Division B
Acceptable Solutions

Part 4 — Structural Design

Section 4.1. Structural Loads and Procedures

4.1.1. General

(See User’s Guide - NBC 2010, Structural Commentaries (Part 4 of Division B).)

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4.1.1.1. Scope

The scope of this Part shall be as described in Subsection 1.3.3. of Division A.

4.1.1.2. Definitions

Words that appear in italics in this Part are defined in Article 1.4.1.2. of Division A.

4.1.1.3. Design Requirements

Buildings and their structural members and connections, including formwork and falsework, shall be designed to have sufficient structural capacity and structural integrity to safely and effectively resist all loads, effects of loads and influences that may reasonably be expected, having regard to the expected service life of buildings, and shall in any case satisfy the requirements of this Section. (See Appendix A.)

Buildings and their structural members shall be designed for serviceability, in accordance with Articles 4.1.3.4., 4.1.3.5. and 4.1.3.6. (See Appendix A.)

3) All permanent and temporary structural members, including the formwork and falsework of a building, shall be protected against loads exceeding the specified loads during the construction period except when, as verified by analysis or test, temporary overloading of a structural member would result in no impairment of that member or any other member.

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Falsework, scaffolding, and formwork shall be designed in conformance with

a) CSA S269.1, “Falsework for Construction Purposes,”

b) CAN/CSA-S269.2-M, “Access Scaffolding for Construction Purposes,” or

c) CAN/CSA-S269.3-M, “Concrete Formwork.”

5) Precautions shall be taken during all phases of construction to ensure that the building is not damaged or distorted due to loads applied during construction.

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4.1.1.4. Structural Drawings and Related Documents

Structural drawings and related documents shall conform to the appropriate requirements of Section 2.2. of Division C. (See Subsection 2.2.4. of Division C.)

4.1.1.5. Design Basis

Except as provided in Sentence (2), buildings and their structural members shall be designed in conformance with the procedures and practices provided in this Part.

Provided the design is carried out by a person especially qualified in the specific methods applied and provided the design demonstrates a level of safety and performance in accordance with the requirements of Part 4, buildings and their structural components falling within the scope of Part 4 that are not amenable to analysis using a generally established theory may be designed by

a) evaluation of a full-scale structure or a prototype by a loading test, or

b) studies of model analogues.

(See Appendix A.)

4.1.2. Specified Loads and Effects

(See User’s Guide - NBC 2010, Structural Commentaries (Part 4 of Division B).)

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4.1.2.1. Loads and Effects

(See Appendix A.)

Except as provided in Article 4.1.2.2., the following categories of loads, specified loads and effects shall be taken into consideration in the design of a building and its structural members and connections:

Ddead load – a permanent load due to the weight of building components, as specified in Subsection 4.1.4.,

Eearthquake load and effects – a rare load due to an earthquake, as specified in Subsection 4.1.8.,

Ha permanent load due to lateral earth pressure, including groundwater,

Llive load – a variable load due to intended use and occupancy (including loads due to cranes and the pressure of liquids in containers), as specified in Subsection 4.1.5.,

L_XClive load exclusive of crane loads,

Clive load due to cranes including self weight,

C_dself weight of all cranes positioned for maximum effects,

C₇crane bumper impact load,

Ppermanent effects caused by pre-stress,

Svariable load due to snow, including ice and associated rain, as specified in Article 4.1.6.2., or due to rain, as specified in Article 4.1.6.4.,

Teffects due to contraction, expansion, or deflection caused by temperature changes, shrinkage, moisture changes, creep, ground settlement, or a combination thereof (see Appendix A), and

Wwind load – a variable load due to wind, as specified in Subsection 4.1.7.,

where

a) load means the imposed deformations (i.e. deflections, displacements or motions that induce deformations and forces in the structure), forces and pressures applied to the building structure,

b) permanent load is a load that changes very little once it has been applied to the structure, except during repair,

c) variable load is a load that frequently changes in magnitude, direction or location, and

d) rare load is a load that occurs infrequently and for a short time only.

Minimum specified values of the loads described in Sentence (1), as set forth in Subsections 4.1.4. to 4.1.8., shall be increased to account for dynamic effects where applicable.

For the purpose of determining specified loads S, W or E in Subsections 4.1.6., 4.1.7. and 4.1.8., buildings shall be assigned an Importance Category based on intended use and occupancy, in accordance with Table 4.1.2.1. (See Appendix A.)

Table 4.1.2.1. Importance Categories for Buildings Forming part of Sentence 4.1.2.1.(3)
Use and Occupancy	Importance Category
Buildings that represent a low direct or indirect hazard to human life in the event of failure, including: low human-occupancy buildings, where it can be shown that collapse is not likely to cause injury or other serious consequences minor storage buildings	Low^⁽¹⁾
All buildings except those listed in Importance Categories Low, High and Post-disaster	Normal
Buildings that are likely to be used as post-disaster shelters, including buildings whose primary use is: as an elementary, middle or secondary school as a community centre Manufacturing and storage facilities containing toxic, explosive or other hazardous substances in sufficient quantities to be dangerous to the public if released⁽¹⁾	High
Post-disaster buildings are buildings that are essential to the provision of services in the event of a disaster, and include: hospitals, emergency treatment facilities and blood banks telephone exchanges power generating stations and electrical substations control centres for air, land and marine transportation public water treatment and storage facilities, and pumping stations sewage treatment facilities buildings having critical national defence functions buildings of the following types, unless exempted from this designation by the Chief Building Official:^⁽²⁾ emergency response facilities fire, rescue and police stations, and housing for vehicles, aircraft or boats used for such purposes communications facilities, including radio and television stations	Post-disaster

Notes to Table 4.1.2.1.:

⁽¹⁾	See Appendix A.
⁽²⁾	See A-1.4.1.2.(1), Post-disaster Buildings, in Appendix A of Division A.

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BC2012 2012-01-01 R1NC2010 2010-01-01 R1

Table 4.1.2.1. Importance Categories for Buildings Forming part of Sentence 4.1.2.1.(3)
Use and Occupancy	Importance Category
Buildings that represent a low direct or indirect hazard to human life in the event of failure, including: low human-occupancy buildings, where it can be shown that collapse is not likely to cause injury or other serious consequences minor storage buildings	Low⁽¹⁾
All buildings except those listed in Importance Categories Low, High and Post-disaster	Normal
Buildings that are likely to be used as post-disaster shelters, including buildings whose primary use is: as an elementary, middle or secondary school as a community centre Manufacturing and storage facilities containing toxic, explosive or other hazardous substances in sufficient quantities to be dangerous to the public if released⁽¹⁾	High
Post-disaster buildings are buildings that are essential to the provision of services in the event of a disaster, and include: hospitals, emergency treatment facilities and blood banks telephone exchanges power generating stations and electrical substations control centres for air, land and marine transportation public water treatment and storage facilities, and pumping stations sewage treatment facilities buildings having critical national defence functions buildings of the following types, unless exempted from this designation by the Chief Building Official~~authority having jurisdiction~~:⁽²⁾ emergency response facilities fire, rescue and police stations, and housing for vehicles, aircraft or boats used for such purposes communications facilities, including radio and television stations	Post-disaster

Notes to Table 4.1.2.1.:

⁽¹⁾	See Appendix A.
⁽²⁾	See A-1.4.1.2.(1), Post-disaster Buildings, in Appendix A of Division A.

4.1.2.2. Loads Not Listed

Where a building or structural member can be expected to be subjected to loads, forces or other effects not listed in Article 4.1.2.1., such effects shall be taken into account in the design based on the most appropriate information available.

4.1.3. Limit States Design

(See Appendix A.)

4.1.3.1. Definitions

In this Subsection, the term

a) limit states means those conditions of a building structure that result in the building ceasing to fulfill the function for which it was designed (those limit states concerning safety are called ultimate limit states (ULS) and include exceeding the load-carrying capacity, overturning, sliding and fracture; those limit states that restrict the intended use and occupancy of the building are called serviceability limit states (SLS) and include deflection, vibration, permanent deformation and local structural damage such as cracking; and those limit states that represent failure under repeated loading are called fatigue limit states),

b) specified loads ( change begin

D, E, H, L, P, S, T and W) means those loads defined in Article 4.1.2.1.,

c) principal load means the specified variable load or rare load that dominates in a given load combination,

d) companion load means a specified variable load that accompanies the principal load in a given load combination,

e) service load means a specified load used for the evaluation of a serviceability limit state,

f) principal-load factor means a factor applied to the principal load in a load combination to account for the variability of the load and load pattern and the analysis of its effects,

g) companion-load factor means a factor that, when applied to a companion load in the load combination, gives the probable magnitude of a companion load acting simultaneously with the factored principal load,

h) importance factor, I, means a factor applied in Subsections 4.1.6., 4.1.7. and 4.1.8. to obtain the specified load and take into account the consequences of failure as related to the limit state and the use and occupancy of the building,

i) factored load means the product of a specified load and its principal-load factor or companion-load factor,

j) effects refers to forces, moments, deformations or vibrations that occur in the structure,

k) nominal resistance, R, of a member, connection or structure, is based on the geometry and on the specified properties of the structural materials,

l) resistance factor, φ, means a factor applied to a specified material property or to the resistance of a member, connection or structure, and that, for the limit state under consideration, takes into account the variability of dimensions and material properties, workmanship, type of failure and uncertainty in the prediction of resistance, and

m) factored resistance, φR, means the product of nominal resistance and the applicable resistance factor.

4.1.3.2. Strength and Stability

A building and its structural components shall be designed to have sufficient strength and stability so that the factored resistance, φR, is greater than or equal to the effect of factored loads, which shall be determined in accordance with Sentence 4.1.3.2.(2).

Except as provided in Sentence (3)

, the effect of factored loads for a building or structural component shall be determined in accordance with change begin

the requirements of this Article and the following load combination cases,

the applicable combination being that which results in the most critical effect:

for load cases without crane loads, the load combinations listed in Table 4.1.3.2.A, and

for load cases with crane loads, the load combinations listed in Table 4.1.3.2.B

(See Appendix A.)

Other load combinations that must also be considered are the principal loads acting with the companion loads taken as zero.

Where the effects due to lateral earth pressure, H, restraint effects from pre-stress, P, and imposed deformation, T, affect the structural safety, they shall be taken into account in the calculations, with load factors of 1.5, 1.0 and 1.25 assigned to H, P and T respectively. (See Appendix A.)

Except as provided in Sentence 4.1.8.16.(1), the counteracting factored dead load—0.9D in load combination cases 2, 3 and 4 and 1.0D in load combination case 5 change begin

in Table 4.1.3.2.A, and 0.9D in load combination cases 1 to 5 and 1.0D in load combination case 6 in Table 4.1.3.2.B

—shall be used when the dead load acts to resist overturning, uplift, sliding, failure due to stress reversal, and to determine anchorage requirements and the factored resistance of members. (See Appendix A.)

The principal-load factor 1.5 for live loads L in Table 4.1.3.2.A change begin

and L_XC in Table 4.1.3.2.B

may be reduced to 1.25 for liquids in tanks.

The companion-load factor 0.5 for live loads L in Table 4.1.3.2.A change begin

and L_XC in Table 4.1.3.2.B

shall be increased to 1.0 for storage areas, and equipment areas and service rooms referred to in Table 4.1.5.3.

Table 4.1.3.2.A Load Combinations Without Crane Loads for Ultimate Limit States Forming part of Sentences 4.1.3.2.(2) and (5) to (10)
Case	Load Combination^⁽¹⁾
Case	Principal Loads	Companion Loads
1	1.4D^⁽²⁾	—
2	(1.25D^⁽³⁾ or 0.9D^⁽⁴⁾) + 1.5L^⁽⁵⁾	0.5S^⁽⁶⁾ or 0.4W
3	(1.25D⁽³⁾ or 0.9D⁽⁴⁾) + 1.5S	0.5L⁽⁶⁾⁽⁷⁾ or 0.4W
4	(1.25D⁽³⁾ or 0.9D⁽⁴⁾ ) + 1.4W	0.5L^⁽⁷⁾ or 0.5S
5	1.0D⁽⁴⁾ + 1.0E^⁽⁸⁾	0.5L⁽⁶⁾⁽⁷⁾ + 0.25S⁽⁶⁾

Notes to Table 4.1.3.2.A:

⁽¹⁾	See Sentences 4.1.3.2.(2), (3) and (4).
⁽²⁾	See Sentence 4.1.3.2.(9).
⁽³⁾	See Sentence 4.1.3.2.(8).
⁽⁴⁾	See Sentence 4.1.3.2.(5).
⁽⁵⁾	See Sentence 4.1.3.2.(6).
⁽⁶⁾	See Article 4.1.5.5.
⁽⁷⁾	See Sentence 4.1.3.2.(7).
⁽⁸⁾	See Sentence 4.1.3.2.(10).

Table 4.1.3.2.B Load Combinations With Crane Loads for Ultimate Limit States Forming part of Sentences 4.1.3.2.(2), (5) to (8), and (10)
Case	Load Combination^⁽¹⁾
Case	Principal Loads	Companion Loads
1	(1.25D^⁽²⁾ or 0.9D^⁽³⁾) + (1.5C + 1.0L_XC)	1.0S^⁽⁴⁾ or 0.4W
2	(1.25D⁽²⁾ or 0.9D⁽³⁾) + (1.5L_XC^⁽⁵⁾ + 1.0C)	0.5S⁽⁴⁾ or 0.4W
3	(1.25D⁽²⁾ or 0.9D⁽³⁾) + 1.5S	(1.0C + 0.5L_XC⁽⁴⁾^⁽⁶⁾)
4	(1.25D⁽²⁾ or 0.9D⁽³⁾) + 1.4W	(1.0C^⁽⁷⁾ + 0.5L_XC⁽⁴⁾⁽⁶⁾)
5	(1.25D⁽²⁾ or 0.9D⁽³⁾) + C₇	—
6	1.0D⁽³⁾ + 1.0E^⁽⁸⁾	1.0C_d + 0.5L_XC⁽⁴⁾⁽⁶⁾+ 0.25S⁽⁴⁾

Notes to Table 4.1.3.2.B:

⁽¹⁾	See Sentences 4.1.3.2.(2), (3) and (4).
⁽²⁾	See Sentence 4.1.3.2.(8).
⁽³⁾	See Sentence 4.1.3.2.(5).
⁽⁴⁾	See Article 4.1.5.5.
⁽⁵⁾	See Sentence 4.1.3.2.(6).
⁽⁶⁾	See Sentence 4.1.3.2.(7).
⁽⁷⁾	Side thrust due to cranes need not be combined with full wind load.
⁽⁸⁾	See Sentence 4.1.3.2.(10).

