CANADIAN STRUCTURAL
DESIGN MANUAL
1970
SUPPLEMENT No.4 TO THE
NATIONAL BUILDING CODE
OF CANADA
Issued by the
ASSOCIATE COMMITTEE ON THE NATIONAL aUI LDING CODE
NATIONAL RESEARCH COUNCIL OF CANADA
OTTAWA
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Th. N.tlon.1 BuHdlng Cod. I. publlsh.d by the N.tlon.1 R .... rch Council of C.n.d. 'or volun-t.ry .doptlon by. provlncl.1 gov.rnm.nt. or munlclp.1 .dmlnlstr.tlon. Th. Cod. Is . . . entl.lly ••• t
0'
minimum regul.tlon. r .. pectlng the •• ,.ty of building. wHh r.f.r.nc. to public h •• Hh, fir. protection .nd .tructur.1 .ufflcl.ncy. It I. not .nd Is not Int.nded to b • • t.xt-book of buDd-Ing d .. lgn, .dvlc. upon which .hould b • • ought from professlon.1 .ourc ... Th. Cod. rel.t .. to buDdlngs .nd .Impl • • tructur .. but It I. not Int.nded for u •• wHh .peclallzed clvl engineering .tructur ... It . . . ntl.1 purpo •• Is the promotion of public •• f.ty through the u •• of d .. lr.bI. buldlng .t.nd.rd. throughout C.n.d •.Th. N.tlon.1 BuDding Cod • • nd It •• uppl.m.nt. m.y b. obt.lned by wrHlng to:
Th. Secr.t.ry,
A •• ocl.t. Commmee on the N.tlon.1 BuDding Cod.,
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CANADIAN STRUCTURAL DESIGN
MANUAL
1970
SUPPLEMENT No. 4 TO THE
NATIONAL BUILDING CODE
OF CANADA, 1970
Issued
by
the
ASSOCIATE COMMITTEE ON THE NATIONAL BUILDING CODE
NATIONAL RESEARCH COUNCIL OF CANADA
OTTAWA
Prin ted in Canada
NRC No. 11530
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@ National Research Council of Canada 1970
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PREFACE
Supplement 1\0. 4 to the National Building Code of Canada, 1970, has
been prepared in this form as a
Canadian Structural Design Manual
for the convenience of structural designers throughout Canada. The
Asso-ciate Committee hopes that it will prove convenient in use containing, as
it does, the complete wording of design codes for timber, masonry, concrete,
steel and aluminum with the Design Sections of Part 4 reprinted from the
Code itself. Additional explanatory material, prepared for the Associate
Committee by officers of the Division of Building Research, NRC, together
with the material on wind pressure and snow load coefficients for buildings,
etc., contained previously in Supplement No.3, "Structural Information
for Building Design in Canada", to the 1965 Code, are included for
conven-ient reference.
The Associate Committee on the National Building Code records its
appreciation to the Canadian Standards Association for its cooperation in
the preparation of this volume, even to the extent of permitting the use of
direct offprints of CSA documents, as will be evident from the unavoidable
variation in type font. Special thanks are due to Dr.
J.
H. Jenkins, past
president of CSA, and members of the CSA staff under Mr. F. A. Sweet
for their personal interest in and assistance with this cooperative venture.
Comments on the utility of this volume will be especially welcome since
it is a new venture in order that the Associate Committee may be guided
in the preparation of the 1975 edition of the Code, work upon which is
a1ready in progress.
Part A and Part B (pages 1 to 509 inclusive) contain the various Sections
of Part 4, Design, NBC 1970 and the appropriate CSA design Standards.
Where a Table of Contents appears at the beginning of these Code Sections
and CSA Standards, the page numbers referred to appear at the top of the
page as in the actual document; the number which appears at the bottom
of each page relates to this Manual.
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...
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CANADIAN STRUCTURAL DESIGN
MANUAL
1970
SUPPLEMENT No. 4 TO THE
NATIONAL BUILDING CODE OF CANADA
TABLE OF CONTENTS
PART A - PART
4,
DESIGN, NBC, 1970
Page
Structural Loads and Procedures (Section 4.1, NBC).... . .
1
Foundations (Section 4.2, NBC). . . ..
. ... , ... "
19
Wood Construction (Section 4.3, NBC) ... , , .... ,
39
Plain and Reinforced l\1asonry (Section 4.4, NBC) .. , ... '
43
Plain, Reinforced and Prestressed Concrete (Section 4.5, NBC)... . .
