Part 4: Structural Integrity
General changes to Part 4
Structural Commentary Material
New
Significant portions of the “User’s Guide – NBC 2010, Structural Commentaries” (Part 4 of Division B) for snow and wind loads have been moved into Part 4 of Ontario’s Building Code.
Supplementary Standard SB-1
Ground Snow Load Values in Table 2
New
The ground snow loads in Table 2 of Supplementary Standard SB-1 have been revised. While most values remain unchanged, approximately 6% increase and 5% decrease for certain locations.
Seismic Design Data in Table 3
New
Seismic hazard values have been updated based on recent seismic source data. The values have also been expanded to incorporate new seismic scenarios. Further, seismic hazard values have been relocated in a new Table 3 of Supplementary Standard SB-1.
Article 4.1.3.2. - Strength and Stability
New
The live load plus snow load combinations in Tables 4.1.3.2.A. and 4.1.3.2.B. have been modified for limit states design to address situations where snow loads and live loads may occur at the same time.
Article 4.1.5.14. - Loads on Guards and Handrails
New
Changes have been made to the load requirements on guards and handrails.
Load requirements for handrails have been moved from Part 3 to Part 4.
Note: These changes come into effect January 1, 2022.
Article 4.1.5.15. - Loads on Vehicular Guardrails
New
The requirements for vehicle guardrail design have been clarified so that guard loads for vehicles and persons do not need to be considered at the same time.
Note: These changes come into effect January 1, 2022.
Article 4.1.5.16. - Loads on Walls Acting as Guards
Clarification
Load requirements for walls acting as guards have been modified to clarify that lateral loads act in the outward direction.
Subsection 4.1.6. - Loads Due to Snow and Rain (General)
New
Much of the guidance material on snow loads found in the “User’s Guide – NBC 2010, Structural Commentaries” have been moved into Subsection 4.1.6. of Ontario’s Building Code. Snow load calculations have also been revised.
Article 4.1.6.5. - Snow Drifts on Multi-Level Roofs
Clarification
Calculations for snow accumulation on multi-level roofs have been modified to better account for snow drifting.
Article 4.1.6.8. - Snow Drifts at Roof Corners
New
A new Article has been added to address snow drift conditions inside roof corners and outside roof corners of multi-level roofs.
Article 4.1.6.12. - Valleys in Curved or Sloped Roofs
New
The calculation of snow loads in valleys of curved or sloped roofs has been moved from the “User’s Guide – NBC 2010, Structural Commentaries” into this new Article.
Article 4.1.6.13. - Specific Weight of Snow
New
A new Article specifies a load calculation to determine the specific weight of snow drifts on roofs.
Article 4.1.6.14. - Prohibition of Load Reduction due to Snow Removal
New
A new Article prohibits the reduction of design snow loads based on snow removal on a structure.
Article 4.1.6.15. - Ice Loading of Structures
New
A new Article addresses ice loading on lattice structures and other components connected to a building.
Subsection 4.1.7. - Wind Load (General)
New
Much of the guidance material on wind loads found in the “User’s Guide – NBC 2010, Structural Commentaries” has been moved to Part 4. Wind load requirements have also been updated.
Article 4.1.7.1. - Specified Wind Load
Clarification
This Article has been modified to clearly define the three acceptable structural design methods for wind, which are static, dynamic and wind tunnel procedures.
Article 4.1.7.3. - Internal Gust Factor
New
The formula of the internal gust factor for large unpartitioned structures has been reduced in these building types because the internal pressure takes significant time to respond to changes in external pressure.
Article 4.1.7.5. - External Pressure Coefficients
New
Requirements for the external pressure coefficients (Cp) for the design of the main structural system for buildings have been moved from the “User’s Guide – NBC 2010, Structural Commentaries” into a new Article.
Article 4.1.7.6. - External Pressure Coefficients for Low Buildings
New
Requirements for the external pressure coefficients (Cp) for designing buildings less than 20 m high have been moved from the “User’s Guide – NBC 2010, Structural Commentaries” into a new Article.
Article 4.1.7.7. - Internal Pressure Coefficient
New
Guidance material from the “User’s Guide – NBC 2010, Structural Commentaries” on internal pressure coefficients from building openings has been moved this new Article.
Article 4.1.7.8. - Dynamic Procedure
New
All factors and coefficients for the dynamic procedures, including the exposure factor and the gust effect factor in the “User’s Guide – NBC 2010, Structural Commentaries” have been moved into this new Article.
Article 4.1.7.9. - Full and Partial Wind Loading
New
A new Article requires all buildings to be designed for partial loading as well as full loading.
Article 4.1.7.11. - Exterior Ornamentations, Equipment and Appendages
New
A new Article has been included to address the group effect in the structural design of a building where wind loads on exterior non-building components could impact the building structure.
Article 4.1.7.12. - Wind Tunnel Procedure
New
Specific requirements for wind tunnel procedures have been introduced for the design of main structures as well as claddings.
Article 4.1.8.1. - Earthquake Loads and Effects - Seismic Design in Low Hazard Areas
New
There are no longer any seismic design exemptions for buildings in low seismic zones as no area is entirely free from earthquake hazard.
This Article has been amended to include a simple and easily applied methodology to design for very low force levels in low hazard, low risk earthquake zones to enhance earthquake resistance.
Article 4.1.8.10. - Earthquake Loads and Effects - Inclined Columns and Large Cantilevers
New
Requirements for the determination of seismic loads to address new building designs incorporating unique structural design elements have been added.
Article 4.1.8.11. - Earthquake Loads and Effects - Higher Mode Factors, Mv, and Base Overturning Reduction Factors, J
New
Values of higher mode factors and base overturning reduction factors have been revised in Table 4.1.8.11.
Article 4.1.8.15. - Earthquake Loads and Effects - Flexible Roof Diaphragms
New
Seismic design provisions have been added for single storey structures with a large area and flexible roof diaphragm of steel or wood.
Article 4.1.8.16. - Earthquake Loads and Effects - Foundation Provisions
New
Significant changes have been made to foundation displacements and overturning resistances.
Article 4.1.8.18. - Earthquake Loads and Effects - Anchorage of Steel Pallet Storage Racks
New
Provisions have been added to account for the seismic design and anchorage of free-standing steel pallet storage racks.
Article 4.1.8.18. - Earthquake Loads and Effects - Anchorage of Elevators and Escalators
New
Provisions have been added to account for the seismic design and anchorage of elevators and escalators for earthquake loads.
Article 4.1.8.18. - Earthquake Loads and Effects - Glazing Systems in Buildings
New
Provisions have been added to account for effects of building lateral displacements on a building’s non-structural glazing systems during an earthquake event.
Articles 4.1.8.19. and 4.1.8.20. - Seismic Isolation
New
New Articles have been added to address seismic isolation in the design of new buildings to reduce the earthquake-induced forces and energy transmitted into the structure.
Articles 4.1.8.21. and 4.1.8.22. - Supplemental Energy Dissipation
New
New Articles have been added to provide design criteria for structures with supplementary energy dissipation systems (also referred to as supplemental damping).
Article 4.3.6.1. - Design Basis for Glass
New
ASTM E1300, “Determining Load Resistance Glass in Buildings”, issued in 2012, has been added to provide more flexibility for structural designers and to harmonize with U.S. Codes.
Article 4.4.2.1. - Design Basis for Storage Garages and Repair Garages
Clarification
This Article has been modified to clarify that CSA S413, “Parking Structures” applies to the defined term “storage garages” rather than “parking structures”.