Except as provided in Sentence (9),

the load factor 1.25 for dead load, D, for soil, superimposed earth, plants and trees given in change begin

Tables 4.1.3.2.A and 4.1.3.2.B

shall be increased to 1.5, except that when the soil depth exceeds 1.2 m, the factor may be reduced to 1 + 0.6/h_s but not less than 1.25, where h_s is the depth of soil in metres supported by the structure.

A principal-load factor of 1.5 shall be applied to the weight of saturated soil used in load combination case 1 of Table 4.1.3.2.A.

10)

Earthquake load, E, in load combination cases 5 of Table 4.1.3.2.A change begin

and 6 of Table 4.1.3.2.B

includes horizontal earth pressure due to earthquake determined in accordance with Sentence 4.1.8.16.(4).

11)

Provision shall be made to ensure adequate stability of the structure as a whole and adequate lateral, torsional and local stability of all structural parts.

12)

Sway effects produced by vertical loads acting on the structure in its displaced configuration shall be taken into account in the design of buildings and their structural members.

4.1.3.3. Fatigue

A building and its structural components, including connections, shall be checked for fatigue failure under the effect of cyclical loads, as required in the standards listed in Section 4.3. (See Appendix A.)

Where vibration effects, such as resonance and fatigue resulting from machinery and equipment, are likely to be significant, a dynamic analysis shall be carried out. (See Appendix A.)

4.1.3.4. Serviceability

A building and its structural components shall be checked for serviceability limit states as defined in Clause 4.1.3.1.(1)(a) under the effect of service loads for serviceability criteria specified or recommended in Articles 4.1.3.5. and 4.1.3.6. and in the standards listed in Section 4.3. (See Appendix A.)

4.1.3.5. Deflection

In proportioning structural members to limit serviceability problems resulting from deflections, consideration shall be given to

a) the intended use of the building or member,

b) limiting damage to non-structural members made of materials whose physical properties are known at the time of design,

c) limiting damage to the structure itself, and

d) creep, shrinkage, temperature changes and pre-stress.

(See Appendix A.)

The lateral deflection of buildings due to service wind and gravity loads shall be checked to ensure that structural elements and non-structural elements whose nature is known at the time the structural design is carried out will not be damaged.

Except as provided in Sentence (4), the total drift per storey under service wind and gravity loads shall not exceed 1/500 of the storey height unless other drift limits are specified in the design standards referenced in Section 4.3. (See Appendix A.)

The deflection limits required in Sentence (3) do not apply to industrial buildings or sheds if experience has proven that greater movement will have no significant adverse effects on the strength and function of the building.

The building structure shall be designed for lateral deflection due to E, in accordance with Article 4.1.8.13.

4.1.3.6. Vibration

Floor systems susceptible to vibration shall be designed so that vibrations will have no significant adverse effects on the intended occupancy of the building. (See Appendix A.)

Where the fundamental vibration frequency of a structural system supporting an assembly occupancy used for rhythmic activities, such as dancing, concerts, jumping exercises or gymnastics, is less than 6 Hz, the effects of resonance shall be investigated by means of a dynamic analysis. (See Appendix A.)

A building susceptible to lateral vibration under wind load shall be designed in accordance with Article 4.1.7.2. so that the vibrations will have no significant adverse effects on the intended use and occupancy of the building. (See Appendix A.)

4.1.4. Dead Loads

4.1.4.1. Dead Loads

1) The specified dead load for a structural member consists of

a) the weight of the member itself,

b) the weight of all materials of construction incorporated into the building to be supported permanently by the member,

c) the weight of partitions,

d) the weight of permanent equipment, and

e) the vertical load due to earth, plants and trees.

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Except as provided in Sentence (5), in areas of a building where partitions other than permanent partitions are shown on the drawings, or where partitions might be added in the future, allowance shall be made for the weight of such partitions.

The partition weight allowance referred to in Sentence (2) shall be determined from the actual or anticipated weight of the partitions placed in any probable position, but shall be not less than 1 kPa over the area of floor being considered.

Partition loads used in design shall be shown on the drawings as provided in Clause 2.2.4.3.(1)(d) of Division C.

In cases where the dead load of the partition is counteractive, the load allowances referred to in Sentences (2) and (3) shall not be included in the design calculations.

Except for structures where the dead load of soil is part of the load-resisting system, where the dead load due to soil, superimposed earth, plants and trees is counteractive, it shall not be included in the design calculations. (See Appendix A.)

4.1.5. Live Loads Due to Use and Occupancy

(See User’s Guide - NBC 2010, Structural Commentaries (Part 4 of Division B).)

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4.1.5.1. Loads Due to Use of Floors and Roofs

Except as provided in Sentence (2), the specified live load on an area of floor or roof depends on the intended use and occupancy, and shall not be less than either the uniformly distributed load patterns listed in Article 4.1.5.3., the loads due to the intended use change begin

and occupancy

, or the concentrated loads listed in Article 4.1.5.9., whichever produces the most critical effect. change begin

(See Appendix A.)

For buildings in the Low Importance Category as described in Table 4.1.2.1., a factor of 0.8 may be applied to the live load.

4.1.5.2. Uses Not Stipulated

Except as provided in Sentence (2), where the use of an area of floor or roof is not provided for in Article 4.1.5.3., the specified live loads due to the use and occupancy of the area shall be determined from an analysis of the loads resulting from the weight of

a) the probable assembly of persons,

b) the probable accumulation of equipment and furnishings, and

c) the probable storage of materials.

For buildings in the Low Importance Category as described in Table 4.1.2.1., a factor of 0.8 may be applied to the live load.

4.1.5.3. Full and Partial Loading

The uniformly distributed live load shall be not less than the value listed in Table 4.1.5.3., which may be reduced as provided in Article 4.1.5.8., applied uniformly over the entire area or on any portions of the area, whichever produces the most critical effects in the members concerned.

Table 4.1.5.3. Specified Uniformly Distributed Live Loads on an Area of Floor or Roof Forming part of Sentence 4.1.5.3.(1)
Use of Area of Floor or Roof	Minimum Specified Load, kPa
Assembly Areas	4.8
a) Except for the areas listed under b), c), d) and e), assembly areas with or without fixed seats including
Arenas^⁽¹⁾ (areas without fixed seats that have backs)
Auditoria
Churches (areas without fixed seats that have backs)
Dance floors
Dining areas^⁽²⁾
Foyers and entrance halls
Grandstands⁽¹⁾ (areas without fixed seats that have backs), reviewing stands and bleachers
Gymnasia
Lecture halls⁽¹⁾ (areas without fixed seats that have backs)
Museums
Promenades
Rinks
Stadia⁽¹⁾ (areas without fixed seats that have backs)
Theatres(areas without fixed seats that have backs)
Other areas with similar uses
b) Classrooms and courtrooms with or without fixed seats⁽¹⁾	2.4
c) Portions of assembly areas with fixed seats that have backs for the following uses:	2.9⁽¹⁾
Arenas
Grandstands
Stadia
d) Portions of assembly areas with fixed seats that have backs for the following uses:	2.4
Churches
Lecture halls⁽¹⁾
Theatres
e) Vomitories, exits, lobbies and corridors⁽¹⁾	4.8
Attics⁽¹⁾
Accessible by a stairway in residential occupancies only	1.4
Having limited accessibility so that there is no storage of equipment or material	0.5
Balconies
Exterior	4.8
Interior and mezzanines that could be used by an assembly of people as a viewing area⁽¹⁾	4.8
Interior and mezzanines other than above	^⁽³⁾
Corridors, lobbies and aisles⁽¹⁾
Other than those listed below	4.8
Not more than 1 200 mm in width and all upper floor corridors of residential areas only of apartments, hotels and motels (that cannot be used by an assembly of people as a viewing area)⁽¹⁾	⁽¹⁾⁽³⁾
Equipment areas and service rooms including	3.6^⁽⁴⁾
Generator rooms
Mechanical equipment exclusive of elevators
Machine rooms
Pump rooms
Transformer vaults
Ventilating or air-conditioning equipment
Exits and fire escapes	4.8
Factories	6.0⁽⁴⁾
Footbridges	4.8
Garages for
Vehicles not exceeding 4 000 kg gross weight	2.4
Vehicles exceeding 4 000 kg but not exceeding 9 000 kg gross weight	6.0
Vehicles exceeding 9 000 kg gross weight	12.0⁽¹⁾
Kitchens (other than residential)	4.8
Libraries
Stack rooms	7.2
Reading and study rooms	2.9
Office areas (not including record storage and computer rooms) located in
Basement and the first storey	4.8
Floors above the first storey	2.4
Operating rooms and laboratories	3.6
Patients' bedrooms	1.9
Recreation areas that cannot be used for assembly purposes including	3.6
Billiard rooms
Bowling alleys
Pool rooms
Residential areas (within the scope of Article 1.3.3.2. of Division A)
Sleeping and living quarters in apartments, hotels, motels, boarding schools and colleges	1.9
Residential areas (within the scope of Article 1.3.3.3. of Division A)
Bedrooms	1.9
Other areas	1.9
Stairs within dwelling units	1.9
Retail and wholesale areas	4.8
Roofs	1.0⁽¹⁾^⁽⁵⁾
Sidewalks and driveways over areaways and basements	12.0⁽¹⁾⁽⁵⁾
Storage areas	4.8⁽⁴⁾
Toilet areas	2.4
Underground slabs with earth cover	⁽⁵⁾
Warehouses	4.8⁽⁴⁾

Notes to Table 4.1.5.3.:

⁽¹⁾	See Appendix A.
⁽²⁾	See Article 4.1.5.6.
⁽³⁾	See Article 4.1.5.4.
⁽⁴⁾	See Sentence 4.1.5.1.(1).
⁽⁵⁾	See Article 4.1.5.5.

4.1.5.4. Loads for Occupancy Served

The following shall be designed to carry not less than the specified load required for the occupancy they serve, provided they cannot be used by an assembly of people as a viewing area:

a) corridors, lobbies and aisles not more than 1 200 mm wide,

b) all corridors above the first storey of residential areas of apartments, hotels and motels, and

c) interior balconies and mezzanines.

4.1.5.5. Loads on Exterior Areas

(See Appendix A.)

Exterior areas accessible to vehicular traffic shall be designed for their intended use, including the weight of firefighting equipment, but not for less than the snow and rain loads prescribed in Subsection 4.1.6.

Except as provided in Sentences (3) and (4), roofs shall be designed for either the uniform live loads specified in Table 4.1.5.3., the concentrated live loads listed in change begin

Table 4.1.5.9.

, or the snow and rain loads prescribed in Subsection 4.1.6., whichever produces the most critical effects in the members concerned.

Exterior areas accessible to pedestrian traffic, but not vehicular traffic, shall be designed for their intended use, but not for less than the greater of

a) the live load prescribed for assembly areas in Table 4.1.5.3., or

b) the snow and rain loads prescribed in Subsection 4.1.6.

Roof parking decks shall be designed for either the uniformly distributed live loads specified in Table 4.1.5.3., the concentrated live loads listed in change begin

Table 4.1.5.9.

, or the roof snow load, whichever produces the most critical effect in the members concerned.

4.1.5.6. Loads for Dining Areas

The minimum specified live load listed in Table 4.1.5.3. for dining areas may be reduced to 2.4 kPa for areas in buildings that are being converted to dining areas, provided that the floor area does not exceed 100 m² and the dining area will not be used for other assembly purposes, including dancing.

4.1.5.7. More Than One Occupancy

Where an area of floor or roof is intended for 2 or more occupancies at different times, the value to be used from Table 4.1.5.3. shall be the greatest value for any of the occupancies concerned.

4.1.5.8. Variation with Tributary Area

(See Appendix A.)

An area used for assembly occupancies designed for a live load of less than 4.8 kPa and roofs designed for the minimum loading specified in Table 4.1.5.3. shall have no reduction for tributary area.

Where a structural member supports a tributary area of a floor or a roof, or a combination thereof, that is greater than 80 m² and either used for assembly occupancies designed for a live load of 4.8 kPa or more, or used for storage, manufacturing, retail stores, garages or as a footbridge, the specified live load due to use and occupancy is the load specified in Article 4.1.5.3. multiplied by

where A is the tributary area in square metres for this type of use and occupancy.

Where a structural member supports a tributary area of a floor or a roof, or a combination thereof, that is greater than 20 m² and used for any use or occupancy other than those indicated in Sentences (1) and (2), the specified live load due to use and occupancy is the load specified in Article 4.1.5.3. multiplied by

where B is the tributary area in square metres for this type of use and occupancy.

Where the specified live load for a floor is reduced in accordance with Sentence 4.1.5.8.(2) or (3), the structural drawings shall indicate that a live load reduction factor for tributary area has been applied.

4.1.5.9. Concentrated Loads

The specified live load due to possible concentrations of load resulting from the use of an area of floor or roof shall not be less than that listed in Table 4.1.5.9. applied over change begin

the loaded area noted and

located so as to cause maximum effects, except that for occupancies not listed in Table 4.1.5.9., the concentrations of load shall be determined in accordance with Article 4.1.5.2.

Table 4.1.5.9. Specified Concentrated Live Loads on an Area of Floor or Roof Forming part of Sentence 4.1.5.9.(1)
Area of Floor or Roof	Minimum Specified Concentrated Load, kN	Loaded Area, mm x mm
Roof surfaces	1.3	200 x 200
Floors of classrooms	4.5	750 x 750
Floors of offices, manufacturing buildings, hospital wards and stages	9.0	750 x 750
Floors and areas used by vehicles not exceeding 4 000 kg gross weight	18	120 x 120
Floors and areas used by vehicles exceeding 4 000 kg but not exceeding 9 000 kg gross weight	36	120 x 120
Floors and areas used by vehicles exceeding 9 000 kg gross weight	54^⁽¹⁾	250 x 600⁽¹⁾
Driveways and sidewalks over areaways and basements	54⁽¹⁾	250 x 600⁽¹⁾

Notes to Table 4.1.5.9.:

⁽¹⁾	See Appendix A.

4.1.5.10. Sway Forces in Assembly Occupancies

The floor assembly and other structural elements that support fixed seats in any building used for assembly occupancies accommodating large numbers of people at one time, such as grandstands, stadia and theatre balconies, shall be designed to resist a horizontal force equal to not less than 0.3 kN for each metre length of seats acting parallel to each row of seats, and not less than 0.15 kN for each metre length of seats acting at right angles to each row of seats, based on the assumption that these forces are acting independently of each other.

4.1.5.11. Crane-Supporting Structures and Impact of Machinery and Equipment

(See Appendix A.)

The minimum specified load due to equipment, machinery or other objects that may produce impact shall be the sum of the weight of the equipment or machinery and its maximum lifting capacity, multiplied by an appropriate factor listed in change begin

Table 4.1.5.11.

Crane-supporting structures shall be designed for the appropriate load combinations listed in Article 4.1.3.2.