47
Steel Construction (Section 4.6, NBC) ... , . . . ..
., ... ',."..
S1
Aluminum Construction (Section 4.7, NBC) .. , , , . , .. , . . .
55
Cladding (Section 4.8, NBC) ... , . . . .
. , . , , , .. , . . . . .. 59
PART B - DESIGN CODES
Code of Recommended Practice for Engineering Design in Timber
(CSA 086-1970) ... , , , , . . . , . . , , , , ... , . , . "
67
Plain and Reinforced :Masonry ... , .... , . . .
169
Code for the Design of Plain or Reinforced Concrete Structures
(CSA A23.3-1970) ... , ... , , ... 205
Prestressed Concrete (CSA A135-1962) ... ,
, ... '
313
Steel Structures for Building (CSA S16-1969), ... ,
, , , , , ., 345
Design of Light Gauge Steel Structural
IvI
em bers
(CSA S136-1963) ... , . , ... " 433
The Structural ese of Aluminum in Buildings (CSA S157-1969) .... 465
Design of Light Gauge Aluminum Products (CSA S190-1968) ... 509
PART C - COMMENTARIES ON PART 4 OF THE NBC
C1 Wind Loads by A. G. Davenport and W. A. Dalgliesh. . . .. 543
C2
Snow Loads by W. R. Schriever, D. A. Lutes and B. G. W.
Peter. . . .. "" 567
C3 Earthquake Loads by R. H. Ferahian ... , ... " 579
C4 Serviceability Criteria for Deflections and Vibrations by D. E.
Allen ... , . , . . .. 597
C5 Ponding Loads on Flat Roofs by D. E. Allen ... , " , 601
C6 Load Combinations for Structural Design by D. E. ABen.. '"
603
C7 Structural Integrity by D. E. Allen, W. R. Schriever and W. G.
Ple\ves. . . .. 60S
C8 Temperature Changes in Building Components by W. R.
Schriever ... , . . . .. 609
PART D - DESIGN DATA FOR SELECTED LOCATIONS
IN CANADA
Table of Climatic Design Data (reproduced from Supplement No.1
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NATIONAL
BUILDING
CODE
OF
CANADA
1970
PART 4 DESIGN
SECTION 4.1
STRUCTURAL LOADS AND
PROCEDURES
TABLE OF CONTENTS
Subsection 4.1.1. General... ...
141
Subsection 4.1.2.
Design Loads and Effects.
143
Subsection 4.1.3.
Dead Loads ... "
..
144
Subsection 4.1.4.
Live Loads Due to Use and Occupancy.
144
Subsection 4.1.5.
Live Loads Due to Snow and Rain. .
147
Subsection 4.1.6. Effects of Wind. . . .
. . .
148
Subsection 4.1.7.
Effects of Earthquakes.
150Subsection 4.1.8. Other Effects . . . .
156
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SECTION 4.1
STRUCTURAL LOADS AND
PROCEDURES
SUBSECTION 4.1.1. GENERAL
Application
4.1.1.1.(1) This Section applies to the design of all structural members and their assemblies used in the following:
(a) all buildings used for the following occupancies:
(i) Group A, Assembly Occupancies
(ii) Group B, Institutional Occupancies
(iii) Group F, Division 1, High Hazard Industrial Occupancies
(b) all buildings exceeding 6000 sq. ft. (558 m2) in building area or exceed-ing 3 storeys in height used for the followexceed-ing occupancies:
(i) Group C, Residential Occupancies
(il) Group D, Business and Personal Services Occupancies
(iii) Group E, Mercantile Occupancies
(iv) Group F, Divisions 2 and 3, Medium and Low Hazard Industrial Occupancies.
(2) For buildings not listed in Sentence (1), requirements for design will be found in Part 9 of this Bylaw.
Definitions
4.1.1.2. Words that appear in italics are defined in Part 2 of this Bylaw.
Design Requirements
4.1.1.3.(1) Buildings and their structural members shall be designed to have sufficient structural capacity.to resist safely and effectively all effects of loads and influences that may be expected, and shall in any case satisfy the require-ments of this Section.
(2) All permanent and temporary structural members of a buildillg shall be protected against loads exceeding the design 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. In addition, precautions shall be taken during all stages of construction to ensure that the building is not damaged or distorted due to loads applied during construction.
4.1.1.4. Buildings and their structural members shall be designed by one of the following methods:
(a) standard design procedures and practices provided by Sections 4.2 to 4.8 inclusive of this Bylaw and any standards and specifications re-ferred to therein except that in cases of conflict the provisions of this Bylaw shall govern.
