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OBC VOLUME 2 · APPENDIX A · NOTES TO PART 4Updated for the 2024 Ontario Building Code

Appendix A — Explanatory Notes to Part 4

Appendix A explanatory notes for Part 4 of Division B of the 2024 Ontario Building Code. These notes are advisory: they explain the intent behind code provisions and how to apply them.

On this page:
A-4.1.1.3.(1)A-4.1.1.3.(2)A-4.1.1.5.(2)A-4.1.2.1.A-4.1.2.1.(1)A-4.1.2.2.(1)A-4.1.3.A-4.1.3.2.(2)A-4.1.3.2.(4)A-4.1.3.2.(5)A-4.1.3.3.(1)A-4.1.3.3.(2)A-4.1.3.4.(1)A-4.1.3.5.(1)A-4.1.3.5.(3)A-4.1.3.6.(1)A-4.1.3.6.(2)A-4.1.3.6(3)A-4.1.3.6.(4)A-4.1.4.1.(2)A-4.1.4.1.(3)A-4.1.4.1.(6)A-4.1.5.1.(1)A-4.1.5.5.A-4.1.5.8.A-4.1.5.11.A-4.1.6.1.(1)A-4.1.6.2.A-4.1.6.2.(2)A-4.1.6.3.(2)A-4.1.6.4.(1)A-4.1.6.4.(3)A-4.1.6.7.(1)A-4.1.6.7.(2)A-4.1.6.9.A-4.1.6.16.A-4.1.6.16.(3)A-4.1.6.16.(4)(b)A-4.1.6.16.(4)(c)A-4.1.6.16.(5)(a)A-4.1.6.16.(5)(b)A-4.1.6.16.(6)A-4.1.6.16.(6)(c)A-4.1.7.1.(6)A-4.1.7.2.A-4.1.7.3.(5)(c)A-4.1.7.3.(10)A-4.1.7.5.(2)A-4.1.7.5.(4)A-4.1.7.7.(2)A-4.1.7.8.(2)A-4.1.7.8.(4)A-4.1.7.9.(1)A-4.1.7.11.A-4.1.7.12.A-4.1.7.13.A-4.1.8.2.(1)A-4.1.8.3.(4)A-4.1.8.3.(6)A-4.1.8.3.(7)(b)A-4.1.8.3.(8)A-4.1.8.4.(2)A-4.1.8.4.(3)A-4.1.8.4.(6)A-4.1.8.4.(3)A-4.1.8.7.(1)A-4.1.8.9.(4)A-4.1.8.9.(5)A-4.1.8.10.(5)A-4.1.8.10.(7)A-4.1.8.10.(9)A-4.1.8.10.(10)(a)A-4.1.8.11.(3)A-4.1.8.12.(1)(a)A-4.1.8.12.(1)(b)A-4.1.8.12.(3)A-4.1.8.12.(4)(a)A-4.1.8.13.(4)A-4.1.8.15.(1)A-4.1.8.15.(3)A-4.1.8.15.(4)A-4.1.8.15.(5)A-4.1.8.15.(6)A-4.1.8.15.(7)A-4.1.8.15.(8)A-4.1.8.16.(1)A-4.1.8.16.(2)A-4.1.8.16.(4)A-4.1.8.16.(6)(a)A-4.1.8.16.(7)A-4.1.8.16.(8)(a)A-4.1.8.16.(9)A-4.1.8.16.(10)A-4.1.8.17.(1)A-4.1.8.18.A-4.1.8.18.(13)A-4.1.8.18.(14)A-4.1.8.19.(2)A-4.1.8.19.(3)(a)A-4.1.8.19.(4)A-4.1.8.21.(2)A-4.1.8.21.(4)(a)A-4.2.2.1.(1)A-4.2.4.1.(1)A-4.2.4.1.(3)A-4.2.4.1.(5)A-4.2.4.4.(1)A-4.2.5.1.(1)A-4.2.6.1.(1)A-4.2.7.1.(1)A-4.2.7.2.(1)A-4.2.7.2.(2)A-4.3.3.1.(1)A-4.3.4.1.(1)A-4.3.4.2.(1)A-4.3.4.3.(1)A-4.3.6.1.(1)A-4.4.2.1.(1)

A-4.1.1.3.(1)Structural Integrity.

The requirements of Part 4, including the CSA design standards, generally provide a satisfactory level of structural integrity. Additional considerations may, however, be required for building systems made of components of different materials, whose interconnection is not covered by existing CSA design standards, buildings outside the scope of existing CSA design standards, and buildings exposed to severe accidental loads such as vehicle impact or explosion. Further guidance can be found in the Commentary entitled “Structural Integrity” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.1.3.(2)Serviceability.

Information on serviceability can be found in the Commentary entitled “Deflection and Vibration Criteria for Serviceability and Fatigue Limit States” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.1.5.(2)Structural Equivalents.

Sentence 4.1.1.5.(2) provides for the use of design methods not specified in Part 4, including full-scale testing and model analogues. This provision is usually used to permit the acceptance of newer and innovative structures or to permit the acceptance of model tests such as those used to determine structural behaviour, or snow or wind loads. Sentence 4.1.1.5.(2) Appendix A • Volume 2 Page 101 specifically requires that the level of safety and performance be at least equivalent to that provided by design to Part 4 and requires that loads and designs conform to Section 4.1. Sentence 4.1.1.5.(2) and the provision for alternative solutions stated in Clause 1.2.1.1.(1)(b) of Division A are not intended to allow structural design using design standards other than those listed in Part 4. The acceptance of structures that have been designed to other design standards would require the designer to prove to the appropriate authority that the structure provides the level of safety and performance required by Clause 1.2.1.1.(l)(b) of Division A. The equivalence of safety and performance can only be established by analyzing the structure for the loads and load factors set out in Section 4.1. and by demonstrating that the structure at least meets the requirements of the design standards listed in Sections 4.3. and 4.4.

A-4.1.2.1.Loads and Effects.

Information on the definitions can be found in the Commentary entitled “Limit States Design” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.2.1.(1)Temperature Changes.