3) Crane runway structures shall be designed to resist a horizontal force applied normal to the top of the rails equal to not less than 20 change begin

per cent

of the sum of the weights of the lifted load and the crane trolley (excluding other parts of the crane).

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The force described in Sentence (3) shall be equally distributed on each side of the runway and shall be assumed to act in either direction.

5) Crane runway structures shall be designed to resist a horizontal force applied parallel to the top of the rails equal to not less than 10 change begin

per cent

of the maximum wheel loads of the crane.

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Table 4.1.5.11. Factors for the Calculation of Impact Loads Forming part of Sentence 4.1.5.11.(1)
Cause of Impact	Factor
Operation of cab or radio-operated cranes	1.25
Operation of pendant or hand-operated cranes	1.10
Operation of elevators	^⁽¹⁾
Supports for light machinery, shaft or motor-driven	1.20
Supports for reciprocating machinery (e.g. compressors)	1.50
Supports for power-driven units (e.g. piston engines)	1.50

Notes to Table 4.1.5.11.:

⁽¹⁾	See ASME A17.1/CSA B44, “Safety Code for Elevators and Escalators.”

4.1.5.12. Bleachers

Bleacher seats shall be designed for a uniformly distributed live load of 1.75 kN for each linear metre or for a concentrated load of 2.2 kN distributed over a length of 0.75 m, whichever produces the most critical effect on the supporting members.

Bleachers shall be checked by the erector after erection to ensure that all structural members, including bracing specified in the design, have been installed.

Telescopic bleachers shall be provided with locking devices to ensure stability while in use.

4.1.5.13. Helicopter Landing Areas

Helicopter landing areas on roofs shall be constructed in conformance with the requirements change begin

for heliports

contained in the “Canadian Aviation Regulations – Part III,” published by Transport Canada.

4.1.5.14. Loads on Guards

(See Appendix A.)

The minimum specified horizontal load applied inward or outward at the change begin

minimum required height

of every required guard shall be

a) 3.0 kN/m change begin

for open viewing stands without fixed seats and

for means of egress in grandstands, stadia, bleachers and arenas,

b) a concentrated load of 1.0 kN applied at any point for access ways to equipment platforms, contiguous stairs and similar areas where the gathering of many people is improbable, and

c) 0.75 kN/m or a concentrated load of 1.0 kN applied at any point, whichever governs for locations other than those described in Clauses (a) and (b).

Individual elements within the guard, including solid panels and pickets, shall be designed for a load of 0.5 kN applied over an area of 100 mm by 100 mm located at any point in the element or elements so as to produce the most critical effect.

The loads required in Sentence (2) need not be considered to act simultaneously with the loads provided for in Sentences (1) and (4).

The minimum specified load applied vertically at the top of every required guard shall be 1.5 kN/m and need not be considered to act simultaneously with the horizontal load provided for in Sentence (1).

For loads on handrails, refer to change begin

Sentence 3.4.6.5.(12)

4.1.5.15. Loads on Vehicle Guardrails

Vehicle guardrails shall be designed for a concentrated load of 22 kN applied horizontally outward at any point 500 mm above the floor surface. (See Appendix A.)

4.1.5.16. Loads on Walls Acting As Guards

Where the floor elevation on one side of a wall, including a wall around a shaft, is more than 600 mm higher than the elevation of the floor or ground on the other side, the wall shall be designed to resist the appropriate lateral design loads prescribed elsewhere in this Section or 0.5 kPa, whichever produces the more critical effect.

4.1.5.17. Firewalls

(See Appendix A.)

Firewalls shall be designed to resist the maximum effect due to

a) the appropriate lateral design loads prescribed elsewhere in this Section, or

b) a factored lateral load of 0.5 kPa under fire conditions, as described in Sentence (2).

Under fire conditions, where the fire-resistance rating of the structure is less than that of the firewall,

a) lateral support shall be assumed to be provided by the structure on one side only, or

b) another structural support system capable of resisting the loads imposed by a fire on either side of the firewall shall be provided.

4.1.5.18. Loads for Building Maintenance

1) Buildings shall be designed to support the loads and forces required to support building maintenance equipment.

4.1.6. Loads Due to Snow and Rain

(See User's Guide - NBC 2010, Structural Commentaries (Part 4 of Division B).)

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4.1.6.1. Specified Load Due to Rain or to Snow and Associated Rain

The specified load on a roof or any other building surface subject to snow and associated rain shall be the snow load specified in Article 4.1.6.2., or the rain load specified in Article 4.1.6.4., whichever produces the more critical effect.

4.1.6.2. Specified Snow Load

(See Appendix A.)

1) The specified load, S, due to snow and associated rain accumulation on a roof or any other building surface subject to snow accumulation shall be calculated using the formula change begin

where

I_s= importance factor for snow load as provided in Table 4.1.6.2.,

S_s= 1-in-50-year ground snow load, in kPa, determined in accordance with Subsection 1.1.3.,

C_b= basic roof snow load factor in Sentence (2),

C_w= wind exposure factor in Sentences (3) and (4),

C_s= slope factor in Sentences (5), (6) and (7),

C_a= shape factor in Sentence (8), and

S_r= 1-in-50-year associated rain load, in kPa, determined in accordance with Subsection 1.1.3., but not greater than S_s(C_bC_wC_sC_a).

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Table 4.1.6.2. Importance Factor for Snow Load, I_S Forming part of Sentence 4.1.6.2.(1)
Importance Category	Importance Factor, I_s
Importance Category	ULS	SLS
Low	0.8	0.9
Normal	1	0.9
High	1.15	0.9
Post-disaster	1.25	0.9

The basic roof snow load factor, C_b, shall be 0.8, except that for large roofs it shall be

a) 1.0 - (30/l_c)², for roofs with C_w = 1.0 and l_c greater than or equal to 70 m, or

b) 1.3 - (140/l_c)², for roofs with C_w = 0.75 or 0.5 and l_c greater than or equal to 200 m,

where

l_c= characteristic length of the upper or lower roof, defined as 2w−w²/l, in metres,

w= smaller plan dimension of the roof, in metres,

l= larger plan dimension of the roof, in metres.

Except as provided for in Sentence (4), the wind exposure factor, C_w, shall be 1.0.

For buildings in the Low and Normal Importance Categories as set out in Table 4.1.2.1., the wind exposure factor given in Sentence (3) may be reduced to 0.75, or to 0.5 in exposed areas north of the treeline, where

a) the building is exposed on all sides to wind over open terrain as defined in Clause 4.1.7.1.(5)(a), and is expected to remain so during its life,

b) the area of roof under consideration is exposed to the wind on all sides with no significant obstructions on the roof, such as parapet walls, within a distance of at least 10 times the difference between the height of the obstruction and C_bC_wS_s/ϒ metres, where ϒ is the unit weight of snow on roofs (see Appendix A), and

c) the loading does not involve the accumulation of snow due to drifting from adjacent surfaces.

Except as provided for in Sentences (6) and (7), the slope factor, C_s, shall be

a) 1.0 where the roof slope, ∝, is equal to or less than 30°,

b) (70° − ∝)/40° where ∝ is greater than 30° but not greater than 70°, and

c) 0 where ∝ exceeds 70°.

The slope factor, C_s, for unobstructed slippery roofs where snow and ice can slide completely off the roof shall be

a) 1.0 where the roof slope, ∝, is equal to or less than 15°,

b) (60° − ∝)/45° where ∝ is greater than 15° but not greater than 60°, and

c) 0 where ∝ exceeds 60°.

The slope factor, C_s, shall be 1.0 when used in conjunction with shape factors for increased snow loads as given in Clauses (8)(b) and (e).

The shape factor, C_a, shall be 1.0, except that where appropriate for the shape of the roof, it shall be assigned other values that account for

a) non-uniform snow loads on gable, arched or curved roofs and domes,

b) increased snow loads in valleys,

c) increased non-uniform snow loads due to snow drifting onto a roof that is at a level lower than other parts of the same building or at a level lower than another building within 5 m of it,

d) increased non-uniform snow loads on areas adjacent to roof projections, such as penthouses, large chimneys and equipment, and

e) increased snow or ice loads due to snow sliding or meltwater draining from adjacent roofs.

4.1.6.3. Full and Partial Loading

A roof or other building surface and its structural members subject to loads due to snow accumulation shall be designed for the specified load given in Sentence 4.1.6.2.(1), distributed over the entire loaded area.

In addition to the distribution mentioned in Sentence (1), flat roofs and shed roofs, gable roofs of 15° slope or less, and arched or curved roofs shall be designed for the specified uniform snow load indicated in Sentence 4.1.6.2.(1), which shall be calculated using C_a = 1.0, distributed on any one portion of the loaded area and half of this load on the remainder of the loaded area, in such a way as to produce the most critical effects on the member concerned. (See Appendix A.)

4.1.6.4. Specified Rain Load

Except as provided in Sentence (4), the specified load, S, due to the accumulation of rainwater on a surface whose position, shape and deflection under load make such an accumulation possible, is that resulting from the one-day rainfall determined in conformance with Subsection 1.1.3. and applied over the horizontal projection of the surface and all tributary surfaces. (See Appendix A.)

The provisions of Sentence (1) apply whether or not the surface is provided with a means of drainage, such as rainwater leaders.

Except as provided in Sentence 4.1.6.2.(1), loads due to rain need not be considered to act simultaneously with loads due to snow. (See Appendix A.)

Where scuppers are provided and where the position, shape and deflection of the loaded surface make an accumulation of rainwater possible, the loads due to rain shall be the lesser of either the one-day rainfall determined in conformance with Subsection 1.1.3. or a depth of rainwater equal to 30 mm above the level of the scuppers, applied over the horizontal projection of the surface and tributary areas.

4.1.7. Wind Load

(See User's Guide - NBC 2010, Structural Commentaries (Part 4 of Division B).)

4.1.7.1. Specified Wind Load

The specified external pressure or suction due to wind on part or all of a surface of a building shall be calculated using the formula

where

p= specified external pressure acting statically and in a direction normal to the surface, either as a pressure directed towards the surface or as a suction directed away from the surface,

I_W= importance factor for wind load, as provided in Table 4.1.7.1.,

q= reference velocity pressure, as provided in Sentence (4),

C_e= exposure factor, as provided in Sentence (5),

C_g= gust effect factor, as provided in Sentence (6), and

C_p= external pressure coefficient, averaged over the area of the surface considered.

(See Appendix A.)

Table 4.1.7.1. Importance Factor for Wind Load, I_W Forming part of Sentences 4.1.7.1.(1) and (3)
Importance Category	Importance Factor, I_W
Importance Category	ULS	SLS
Low	0.8	0.75
Normal	1	0.75
High	1.15	0.75
Post-disaster	1.25	0.75

The net wind load for the building as a whole shall be the algebraic difference of the loads on the windward and leeward surfaces, and in some cases, may be calculated as the sum of the products of the external pressures or suctions and the areas of the surfaces over which they are averaged as provided in Sentence (1). (See Appendix A.)

The net specified pressure due to wind on part or all of a surface of a building shall be the algebraic difference of the external pressure or suction as provided in Sentence (1) and the specified internal pressure or suction due to wind calculated using the following formula:

where

p_i= specified internal pressure acting statically and in a direction normal to the surface, either as a pressure directed towards the surface or as a suction directed away from the surface,

I_W= importance factor for wind load, as provided in Table 4.1.7.1.,

q= reference velocity pressure, as provided in Sentence (4),

C_e= exposure factor, as provided in Sentence (5),

C_gi= internal gust effect factor, as provided in Sentence (6), and

C_pi= internal pressure coefficient.

(See Appendix A.)

The reference velocity pressure, q, shall be the appropriate value determined in conformance with Subsection 1.1.3., based on a probability of being exceeded in any one year of 1 in 50.

The exposure factor, C_e, shall be

a) (h/10)^0.2 but not less than 0.9 for open terrain, where open terrain is level terrain with only scattered buildings, trees or other obstructions, open water or shorelines thereof, h being the reference height above grade in metres for the surface or part of the surface (see Appendix A),

b) 0.7(h/12)^0.3 but not less than 0.7 for rough terrain, where rough terrain is suburban, urban or wooded terrain extending upwind from the building uninterrupted for at least 1 km or change begin

20 times the height of the building

, whichever is greater, h being the reference height above grade in metres for the surface or part of the surface (see Appendix A),

c) an intermediate value between the two exposures defined in Clauses (a) and (b) in cases where the site is less than 1 km or change begin

20 times the height of the building

from a change in terrain conditions, whichever is greater, provided an appropriate interpolation method is used (see Appendix A), or

d) if a dynamic approach to the action of wind gusts is used, an appropriate value depending on both height and shielding (see Appendix A).

The gust effect factor, C_g, shall be one of the following values:

a) for the building as a whole and main structural members, C_g = 2.0 (see Appendix A),

b) for external pressures and suctions on small elements including cladding, C_g = 2.5,

c) for internal pressures, C_gi = 2.0 or a value determined by detailed calculation that takes into account the sizes of the openings in the building envelope, the internal volume and the flexibility of the building envelope (see Appendix A), or

d) if a dynamic approach to wind action is used, C_g is a value that is appropriate for the turbulence of the wind and the size and natural frequency of the structure (see Appendix A).

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BC2012 2012-01-01 R1NC2010 2010-01-01 R1

4.1.7.1. Specified Wind Load

1) The specified external pressure or suction due to wind on part or all of a surface of a building shall be calculated using the formula

where

p= specified external pressure acting statically and in a direction normal to the surface, either as a pressure directed towards the surface or as a suction directed away from the surface,

I_W= importance factor for wind load, as provided in Table 4.1.7.1.,

q= reference velocity pressure, as provided in Sentence (4),

C_e= exposure factor, as provided in Sentence (5),

C_g= gust effect factor, as provided in Sentence (6), and

C_p= external pressure coefficient, averaged over the area of the surface considered.

(See Appendix A.)

Table Importance Factor for Wind Load, I_W Forming part of Sentences 4.1.7.1.(1) and (3)
Importance Category	Importance Factor, I_W
	ULS	SLS
Low	0.8	0.75
Normal	1	0.75
High	1.15	0.75
Post-disaster	1.25	0.75

2) The net wind load for the building as a whole shall be the algebraic difference of the loads on the windward and leeward surfaces, and in some cases, may be calculated as the sum of the products of the external pressures or suctions and the areas of the surfaces over which they are averaged as provided in Sentence (1). (See Appendix A.)

3) The net specified pressure due to wind on part or all of a surface of a building shall be the algebraic difference of the external pressure or suction as provided in Sentence (1) and the specified internal pressure or suction due to wind calculated using the following formula:

where

p_i= specified internal pressure acting statically and in a direction normal to the surface, either as a pressure directed towards the surface or as a suction directed away from the surface,

I_W= importance factor for wind load, as provided in Table 4.1.7.1.,

q= reference velocity pressure, as provided in Sentence (4),

C_e= exposure factor, as provided in Sentence (5),

C_gi= internal gust effect factor, as provided in Sentence (6), and

C_pi= internal pressure coefficient.