(b) one of the following three bases of design (i) analysis based on generally recognized theory
(ii) evaluation of a given full-scale structure or a prototype by a loading test
(Hi) studies of model analogues,
provided the design is carried out to the satisfaction of the authority having jurisdiction by a person especially qualified in the specific method appHed and provided the design ensures a level of safety and performance at least equivalent to that provided for or implicit in design carried out by the methods referred to in Clause 4.1.1.4.(a).
141
!vlinimum safety and performance Loads during construction Design basisCopyright
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142
Deflections Creep, shrinkage and other effects Lateral deflection of tall buildings due to wind Stability under compressive stress Structural integrity Drawings and ca 1culations4.1.1.5.(1) Structural members shall be designed so that their deflections and vibrations under expected service loads will be acceptable with regard to
(a) the intended use of the building or member
(b) possible damage to nonstructural members and materials (c) possible damage to the structure itself.
(Information on deflections and vibrations can be found in NBC Supplement No.4. Canadian Structural Design Manual 1970.)
(2) Dellections lisll:U in Sl:ntl'nce (I) shall be: taken into UL'COltnl in all
~truclures and structural members made of material susceptible to Jeflec-tions, deformaJeflec-tions, or changes in 10aJ distribution due to creer. shrinkage or other e1ft·cts in the material" of which they are composed.
(3) The lateral deflection due to wind of slender buildings whose height is greater than four times their minimum effective width shall not exceed the following ratios:
Storey deflection to storey height 11500 Total deflection to total height 11500
These limits may be waived if the design is based on a detailed dynamic analysis of the deflections and their effects.
(Information on lateral deflection of tall buildings may be found in the chapter on wind loads of NBC Supplement No.4, Canadian Structural Design Manual. 1970.)
4.1.1.6. 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 which may be subjected to compressive stress.
4.1.1.7. Buildings and structural systems shall provide such structural integrity that the hazards associated with progressive collapse due to local failure caused by severe overloads or abnormal loads not specifically covered in this Section are reduced to a level commensurate with good engineering practice.
<Information on structural integrity can be found in NBC Supplement No.4. Canadian Structural Design Manual. 1970.)
Drawings and Calculations
4.1.1.8.(1) Drawings submitted with the application to build shall be signed by, or bear the seal of, the designer.
(2) Drawings submitted with the application to build shall indicate in addi-tion to those items specified in other Secaddi-tions of Part 4 applicable to a specific material
(a) the name and address of the person responsible for the structural design,
(b) the dimensions, location and size of all structural members in sufficient detail to enable the design to be checked,
( c) sufficient detail to enable the loads due to materials of construction incorporated in the building to be determined,
(d) all intended uses and occupancies, and
(e) all effects and loads, other than dead loads used in the design of the structural members.
(3) The calculations and analysis made in the design of the structural
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--.~--
... ..
,lnd to 4, all gc is ~e ic y e sI
J
I n,
I
i
Inspection of Construction4.1.1.9. Engineering inspection of the construction of any building or part thereof shall be carried out to ensure that construction is consistent with design, by the person responsible for its design or by another person qualified in the inspection of building construction.
SUBSECTION 4.1.2. DESIGN LOADS AND EFFECTS
143
Inspection of construction
4.1.2.1.(1) Except as provided for in Article 4.1.2.2. the following loads, forces Loads and effects shall be considered in the design of a building and its structural
members and connections:
D - dead loads as provided for in Subsection 4.1.3.
L - live load due to intended use and occupancy (includes loads due to
movable partitions and vertical loads due to cranes); snow, ice and rain; earth and hydrostatic pressure; horizontal components of static or inertia forces.
W-wind
E - earthquake
T - contraction or expansion due to temperature changes, shrinkage, moisture changes, creep in component materials, movement due to differential settlement or combination thereof.
(Information on effects due to temperature changes can be found in NBC Supplement No.4. Canadian Structural Desii,'D Manual, 1970.)
(2) Minimum design values of these loads as set forth in Subsections 4.1.3. to 4.1.8. shall be increased to account for dynamic effects where applicable. 4.1.2.2.(1) Where a building or structural member can be expected to be sub-jected 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 in-formation available.
(2) If it can be shown by engineering principles, or if it is known from experience, that neglect of some or all of the effects due to T do not affect the structural safety and serviceability, they need not be considered in the strength calculations.