Information on effects due to temperature changes can be found in the Commentary entitled “Effects of Deformations in Building Components” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. A.4.1.2.1.(3) Major Occupancies. In a building containing more than one major occupancy and classified in more than one Importance Category, the classification of each independent structural system shall be the same as for any part of the building that is dependent on that structural system and for the highest usage group according to Table 4.1.2.1. A-Table 4.1.2.1.B. Importance Categories for Buildings. Low Importance Category Buildings A minor storage building is an example of a Low Importance Category building. Low-human-occupancy farm buildings with an occupant load of 1 person or less per 40 m of floor area are also examples of Low Importance Category buildings. Normal Importance Category Most buildings will fall into the Normal Importance Category. The following types of buildings may be classified in the Normal Importance Category: buildings that are equipped with secondary containment of dangerous goods, including, but not limited to, double-walled tanks, dikes of sufficient size to contain a spill, and other means to contain a spill or a blast within the property boundary of the facility and prevent the release of harmful quantities of contaminants to the air, soil, groundwater, surface water or atmosphere, as the case may be. High Importance Category The following buildings may contain sufficient quantities of dangerous goods to be classified in the High Importance Category: • petrochemical facilities, • fuel storage facilities (other than those required for post-disaster use), and • manufacturing or storage facilities containing dangerous goods. Information on community centres can be found in the Commentary entitled “Limit States Design” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Page 102 Appendix A • Volume 2 Post-Disaster Importance Category Before classifying a building as a post-disaster building, Code users should consider the intent of the classification and look beyond the name of the building. For example, a building that is named “ABC Treatment” but is used for emergency care should be considered as a hospital and, as such, classified as a post-disaster building. Conversely, a building named “XYZ Hospital” that is only used for walk-in medical services could be classified as a Normal Importance Category building.

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

A-4.1.2.2.(1)Loads Not Listed.

The intent of Sentence 4.1.2.2.(1) is to draw attention to the fact that there are loads, forces and effects that need to be considered in addition to those specified in the Code. These loads, forces and effects will vary in need, application, and magnitude for each use and location. Some may result from environmental considerations (e.g., ice accretion, wave and ice action, water flow) while others will result from the use and occupancy of the facility (e.g., dangerous goods storage, manufacturing and mining operations). The reasonable determination of the probability, type and magnitude of project- specific loads must be assessed by a knowledgeable project team that includes the building owner/operator and experienced design professionals, and incorporated into the design where deemed necessary to maintain the safety and integrity of the facility. In recent years, security issues have prompted the consideration of loads and effects due to improvised explosive devices and other methods of sabotage. Consideration of these loads is driven by operational and public safety requirements, and their incorporation in the design is not considered a mandatory provision of the Code.

A-4.1.3.Limit States Design.

Information on limit states design can be found in the Commentary entitled “Limit States Design” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.3.2.(2)Load Combinations.

Load Combination Equations The load combinations in Tables 4.1.3.2.-A and 4.1.3.2.-B apply to most situations for loadbearing building structures. Guidance on special situations such as load combinations for fire resistance and building envelopes is given in the Commentary entitled “Limit States Design” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Load Cases and Crane Load Effects The load combinations in Table 4.1.3.2.-A are to be evaluated for structures with crane load effects for the scenario where the crane loads are zero, and for structures without crane loads. The load combinations in Table 4.1.3.2.-B are to be evaluated for structures with crane loads for the scenario where the crane load effects are other than zero. Crane Loads Crane-supporting structures that have cranes in multiple parallel bays should be designed for the maximum vertical crane load with the cranes positioned for the most critical effect in conjunction with a lateral load with each crane in turn positioned for the most critical effect. For load combinations that include crane loads, additional guidance can be found in CISC/ICCA 2013, “Crane-Supporting Steel Structures: Design Guide”.

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

A-4.1.3.2.(4)Effects of Lateral Earth Pressure, H, Pre-Stress, P, and Imposed

Deformation, T, in Design Calculations. Effects of Lateral Earth Pressure, H, in Design Calculations For common building structures below ground level, such as walls, columns and frames, 1.5 H is added to load combinations 2 to 4. For cantilever retaining wall structures, see the Commentary entitled “Limit States Design” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Appendix A • Volume 2 Page 103 Effects of Pre-Stress, P, and Imposed Deformation, T, in Design Calculations For structures and building envelopes designed in accordance with the requirements specified in the standards listed in Section 4.3., with the exception of Clauses 8 and 18 of CSA A23.3, P and T need not be included in the load combinations of Table 4.1.3.2.-A. For structures not within the scope of the standards listed in Section 4.3., including building envelopes, P and T must be taken into account in the design calculations. For recommended load combinations including T, see the Commentary entitled “Limit States Design” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

A-4.1.3.2.(5)Overturning, Uplift or Sliding.

Information on overturning, uplift and sliding can be found in the Commentary entitled “Limit States Design” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.3.3.(1)Failure Due to Fatigue.

Failure due to fatigue of building structures referred to in Section 4.3. and designed for serviceability in accordance with Article 4.1.3.6. is, in general, unlikely except for girders supporting heavily used cranes, on which Article 4.1.5.11. provides guidance.

A-4.1.3.3.(2)Vibration Effects.

Guidance on vibration effects can be found in the Commentary entitled “Deflection and Vibration Criteria for Serviceability and Fatigue Limit States” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.3.4.(1)Loads and Load Combinations for Serviceability.

The loads and load combinations for serviceability depend on the serviceability limit states and on the properties of the structural materials. Information on loads and load combinations for the serviceability limit states, other than those controlled by deflection, can be found in the Commentary entitled “Deflection and Vibration Criteria for Serviceability and Fatigue Limit States” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. A-Table 4.1.3.4. Acceleration Due to Vibrations. Information on the determination of acceleration due to vibrations resulting from loads L and W can be found in the Commentary entitled Wind Load and Effects in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B).”

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

A-4.1.3.5.(1)Deflections.

Serviceability criteria for deflections that cause damage to non-structural building components can be found in the standards listed in Section 4.3. Information on deflections can be found in the Commentary entitled “Deflection and Vibration Criteria for Serviceability and Fatigue Limit States” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Information on loads and load combinations for calculating deflection can be found in the Commentary entitled “Limit States Design” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.3.5.(3)Lateral Deflection of Buildings.

The limitation of 1/500 drift per storey may be exceeded if it can be established that the drift as calculated will not result in damage to non-structural elements. Information on lateral deflection can be found in the Commentary entitled “Wind Load and Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.3.6.(1)Floor Vibration.

Information on floor vibration can be found in the Commentary entitled “Deflection and Vibration Criteria for Serviceability and Fatigue Limit States” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Information on loads and load combinations for the calculation of vibration can be found in the Commentary entitled “Limit States Design” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Page 104 Appendix A • Volume 2

A-4.1.3.6.(2)Floor Vibrations Caused by Resonance with Operating Machinery or

Equipment. Guidance on floor vibration effects caused by operating machinery and equipment can be found in the Commentary entitled Deflection and Vibration Criteria for Serviceability and Fatigue Limit States in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.3.6(3)Dynamic Analyses of Floor Vibrations.