(See Appendix A.)

4) The reference velocity pressure, q, shall be the appropriate value determined in conformance with Subsection 1.1.3., based on a probability of being exceeded in any one year of 1 in 50.

5) The exposure factor, C_e, shall be

b) 0.7(h/12)^0.3 but not less than 0.7 for rough terrain, where rough terrain is suburban, urban or wooded terrain extending upwind from the building uninterrupted for at least 1 km or 20 times the height of the building ~~height~~, whichever is greater, h being the reference height above grade in metres for the surface or part of the surface (see Appendix A),

c) an intermediate value between the two exposures defined in Clauses (a) and (b) in cases where the site is less than 1 km or 20 times the height of the building ~~height~~ from a change in terrain conditions, whichever is greater, provided an appropriate interpolation method is used (see Appendix A), or

d) if a dynamic approach to the action of wind gusts is used, an appropriate value depending on both height and shielding (see Appendix A).

6) The gust effect factor, C_g, shall be one of the following values:

a) for the building as a whole and main structural members, C_g = 2.0 (see Appendix A),

b) for external pressures and suctions on small elements including cladding, C_g = 2.5,

d) if a dynamic approach to wind action is used, C_g is a value that is appropriate for the turbulence of the wind and the size and natural frequency of the structure (see Appendix A).

4.1.7.2. Dynamic Effects of Wind

Except as provided in Sentence (2),

buildings whose height is greater than 4 times their minimum effective width, which is defined in Sentence (3), or greater than change begin

60 m,

and buildings whose change begin

lowest natural frequency is less than 1 Hz, as determined by rational analysis (see Appendix A),

shall be designed

a) by experimental methods for the danger of dynamic overloading, vibration and the effects of fatigue, or

b) by using a dynamic approach to the action of wind gusts (see Appendix A).

Buildings whose lowest natural frequency is less than ¼ Hz, as determined by rational analysis, shall be designed by experimental methods in accordance with Clause (1)(a). (See Appendix A.)

The effective width, w, of a building shall be calculated using

where the summations are over the height of the building for a given wind direction, h_i is the height above grade to level i, as defined in Sentence 4.1.7.1.(5), and w_i is the width normal to the wind direction at height h_i; the minimum effective width is the lowest value of the effective width considering all possible wind directions.

4.1.7.3. Full and Partial Loading

1) Buildings and structural members shall be capable of withstanding the effects of

a) the full wind loads acting along each of the 2 principal horizontal axes considered separately,

b) the wind loads as described in Clause (a) but with 100 change begin

per cent

of the load removed from any portion of the area,

c) the wind loads as described in Clause (a) but considered simultaneously at 75 change begin

per cent

of their full value, and

d) the wind loads as described in Clause (c) but with 50 change begin

per cent

of these loads removed from any portion of the area.

(See Appendix A.)

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4.1.7.4. Interior Walls and Partitions

In the design of interior walls and partitions, due consideration shall be given to differences in air pressure on opposite sides of the wall or partition which may result from

a) pressure differences between the windward and leeward sides of a building,

b) stack effects due to a difference in air temperature between the exterior and interior of the building, and

c) air pressurization by the mechanical services of the building.

4.1.7.5. Exterior Wall Air Barrier

1) An exterior wall assembly incorporating an air barrier required by Subsection 5.4.1. shall be designed to accommodate loading due to air pressure differences on opposite sides of the air barrier.

4.1.8. Earthquake Load and Effects

(See User's Guide - NBC 2010, Structural Commentaries (Part 4 of Division B).)

4.1.8.1. Analysis

The deflections and specified loading due to earthquake motions shall be determined according to the requirements in this Subsection, except that the requirements in this Subsection need not be considered in design if S(0.2), as defined in Sentence 4.1.8.4.(7), is less than or equal to 0.12.

4.1.8.2. Notation

1) In this Subsection

A_r= response amplification factor to account for type of attachment of mechanical/electrical equipment, as defined in change begin

Sentence 4.1.8.18.(1)

A_x= amplification factor at level x to account for variation of response of mechanical/electrical equipment with elevation within the building, as defined in change begin

Sentence 4.1.8.18.(1)

B_x= ratio at level x used to determine torsional sensitivity, as defined in Sentence 4.1.8.11.(9),

B= maximum value of B_x, as defined in Sentence 4.1.8.11.(9),

C_p= seismic coefficient for mechanical/electrical equipment, as defined in change begin

Sentence 4.1.8.18.(1)

D_nx= plan dimension of the building at level x perpendicular to the direction of seismic loading being considered,

e_x= distance measured perpendicular to the direction of earthquake loading between centre of mass and centre of rigidity at the level being considered (see Appendix A),

F_a= acceleration-based site coefficient, as defined in Sentence 4.1.8.4.(4),

F_t= portion of V to be concentrated at the top of the structure, as defined in Sentence 4.1.8.11.(6),

F_v= velocity-based site coefficient, as defined in Sentence 4.1.8.4.(4),

F_x= lateral force applied to level x, as defined in Sentence 4.1.8.11.(6),

h_i, h_n, h_x= the height above the base (i = 0) to level i, n, or x respectively, where the base of the structure is the level at which horizontal earthquake motions are considered to be imparted to the structure,

h_s= interstorey height (h_i - h_i-1),

I_E= earthquake importance factor of the structure, as described in Sentence 4.1.8.5.(1),

J= numerical reduction coefficient for base overturning moment, as defined in Sentence 4.1.8.11.(5),

J_x= numerical reduction coefficient for overturning moment at level x, as defined in Sentence 4.1.8.11.(7),

Level i= any level in the building, i = 1 for first level above the base,

Level n= level that is uppermost in the main portion of the structure,

Level x= level that is under design consideration,

M_v= factor to account for higher mode effect on base shear, as defined in Sentence 4.1.8.11.(5),

M_x= overturning moment at level x, as defined in Sentence 4.1.8.11.(7),

N= total number of storeys above exterior grade to level n,

N̅₆₀= Average Standard Penetration Resistance for the top 30 m, corrected to a rod energy efficiency of 60 change begin

per cent

of the theoretical maximum,

PGA= Peak Ground Acceleration expressed as a ratio to gravitational acceleration, as defined in Sentence 4.1.8.4.(1),

PI= plasticity index for clays,

R_d= ductility-related force modification factor reflecting the capability of a structure to dissipate energy through change begin

reversed cyclic

inelastic behaviour, as given in Article 4.1.8.9.,

R_o= overstrength-related force modification factor accounting for the dependable portion of reserve strength in a structure designed according to these provisions, as defined in Article 4.1.8.9.,

S_p= horizontal force factor for part or portion of a building and its anchorage, as given in change begin

Sentence 4.1.8.18.(1)

S(T)= design spectral response acceleration, expressed as a ratio to gravitational acceleration, for a period of T, as defined in change begin

Sentence 4.1.8.4.(7)

S_a(T)= 5

per cent

damped spectral response acceleration, expressed as a ratio to gravitational acceleration, for a period of T, as defined in Sentence 4.1.8.4.(1),

SFRS= Seismic Force Resisting System(s) is that part of the structural system that has been considered in the design to provide the required resistance to the earthquake forces and effects defined in Subsection 4.1.8.,

s_u= average undrained shear strength in the top 30 m of soil,

T= period in seconds,

T_a= fundamental lateral period of vibration of the building or structure in seconds in the direction under consideration, as defined in Sentence 4.1.8.11.(3),

T_x= floor torque at level x, as defined in Sentence 4.1.8.11.(10),

V= lateral earthquake design force at the base of the structure, as determined by Article 4.1.8.11.,

V_d= lateral earthquake design force at the base of the structure, as determined by Article 4.1.8.12.,

V_e= lateral earthquake elastic force at the base of the structure, as determined by Article 4.1.8.12.,

V_ed= lateral earthquake design elastic force at the base of the structure, as determined by Article 4.1.8.12.,

V_p= lateral force on a part of the structure, as determined by change begin

Article 4.1.8.18.

V̅_s= average shear wave velocity in the top 30 m of soil or rock,

W= dead load, as defined in Article 4.1.4.1., except that the minimum partition load as defined in Sentence 4.1.4.1.(3) need not exceed 0.5 kPa, plus 25 change begin

per cent

of the design snow load specified in Subsection 4.1.6., plus 60 change begin

per cent

of the storage load for areas used for storage, except that storage garages need not be considered storage areas, and the full contents of any tanks (see Appendix A),

W_i, W_x= portion of W that is located at or is assigned to level i or x respectively,

W_p= weight of a part or portion of a structure, e.g., cladding, partitions and appendages,

δ_ave= average displacement of the structure at level x, as defined in Sentence 4.1.8.11.(9), and

δ_max= maximum displacement of the structure at level x, as defined in Sentence 4.1.8.11.(9).

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NC2010 2010-01-01 R1

1) In this Subsection

A_r= response amplification factor to account for type of attachment of mechanical/electrical equipment, as defined in Sentence 4.1.8.18.(1),

A_x= amplification factor at level x to account for variation of response of mechanical/electrical equipment with elevation within the building, as defined in Sentence 4.1.8.18.(1),

B_x= ratio at level x used to determine torsional sensitivity, as defined in Sentence 4.1.8.11.(9),

B= maximum value of B_x, as defined in Sentence 4.1.8.11.(9),

C_p= seismic coefficient for mechanical/electrical equipment, as defined in Sentence 4.1.8.18.(1),

D_nx= plan dimension of the building at level x perpendicular to the direction of seismic loading being considered,

e_x= distance measured perpendicular to the direction of earthquake loading between centre of mass and centre of rigidity at the level being considered (see Appendix A),

F_a= acceleration-based site coefficient, as defined in Sentence 4.1.8.4.(4),

F_t= portion of V to be concentrated at the top of the structure, as defined in Sentence 4.1.8.11.(6),

F_v= velocity-based site coefficient, as defined in Sentence 4.1.8.4.(4),

F_x= lateral force applied to level x, as defined in Sentence 4.1.8.11.(6),

h_s= interstorey height (h_i - h_i-1),

I_E= earthquake importance factor of the structure, as described in Sentence 4.1.8.5.(1),

J= numerical reduction coefficient for base overturning moment, as defined in Sentence 4.1.8.11.(5),

J_x= numerical reduction coefficient for overturning moment at level x, as defined in Sentence 4.1.8.11.(7),

Level i= any level in the building, i = 1 for first level above the base,

Level n= level that is uppermost in the main portion of the structure,

Level x= level that is under design consideration,

M_v= factor to account for higher mode effect on base shear, as defined in Sentence 4.1.8.11.(5),

M_x= overturning moment at level x, as defined in Sentence 4.1.8.11.(7),

N= total number of storeys above exterior grade to level n,

N̅₆₀= Average Standard Penetration Resistance for the top 30 m, corrected to a rod energy efficiency of 60 per cent ~~60%~~ of the theoretical maximum,

PGA= Peak Ground Acceleration expressed as a ratio to gravitational acceleration, as defined in Sentence 4.1.8.4.(1),

PI= plasticity index for clays,

R_d= ductility-related force modification factor reflecting the capability of a structure to dissipate energy through reversed cyclic inelastic behaviour, as given in Article 4.1.8.9.,

R_o= overstrength-related force modification factor accounting for the dependable portion of reserve strength in a structure designed according to these provisions, as defined in Article 4.1.8.9.,

S_p= horizontal force factor for part or portion of a building and its anchorage, as given in Sentence 4.1.8.18.(1),

S(T)= design spectral response acceleration, expressed as a ratio to gravitational acceleration, for a period of T, as defined in Sentence 4.1.8.4.(7),

S_a(T)= 5 per cent 5% damped spectral response acceleration, expressed as a ratio to gravitational acceleration, for a period of T, as defined in Sentence 4.1.8.4.(1),

s_u= average undrained shear strength in the top 30 m of soil,

T= period in seconds,

T_a= fundamental lateral period of vibration of the building or structure in seconds in the direction under consideration, as defined in Sentence 4.1.8.11.(3),

T_x= floor torque at level x, as defined in Sentence 4.1.8.11.(10),

V= lateral earthquake design force at the base of the structure, as determined by Article 4.1.8.11.,

V_d= lateral earthquake design force at the base of the structure, as determined by Article 4.1.8.12.,

V_e= lateral earthquake elastic force at the base of the structure, as determined by Article 4.1.8.12.,

V_ed= lateral earthquake design elastic force at the base of the structure, as determined by Article 4.1.8.12.,

V_p= lateral force on a part of the structure, as determined by Article 4.1.8.18.,

V̅_s= average shear wave velocity in the top 30 m of soil or rock,

W= dead load, as defined in Article 4.1.4.1., except that the minimum partition load as defined in Sentence 4.1.4.1.(3) need not exceed 0.5 kPa, plus 25 per cent ~~25%~~ of the design snow load specified in Subsection 4.1.6., plus 60 per cent ~~60%~~ of the storage load for areas used for storage, except that storage garages need not be considered storage areas, and the full contents of any tanks (see Appendix A),

W_i, W_x= portion of W that is located at or is assigned to level i or x respectively,

W_p= weight of a part or portion of a structure, e.g., cladding, partitions and appendages,

δ_ave= average displacement of the structure at level x, as defined in Sentence 4.1.8.11.(9), and

δ_max= maximum displacement of the structure at level x, as defined in Sentence 4.1.8.11.(9).

4.1.8.3. General Requirements

The building shall be designed to meet the requirements of this Subsection and of the design standards referenced in Section 4.3.

Structures shall be designed with a clearly defined load path, or paths, that will transfer the inertial forces generated in an earthquake to the supporting ground.

The structure shall have a clearly defined Seismic Force Resisting System(s) (SFRS), as defined in Article 4.1.8.2.

4) The SFRS shall be designed to resist 100 change begin

per cent

of the earthquake loads and their effects. (See Appendix A.)

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All structural framing elements not considered to be part of the SFRS must be investigated and shown to behave elastically or to have sufficient non-linear capacity to support their gravity loads while undergoing earthquake-induced deformations calculated from the deflections determined in Article 4.1.8.13.

Stiff elements that are not considered part of the SFRS, such as concrete, masonry, brick or pre-cast walls or panels, shall be

a) separated from all structural elements of the building such that no interaction takes place as the building undergoes deflections due to earthquake effects as calculated in this Subsection, or

b) made part of the SFRS and satisfy the requirements of this Subsection.

(See Appendix A.)