Loads not listed
4.1.2.3.(1) In designing buildings and their structural members all of the Load loads listed in Article 4.1.2.1. shall be considered to act in the following combinations combinations, whichever combination produces the most unfavourable effects
in the buildiJ.~, foundation or structural member concerned, when reduced, as appropriate, according to Sentence (2). The most unfavourable effect may occur when one or more of the contributing loads is not acting:
(i) D (ii) D
+
L (iii) D+
(W or E) (iv) D+
T (v) D+
L+
(W or E) (vi) D+
L+
T (vii) D+
(W or E)+
T (viii) D+
L+
(W or E)+
T(2) The total of the combined load effects may be multiplied by the fol-lowing load combination probability factors:
(a) 1.0 for combinations (i) to (iv); (b) 0.75 for combinations (v) to (vii); (c) 0.66 for combination (viii).
Probability factors
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144
Stress reversal Overturning and sliding Dead loads Load8 due to use of floors aod roofs Uses not stipulated Full and partial loading More than one occupancy Change in occupancy Variation(3) When loads other than D counteract D in a structural member or joint, special caution shall be exercised by the designer to ensure adequate safety for possible stress reversal.
(Information on load combinations can be found in NBC Supplement No. 4. Canadiau Structural Desiarn Manual. 1970.)
(4) A bUilding shall be proportioned to resist an overturning moment and sliding force of not less than twice that due to the loads acting on the struc-ture when the strucstruc-ture is considered as an entire unit acting on or anchored to its bearing stratum or supporting structure. The resistance to overturning shall be calculated as the sum of the stabilizing moment of the dead load
only plus the ultimate resistance of any anchoring devices. SUBSECTION 4.1.3. DEAD LOADS
4.1.3.1. The design 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 build· ing to be supported permanently by the member, including permanent partitions,
( c) the weight of permanent equipment, (d) forces due to prestressing.
SUBSECTION 4.1.4.. LIVE LOADS DUE TO USE AND OCCUPANCY 4.1.4.1. The design load on an area of floor or roof depends on the intended use and occupancy and shall not be less than the uniformly distributed load patterns in Article 4.1.4.3. or the concentrated loads in Article 4.1.4.4., whichever produces the most critical effect.
4.1.4.2. Where the use of an area of floor is not provided for in Articles 4.1.4.3. and 4.1.4.4., the design loads due to the use and occupancy of the area shall be determined from an analysis of the loads resulting from
(a) the weight of the probable assembly of persons
(b) the weight of the probable accumulation of equipment and furnishing, and
(c) the weight of the probable storage of materials.
4.1.4.3.(1) The uniformly distributed load shall be not less than the values listed in Table 4.1.4.A, reduced as may be provided for in Sentence (4) or (5),
applied
(a) uniformly over the entire area, or (b) on any portions of the area,
whichever produces the most critical effects in the members concerned.
(2) Where an area of floor or roof is intended for two or more occupancie!
at different times, the value to be used from Table 4.1.4.A shall be the greatest value for any of the occupancies concerned.
(3) When the occupancy of a building is changed, the building shall con-form to the requirements of this Bylaw for the new occupancy.
(4) Where a structural member supports a tributary area of floor, roof, or
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use and occupancy, excluding snow, is the load provided for in Sentence (I) multiplied by
O.S
+
ISlVAwhere A is the tributary area in square feet for this type of use and occupancy.
(5) Where a structural member supports a tributary area of tloor, roof or combination of these greater than 200 sq ft (18.60 m2) for any use or
occupancy other than those indicated in Sentence (4), the design live load due to use and occupancy. excluding snow, is the load provided for in Sentence (1)
multiplied by
0.3
+
to/vB
where B is the tributary area in square feet for this type of use and occupancy.
(6) In areas of a building where partitions other than permanent partition.r
are shown on the drawings or where partitions might be added in the future, allowance shall be made for the weight of such partitions. This allowance shall be determined from the actual or anticipated weight of the partitions
placed in any probable position, but shall be not less than 20 psf (958 N/m2) over the area of tloor being considered. Partition loads used in design shall be shown on the drawings as provided in Clause 4.1.1.8.(2)(e).