Information on a dynamic analysis of floor vibrations from rhythmic activities can be found in the Commentary entitled “Deflection and Vibration Criteria for Serviceability and Fatigue Limit States” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.3.6.(4)Lateral Vibration Under Wind Load.

Information on lateral vibrations and accelerations under dynamic wind loads can be found in the Commentary entitled “Wind Load and Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.4.1.(2)Permanent Partitions Fixed to the Structure.

Partitions in residential buildings, including condominiums, apartments and hotels, are typically permanent and fixed to the structure. In such cases, the weight of partitions referred to in Clause 4.1.4.1.(1)(c) is the actual weight of the partitions that are shown on the drawings.

A-4.1.4.1.(3)Partitions Not Shown on the Drawings.

The potential locations of partitions in work areas, such as offices, are not typically shown on the drawings. For such areas, a partition weight allowance must be considered based on the anticipated weight and location of partitions, but not less than 1 kPa over the area of floor being considered.

A-4.1.4.1.(6)Counteracting Dead Load Due to Soil.

Examples of structures that traditionally employ the dead load of soil to resist loadings are pylon signs, tower structures, retaining walls, and deadmen, which resist wind uplift and overturning in light structures.

A-4.1.5.1.(1)Loads Due to Use of Floors and Roofs.

In many areas of buildings, such as equipment areas, service rooms, factories, storage areas, warehouses, museums, and office filing areas, live loads due to their intended use may exceed the minimum specified loads listed in Table 4.1.5.3. In these instances, the probable live load shall be calculated and used as the specified live load for the design of that particular area. A-Table 4.1.5.3. Considerations for Live Loads. Arenas, Grandstands and Stadia The designer should give special consideration to the effects of vibration. Attics - Limited Accessibility Attic live loading is not required when the ceiling below the attic consists of removable panels that permit access to the ceiling space without loading the ceiling supporting members. Attic live loading is not required in any area of the attic where the least dimension of the attic space is less than 500 mm. Corridors, Aisles and Rows of Seats The spaces between rows of seats are typically designed for the loads of the occupancy they serve. Rows typically discharge into aisles that are designed for the loads used for the rows of seats. Corridors have a minimum width 1 100 mm and may serve as collectors for aisles; they are therefore part of the exit system and are required to be designed for a minimum live load of 4.8 kPa. Appendix A • Volume 2 Page 105 Floor Areas That Could Be Used As Viewing Areas Some interior balconies, mezzanines, corridors, lobbies and aisles that are not intended to be used by an assembly of people as viewing areas are sometimes used as such; consequently, they are subject to loadings much higher than those for the occupancies they serve. Floor areas that may be subject to such higher loads must, therefore, be designed for a loading of 4.8 kPa. Lecture Halls and Classrooms For the purpose of applying the requirements of Table 4.1.5.3., lecture halls with fixed seats are similar to theatres in configuration (the seats may have a writing tablet affixed to one arm). Classrooms are typically furnished with full-sized desks having separate or integrated seats. Minimum Roof Live Load Articles 4.1.5.3. and 4.1.5.10. stipulate a minimum uniform roof live load of 1.0 kPa and a minimum concentrated live load of 1.3 kN. These live loads are “use and occupancy loads” intended to provide for maintenance loadings: they are not reduced as a function of area or as a function of the roof slope due to their variability in distribution and location. Office Areas The general minimum specified load for office areas, including mezzanines, is 2.4 kPa. A minimum specified load of 4.8 kPa applies to office areas in basements, which are normally slab-on-grade, and to office areas in floor areas that may be subject to an increase in loading for brief periods, for example, when tenants temporarily use that floor area to store furniture, equipment and files while moving in or out of the building. Where an office building is situated on a level site, all floors are uniform in elevation, and there are no mezzanines, allocating the correct loads is straightforward. However, where the site is steeply sloped, the situation is more complex— even more so where there are also mezzanines. The principle is that floor levels and mezzanines with access to the exterior at ground level could be used as staging areas during a move, and so, must be designed for a minimum of 4.8 kPa. Also, there is usually an area adjacent to the exterior exit that can accommodate trucks. Vehicle Loads A special study should be undertaken to determine the distributed loads to be used for the design of floors and areas used by vehicles exceeding 9 000 kg gross weight and of driveways and sidewalks over areaways and basements. Where appropriate, the designer should refer to CAN/CSA-S6, “Canadian Highway Bridge Design Code”.

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

A-4.1.5.5.Loads on Exterior Areas.

In Article 4.1.5.5., “accessible” refers to the lack of a physical barrier that prevents or restricts access by vehicles or persons to the site in the context of the specific use. Information on the design of roof parking decks and exterior areas that are accessible to vehicular traffic can be found in the Commentary entitled “Live Loads” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.5.8.Tributary Area.

Information on tributary area can be found in the Commentary entitled “Live Loads” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. A-Table 4.1.5.9. Loads Due to Concentrations. Special study is required to determine concentrated loads for the design of floors and areas used by vehicles exceeding 9 000 kg gross weight, and of driveways and sidewalks over areaways and basements. Where appropriate, the designer should refer to CAN/CSA-S6, “Canadian Highway Bridge Design Code”. Page 106 Appendix A • Volume 2

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

A-4.1.5.11.Crane-Supporting Structures.

Guidance on crane-supporting structures can be found in CSA S16, “Design of Steel Structures”. A.4.1.5.14. and 4.1.5.15.(1) Design of Guards. In the design of guards, due consideration should be given to the durability of the members and their connections. A.4.1.5.17. Loads on Firewalls. Information on loads on firewalls can be found in the Commentary entitled “Structural Integrity of Firewalls” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.6.1.(1)Specified Load Due to Rain or to Snow and Associated Rain.

The location of a new building or obstruction may affect the snow loads on the roof of an adjacent existing building—on the same property or on an adjacent one—that is lower in height. Additional guidance can be found in the Commentary entitled “Snow Loads” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.6.2.Coefficients for Snow Loads on Roofs.

Information on coefficients for snow loads on roofs can be found in the Commentary entitled “Snow Loads” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.6.2.(2)Basic Roof Snow Load Factor, Cb.

Figure A-4.1.6.2.(2) shows the basic roof snow load, , plotted against . Figure A-4.1.6.2.(2) Basic Roof Snow Load Factor, Cb

A-4.1.6.3.(2)Full and Partial Loading Under Snow Loads.