7) Stiffness imparted to the structure from elements not part of the SFRS, other than those described in Sentence (6), shall not be used to resist earthquake deflections but shall be accounted for

a) in calculating the period of the structure for determining forces if the added stiffness decreases the fundamental lateral period by more than 15 change begin

per cent

b) in determining the irregularity of the structure, except the additional stiffness shall not be used to make an irregular SFRS regular or to reduce the effects of torsion (see Appendix A), and

c) in designing the SFRS if inclusion of the elements not part of the SFRS in the analysis has an adverse effect on the SFRS (see Appendix A).

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Structural modelling shall be representative of the magnitude and spatial distribution of the mass of the building and of the stiffness of all elements of the SFRS, including stiff elements that are not separated in accordance with Sentence (6), and shall account for

a) the effect of cracked sections in reinforced concrete and reinforced masonry elements,

b) the effect of the finite size of members and joints,

c) sway effects arising from the interaction of gravity loads with the displaced configuration of the structure, and

d) other effects that influence the lateral stiffness of the building.

(See Appendix A.)

4.1.8.4. Site Properties

1) The peak ground acceleration (PGA) and the 5 change begin

per cent

damped spectral response acceleration values, S_a(T), for the reference ground conditions (Site Class C in Table 4.1.8.4.A) for periods T of 0.2 s, 0.5 s, 1.0 s, and 2.0 s, shall be determined in accordance with Subsection 1.1.3. and are based on a 2 change begin

per cent

probability of exceedance in 50 years.

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Table 4.1.8.4.A Site Classification for Seismic Site Response Forming part of Sentences 4.1.8.4.(1) to (3)
Site Class	Ground Profile Name	Average Properties in Top 30 m, as per Appendix A
Site Class	Ground Profile Name	Average Shear Wave Velocity, V̅_s (m/s)	Average Standard Penetration Resistance, N̅₆₀	Soil Undrained Shear Strength, s_u
A	Hard rock<^⁽¹⁾><^⁽²⁾>	V̅_s > 1500	n/a	n/a
B	Rock^⁽²⁾	760 < V̅_s ≤ 1500	n/a	n/a
C	Very dense soil and soft rock	360 < V̅_s < 760	N̅₆₀ > 50	s_u > 100 kPa
D	Stiff soil	180 < V̅_s < 360	15 ≤ N̅₆₀ ≤ 50	50 kPa < s_u ≤ 100 kPa
E	Soft soil	V̅_s < 180	N̅₆₀ < 15	s_u < 50 kPa
E	Soft soil	Any profile with more than 3 m of soil with the following characteristics: plasticity index: PI > 20 moisture content: w ≥ 40%, and undrained shear strength: s_u < 25 kPa
F	Other soils<^⁽³⁾>	Site-specific evaluation required

Notes to Table 4.1.8.4.A:

⁽¹⁾	Site Classes A and B, hard rock and rock, are not to be used if there is more than 3 m of softer materials between the rock and the underside of footing or mat foundations. The appropriate Site Class for such cases is determined on the basis of the average properties of the total thickness of the softer materials (see Appendix A).
⁽²⁾	If V̅_s has been measured in-situ, the F_a and F_v values derived from Tables 4.1.8.4.B and C may be multiplied by (1500/V̅_s)^½.
⁽³⁾	Other soils include: liquefiable soils, quick and highly sensitive clays, collapsible weakly cemented soils, and other soils susceptible to failure or collapse under seismic loading, peat and/or highly organic clays greater than 3 m in thickness, highly plastic clays (PI > 75) more than 8 m thick, and soft to medium stiff clays more than 30 m thick.

Site classifications for ground shall conform to Table 4.1.8.4.A and shall be determined using V̅_s except as provided in Sentence (3).

If average shear wave velocity, V̅_s, is not known, Site Class shall be determined from energy-corrected Average Standard Penetration Resistance, N̅₆₀, or from soil average undrained shear strength, s_u, as noted in Table 4.1.8.4.A, N̅₆₀ and s_u being calculated based on rational analysis. (See Appendix A.)

Acceleration- and velocity-based site coefficients, F_a and F_v, shall conform to Tables 4.1.8.4.B and 4.1.8.4.C using linear interpolation for intermediate values of S_a(0.2) and S_a(1.0).

Table 4.1.8.4.B Values of F_a as a Function of Site Class and S_a(0.2) Forming part of Sentence 4.1.8.4.(4)
Site Class	Values of F_a
Site Class	S_a(0.2) ≤ 0.25	S_a(0.2) = 0.50	S_a(0.2) = 0.75	S_a(0.2) = 1.00	S_a(0.2) ≥ 1.25
A	0.7	0.7	0.8	0.8	0.8
B	0.8	0.8	0.9	1.0	1.0
C	1.0	1.0	1.0	1.0	1.0
D	1.3	1.2	1.1	1.1	1.0
E	2.1	1.4	1.1	0.9	0.9
F	^⁽¹⁾	⁽¹⁾	⁽¹⁾	⁽¹⁾	⁽¹⁾

Notes to Table 4.1.8.4.B:

⁽¹⁾	See Sentence 4.1.8.4.(5).

Table 4.1.8.4.C Values of F_v as a Function of Site Class and S_a(1.0) Forming part of Sentence 4.1.8.4.(4)
Site Class	Values of F_v
Site Class	S_a(1.0) ≤ 0.1	S_a(1.0) = 0.2	S_a(1.0) = 0.3	S_a(1.0) = 0.4	S_a(1.0) ≥ 0.5
A	0.5	0.5	0.5	0.6	0.6
B	0.6	0.7	0.7	0.8	0.8
C	1.0	1.0	1.0	1.0	1.0
D	1.4	1.3	1.2	1.1	1.1
E	2.1	2.0	1.9	1.7	1.7
F	^⁽¹⁾	⁽¹⁾	⁽¹⁾	⁽¹⁾	⁽¹⁾

Notes to Table 4.1.8.4.C:

⁽¹⁾	See Sentence 4.1.8.4.(5).

Site-specific evaluation is required

to determine F_a and F_v for Site Class F. change begin

(See A-4.1.8.4.(3) and Table 4.1.8.4.A. in Appendix A.)

For structures with a fundamental period of vibration equal to or less than 0.5 s that are built on liquefiable soils, Site Class and the corresponding values of F_a and F_v may be determined as described in Tables 4.1.8.4.A , B, and C by assuming that the soils are not liquefiable. (See A-4.1.8.4.(3) and Table 4.1.8.4.A. in Appendix A.)

The design spectral acceleration values of S(T) shall be determined as follows, using linear interpolation for intermediate values of T:

S(T)= F_aS_a(0.2) for T ≤ 0.2 s= F_vS_a(0.5) or F_aS_a(0.2), whichever is smaller for T = 0.5 s= F_vS_a(1.0) for T = 1.0 s = F_vS_a(2.0) for T = 2.0 s= F_vS_a(2.0)/2 for T ≥ 4.0 s

4.1.8.5. Importance Factor

The earthquake importance factor, I_E, shall be determined according to Table 4.1.8.5.

Table 4.1.8.5. Importance Factor for Earthquake Loads and Effects, I_E Forming part of Sentence 4.1.8.5.(1)
Importance Category	Importance Factor, I_E
Importance Category	ULS	SLS^⁽¹⁾
Low	0.8	^⁽²⁾
Normal	1.0
High	1.3
Post-disaster	1.5

Notes to Table 4.1.8.5.:

⁽¹⁾	See Article 4.1.8.13.
⁽²⁾	See Appendix A.

4.1.8.6. Structural Configuration

Structures having any of the features listed in Table 4.1.8.6. shall be designated irregular.

Structures not classified as irregular according to Sentence (1) may be considered regular.

Except as required by Article 4.1.8.10., in cases where I_EF_aS_a(0.2) is equal to or greater than 0.35, structures designated as irregular must satisfy the provisions referenced in Table 4.1.8.6.

Table 4.1.8.6. Structural Irregularities^⁽¹⁾ Forming part of Sentence 4.1.8.6.(1)
Type	Irregularity Type and Definition	Notes
1	Vertical Stiffness Irregularity Vertical stiffness irregularity shall be considered to exist when the lateral stiffness of the SFRS in a storey is less than 70% of the stiffness of any adjacent storey, or less than 80% of the average stiffness of the three storeys above or below.	^⁽²⁾^⁽³⁾^⁽⁴⁾
2	Weight (mass) Irregularity Weight irregularity shall be considered to exist where the weight, W_i, of any storey is more than 150% of the weight of an adjacent storey. A roof that is lighter than the floor below need not be considered.	⁽²⁾
3	Vertical Geometric Irregularity Vertical geometric irregularity shall be considered to exist where the horizontal dimension of the SFRS in any storey is more than 130% of that in an adjacent storey.	⁽²⁾⁽³⁾⁽⁴⁾^⁽⁵⁾
4	In-Plane Discontinuity in Vertical Lateral-Force-Resisting Element Except for braced frames and moment-resisting frames, an in-plane discontinuity shall be considered to exist where there is an offset of a lateral-force-resisting element of the SFRS or a reduction in lateral stiffness of the resisting element in the storey below.	⁽²⁾⁽³⁾⁽⁴⁾⁽⁵⁾
5	Out-of-Plane Offsets Discontinuities in a lateral force path, such as out-of-plane offsets of the vertical elements of the SFRS.	⁽²⁾⁽³⁾⁽⁴⁾⁽⁵⁾
6	Discontinuity in Capacity - Weak Storey A weak storey is one in which the storey shear strength is less than that in the storey above. The storey shear strength is the total strength of all seismic-resisting elements of the SFRS sharing the storey shear for the direction under consideration.	⁽³⁾
7	Torsional Sensitivity (to be considered when diaphragms are not flexible) Torsional sensitivity shall be considered to exist when the ratio B calculated according to Sentence 4.1.8.11.(9) exceeds 1.7.	⁽²⁾⁽³⁾⁽⁴⁾^⁽⁶⁾
8	Non-orthogonal Systems A non-orthogonal system irregularity shall be considered to exist when the SFRS is not oriented along a set of orthogonal axes.	⁽⁴⁾^⁽⁷⁾

Notes to Table 4.1.8.6.:

⁽¹⁾	One-storey penthouses with a weight of less than 10 per cent of the level below need not be considered in the application of this table.
⁽²⁾	See Article 4.1.8.7.
⁽³⁾	See Article 4.1.8.10.
⁽⁴⁾	See Appendix A.
⁽⁵⁾	See Article 4.1.8.15.
⁽⁶⁾	See Sentences 4.1.8.11.(9), (10) and 4.1.8.12.(4).
⁽⁷⁾	See Article 4.1.8.8.

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NC2010 2010-01-01 R1

Table 4.1.8.6. Structural Irregularities⁽¹⁾ Forming part of Sentence 4.1.8.6.(1)
Type	Irregularity Type and Definition	Notes
1	Vertical Stiffness Irregularity Vertical stiffness irregularity shall be considered to exist when the lateral stiffness of the SFRS in a storey is less than 70% of the stiffness of any adjacent storey, or less than 80% of the average stiffness of the three storeys above or below.	⁽²⁾⁽³⁾⁽⁴⁾
2	Weight (mass) Irregularity Weight irregularity shall be considered to exist where the weight, W_i, of any storey is more than 150% of the weight of an adjacent storey. A roof that is lighter than the floor below need not be considered.	⁽²⁾
3	Vertical Geometric Irregularity Vertical geometric irregularity shall be considered to exist where the horizontal dimension of the SFRS in any storey is more than 130% of that in an adjacent storey.	⁽²⁾⁽³⁾⁽⁴⁾⁽⁵⁾
4	In-Plane Discontinuity in Vertical Lateral-Force-Resisting Element Except for braced frames and moment-resisting frames, an in-plane discontinuity shall be considered to exist where there is an offset of a lateral-force-resisting element of the SFRS or a reduction in lateral stiffness of the resisting element in the storey below.	⁽²⁾⁽³⁾⁽⁴⁾⁽⁵⁾
5	Out-of-Plane Offsets Discontinuities in a lateral force path, such as out-of-plane offsets of the vertical elements of the SFRS.	⁽²⁾⁽³⁾⁽⁴⁾⁽⁵⁾
6	Discontinuity in Capacity - Weak Storey A weak storey is one in which the storey shear strength is less than that in the storey above. The storey shear strength is the total strength of all seismic-resisting elements of the SFRS sharing the storey shear for the direction under consideration.	⁽³⁾
7	Torsional Sensitivity (to be considered when diaphragms are not flexible) Torsional sensitivity shall be considered to exist when the ratio B calculated according to Sentence 4.1.8.11.(9) exceeds 1.7.	⁽²⁾⁽³⁾⁽⁴⁾⁽⁶⁾
8	Non-orthogonal Systems A non-orthogonal system irregularity shall be considered to exist when the SFRS is not oriented along a set of orthogonal axes.	⁽⁴⁾⁽⁷⁾

Notes to Table 4.1.8.6.:

⁽¹⁾	One-storey penthouses with a weight of less than 10 per cent ~~10%~~ of the level below need not be considered in the application of this table.
⁽²⁾	See Article 4.1.8.7.
⁽³⁾	See Article 4.1.8.10.
⁽⁴⁾	See Appendix A.
⁽⁵⁾	See Article 4.1.8.15.
⁽⁶⁾	See Sentences 4.1.8.11.(9), (10) and 4.1.8.12.(4).
⁽⁷⁾	See Article 4.1.8.8.

4.1.8.7. Methods of Analysis

Analysis for design earthquake actions shall be carried out in accordance with the Dynamic Analysis Procedure described in Article 4.1.8.12. (see Appendix A), except that the Equivalent Static Force Procedure described in Article 4.1.8.11. may be used for structures that meet any of the following criteria:

a) in cases where I_EF_aS_a(0.2) is less than 0.35,

b) regular structures that are less than 60 m in height and have a fundamental lateral period, T_a, less than 2 s in each of two orthogonal directions as defined in Article 4.1.8.8., or

c) structures with structural irregularity, of Type 1, 2, 3, 4, 5, 6 or 8 as defined in Table 4.1.8.6., that are less than 20 m in height and have a fundamental lateral period, T_a, less than 0.5 s in each of two orthogonal directions as defined in Article 4.1.8.8.

4.1.8.8. Direction of Loading

1) Earthquake forces shall be assumed to act in any horizontal direction, except that the following shall be considered to provide adequate design force levels in the structure:

a) where components of the SFRS are oriented along a set of orthogonal axes, independent analyses about each of the principal axes of the structure shall be performed,

b) where the components of the SFRS are not oriented along a set of orthogonal axes and I_EF_aS_a(0.2) is less than 0.35, independent analyses about any two orthogonal axes is permitted, or

c) where the components of the SFRS are not oriented along a set of orthogonal axes and I_EF_aS_a(0.2) is equal to or greater than 0.35, analysis of the structure independently in any two orthogonal directions for 100 change begin

per cent

of the prescribed earthquake loads applied in one direction plus 30 change begin

per cent

of the prescribed earthquake loads in the perpendicular direction, with the combination requiring the greater element strength being used in the design.