Table 4.1.4.A
Forming Part of Sentence 4.1.4.3.(1)
Minimum
Use of Area of Floor or Roof Design Load,
psf Apartment buildings
Living and sleeping quarters, upper floor corridors 40
Locker rooms
SO
Entrance halls, ground floor corridors, eril3 and
stairs 100
A tlics and crawl spaces where there is no storage of
equipment or material 10
Bowling alleys, pool and billiard rooms
7S
Offices and toilets
SO
Corridors, erils and stairs 100
Churches and Sunday schools
Class rooms, movable seats; assembly areas, fixed
seats; private rooms, toilets 50
Assembly areas, movable seats; entrance halls,
lob-bies, exit halls, stairs and kitchens 100
Courtrooms 100
Dance halls, gymnasia, including entrance halls, stairs,
corridors and erits 100
Offices and toilets 50
Exterior balconies 100
Factories, warehouses and storage buildings 125
Separate floors for offices, toilets
SO
Fire escapes 100
Garages
For passenger cars
SO
For unloaded buses and light trucks
12S
For loaded trucks and buses and all trucking spaces
2S0
145
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146
Concentrated loads
Table 4.1.4.A (Cont'd)
Use of Area of Floor or Roof
Grandstands, stadia, rinks, arenas, reviewing stands and bleachers
Hospitals
Wards, sleeping and living quarters, general offices and waiting rooms
Entrance halls, dining rooms, kitchens, stairs, cor-ridors, exits, and X-ray rooms
Operating and lecture rooms Hotels, motels, restaurants, club houses
Sleeping quarters and related corridors Offices, toilets and locker rooms
Lobbies, rotundas, assembly halls, kitchens, stairs, corridors thereto and exits
Retail stores, maintenance and service areas Libraries
Stack rooms, depending on arrangement of stacks, not less than
Reading rooms Office buildings
Basement and first floor, corridors and exits Upper floors for office use
Retail stores or shops for light merchandise Separate floors for offices, toilets Schools and colleges
Sleeping quarters and related corridors Offices and toilets
Class rooms with or without fixed seats Lecture and assembly rooms with fixed seats
Entrance halls, assembly halls without fixed seats, reception rooms, dining rooms, kitchens, exits, corridors and stairs
Sidewalks and driveways over areaways and basements Theatres, assembly halls, auditoria
Private rooms, offices and toilets
Seating area with fixed seats, projection and rewind rooms
Seating area with movable seats, entrance halls, lob-bies, foyers, stage, corridors, aisles, exits and stairs
Column 1 Minimum Design Load, psf 100 40
100
1S
40SO
100100
ISO
60100
SO
100
SO
40SO
SO
SO
100
2S0SO
SO
100
Column 24.1.4.4. The design load due to possible concentrations of load reSUlting from use of an area of floor or roof shall not be less than that listed in Table
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Table 4.1.4..B.
Forming Part of Article 4.1.4.4.
Minimum
Area of Floor or Roof Concentrated
Load, Ib
Roof iurfaces 300
Classrooms 1,000
Floors of offices, manufacturing buildings, hospital
wards, stages 2,000
Floors and areas used by passenger cars 2,500
Floors and areas used by vehicles not exceeding 8000 lb
gross weight 4,000
Floors and areas used by vehicles not exceeding 20,000
lb gross weight 8,000
Floors and areas used by vehicles exceeding 20,000 lb
gross weight 12,000
Driveways and sidewalks over areaways and
basements 12,000
Column 1 Column 2
SUBSECTION 4.1.5. LIVE LOADS DUE TO SNOW AND RAIN
4.1.5.1. The design load due to the accumulation of snow on a surface shall not be less than the ground snow load specified in the Table of Climatic Data in Part 1 of this Bylaw decreased or increased as provided for in Articles
4.1.5.2. to 4.1.5.4.
4.1.5.2.(1) The design snow load on a roof or other building surface subject to snow accumulation shall be determined by multiplying the ground snow load given in Article 4.1.5.1. by appropriate snow load coefficient Cs given in Articles 4.1.5.3. and 4.1.5.4.
(2) A roof or other bUilding surface and its structural members subject to snow accumulation shall be designed for the following two snow load dis-tributions:
(a) full load distributed over the entire area, or
(b) full load distributed on anyone portion of the area and zero load on the remainder of the area,
whichever produces the greatest effects on the member concerned.