Information on full and partial snow loading on roofs can be found in the Commentary entitled “Snow Loads” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Appendix A • Volume 2 Page 107

A-4.1.6.4.(1)Rain Loads.

Information on rain loads can be found in the Commentary entitled “Rain Loads” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.6.4.(3)Flow Control Drains.

Part 7 contains requirements regarding the use of flow control roof drains. The designer must ensure that the building complies with both Part 4 and Part 7.

A-4.1.6.7.(1)Roof Projections.

Elevator, air-conditioning and fan housings, small penthouses and wide chimneys are examples of roof projections. Figure A-4.1.6.7.(1) Roof Projections

A-4.1.6.7.(2)Values of Ca for Small Roof Projections.

Calculating Ca in accordance with Article 4.1.6.5. rather than Sentence 4.1.6.7.(1) results in lower values for small projections.

A-4.1.6.9.Load Cases for Gable Roofs.

Figure A-4.1.6.9. Load Cases for Gable Roofs Page 108 Appendix A • Volume 2 Table A-4.1.6.9. Wind Exposure, Slope and Accumulation Factors for Load Cases in Figure A-4.1.6.9. Factors Load Case Roof Slope, Ca Cw Cs(1) Upwind Side Downwind Side I 0° ≤ ≤ 90° (2) f( ) 1.0 1.0 15° < ≤ 20° 1.0 f( ) 0.0 0.25 + /20 II(3) 20° < ≤ 90° 1.0 f( ) 0.0 1.25 Notes to Table A-4.1.6.9.: (1) Varies as a function of slope, α, as defined in Sentences 4.1.6.2.(5) and (6). (2) The value of Cw for load case I is as prescribed in Sentences 4.1.6.2.(3) and (4). (3) Case II loading does not apply to gable roofs with slopes of 15º or less, to single-sloped (shed) roofs, or to flat roofs.

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

A-4.1.6.16.Roofs with Solar Panels.

Information on the design of roofs with solar panels can be found in the Commentary entitled “Snow Loads” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.6.16.(3)Snow Obstructed from Sliding by Solar Panels.

Figure A-4.1.6.16.(3) shows the areas on sloped roofs with solar panels where snow is considered to be obstructed from sliding by the solar panels and the slope factor, Cs, must be taken as 1.0. Figure A-4.1.6.16.(3) Areas on Sloped Roofs With Solar Panels Where Snow is Obstructed From Sliding by the Solar Panels Notes to Figure A-4.1.6.16.(3): (1) Cs = as specified in Sentences 4.1.6.2.(5) to (7). Appendix A • Volume 2 Page 109

A-4.1.6.16.(4)(b)Snow Loads for a Sloped Roof with Parallel Flush Solar Panels

Where wg ≥ wp. Figure A-4.1.6.16.(4)(b) shows the snow loads for a sloped roof with Parallel Flush solar panels where the gap width, w g, between the panels is greater than or equal to the panel width, w p. Figure A-4.1.6.16.(4)(b) Snow Loads for a Sloped Roof With Parallel Flush Solar Panels Where Wg ≥ Wp

A-4.1.6.16.(4)(c)Snow Loads for a Sloped Roof with Parallel Flush Solar Panels

Where wg < wp. Figure A-4.1.6.16.(4)(c) shows the snow loads for a sloped roof with Parallel Flush solar panels where the gap width, w g, between the panels is less than the panel width, wp. Figure A-4.1.6.16.(4)(c) Snow Loads for a Sloped Roof With Parallel Flush Solar Panels Where Wg < Wp Page 110 Appendix A • Volume 2

A-4.1.6.16.(5)(a)Snow Loads for a Flat Roof with Parallel Raised Solar

Panels. Figure A-4.1.6.16.(5)(a) shows the snow loads for a flat roof with Parallel Raised solar panels. Figure A-4.1.6.16.(5)(a) Snow Loads for a Flat Roof With Parallel Raised Solar Panels

A-4.1.6.16.(5)(b)Snow Loads for a Sloped Roof with Parallel Raised Solar Panels.

Figure A-4.1.6.16.(5)(b) shows the snow loads for a sloped roof with Parallel Raised solar panels. Figure A-4.1.6.16.(5)(b) Snow Loads for a Sloped Roof With Parallel Raised Solar Panels Appendix A • Volume 2 Page 111

A-4.1.6.16.(6)Snow Loads for a Flat Roof with Tilted Solar Panels.

Figure A-4.1.6.16.(6) shows the snow loads for a flat roof with Tilted solar panels. Figure A-4.1.6.16.(6) Snow Loads for a Flat Roof With Tilted Solar Panels

A-4.1.6.16.(6)(c)Variation of Ca with hg − CbCwSs/γ.

Figure A-4.1.6.16.(6)(c) shows the variation of the accumulation factor, C a, with the height of the lowest edge of the panels above the surface of the uniform snow load, h g − CbCwSs/γ, for a flat roof with Tilted solar panels. Figure A-4.1.6.16.(6)(c) Variation of Ca With hg − CbCwSs/γ for a Flat Roof with Tilted Solar Panels

A-4.1.7.1.(6)Computational Fluid Dynamics (CFD).

It is not currently possible to verify the reliability and accuracy of CFD and no standards address it; as such, this method is not permitted to be used to determine specified wind loads.

A-4.1.7.2.Natural Frequency.

Information on calculating the natural frequency of a building can be found in the Commentary entitled “Wind Load and Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Page 112 Appendix A • Volume 2

A-4.1.7.3.(5)(c)Procedure for Calculating Intermediate Ce.

Information on calculating intermediate values of Ce between two exposures can be found in the Commentary entitled “Wind Load and Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.7.3.(10)Internal Gust Factor, Cqi.

The effect of building envelope flexibility can be included in the calculation of C gi. See the Commentary entitled “Wind Load and Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.7.5.(2)and (3) Pressure Coefficients for Main Structural System on

Rectangular Buildings. Figure A-4.1.7.5.(2) and (3) Values of CP for Main Structural System on Rectangular Buildings Appendix A • Volume 2 Page 113

A-4.1.7.5.(4)Pressure Coefficients for Roof and Wall Claddings and Secondary

Structural Supports of Cladding on Rectangular Buildings. Figure A-4.1.7.5.(4) Values of Cp for Roof and Wall Claddings and Secondary Structural Supports of Cladding on Rectangular Buildings Notes to Figure A-4.1.7.5.(4): (1) The larger of W or D is to be used. (2) Where vertical ribs deeper than 1 m are present on the walls, the dimensions 0.1D and 0.1W must be changed to 0.2D and 0.2W and the negative value of Cp must be changed from –1.2 to –1.4.