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4.1.8.9. SFRS Force Reduction Factors, System Overstrength Factors, and General Restrictions

The values of R_d and R_o and the corresponding system restrictions shall conform to Table 4.1.8.9. and the requirements of this Subsection.

When a particular value of R_d is required by this Article, the corresponding R_o shall be used.

For combinations of different types of SFRS acting in the same direction in the same storey, R_dR_o shall be taken as the lowest value of R_dR_o corresponding to these systems.

4) For vertical variations of R_dR_o, excluding change begin

rooftop structures not exceeding two storeys in height

whose weight is less than change begin

the greater of

per cent

W and 30

per cent

of W_i

of the level below, the value of R_dR_o used in the design of any storey shall be less than or equal to the lowest value of R_dR_o used in the given direction for the storeys above, and the requirements of Sentence 4.1.8.15.(5) must be satisfied. (See Appendix A.)

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If it can be demonstrated through testing, research and analysis that the seismic performance of a structural system is at least equivalent to one of the types of SFRS mentioned in Table 4.1.8.9., then such a structural system will qualify for values of R_d and R_o corresponding to the equivalent type in that Table. (See Appendix A.)

Table 4.1.8.9. SFRS Ductility-Related Force Modification Factors, R_d, Overstrength-Related Force Modification Factors, R_o, and General Restrictions^⁽¹⁾ Forming part of Sentence 4.1.8.9.(1)
Type of SFRS	R_d	R_o	Restrictions<^⁽²⁾>
			Cases Where I_EF_aS_a(0.2)				Cases Where I_EF_vS_a(1.0)
			< 0.2	≥ 0.2 to < 0.35	≥ 0.35 to ≤ 0.75	> 0.75	> 0.3
Steel Structures Designed and Detailed According to CSA S16<^⁽³⁾>
Ductile moment-resisting frames	5.0	1.5	NL	NL	NL	NL	NL
Moderately ductile moment-resisting frames	3.5	1.5	NL	NL	NL	NL	NL
Limited ductility moment-resisting frames	2.0	1.3	NL	NL	60	30	30
Moderately ductile concentrically braced frames
Tension-compression braces	3.0	1.3	NL	NL	40	40	40
Tension only braces	3.0	1.3	NL	NL	20	20	20
Limited ductility concentrically braced frames
Tension-compression braces	2.0	1.3	NL	NL	60	60	60
Tension only braces	2.0	1.3	NL	NL	40	40	40
Ductile buckling-restrained braced frames	4.0	1.2	NL	NL	40	40	40
Ductile eccentrically braced frames	4.0	1.5	NL	NL	NL	NL	NL
Ductile plate walls	5.0	1.6	NL	NL	NL	NL	NL
Limited ductility plate walls	2.0	1.5	NL	NL	60	60	60
Conventional construction of moment-resisting frames, braced frames or plate walls
Assembly occupancies	1.5	1.3	NL	NL	15	15	15
Other occupancies	1.5	1.3	NL	NL	60	40	40
Other steel SFRS(s) not defined above	1.0	1.0	15	15	NP	NP	NP
Concrete Structures Designed and Detailed According to CAN/CSA-A23.3
Ductile moment-resisting frames	4.0	1.7	NL	NL	NL	NL	NL
Moderately ductile moment-resisting frames	2.5	1.4	NL	NL	60	40	40
Ductile coupled walls	4.0	1.7	NL	NL	NL	NL	NL
Ductile partially coupled walls	3.5	1.7	NL	NL	NL	NL	NL
Ductile shear walls	3.5	1.6	NL	NL	NL	NL	NL
Moderately ductile shear walls	2.0	1.4	NL	NL	NL	60	60
Conventional construction
Moment-resisting frames	1.5	1.3	NL	NL	15	NP	NP
Shear walls	1.5	1.3	NL	NL	40	30	30
Other concrete SFRS(s) not listed above	1.0	1.0	15	15	NP	NP	NP
Timber Structures Designed and Detailed According to CSA O86
Shear walls
Nailed shear walls: wood-based panel	3.0	1.7	NL	NL	30	20	20
Shear walls: wood-based and gypsum panels in combination	2.0	1.7	NL	NL	20	20	20
Braced or moment-resisting frames with ductile connections
Moderately ductile	2.0	1.5	NL	NL	20	20	20
Limited ductility	1.5	1.5	NL	NL	15	15	15
Other wood- or gypsum-based SFRS(s) not listed above	1.0	1.0	15	15	NP	NP	NP
Masonry Structures Designed and Detailed According to CSA S304.1
Moderately ductile shear walls	2.0	1.5	NL	NL	60	40	40
Limited ductility shear walls	1.5	1.5	NL	NL	40	30	30
Conventional construction
Shear walls	1.5	1.5	NL	60	30	15	15
Moment-resisting frames	1.5	1.5	NL	30	NP	NP	NP
Unreinforced masonry	1.0	1.0	30	15	NP	NP	NP
Other masonry SFRS(s) not listed above	1.0	1.0	15	NP	NP	NP	NP
Cold-Formed Steel Structures Designed and Detailed According to CAN/CSA-S136
Shear walls
Screw-connected shear walls – wood-based panels	2.5	1.7	20	20	20	20	20
Screw-connected shear walls – wood-based and gypsum panels in combination	1.5	1.7	20	20	20	20	20
Diagonal strap concentrically braced walls
Limited ductility	1.9	1.3	20	20	20	20	20
Conventional construction	1.2	1.3	15	15	NP	NP	NP
Other cold-formed SFRS(s) not defined above	1.0	1.0	15	15	NP	NP	NP

Notes to Table 4.1.8.9.:

⁽¹⁾	See Article 4.1.8.10.
⁽²⁾	NP = system is not permitted. NL = system is permitted and not limited in height as an SFRS; height may be limited in other Parts of the By-law. Numbers in this Table are maximum height limits in m. The most stringent requirement governs.
⁽³⁾	Higher design force levels are prescribed in CSA S16 for some heights of buildings.

contentHistory

NC2010 2010-01-01 R1

Table 4.1.8.9. SFRS Ductility-Related Force Modification Factors, R_d, Overstrength-Related Force Modification Factors, R_o, and General Restrictions⁽¹⁾ Forming part of Sentence 4.1.8.9.(1)
Type of SFRS	R_d	R_o	Restrictions<⁽²⁾>
			Cases Where I_EF_aS_a(0.2)				Cases Where I_EF_vS_a(1.0)
			< 0.2	≥ 0.2 to < 0.35	≥ 0.35 to ≤ 0.75	> 0.75	> 0.3
Steel Structures Designed and Detailed According to CSA S16<⁽³⁾>
Ductile moment-resisting frames	5.0	1.5	NL	NL	NL	NL	NL
Moderately ductile moment-resisting frames	3.5	1.5	NL	NL	NL	NL	NL
Limited ductility moment-resisting frames	2.0	1.3	NL	NL	60	30	30
Moderately ductile concentrically braced frames
Tension-compression braces	3.0	1.3	NL	NL	40	40	40
Tension only braces	3.0	1.3	NL	NL	20	20	20
Limited ductility concentrically braced frames
Tension-compression braces	2.0	1.3	NL	NL	60	60	60
Tension only braces	2.0	1.3	NL	NL	40	40	40
Ductile buckling-restrained braced frames	4.0	1.2	NL	NL	40	40	40
Ductile eccentrically braced frames	4.0	1.5	NL	NL	NL	NL	NL
Ductile plate walls	5.0	1.6	NL	NL	NL	NL	NL
Limited ductility plate walls	2.0	1.5	NL	NL	60	60	60
Conventional construction of moment-resisting frames, braced frames or plate walls
Assembly occupancies	1.5	1.3	NL	NL	15	15	15
Other occupancies	1.5	1.3	NL	NL	60	40	40
Other steel SFRS(s) not defined above	1.0	1.0	15	15	NP	NP	NP
Concrete Structures Designed and Detailed According to CAN/CSA-A23.3
Ductile moment-resisting frames	4.0	1.7	NL	NL	NL	NL	NL
Moderately ductile moment-resisting frames	2.5	1.4	NL	NL	60	40	40
Ductile coupled walls	4.0	1.7	NL	NL	NL	NL	NL
Ductile partially coupled walls	3.5	1.7	NL	NL	NL	NL	NL
Ductile shear walls	3.5	1.6	NL	NL	NL	NL	NL
Moderately ductile shear walls	2.0	1.4	NL	NL	NL	60	60
Conventional construction
Moment-resisting frames	1.5	1.3	NL	NL	15	NP	NP
Shear walls	1.5	1.3	NL	NL	40	30	30
Other concrete SFRS(s) not listed above	1.0	1.0	15	15	NP	NP	NP
Timber Structures Designed and Detailed According to CSA O86
Shear walls
Nailed shear walls: wood-based panel	3.0	1.7	NL	NL	30	20	20
Shear walls: wood-based and gypsum panels in combination	2.0	1.7	NL	NL	20	20	20
Braced or moment-resisting frames with ductile connections
Moderately ductile	2.0	1.5	NL	NL	20	20	20
Limited ductility	1.5	1.5	NL	NL	15	15	15
Other wood- or gypsum-based SFRS(s) not listed above	1.0	1.0	15	15	NP	NP	NP
Masonry Structures Designed and Detailed According to CSA S304.1
Moderately ductile shear walls	2.0	1.5	NL	NL	60	40	40
Limited ductility shear walls	1.5	1.5	NL	NL	40	30	30
Conventional construction
Shear walls	1.5	1.5	NL	60	30	15	15
Moment-resisting frames	1.5	1.5	NL	30	NP	NP	NP
Unreinforced masonry	1.0	1.0	30	15	NP	NP	NP
Other masonry SFRS(s) not listed above	1.0	1.0	15	NP	NP	NP	NP
Cold-Formed Steel Structures Designed and Detailed According to CAN/CSA-S136
Shear walls
Screw-connected shear walls – wood-based panels	2.5	1.7	20	20	20	20	20
Screw-connected shear walls – wood-based and gypsum panels in combination	1.5	1.7	20	20	20	20	20
Diagonal strap concentrically braced walls
Limited ductility	1.9	1.3	20	20	20	20	20
Conventional construction	1.2	1.3	15	15	NP	NP	NP
Other cold-formed SFRS(s) not defined above	1.0	1.0	15	15	NP	NP	NP

Notes to Table 4.1.8.9.:

⁽¹⁾	See Article 4.1.8.10.
⁽²⁾	NP = system is not permitted. NL = system is permitted and not limited in height as an SFRS; height may be limited in other Parts of the By-law~~Code~~. Numbers in this Table are maximum height limits in m. The most stringent requirement governs.
⁽³⁾	Higher design force levels are prescribed in CSA S16 for some heights of buildings.

4.1.8.10. Additional System Restrictions

Except as required by Clause (2)(b), structures with a Type 6 irregularity, Discontinuity in Capacity - Weak Storey, as described in Table 4.1.8.6., are not permitted unless I_EF_aS_a(0.2) is less than 0.2 and the forces used for design of the SFRS are multiplied by R_dR_o.

Post-disaster buildings shall

a) not have any irregularities conforming to Types 1, 3, 4, 5 and 7 as described in Table 4.1.8.6., in cases where I_EF_aS_a(0.2) is equal to or greater than 0.35,

b) not have a Type 6 irregularity as described in Table 4.1.8.6.,

c) have an SFRS with an R_d of 2.0 or greater, and

have no storey with a lateral stiffness that is less than that of the storey above it.

For buildings having fundamental lateral periods, T_a, of 1.0 s or greater, and where I_EF_vS_a(1.0) is greater than 0.25, walls forming part of the SFRS shall be continuous from their top to the foundation and shall not have irregularities of Type 4 or 5 as described in Table 4.1.8.6.

4) In cases where I_EF_aS_a(0.2) is equal to or greater than 0.35, for buildings constructed with 5 or 6 storeys of continuous combustible construction as permitted by Article 3.2.2.50. and having any fundamental lateral period, Ta, walls forming part of the SFRS within the continuous combustible construction shall not have irregularities of Type 4 or 5 as described in Table 4.1.8.6.

4.1.8.11. Equivalent Static Force Procedure for Structures Satisfying the Conditions of Article 4.1.8.7.

The static loading due to earthquake motion shall be determined according to the procedures given in this Article.

The minimum lateral earthquake force, V, shall be calculated using the following formula:

except

for walls, coupled walls and wall-frame systems, V shall not be less than

for moment-resisting frames, braced frames, and other systems,

V shall not be less than

c) for

buildings located on a site other than Class F and having

an SFRS with an R_d equal to or greater than 1.5, V need not be greater than

3) The fundamental lateral period, T_a, in the direction under consideration in Sentence (2), shall be determined as:

a) for moment-resisting frames that resist 100 change begin

per cent

of the required lateral forces and where the frame is not enclosed by or adjoined by more rigid elements that would tend to prevent the frame from resisting lateral forces, and where h_n is in metres:

i) 0.085 (h_n)^3/4 for steel moment frames,

ii) 0.075 (h_n)^3/4 for concrete moment frames, or

iii) 0.1 N for other moment frames,

b) 0.025h_n for braced frames where h_n is in metres,

c) 0.05 (h_n)^3/4 for shear wall and other structures where h_n is in metres, or

d) other established methods of mechanics using a structural model that complies with the requirements of Sentence 4.1.8.3.(8), except that

i) for moment-resisting frames, T_a shall not be taken greater than 1.5 times that determined in Clause (a),

ii) for braced frames, T_a shall not be taken greater than 2.0 times that determined in Clause (b),

iii) for shear wall structures, T_a shall not be taken greater than 2.0 times that determined in Clause (c),

iv)

for other structures, T_a shall not be taken greater than that determined in Clause (c), and

v) for the purpose of calculating the deflections, the period without the upper limit specified change begin

in Subclauses (d)(i) to (d)(iv) may be used, except that, for walls, coupled walls and wall-frame systems, T_a shall not exceed 4.0 s, and for moment-resisting frames, braced frames, and other systems, T_a shall not exceed 2.0 s.

(See Appendix A.)