4.1.5.3. The basic snow load coefficient Cs is 0.8, except for roofs exposed to wind as provided for in Article 4.1.5.4. The basic snow load coefficient shall be further increased or decreased to account for the following influences
(a) the decrease of snow load because of the effect of slope for roof slopes exceeding 30 deg.,
(b) the accumulation of nonuniform snow load on gable and hip roofs, (c) the accumulation of nonuniform snow load on arched and curved roofs, (d) the accumulation of increased snow loads in valleys of butterfly as well
as multispan curved or sloped roofs,
(e) the accumulation of increased nonuniform snow loads due to drifting snow on the lower of two-level or multi-level roofs, such as a canopy, marquee or porch roof provided the upper roof is part of the same
building or of an adjacent building not more than 15 ft (4.6 m) away,
147
Ground snow Joad Roof snow load Full and partial loading Snow load coefficientsCopyright
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Roofs exposed to wind Rain loads External pressure or suction(f) the accumulation of increased nonuniform snow loads on areas ad-jacent to roof Fojections such as penthouses. large chimneys, ventilat-ing equipment,
(g) the accumulation of increased snow or ice loads on areas due to snow sliding or melt water draining onto these areas from an adjacent roof sloping towards this area. The magnitude and distribution of the in-crease shall be appropriate to the relative portions and sizes of the surfaces.
(Information on eoefftcienta for snow loads on roofs ean be found In NBC Supplement No .... Canadian Structural Desiarn Manual. 1970.)
4.1.5.4. For roofs exposed to the wind, a basic snow load coefficient C, of 0.6 may be used instead of 0.8 if both the following conditions are satisfied:
(a) if the roof is not shielded from the wind on any side, and is not likely to become shielded by obstructions higher than the roof within a dis-tance of 10h from the building (where h is the height of the obstruction above the roof level),
(b) if the roof does not have any projections, such as parapet walls, which prevent the snow from being blown off.
4.1.5.5.(1) The design load. due to the accumulation of rain water on a sur-face whose position and shape, and deflection under load, is such as to make such an accumulation possible, is that reSUlting from the 24-hr rainfall specified in the Table of Climatic Data in Part 1 of this Bylaw over the horizontal projection of the surface and all tributary surfaces. This provision applies whether or not the surface is provided with drainage. such as rain water leaders.
(Information on pondinar on roofs can be found in NBC Supplement No .... Canadian Structural Desiarn Manual, 1970.)
(2) Loads due to rain need not be considered to act simultaneously with loads due to snow.
SUBSECTION 4.1.6. EFFECTS OF WIND
4.1.6.1.(1) The design external pressure or suction due to wind on a building
as a whole or on cladding shall be calculated from:
p
=
qCeCgCpwhere p
=
the design 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);q
=
the reference velocity pressure as provided for in Sentence (3); C.=
the exposure factor as provided for in Sentence (4);Co
=
the gust effect factor as provided for in Sentence (5); Cp=
the external pressure coefficient for the cladding locationcon-sidered or the shape factor for the bUilding as a whole. The shape factor is equal to the algebraic difference of the external pressure coefficients for the windward and leeward sides of the building.
(Information on pressure coefficients can be found in the chapter on wind loads In NBC Supplement No ... , Canadian Structural Deaiarn Manual.
uno.)
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difference of the external pressure or suction as provided for (2) The net design pressure due to wind on cladding shall be the algebraic in Sentence (1)and the design internal pressure or suction due to wind calculated from either:
(a) Pi
=
qCeCpior
(b) Pi
=
qCeCgCpiwhere Pl
=
the design internal pressure acting statically and in a direction normal to the cladding either as a pressure (directed outwards) or as a suction (directed inwards);q, Ce, C" are as provided for in Sentences (3). (4) and (5) respec-tively, except that Ce shall be evaluated at the building
mid-height instead of the height of the element con-sidered;
Cpi
=
the internal pressure coefficient.Formula (b) shall be used if the building has large openings such that the effects of wind gusts are transmitted to the internal air space of the building.
In the design of cladding adequate allowance shall be made for regions of high local external pressure!) or suctions.
(Information on pressure coefficients can be found in the chapter on WlDCl loads in NBC Supplement No.4, Canadian Structural DesilCn Manual, 1970.)
(3) The reference velocity pressure q is the appropriate value specified in the Table of Climatic Data in Part 1 of this Bylaw for the conditions listed
in Clauses (a), (b), (c) and (d).
(a) The reference velocity pressure q for the design of cladding shall be based on a probability of being exceeded in anyone year of 1 in 10.
(b) The reference velocity pressure q for the design of structural members for deflection and vibration shall be based on a probability of being exceeded in anyone year of 1 in 10.
(c) For all buildings except those listed in Clause (d) the reference velocity pressure q for the design of structural members for strength shall be based on a probability of being exceeded in anyone year of 1 in 30. (d) The reference velocity pressure q for the design of structural members for strength for buildings essential for post-disaster services shall be based on a probability of being exceeded in anyone year of 1 in 100. (4) The exposure factor C. shall be:
(a) the value shown in Table 4.1.6.A. for the appropriate height of the surface or part of the surface, or
(b) the value of the function: (h/30)1Al but not less than 1.0 where h is the height above grade in feet of the surface or part of the surface, or
(c) if a dynamic approach to the action of wind gusts is used, an
appro-priate value depending on both height and shielding.