A-4.1.7.7.(2)Cladding on Parapets.

Information on the design of cladding on parapets can be found in the Commentary entitled “Wind Load and Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Page 114 Appendix A • Volume 2

A-4.1.7.8.(2)and (3) Exposure Factor for Dynamic Procedure.

Figure A-4.1.7.8.(2) and (3) Exposure Factor, Ce, for Dynamic Procedure Notes to Figure A-4.1.7.8.(2) and (3): (1) Curve A represents Ce for open terrain, as defined in Clause 4.1.7.3.(5)(a). (2) Curve B represents Ce for rough terrain, as defined in Clause 4.1.7.3.(5)(b).

A-4.1.7.8.(4)Peak Factor, Size Reduction Factor and Gust Energy Ratio.

Figure A-4.1.7.8.(4) Peak Factor, gp Appendix A • Volume 2 Page 115 Figure A-4.1.7.8.(4)-B Size Reduction Factor, Figure A-4.1.7.8.(4)-C Gust Energy Ratio, F

A-4.1.7.9.(1)Full and Partial Wind Loading.

Information on full and partial loading under wind loads can be found in the Commentary entitled “Wind Load and Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Page 116 Appendix A • Volume 2 Figure A-4.1.7.9.(1) Full and Partial Wind Loads Appendix A • Volume 2 Page 117

A-4.1.7.11.Exterior Ornamentations, Equipment and Appendages.

Appendages may increase the overall forces in the design of the building structure and need to be accounted for.

A-4.1.7.12.Attached Canopies on Low Buildings (H ≤ 20 m).

An attached canopy is different from an overhang, which is an extension of the roof surface. Figure 4.1.7.12.-A, which provides the gust pressure coefficients on the upper and lower surfaces of the canopy, is used to design the cladding for the canopy and the associated fasteners. Figure 4.1.7.12.-B, which provides the net gust pressure coefficients on the canopy, is used to design the structure of the canopy (e.g., joists, posts, building fasteners). In addition to the external wind pressure addressed in Article 4.1.7.12., the internal pressure addressed in Table 4.1.7.7. should also be considered, where applicable to the canopy.

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

A-4.1.7.13.Roof-Mounted Solar Panels on Buildings of Any Height.

Article 4.1.7.13. provides procedures for calculating the wind loads on roof-mounted arrays of solar panels that satisfy particular geometrical requirements. The area of the roof that is covered by a solar array does not need to be designed for the simultaneous application of the solar array wind loads and the roof wind loads. However, the cumulative load effect of all solar panels does need to be accounted for in accordance with Article 4.1.7.11. Furthermore, the roof needs to be designed for the case where the solar array has been removed. Solar arrays that are mechanically fastened to the underlying roof structure can modify the load distribution on the roof. The loads from such arrays must be applied to the structural components of the roof as concentrated loads at the points of attachment. The calculations in Article 4.1.7.13. assume that the solar panels and their mounting system are rigid. Therefore, there is no allowance for wind-induced vibration of these components. However, if the panels and their mounting system have a natural frequency less than about 10 Hz, it is possible that loads will be magnified as a result of wind-induced vibration. In such cases, it is recommended that expert opinion be sought and that the dynamic effects be investigated in more detail. Figure A-4.1.7.13. shows an example of a roof-mounted solar array with exposed and unexposed panels. For the purpose of determining the edge factor, E, to be applied in the calculations of Article 4.1.7.13., a panel is defined as exposed if it is located within a distance of 1.5 times the panel chord length, Lp, from an exposed edge of the array. An exposed edge of the array is considered to occur where the horizontal distance, d1, from the panel edge to the roof edge (ignoring any rooftop equipment) is greater than 0.5h, h being the reference height of the roof, and greater than max(4h 2, 1.2 m), h2 being the height of the panel's highest point above the roof surface. An exposed edge is also considered to occur where the horizontal distance, d2, from the panel edge to the nearest edge in the next panel row (or across a gap in the same panel row) is greater than max(4h2, 1.2 m). A sample calculation of net design wind pressure for roof-mounted solar panels is provided in the Commentary entitled Wind Load and Effects in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. The installation of solar arrays on a roof can significantly affect the distribution of snow loads on the roof. Designers should be aware that the accumulation of snow and ice around solar panels can influence the calculations described in Article 4.1.7.13. For example, accumulated snow may obstruct the ventilation areas between the roof and the underside of the panels, thereby increasing wind loads on the panels. For the design of the anchorage of a solar array to the roof and of the array itself, the pressure equalization factor, γ a, in Sentence 4.1.7.13.(2) should be taken as 1.0, unless it can be shown that the accumulation of snow and ice will not obstruct the gaps between the panels in the array. Page 118 Appendix A • Volume 2 Figure A-4.1.7.13. Plan View of a Roof-Mounted Solar Array With Exposed and Unexposed Panels

A-4.1.8.2.(1)Notation.

Definition of ex Information on the calculation of torsional moments can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Definition of W Information on the definition of dead load, W, can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.3.(4)General Design of the SFRS.

Information on the general design requirements for the SFRS can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.3.(6)General Design of Stiff Elements.

Information on the general design requirements for stiff elements can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.3.(7)(b)and (c) Stiffness Imparted to the Structure from Elements

Not Part of the SFRS. Information on stiffness imparted to the structure from elements not part of the SFRS can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.3.(8)Structural Modelling.

Information on structural modelling can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Appendix A • Volume 2 Page 119

A-4.1.8.4.(2)and (3) Site Designation.

It is preferable to determine the site designation as XV on the basis of the average shear wave velocity, V s 30 , calculated from in situ measurements of shear wave velocity. This site designation will typically result in a lower seismic demand than a site designation XS determined using the energy-corrected average standard penetration resistance, N 60 , or the average undrained shear strength, su. Further information on site designation can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.4.(3)Site Class.

The V s 30 ranges in Table 4.1.8.4.-B are retained from the 2012 Building Code. Where required for the application of a standard referenced in Subsection 4.1.8., the Site Class for a particular site designation X v can be determined from Table 4.1.8.4.-B on the basis of the value of V s 30 . Further information on Site Class can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

A-4.1.8.4.(6)Log–Log Interpolation.

The value of S(T) for Ti < T < Tj can be determined using log–log interpolation as follows: where log = logarithm to base 10.

A-4.1.8.4.(3)and Table 4.1.8.4.A. Site Class.