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NC2010 2010-01-01 R1

3) The fundamental lateral period, T_a, in the direction under consideration in Sentence (2), shall be determined as:

a) for moment-resisting frames that resist 100 per cent ~~100%~~ of the required lateral forces and where the frame is not enclosed by or adjoined by more rigid elements that would tend to prevent the frame from resisting lateral forces, and where h_n is in metres:

i) 0.085 (h_n)^3/4 for steel moment frames,

ii) 0.075 (h_n)^3/4 for concrete moment frames, or

iii) 0.1 N for other moment frames,

b) 0.025h_n for braced frames where h_n is in metres,

c) 0.05 (h_n)^3/4 for shear wall and other structures where h_n is in metres, or

d) other established methods of mechanics using a structural model that complies with the requirements of Sentence 4.1.8.3.(8), except that

i) for moment-resisting frames, T_a shall not be taken greater than 1.5 times that determined in Clause (a),

ii) for braced frames, T_a shall not be taken greater than 2.0 times that determined in Clause (b),

iii) for shear wall structures, T_a shall not be taken greater than 2.0 times that determined in Clause (c),

iv) for other structures, T_a shall not be taken greater than that determined in Clause (c), and

v) for the purpose of calculating the deflections, the period without the upper limit specified in Subclauses (d)(i) to (d)(iv) may be used, except that, for walls, coupled walls and wall-frame systems, T_a shall not exceed 4.0 s, and for moment-resisting frames, braced frames, and other systems, T_a shall not exceed 2.0 s.

(See Appendix A.)

The weight, W, of the building shall be calculated using the following formula:

The higher mode factor, M_v, and its associated base overturning moment reduction factor, J, shall conform to Table 4.1.8.11.

Table 4.1.8.11. Higher Mode Factor, M_v, and Base Overturning Reduction Factor, J^⁽¹⁾^⁽²⁾ Forming part of Sentence 4.1.8.11.(5)
S_a(0.2)/S_a(2.0)	Type of Lateral Resisting Systems	M_v for T_a ≤ 1.0	M_v for T_a = 2.0	M_v for T_a ≥ 4.0	J for T_a ≤ 0.5	J for T_a = 2.0	J for T_a ≥ 4.0
< 8.0	Moment-resisting frames	1.0	1.0	^⁽³⁾	1.0	0.9	⁽³⁾
	Coupled walls^⁽⁴⁾	1.0	1.0	1.0	1.0	0.9	0.8
	Braced frames	1.0	1.0	⁽³⁾	1.0	0.8	⁽³⁾
	Walls, wall-frame systems	1.0	1.2	1.6	1.0	0.6	0.5
	Other systems^⁽⁵⁾	1.0	1.2	⁽³⁾	1.0	0.6	⁽³⁾
≥ 8.0	Moment-resisting frames	1.0	1.2	⁽³⁾	1.0	0.7	⁽³⁾
	Coupled walls⁽⁴⁾	1.0	1.2	1.2	1.0	0.7	0.6
	Braced frames	1.0	1.5	⁽³⁾	1.0	0.6	⁽³⁾
	Walls, wall-frame systems	1.0	2.2	3.0	1.0	0.4	0.3
	Other systems⁽⁵⁾	1.0	2.2	⁽³⁾	1.0	0.4	⁽³⁾

Notes to Table 4.1.8.11.:

⁽¹⁾	For values of M_v between fundamental lateral periods, T_a, of 1.0 s and 2.0 s and between 2.0 s and 4.0 s, the product S(T_a)•M_v shall be obtained by linear interpolation.
⁽²⁾	Values of J between fundamental lateral periods, T_a, of 0.5 s and 2.0 s and between 2.0 s and 4.0 s shall be obtained by linear interpolation.
⁽³⁾	For fundamental lateral periods, T_a, greater than 2.0 s, use the values for T_a = 2.0.
⁽⁴⁾	A “coupled wall” is a wall system with coupling beams, where at least 66 per cent of the base overturning moment resisted by the wall system is carried by the axial tension and compression forces resulting from shear in the coupling beams.
⁽⁵⁾	For hybrid systems, values corresponding to walls must be used or a dynamic analysis must be carried out as per Article 4.1.8.12.

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NC2010 2010-01-01 R1

Table 4.1.8.11. Higher Mode Factor, M_v, and Base Overturning Reduction Factor, J⁽¹⁾⁽²⁾ Forming part of Sentence 4.1.8.11.(5)
S_a(0.2)/S_a(2.0)	Type of Lateral Resisting Systems	M_v for T_a ≤ 1.0	M_v for T_a = 2.0	M_v for T_a ≥ 4.0	J for T_a ≤ 0.5	J for T_a = 2.0	J for T_a ≥ 4.0
< 8.0	Moment-resisting frames	1.0	1.0	⁽³⁾	1.0	0.9	⁽³⁾
	Coupled walls⁽⁴⁾	1.0	1.0	1.0	1.0	0.9	0.8
	Braced frames	1.0	1.0	⁽³⁾	1.0	0.8	⁽³⁾
	Walls, wall-frame systems	1.0	1.2	1.6	1.0	0.6	0.5
	Other systems⁽⁵⁾	1.0	1.2	⁽³⁾	1.0	0.6	⁽³⁾
≥ 8.0	Moment-resisting frames	1.0	1.2	⁽³⁾	1.0	0.7	⁽³⁾
	Coupled walls⁽⁴⁾	1.0	1.2	1.2	1.0	0.7	0.6
	Braced frames	1.0	1.5	⁽³⁾	1.0	0.6	⁽³⁾
	Walls, wall-frame systems	1.0	2.2	3.0	1.0	0.4	0.3
	Other systems⁽⁵⁾	1.0	2.2	⁽³⁾	1.0	0.4	⁽³⁾

Notes to Table 4.1.8.11.:

⁽¹⁾	For values of M_v between fundamental lateral periods, T_a, of 1.0 s and 2.0 s and between 2.0 s and 4.0 s, the product S(T_a)•M_v shall be obtained by linear interpolation.
⁽²⁾	Values of J between fundamental lateral periods, T_a, of 0.5 s and 2.0 s and between 2.0 s and 4.0 s shall be obtained by linear interpolation.
⁽³⁾	For fundamental lateral periods, T_a, greater than 2.0 s, use the values for T_a = 2.0.
⁽⁴⁾	A “coupled wall” is a wall system with coupling beams, where at least 66 per cent ~~66%~~ of the base overturning moment resisted by the wall system is carried by the axial tension and compression forces resulting from shear in the coupling beams.
⁽⁵⁾	For hybrid systems, values corresponding to walls must be used or a dynamic analysis must be carried out as per Article 4.1.8.12.

The total lateral seismic force, V, shall be distributed such that a portion, F_t, shall be assumed to be concentrated at the top of the building, where F_t is equal to 0.07 T_aV but need not exceed 0.25 V and may be considered as zero where the fundamental lateral period, T_a, does not exceed 0.7 s; the remainder, V - F_t, shall be distributed along the height of the building, including the top level, in accordance with the following formula:

The structure shall be designed to resist overturning effects caused by the earthquake forces determined in Sentence (6) and the overturning moment at level x, M_x, shall be determined using the following equation:

where

J_x= 1.0 for h_x ≥ 0.6h_n, and

J_x= J + (1 - J)(h_x / 0.6h_n) for h_x < 0.6h_n

where

J= base overturning moment reduction factor conforming to Table 4.1.8.11.

Torsional effects that are concurrent with the effects of the forces mentioned in Sentence (6) and are caused by the change begin

simultaneous actions of the

following torsional moments shall be considered in the design of the structure according to Sentence (10):

a) torsional moments introduced by eccentricity between the centres of mass and resistance and their dynamic amplification, change begin

and

b) torsional moments due to accidental eccentricities.

9) Torsional sensitivity shall be determined by calculating the ratio B_x for each level x according to the following equation for each orthogonal direction determined independently:

where

B= maximum of all values of B_x in both orthogonal directions, except that the B_x for one-storey penthouses with a weight less than 10 change begin

per cent

of the level below need not be considered,

δ_max= maximum storey displacement at the extreme points of the structure, at level x in the direction of the earthquake induced by the equivalent static forces acting at distances ± 0.10 D_nx from the centres of mass at each floor, and

δ_ave= average of the displacements at the extreme points of the structure at level x produced by the above-mentioned forces.

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10)

Torsional effects shall be accounted for as follows:

a) for a building with B ≤ 1.7 change begin

or where I_EF_aS_a(0.2) is less than 0.35,

by applying torsional moments about a vertical axis at each level throughout the building, derived for each of the following load cases considered separately:

i) T_x = F_x(e_x + 0.10 D_nx), and

ii) T_x = F_x(e_x - 0.10 D_nx)

where F_x is the lateral force at each level determined according to Sentence (6) and where each element of the building is designed for the most severe effect of the above load cases, or

b) for a building with B > 1.7, in cases where I_EF_aS_a(0.2) is equal to or greater than 0.35, by a Dynamic Analysis Procedure as specified in Article 4.1.8.12.

11) Where the fundamental lateral period, T_a, is determined by Clause (3)(d) for buildings constructed with 5 or 6 storeys of continuous combustible construction as permitted by Article 3.2.2.50. and having an SFRS of nailed shear walls with wood-based panels, the lateral earthquake force, V, as determined in Sentence (2) shall be multiplied by 1.2.

4.1.8.12. Dynamic Analysis Procedure

The Dynamic Analysis Procedure shall be in accordance with one of the following methods:

a) Linear Dynamic Analysis by either the Modal Response Spectrum Method or the Numerical Integration Linear Time History Method using a structural model that complies with the requirements of Sentence 4.1.8.3.(8) (see Appendix A), or

b) Non-linear Dynamic Analysis, in which case a special study shall be performed (see Appendix A).

The spectral acceleration values used in the Modal Response Spectrum Method shall be the design spectral acceleration values, S(T), defined in change begin

Sentence 4.1.8.4.(7)

The ground motion histories used in the Numerical Integration Linear Time History Method shall be compatible with a response spectrum constructed from the design spectral acceleration values, S(T), defined in change begin

Sentence 4.1.8.4.(7)

. (See Appendix A.)

The effects of accidental torsional moments acting concurrently with the lateral earthquake forces that cause them shall be accounted for by the following methods:

a) the static effects of torsional moments due to (± 0.10 D_nx)F_x at each level x, where F_x is change begin

either determined from the elastic dynamic analysis or

determined from Sentence 4.1.8.11.(6) change begin

multiplied by R_dR_o/I_E

, shall be combined with the effects determined by dynamic analysis (see Appendix A), or

b) if B, as defined in Sentence 4.1.8.11.(9), is less than 1.7, it is permitted to use a three-dimensional dynamic analysis with the centres of mass shifted by a distance of –0.05 D_nx and + 0.05 D_nx.

Except as provided in Sentence (6), the design elastic base shear, V_ed, is equal to the elastic base shear, V_e, obtained from a Linear Dynamic Analysis.

For structures located on sites other than Class F that have an SFRS with R_d equal to or greater than 1.5, the elastic base shear obtained from a Linear Dynamic Analysis may be multiplied by the following factor to obtain the design elastic base shear, V_ed:

The

design elastic base shear, V_ed

, shall be multiplied by the importance factor, I_E, as determined in Article 4.1.8.5., and shall be divided by R_dR_o, as determined in Article 4.1.8.9., to obtain the change begin

design

base shear, V_d.

8) Except as required by change begin

Sentences (9)

or (12), if the base shear, V_d, obtained in change begin

Sentence (7)

is less than 80 change begin

per cent

of the lateral earthquake design force, V, of Article 4.1.8.11., V_d shall be taken as 0.8 V.

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9) For irregular structures requiring dynamic analysis in accordance with Article 4.1.8.7., V_d shall be taken as the larger of the V_d determined in Sentence (7) and 100 change begin

per cent

of V.

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10)

Except as required by change begin

Sentence (11)

, the values of elastic storey shears, storey forces, member forces, and deflections obtained from the Linear Dynamic Analysis change begin

, including the effect of accidental torsion determined in Sentence (4),

shall be multiplied by V_d/V_e to determine their design values, where V_d is the base shear.

11)

For the purpose of calculating deflections, it is permitted to use a value for V based on the value for T_a determined in Clause 4.1.8.11.(3)(d) to obtain V_d in change begin

Sentences (8) and (9)

12) The base shear, V_d, shall be taken as 100 change begin

per cent

of the lateral earthquake design force, V, as determined by Article 4.1.8.11. for buildings

a) constructed with 5 or 6 storeys of continuous combustible construction as permitted by Article 3.2.2.50.,

b) having an SFRS of nailed shear walls with wood-based panels, and

c) having a fundamental lateral period, T_a, as determined by Clause 4.1.8.11.(3)(d).

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4.1.8.13. Deflections and Drift Limits

Lateral deflections of a structure shall be calculated in accordance with the loads and requirements defined in this Subsection.

Lateral deflections obtained from a linear elastic analysis using the methods given in Articles 4.1.8.11. and 4.1.8.12. and incorporating the effects of torsion, including accidental torsional moments, shall be multiplied by R_dR_o/I_E to give realistic values of anticipated deflections.

Based on the lateral deflections calculated in Sentence (2), the largest interstorey deflection at any level shall be limited to 0.01 h_s for post-disaster buildings, 0.02 h_s for change begin

High Importance Category buildings

, and 0.025 h_s for all other buildings.

The deflections calculated in Sentence (2) shall be used to account for sway effects as required by change begin

Sentence 4.1.3.2.(12)

. (See Appendix A.)

4.1.8.14. Structural Separation

Adjacent structures shall either be separated by the square root of the sum of the squares of their individual deflections calculated in Sentence 4.1.8.13.(2), or shall be connected to each other.

The method of connection required in Sentence (1) shall take into account the mass, stiffness, strength, ductility and anticipated motion of the connected buildings and the character of the connection.

Rigidly connected buildings shall be assumed to have the lowest R_dR_o value of the buildings connected.

Buildings with non-rigid or energy-dissipating connections require special studies.

4.1.8.15. Design Provisions

Except as provided in Sentences (2) and (3), diaphragms, collectors, chords, struts

and connections shall be designed so as not to yield, and the design shall account for the shape of the diaphragm, including openings, and for the forces generated in the diaphragm due to the following cases, whichever one governs (see Appendix A):

a) forces due to loads determined in Article 4.1.8.11. or 4.1.8.12. applied to the diaphragm are increased to reflect the lateral load capacity of the SFRS, plus forces in the diaphragm due to the transfer of forces between elements of the SFRS associated with the lateral load capacity of such elements and accounting for discontinuities and changes in stiffness in these elements, or

b) a minimum force corresponding to the design-based shear divided by N for the diaphragm at level x.

Steel deck roof diaphragms in buildings of less than 4 storeys or wood diaphragms that are designed and detailed according to the applicable referenced design standards to exhibit ductile behaviour shall meet the requirements of Sentence (1), except that they may yield and the forces shall be

a) for wood diaphragms acting in combination with vertical wood shear walls, equal to the lateral earthquake design force,

b) for wood diaphragms acting in combination with other SFRS, not less than the force corresponding to R_dR_o = 2.0, and

c) for steel deck roof diaphragms, not less than the force corresponding to R_dR_o = 2.0.