(Information on a dynamic approach can be found in NBC Supplement No.4, Canadian Structural Design Manual, 1970.)
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Gust effect factor Dynamic effects of wind Full and partial loading Table 4.1.6.A.Forming Part of Sentence 4.1.6.1.(4)
Height, ft Exposure Factor
o
to 40 1.0 Over 40 to 60 1.1 " 60 to 90 1.2 tt 90 to 130 1.3..
130 to 190 1.4 " 190 to 270 1.5 " 270 to 420 1.6 " 420 to 740 1.8 " 740 to 1200 2.0 Column 1 Column(5) The gust effect factor Cg is one of the following values: (a) 2.0 for structural members;
(b) 2.5 for small elements including cladding;
2
( c) if a dynamic approach to the action of wind gusts is used, an appro-priate value depending on the turbulence of the wind and the size and natural frequency of the structure.
(Information on a dynamic approach to the action of wind gusts can be found in the chapter on wind loads in NBC Supplement No.4, Canadian Structural DesiK'n Manual,
1970.)
4.1.6.2. Buildings whose height is greater than four times their minimum effective width or greater than 400 ft (122 m) and other buildings whose light weight, low frequency and low damping properties make them susceptible to vibration shall be
(a) designed by experimental methods for the danger of dynamic over-loading and vibration and the effects of fatigue, or
(b) designed using a dynamic approach to the action of wind gusts.
(Information on dynamic approach to the action of wind gusts can be found In the chapter on wind loads in NBC Supplement No.4, Canadian Structural Desia-n Manual, 1970.)
4.1.6.3. Buildings and structural members shall be capable of withstanding the effects of:
(a) the full wind load over the entire area, or
(b) 0.75 times the full wind load acting over any portion of the area and zero load on the rest of the area,
whichever produces the greatest effect on the building or member concerned.
SUBSECTION 4.1.7. EFFECTS OF EARmQUAKES
4.1.7.1.(1) The design loading due to earthquake motion shall be determined (a) by the analysis given in this Subsection, or
(b) by a dynamic analysis.
(Information on loads due to earthquakes can be found In NBC Supplement No. ".
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(2) Nomenclature In this Subsection:
D
=
the dimension of the building in feet in a direction parallel to the applied forces.D.
=
the dimension of the lateral force-resisting system in feet in a direction parallel to the applied forces. .ht, htl, hz
=
The height in feet above the base (i=
0) to level .. ,..., "nu, orurn respectively.
Level i
=
Any level in the building, i=
1 first level above the base. Level n=
That level which is uppermost in the main portion of thestructure.
Level r
=
That level which is under design consideration.W
=
Dead load including the following:25% of the design snow load specified in Subsection 4.1.5.; for areas used for storage, the full design live load modified
according to Sentence 4.1.4.3.(4); the full contents of any tanks.
Wi, W z
=
That portion of W which is located at or is assigned to level ",... or "r" respectively.I
=
Numerical reduction coefficient for base overturning moment as defined in Clause 4.1.7 .1.(7)(a).I z
=
Numerical reduction coefficient for moment at level "x" as defined in Clause 4.1.7.1.(7)(b).N
=
The total number of storeys above exterior grade to level ",,".(N is usually numerically equal to ll).
T
=
Fundamental period of vibration of the buildillg or stmcture in seconds in the direction under consideration.R
=
Seismic regionalization factor which is a measure of the seismic activity and risk in the area considered.K
=
Numerical coefficient that reflects the material and type of construction, damping, ductility, andlor energy-absorptive capacity of the structure.I
=
Importance factor of the structure. F=
Foundation factor.C
=
Numerical coefficient for base shear as defined in Sentence 4.1.7.1.(4).Wp
=
The weight of a part or portion of a structure, e.g. cladding,partitions, appendages.
Cp
=
Horizontal force factor for part or portion of a structure, asgiven in Table 4.1.7.B.
V p
=
Lateral force on a part or portion of the structure.V
=
Minimum lateral seismic force at the base of the structure. F,=
Portion of V to be concentrated at the top of the structure asdefined in Clause 4.1.7.1.(5)(a). F s
=
Lateral force applied to levelr.(3) Earthquake forces shall be assumed to act in any horizontal direction. Except where required otherwise by the authority having jurisdiction,
in-dependent design about each of the principal axes shall be considered to provide adequate resi.,tance in the structure for earthauake forces applied in
any direction.
