wind load requirements provided by the 2015 CNB and the test reports of roof assemblies tested by the dynamic wind chopping standard CSA A123.21.
Recognize the importance of the terminology used in specifications to ensure that the professional retains responsibility for the resistance to wind pulling of the roof assembly selected.
Understand the passage by the CNB 2015 of load calculations from in-service withstand limit states to ultimate limit states, as well as the impact of this change on safety and resistance factors.

April 16, 2019 - EST (Eastern Standard Time, GMT-5)

April 16, 2019 - EST (Eastern Standard Time, GMT-5)