Information on Site Class can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. A-Table 4.1.8.5.A. Serviceability Limit States for Earthquake. Information on serviceability limit states for earthquake can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.). A-Table 4.1.8.6. Structural Irregularities. Information on structural irregularities can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Gravity-Induced Lateral Demand – Type 9 Irregularity Uncoupled concrete and masonry shear walls where a large fraction of the overturning resistance is provided by axial compression, rather than through yielding of the longitudinal reinforcement, are less susceptible to amplified displacements due to gravity-induced lateral demands because the axial loads have a self-centering effect on the shear walls. Walls that are stronger than the foundation and other systems such as coupled walls, braced frames and moment frames are more susceptible to amplified displacements due to gravity-induced lateral demands. A lower limit on α is thus specified for such systems. Further information on the impacts of gravity-induced lateral demands on the seismic response of buildings can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Page 120 Appendix A • Volume 2

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

A-4.1.8.7.(1)Dynamic Analysis Procedures.

Information on dynamic analysis procedures can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. A-Table 4.1.8.9. Industrial-Type Steel Structures. Guidance on the height limits, system restrictions and additional analysis and design requirements for steel SFRSs in industrial-type structures, intended essentially to support equipment, tanks or an industrial process, can be found in Annex M “Seismic Design of Industrial Steel Structures” of CSA S16, “Design of Steel Structures”.

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

A-4.1.8.9.(4)Vertical Variations in RdRo.

Information on vertical variations in RdRo can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.9.(5)RdRo and Equivalent Systems.

Information on the RdRo, of equivalent systems can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.10.(5)and (6) Mid-Rise Timber SFRS.

Information on structural irregularities in mid-rise wood construction and on how to determine the number of storeys for application in Sentence 4.1.8.10.(5) can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.10.(7)Gravity-Induced Lateral Demand – Type 9 Irregularity.

Structural systems that include components such as inclined columns or horizontal floor cantilevers can induce lateral force demands on the SFRS under gravity loads. Buildings with such gravity-induced lateral demands on the SFRS are more likely to experience severe damage during strong ground shaking due to their tendency to drift only in one direction, leading to large residual displacements or instability. To determine if a building is susceptible to amplification of displacements due to gravity-induced lateral demands, the lateral resistance of the yielding mechanism to resist earthquake forces alone, Q y, must be compared with the gravity-induced lateral demand, QG, at the same location. The force component selected for this comparison depends on the yielding mechanism for the SFRS. For example, for a coupled wall, the overturning moment resistance at the level of the expected plastic hinges should be compared with overturning moment demand (at the same level) due to gravity loads alone; whereas for a steel braced-frame, the storey shear at the critical level of the yielding system should be compared with the storey shear demand (at the same level) due to the gravity loads alone. If the gravity-induced lateral demands exceed the limits prescribed in Sentence 4.1.8.10.(7), amplifications in seismic displacements due to gravity- induced lateral demands can only be identified through nonlinear dynamic analyses using models which adequately represent the hysteretic behaviour of the SFRS. Further information on the impacts of gravity-induced lateral demands on the seismic response of buildings can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.10.(9)Gravity-Induced Lateral Demand – Non-Linear Dynamic Analysis.

Information on non-linear dynamic analysis, including ground motion time histories, target response spectra and acceptance criteria, can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.10.(10)(a)Sloped Column Irregularity.

The presence of inclined vertical members in a building lead to a coupling of its horizontal and vertical vibrational modes. As a result of this coupling, horizontal accelerations of the building cause vertical accelerations of the mass supported by the inclined vertical members. Vertical ground motions cause additional vertical accelerations of the mass. The additional earthquake forces resulting from both the coupling of horizontal and vertical vibrational modes and the vertical ground motions can be determined using the Dynamic Analysis Procedure described in Article 4.1.8.12. with RdRo = 1.0. The structural model used in the analysis must account for the vertical accelerations of all mass supported by Appendix A • Volume 2 Page 121 inclined vertical members and must include the SFRS, the inclined vertical members, and all structural framing elements that transfer inertial forces generated by the vertical accelerations of the mass supported by the inclined vertical members. The additional earthquake forces are sensitive to the degree of coupling between the vertical and horizontal vibrational modes of the building. Thus, to determine the maximum additional earthquake forces for design, the range of possible stiffness values for all structural members must be considered. Further information on the analysis of structures with a sloped column irregularity, including a simple procedure for scaling the analysis results to avoid having to perform multiple analyses with a range of stiffness values and vertical ground motions, can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.11.(3)Determination of the Fundamental Period, Ta.

Information on the determination of the fundamental period, T a, can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.12.(1)(a)Linear Dynamic Analysis.

Information on Linear Dynamic Analysis can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.12.(1)(b)Nonlinear Dynamic Analysis.

Information on Nonlinear Dynamic Analysis can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.12.(3)Ground Motion Histories.

Information on ground motion histories can be found in the Commentary entitled “Design for Seismic Effects” in “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.12.(4)(a)Accidental Torsional Moments.

Information on accidental torsional moments can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.13.(4)Deflections and Sway Effects.

Information on deflections and sway effects can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.15.(1)Diaphragms and their Connections.

Information on diaphragms and their connections can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.15.(3)Ductile Diaphragms

Information on the design of struts, collectors, chords and connections for ductile diaphragms can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.15.(4)Influence of Dynamic Diaphragm In-Plane Response.

Clause 4.1.8.15.(4)(a) In lieu of carrying out a special study as stated in Subclause 4.1.8.15.(4)(a)(iii), the anticipated total deformation demand on the vertical elements of the SFRS, including inelastic deformations, may be taken as equal to R oRd(ΔB + ΔD) - RoΔD, i.e., the difference between the total storey drift including inelastic deformation effects and diaphragm deformations, Page 122 Appendix A • Volume 2 RoRd(ΔB + ΔD), and the diaphragm deformation under Ro times the seismic load, where Ro may be replaced by the actual overstrength of the SFRS vertical elements. The design engineer must verify that the SFRS vertical elements have sufficient deformation capacity to accommodate the computed deformation demand. If the vertical elements of the SFRS do not have sufficient deformation capacity, the design forces for the vertical elements of the SFRS must be magnified by Rd(1 + ΔD/ΔB)/(Rd + ΔD/ΔB). The calculation of the magnified design forces is iterative as the ΔD/ΔB ratio may change when using higher design forces for the vertical elements of the SFRS. Reducing the ΔD/ΔB ratio by increasing the stiffness of the roof diaphragm relative to that of the vertical elements of the SFRS may be considered to reduce the deformation demand on the vertical elements of the SFRS. Additional information can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.). Clause 4.1.8.15.(4)(b) The dynamic response of the diaphragm with the vertical elements of the SFRS under seismic excitation involves several modes of vibration that affect both the amplitude and distribution of in-plane shears and bending moments in the roof diaphragm. The shape of the fundamental mode of vibration resembles the deflected shape of the diaphragm/vertical SFRS elements under a distributed lateral load while higher modes involve increasing numbers of zero crossings of the deflected shapes along the length of the diaphragm, similar to the modes of a simply supported beam with distributed mass. Shears and bending moments therefore deviate from the values obtained from the equivalent static force procedure essentially due to higher mode response. Modal contributions to shears and bending moments in the diaphragms can be obtained from a Linear Dynamic Analysis. The contribution from the higher modes is generally more pronounced when the ΔD/ΔB ratio, the period in the first mode, or the ratio Sa(0.2)/Sa(2.0) is increased. It also increases when the SFRS is designed with a higher Rd factor as inelastic deformations of the vertical elements of the SFRS attenuate the first mode response. Methods to take into account the inelastic higher mode effects on in-plane diaphragm shears and moments are discussed in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.).