Where diaphragms are designed in accordance with Sentence (2), the struts shall be designed in accordance with Clause 4.1.8.15.(1)(a) and the collectors, chords and connections between the diaphragms and the vertical elements of the SFRS shall be designed for forces corresponding to the capacity of the diaphragms in accordance with the applicable CSA standards. (See Appendix A.)

In cases where I_EF_aS_a(0.2) is equal to or greater than 0.35, the elements supporting any discontinuous wall, column or braced frame shall be designed for the lateral load capacity of the components of the SFRS they support. (See Appendix A.)

Where structures have vertical variations of R_dR_o satisfying Sentence 4.1.8.9.(4), the elements of the SFRS below the level where the change in R_dR_o occurs shall be designed for the forces associated with the lateral load capacity of the SFRS above that level. (See Appendix A.)

Where earthquake effects can produce forces in a column or wall due to lateral loading along both orthogonal axes, account shall be taken of the effects of potential concurrent yielding of other elements framing into the column or wall from all directions at the level under consideration and as appropriate at other levels. (See Appendix A.)

Except as provided in Sentence (8), the design forces change begin

associated with the lateral capacity of the SFRS

need not exceed the forces determined in accordance with Sentence 4.1.8.7.(1) change begin

with R_dR_o taken as 1.0, unless otherwise provided by the applicable referenced design standards for elements, in which case the design forces associated with the lateral capacity of the SFRS need not exceed the forces determined in accordance with Sentence 4.1.8.7.(1) with R_dR_o taken as 1.3.

(See Appendix A.)

If foundation rocking is accounted for, the design forces for the SFRS need not exceed the maximum values associated with foundation rocking, provided that R_d and R_o for the type of SFRS used conform to Table 4.1.8.9. and that the foundation is designed in accordance with Sentence 4.1.8.16.(1).

4.1.8.16. Foundation Provisions

Foundations shall be designed to resist the lateral load capacity of the SFRS, except that when the foundations are allowed to rock, the design forces for the foundation need not exceed those determined in Sentence 4.1.8.7.(1) using an R_dR_o equal to 2.0. (See Appendix A.)

The design of foundations shall be such that they are capable of transferring earthquake loads and effects between the building and the ground without exceeding the capacities of the soil and rock.

In cases where I_EF_aS_a(0.2) is equal to or greater than 0.35, the following requirements shall be satisfied:

a) piles or pile caps, drilled piers, and caissons shall be interconnected by continuous ties in not less than two directions (see Appendix A),

b) piles, drilled piers, and caissons shall be embedded a minimum of 100 mm into the pile cap or structure, and

c) piles, drilled piers, and caissons, other than wood piles, shall be connected to the pile cap or structure for a minimum tension force equal to 0.15 times the factored compression load on the pile.

At sites where I_EF_aS_a(0.2) is equal to or greater than 0.35, basement walls shall be designed to resist earthquake lateral pressures from backfill or natural ground. (See Appendix A.)

5) At sites where I_EF_aS_a(0.2) is greater than 0.75, the following requirements shall be satisfied:

a) piles, drilled piers, or caissons shall be designed and detailed to accommodate cyclic inelastic behaviour when the design moment in the element due to earthquake effects is greater than 75 change begin

per cent

of its moment capacity (see Appendix A), and

b) spread footings founded on soil defined as Site Class E or F shall be interconnected by continuous ties in not less than two directions.

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Each segment of a tie between elements that is required by Clauses (3)(a) or (5)(b) shall be designed to carry by tension or compression a horizontal force at least equal to the greatest factored pile cap or column vertical load in the elements it connects, multiplied by a factor of 0.10 I_EF_aS_a(0.2), unless it can be demonstrated that equivalent restraints can be provided by other means. (See Appendix A.)

The potential for liquefaction of the soil and its consequences, such as significant ground displacement and loss of soil strength and stiffness, shall be evaluated based on the ground motion parameters referenced in Subsection 1.1.3. and shall be taken into account in the design of the structure and its foundations. (See Appendix A.)

4.1.8.17. Site Stability

The potential for slope instability and its consequences, such as slope displacement, shall be evaluated based on site-specific material properties and ground motion parameters referenced in Subsection 1.1.3. and shall be taken into account in the design of the structure and its foundations. (See Appendix A.)

4.1.8.18. Elements of Structures, Non-structural Components and Equipment

(See Appendix A.)

Except as provided in Sentences (2) and (8), elements and components of buildings described in Table 4.1.8.18. and their connections to the structure shall be designed to accommodate the building deflections calculated in accordance with Article 4.1.8.13. and the element or component deflections calculated in accordance with Sentence (10), and shall be designed for a lateral force, V_p, change begin

distributed according to the distribution of mass:

where

F_a= as defined in change begin

Table 4.1.8.4.B

S_a(0.2)= spectral response acceleration value at 0.2 s, as defined in Sentence 4.1.8.4.(1),

I_E= importance factor for the building, as defined in Article 4.1.8.5.,

S_p= C_pA_rA_x/R_p (the maximum value of S_p shall be taken as 4.0 and the minimum value of S_p shall be taken as 0.7), whereC_p = element or component factor from Table 4.1.8.18.,A_r = element or component force amplification factor from Table 4.1.8.18.,A_x = height factor (1 + 2 h_x / h_n),R_p = element or component response modification factor from Table 4.1.8.18., and

W_p= weight of the component or element.

For buildings other than post-disaster buildings, where I_EF_aS_a(0.2) is less than 0.35, the requirements of Sentence (1) need not apply to Categories 6 through 21 of Table 4.1.8.18.

The values of C_p in Sentence (1) shall conform to Table 4.1.8.18.

For the purpose of applying Sentence (1) and Categories 11 and 12 of Table 4.1.8.18., elements or components shall be assumed to be flexible or flexibly connected unless it can be shown that the fundamental period of the element or component and its connection is less than or equal to 0.06 s, in which case the element or component is classified as being rigid or rigidly connected.

5) The weight of access floors shall include the dead load of the access floor and the weight of permanent equipment, which shall not be taken as less than 25 change begin

per cent

of the floor live load.

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6) When the mass of a tank plus its contents change begin

or the mass of a flexible or flexibly connected piece of machinery, fixture or equipment

is greater than 10 change begin

per cent

of the mass of the supporting floor, the lateral forces shall be determined by rational analysis.

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Forces shall be applied in the horizontal direction that results in the most critical loading for design, except for Category 6 of Table 4.1.8.18., where the forces shall be applied up and down vertically.

Connections to the structure of elements and components listed in Table 4.1.8.18. shall be designed to support the component or element for gravity loads, shall conform to the requirements of Sentence (1), and shall also satisfy these additional requirements:

a) friction due to gravity loads shall not be considered to provide resistance to seismic forces,

b) R_p for non-ductile connections, such as adhesives or power-actuated fasteners, shall be taken as 1.0,

c) R_p for anchorage using shallow expansion, chemical, epoxy or cast-in-place anchors shall be 1.5, where shallow anchors are those with a ratio of embedment length to diameter of less than 8,

d) power-actuated fasteners and drop-in anchors shall not be used for tension loads,

e) connections for non-structural elements or components of Category 1, 2 or 3 of Table 4.1.8.18. attached to the side of a building and above the first level above grade shall satisfy the following requirements:

i) for connections where the body of the connection is ductile, the body shall be designed for values of C_p, A_r and R_p given in Table 4.1.8.18., and change begin

all of the other parts of the connection,

such as anchors, welds, bolts and inserts, change begin

shall be capable of developing 2.0 times the nominal yield resistance of the body of the connection,

and

ii) connections where the body of the connection is not ductile shall be designed for values of C_p = 2.0, R_p = 1.0 and A_r given in Table 4.1.8.18., and

f) for the purpose of applying Clause (e), a ductile connection is one where the body of the connection change begin

is capable of dissipating energy through cyclic inelastic behaviour

Floors and roofs acting as diaphragms shall satisfy the requirements for diaphragms stated in Article 4.1.8.15.

10)

Lateral deflections of elements or components shall be based on the loads defined in Sentence (1) and lateral deflections obtained from an elastic analysis shall be multiplied by R_p/I_E to give realistic values of the anticipated deflections.

11)

The elements or components shall be designed so as not to transfer to the structure any forces unaccounted for in the design, and rigid elements such as walls or panels shall satisfy the requirements of Sentence 4.1.8.3.(6).

12)

Seismic restraint for suspended equipment, pipes, ducts, electrical cable trays, etc. shall be designed to meet the force and displacement requirements of this Article and be constructed in a manner that will not subject hanger rods to bending.

13)

Isolated suspended equipment and components, such as pendent lights, may be designed as a pendulum system provided that adequate chains or cables capable of supporting 2.0 times the weight of the suspended component are provided and the deflection requirements of Sentence (11) are satisfied.

Table 4.1.8.18. Elements of Structures and Non-structural Components and Equipment Forming part of Sentence 4.1.8.18.(1)
Category	Part or Portion of Building	C_p	A_r	R_p
1	All exterior and interior walls except those in Category 2 or 3^⁽¹⁾	1.00	1.00	2.50
2	Cantilever parapet and other cantilever walls except retaining walls⁽¹⁾	1.00	2.50	2.50
3	Exterior and interior ornamentations and appendages⁽¹⁾	1.00	2.50	2.50
4	Floors and roofs acting as diaphragms^⁽²⁾	-	-	-
5	Towers, chimneys, smokestacks and penthouses when connected to or forming part of a building	1.00	2.50	2.50
6	Horizontally cantilevered floors, balconies, beams, etc.	1.00	1.00	2.50
7	Suspended ceilings, light fixtures and other attachments to ceilings with independent vertical support	1.00	1.00	2.50
8	Masonry veneer connections	1.00	1.00	1.50
9	Access floors	1.00	1.00	2.50
10	Masonry or concrete fences more than 1.8 m tall	1.00	1.00	2.50
11	Machinery, fixtures, equipment, ducts and tanks (including contents)
	that are rigid and rigidly connected^⁽³⁾	1.00	1.00	1.25
	that are flexible or flexibly connected⁽³⁾	1.00	2.50	2.50
12	Machinery, fixtures, equipment, ducts and tanks (including contents) containing toxic or explosive materials, materials having a flash point below 38°C or firefighting fluids
	that are rigid and rigidly connected⁽³⁾	1.50	1.00	1.25
	that are flexible or flexibly connected⁽³⁾	1.50	2.50	2.50
13	Flat bottom tanks (including contents) attached directly to a floor at or below grade within a building	0.70	1.00	2.50
14	Flat bottom tanks (including contents) attached directly to a floor at or below grade within a building containing toxic or explosive materials, materials having a flash point below 38°C or firefighting fluids	1.00	1.00	2.50
15	Pipes, ducts, cable trays (including contents)	1.00	1.00	3.00
16	Pipes, ducts (including contents) containing toxic or explosive materials	1.50	1.00	3.00
17	Electrical cable trays, bus ducts, conduits	1.00	2.50	5.00
18	Rigid components with ductile material and connections	1.00	1.00	2.50
19	Rigid components with non-ductile material or connections	1.00	1.00	1.00
20	Flexible components with ductile material and connections	1.00	2.50	2.50
21	Flexible components with non-ductile material or connections	1.00	2.50	1.00

Notes to Table 4.1.8.18.:

⁽¹⁾	See Sentence 4.1.8.18.(8).
⁽²⁾	See Sentence 4.1.8.18.(9).
⁽³⁾	See Sentence 4.1.8.18.(4).

Division BAcceptable Solutions

Part 4 — Structural Design

Section 4.1. Structural Loads and Procedures

4.1.1. General

4.1.1.General

4.1.1.1. Scope

4.1.1.2. Definitions

4.1.1.3. Design Requirements

4.1.1.4. Structural Drawings and Related Documents

4.1.1.5. Design Basis

4.1.2. Specified Loads and Effects

4.1.2.Specified Loads and Effects

4.1.2.1. Loads and Effects

4.1.2.2. Loads Not Listed

4.1.3. Limit States Design

4.1.3.1. Definitions

4.1.3.2. Strength and Stability

4.1.3.3. Fatigue

4.1.3.4. Serviceability

4.1.3.5. Deflection

4.1.3.6. Vibration

4.1.4. Dead Loads

4.1.4.1. Dead Loads

4.1.5. Live Loads Due to Use and Occupancy

4.1.5.Live Loads Due to Use and Occupancy

4.1.5.1. Loads Due to Use of Floors and Roofs

4.1.5.2. Uses Not Stipulated

4.1.5.3. Full and Partial Loading

4.1.5.4. Loads for Occupancy Served

4.1.5.5. Loads on Exterior Areas

4.1.5.6. Loads for Dining Areas

4.1.5.7. More Than One Occupancy

4.1.5.8. Variation with Tributary Area

4.1.5.9. Concentrated Loads

4.1.5.10. Sway Forces in Assembly Occupancies

4.1.5.11. Crane-Supporting Structures and Impact of Machinery and Equipment

4.1.5.12. Bleachers

4.1.5.13. Helicopter Landing Areas

4.1.5.14. Loads on Guards

4.1.5.15. Loads on Vehicle Guardrails

4.1.5.16. Loads on Walls Acting As Guards

4.1.5.17. Firewalls

4.1.5.18. Loads for Building Maintenance

4.1.6. Loads Due to Snow and Rain

4.1.6.Loads Due to Snow and Rain

4.1.6.1. Specified Load Due to Rain or to Snow and Associated Rain

4.1.6.2. Specified Snow Load

4.1.6.3. Full and Partial Loading

4.1.6.4. Specified Rain Load

4.1.7. Wind Load

4.1.7.1. Specified Wind Load

4.1.7.1. Specified Wind Load

4.1.7.1. Specified Wind Load

4.1.7.2. Dynamic Effects of Wind

4.1.7.3. Full and Partial Loading

4.1.7.4. Interior Walls and Partitions

4.1.7.5. Exterior Wall Air Barrier

4.1.8. Earthquake Load and Effects

4.1.8.1. Analysis

4.1.8.2. Notation

4.1.8.3. General Requirements

4.1.8.4. Site Properties

4.1.8.5. Importance Factor

4.1.8.6. Structural Configuration

4.1.8.7. Methods of Analysis

4.1.8.8. Direction of Loading

4.1.8.9. SFRS Force Reduction Factors, System Overstrength Factors, and General Restrictions

4.1.8.10. Additional System Restrictions

4.1.8.11. Equivalent Static Force Procedure for Structures Satisfying the Conditions of Article 4.1.8.7.

4.1.8.12. Dynamic Analysis Procedure

4.1.8.13. Deflections and Drift Limits

4.1.8.14. Structural Separation

4.1.8.15. Design Provisions

4.1.8.16. Foundation Provisions

4.1.8.17. Site Stability

4.1.8.18. Elements of Structures, Non-structural Components and Equipment

Division B
Acceptable Solutions