A-4.1.8.15.(5)Discontinuities.

Information on elements supporting discontinuities can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.15.(6)Vertical Variations in RdRo.

Information on elements of the SFRS below the variation in RdRo can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.15.(7)Concurrent Yielding.

Information on the effects of concurrent yielding of elements can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.15.(8)Design Force in Elements.

Information on the design force in elements can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.16.(1)Foundation Movement.

The bearing stress distribution in soil or rock that is used to determine the factored overturning resistance of the foundation influences the rotation of the foundation, which occurs due to the forces applied by the SFRS. Generally, all foundations will rotate on soil or rock. In particular, footings (a type of foundation unit) often undergo uplift at one end, and if the factored bearing stress at the other end is only over a short length, then the uplift and rotation of the footing can be significant. CSA A23.3, “Design of Concrete Structures”, contains design requirements for footings that rotate and uplift; see also the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)” for guidance and methods to account for foundation movement.

A-4.1.8.16.(2)Actual Lateral Load Capacity of the SFRS.

The actual lateral load capacity of the SFRS includes the effects of member overstrengths similar to those used to determine the Ro factors. The applicable CSA design standards include requirements on calculating the overstrengths and capacities, which may be based on the members’ nominal or probable resistance. The actual capacities are larger than the factored loads Appendix A • Volume 2 Page 123 and factored resistances and, in many cases, can be significantly larger. Note that the foundations designed to develop the capacity of the SFRS will undergo movements and Sentence 4.1.8.16.(1) still applies.

A-4.1.8.16.(4)Overturning Resistance of the Foundation.

For the special case where the foundation is a footing, and where it and the attached SFRS are not constrained against rotation, it is permitted, with certain limitations, to size the footing to have a factored overturning resistance less than the overturning capacity of the supported SFRS. This approach results in a smaller footing, increased footing rotations, increased drifts in the structure, and increased soil stresses, all of which are over and above those associated with footings sized to have a factored overturning resistance equal to or greater than the overturning capacity of the SFRS. The footing itself must have a factored resistance capable of developing the required soil or rock reactions. An example of a footing and SFRS that are not constrained against rotation is an SFRS on a footing near the ground surface such that it can rotate freely and is attached to a gravity-load-resisting system (non-SFRS) that is laterally flexible and provides little lateral resistance. For this case, the SFRS is usually analyzed on its own and the resulting displacements are imposed on the non-SFRS elements in order to assess the effects on them. Cases where the footing and SFRS are attached to a system that has significant lateral stiffness require careful analysis and engineering judgement, or the footing can be capacity-designed. Limiting the overturning moment on the foundation and the R dRo value provides some control on the increase in lateral displacement, drift and stress in the soil or rock. Cases that exceed these limits require special study. For the common case where the SFRS and/or the footing are constrained in some way against rotation, the footing’s factored resistance must be equal to or greater than the capacity of the supported SFRS. An example of an SFRS constrained against freely rotating with the footing is an SFRS attached to adjacent foundation walls by below-grade diaphragms. Examples of footings constrained against free rotation are footings that use soil anchors to resist overturning, footings on piles, and raft foundations. Note that Sentence 4.1.8.16.(1) still applies. See CSA A23.3, “Design of Concrete Structures,” and the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.16.(6)(a)Interconnection of Foundation Elements.

Information on the interconnection of piles or pile caps, drilled piers, and caissons can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.16.(7)Earthquake Lateral Pressures from Backfill or Natural Ground.

Information on methods of computing the seismic lateral pressures from backfill or natural ground can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.16.(8)(a)Cyclic Inelastic Behaviour of Foundation Elements.

Information on the cyclic inelastic behaviour of piles or pile caps, drilled piers, and caissons can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.16.(9)Alternative Foundation Ties.

Alternative methods of tying foundations together, such as a properly reinforced floor slab capable of resisting the required tension and compression forces, may be used. Passive soil pressure against buried pile caps may not be used to resist these forces.

A-4.1.8.16.(10)Liquefaction.

Information on liquefaction can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.17.(1)Slope Stability.

Information on slope stability can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Page 124 Appendix A • Volume 2

A-4.1.8.18.Elements of Structures, Non-Structural Components and Equipment.

Information on the requirements of Article 4.1.8.18. can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. A-Table 4.1.8.18. Non-Structural Components and Equipment. The failure or detachment of non-structural components and equipment during an earthquake can present a major threat to life safety. The design requirements presented in Article 4.1.8.18. are intended to ensure that such components and their connections to the building will retain their integrity during strong ground shaking. Guidelines for the seismic risk reduction of such components are given in CSA S832, “Seismic Risk Reduction of Operational and Functional Components (OFCs) of Buildings”. 4.1.8.18.(7)(e) Post-Installed Anchors. Information on the cyclic tension load testing of anchors referred to in Clause 4.1.8.18.(7)(e) can be found in International Code Council Evaluation Service (ICC-ES) Evaluation Reports. Additional information can be found in the Commentary entitled Design for Seismic Effects in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

A-4.1.8.18.(13)Storage Racks.

Free-standing storage racks contain materials typically loaded by forklift. Some are designed to store loaded pallets; however, in some cases, the stored material does not sit on a pallet. Information on storage racks can be found in the Commentary entitled Design for Seismic Effects in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.18.(14)and (15) Glass Fallout and Failure.

Information on glass fallout and testing for glass fallout can be found in AAMA 501.6, “Recommended Dynamic Test Method For Determining The Seismic Drift Causing Glass Fallout From A Wall System”. Every surface other than inaccessible areas or areas where occupancy is prevented or access is prevented should be considered a “walking surface”. Additional information can be found in ASCE/SEI 7, “Minimum Design Loads for Buildings and Other Structures”, in FEMA P-750, “NEHRP Recommended Seismic Provisions for New Buildings and Other Structures”, and FEMA 450-1, “NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures”, and related commentaries, and in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. 4.1.8.18.(16) Elements of Structures, Non-structural Components and Equipment in Structures with Supplemental Energy Dissipation. Information on the requirements of Sentence 4.1.8.18.(16) can be found in the Commentary entitled Design for Seismic Effects in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. 4.1.8.18.(18) Climatic Conditions. Climatic conditions leading to wetness or frost at the interface between the supporting base of the array and the roof surface may adversely affect the resistance provided by friction due to gravity loads.

A-4.1.8.19.(2)Design Review.

It is strongly recommended that a design review of the seismically isolated structure and its isolation system be carried out by an independent team of professional engineers and geoscientists experienced in seismic analysis methods and the theory and application of seismic isolation. The design review should include, but not be limited to, the following: (a) site-specific spectra, (b) ground motion time histories, (c) modeling and analyses, (d) testing program and results, and (e) final design of all structural framing elements and isolation system components. Appendix A • Volume 2 Page 125

A-4.1.8.19.(3)(a)Non-Linear Dynamic Analysis.

Three-dimensional non-linear dynamic analysis is a complex process requiring special expertise. Guidance on non-linear dynamic analysis can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.19.(4)and A-4.1.8.21.(5) Ground Motion Time Histories.

Ground motion time histories and the horizontal and vertical components shall be appropriately selected and scaled according to accepted practice. Further information on ground motion time histories can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.1.8.21.(2)Design Review.

It is strongly recommended that a design review of the structure and the supplementary energy dissipation system be carried out by an independent team of professional engineers and geoscientists experienced in seismic analysis methods and the theory and application of supplementary energy dissipation. The design review should include, but not be limited to, the following: (a) ground motion time histories, (b) modeling and analyses, (c) testing program and results, and (d) final design of all structural framing elements and supplemental energy dissipation system components.

A-4.1.8.21.(4)(a)Non-Linear Dynamic Analysis.

Three-dimensional non-linear dynamic analysis is a complex process requiring special expertise. Guidance on non-linear dynamic analysis can be found in the Commentary entitled “Design for Seismic Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.2.2.1.(1)Subsurface Investigation.

Where acceptable information on subsurface conditions already exists, the investigation may not require further physical subsurface exploration or testing.

A-4.2.4.1.(1)Innovative Designs.

It is important that innovative approaches to foundation design be carried out by a person especially qualified in the specific method applied and that the design provide a level of safety and performance at least equivalent to that provided for or implicit in the design carried out by the methods referred to in Part 4. Provision must be made for monitoring the subsequent performance of such structures so that the long-term sufficiency of the design can be evaluated.

A-4.2.4.1.(3)Ultimate Limit States for Foundations.

Information on ultimate limit states for foundations, including terminology and resistance factors, can be found in the Commentary entitled “Foundations” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.2.4.1.(5)Design of Foundations for Differential Movements.

Information on the design of foundations for differential movements can be found in the Commentary entitled “Foundations” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.2.4.4.(1)Depth of Foundations.

When adfreezing has occurred and subsequent freezing results in soil expansion beneath this area, the resulting uplift effect is sometimes referred to as frost jacking. A heated building that is insulated to prevent heat loss through the foundation walls should be considered as an unheated structure unless the effect of the insulation is taken into account in determining the maximum depth of frost penetration. Page 126 Appendix A • Volume 2

A-4.2.5.1.(1)Excavations.

Information on excavations can be found in the Commentary entitled “Foundations” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.2.6.1.(1)Shallow Foundations.

Information on shallow foundations can be found in the Commentary entitled “Foundations” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.2.7.1.(1)Deep Foundation Units.

A deep foundation unit can be pre-manufactured or cast-in-place; it can be driven, jacked, jetted, screwed, bored or excavated; it can be of wood, concrete or steel or a combination thereof.

A-4.2.7.2.(1)Deep Foundations.

Information on deep foundations can be found in the Commentary entitled “Foundations” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

A-4.2.7.2.(2)Load Testing of Piles.

ASTM D1143, “Piles Under Static Axial Compressive Load”, defines routine load test procedures that have been extensively used.

A-4.3.3.1.(1)Precast Concrete.

CSA-A23.3, “Design of Concrete Structures”, requires precast concrete members to conform to CSA A23.4, “Precast Concrete - Materials and Construction”.

A-4.3.4.1.(1)Welded Construction.

Qualification for fabricators and erectors of welded construction is found in Clause 24.3 of CSA S16, “Design of Steel Structures”.

A-4.3.4.2.(1)Cold-Formed Stainless Steel Members.

There is currently no Canadian standard for the design of cold-formed stainless steel structural members. As an interim measure, design may be carried out using the limit states design provisions of ASCE/SEI 8, “Design of Cold Formed Stainless Steel Structural Members”, except that load factors, load combinations and load combination factors shall be in accordance with Subsection 4.1.3.

A-4.3.4.3.(1)Steel Building Systems.

A steel building system is defined in Section 3 of CAN/CSA-A660, “Certification of Manufacturers of Steel Building Systems”.

A-4.3.6.1.(1)Design Basis for Glass.

The load factors in Tables 4.1.3.2.A. and 4.1.3.2.B. must be applied to the adjusted wind load before designing in accordance with the referenced standard. Additional information is given in the Commentary entitled “Wind Load and Effects” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”.

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

A-4.4.2.1.(1)Design Basis for Storage Garages and Repair Garages.

Although the scope of CSA S413, “Parking Structures,” is limited to structural steel and reinforced concrete (including prestressed and post-tensioned), the intent of Sentence 4.4.2.1.(1) is to require any type of material used in the construction of storage garages and repair garages to conform to the performance level outlined in the standard. See the Commentary entitled “Live Loads” in the “Structural Commentaries (User's Guide – NBC 2020: Part 4 of Division B)”. Appendix A • Volume 2 Page 127

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Code text is reproduced for reference from the Ontario Building Code (O. Reg. 163/24, 2024 Building Code Compendium). This page is provided for general information and is not an official copy. Always verify requirements against the official Ontario Building Code and confirm with your local building department.