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(4) The minimum lateral seismic force assumed to act nonconcurrentIy in any direction shall be:
V
=
1,4 RKCIFWwhere R
=
the values given in the Table of Climatic Data in Part 1 of this Bylaw.K
=
the value given in Table 4.1.7 .A. C=
0.10 for all one and two-storey buildingsC
=
O.OS/vT for all other buildings The maximum value of C shall be 0.10.Except where properly substantiated technical data are submitted, T shall be determined by one of the following formulae:
T
=
0.05 hnh/D orT
=
0.1 N.The latter formula applies to all buildings in which the lateral force-resisting system consists of a moment-resisting space frame which resists lOOper cent of the required lateral forces and the frame is not enclosed by or adjoined by more rigid elements that would tend to prevent the frame from resisting lateral forces.
(Information on natural periods of buildings can be found in the chapter on loads due to earthquakes in NBC Supplement No.4. Canadian Structural Design Manual. 1970.) I
=
1.3 for all buildings designed for post disaster services andschools.
For all other buildings I
=
1.0F
=
1.5 when the structure is founded on soils having low dynamic shear modulus such as highly compressible soils.For all other soils F 1.0
n
W=2: W,
i=l
(5) (a) A portion Ft of the total lateral load V shall be concentrated at the
top of the structure, where
F;
=
0.004V(hnIDs)2The remainder V-Ft shall be distributed along the height of the bUilding
including the top level in compliance with the following formula:
F.{"= (V-Ft ) W .. h,
n
2:W
ih,i=1
F/ need not exceed O.ISV and may be considered as zero for
(hnIDs)~3.
(b) The total shear in any horizontal plane shall be distributed to the various elements of the lateral-force resistive system in proportion to their rigidities with due regard to the capacities and stiffnesses of the nonstructural elements.
(6) Parts or portions of buildings and their anchorage shall be designed for lateral forces V p where
Vp
=
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(7) (a) The overturning moment M at the base of the structure shall be multipJied by I where
J
=
0.5+
0.25/ .,yT2.I shall not exceed 1.0.
Table 4.1.7.A.
Forming Part of Sentence 4.1.7.1.(4) Type or Arrangement of Resisting Elements
Buildings with a ductile moment resisting space frame
(1), (2) with the capacity to resist the total required
lateral force.
Buildings with a dual structural system consisting of a complete ductile moment resisting space frame and shear walls designed in accordance with the following three criteria:
1. The frames and shear walls shall resist the total lateral force in accordance with their relative rigidI-ties considering the interaction of the shear walls and frames.
2. The shear walls acting independently of the ductile moment resisting space frame shall resist the total required lateral force.
3. The ductile moment resisting space frame shall have the capacity to resist not less than 25 per cent of the required lateral force.
All building framing systems except as hereinafter classified.
Buildings with a box
system(3)-Structures other than buildings and other than those set forth in Table 4.1.7.B.
Elevated tanks plus full contents, on four or more cross-braced legs and not supported by a building, de-signed in accordance with the following three criteria: 1. The minimum and maximum value of the product
Kef shall be taken as 0.12 and 0.25 respectively. 2. For overturning the factor J as set forth in Clause
Value of K 0.67 0.80 1.00 1.33 2.00 4. 1.7. 1.(7)(a) shall be 1.0. 3.00
3. The torsional requirements of Sentence 4.1.7.1.(8) shall apply.
Notes to Table 4.1.7.A.:
(1) A apace frame is a three-dImensional structural system composed of interconnected members laterally supported 80 aa to fUnction aa a complete self-contained unit with or without horizontal diaphragms.
(2) A ductile moment-resistinlr space frame is a space frame that is designed to resist
all the specified seismic forces and that. in addition. baa adequate ductility or energy-absorptIve capacity.
(Information on ductile moment-resisting space frames can be found in the chapter on loads due to earthquakes In NBC Supplement No.4. Canadian Structural Design Manual, 1970.)
(8) A box system is a structural system without a complete vertical 10ad-carrYinll: space frame.
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Table 4..1.:'.11.
Forming Part of Sentence 4.1.7.1.(6)
Category Part or Portion of Direction Value of
Buildings of Forco Cp
1 All exterior and interior walls, Normal to
except those of category 2 and 3 flat surface 0.20 Cantilever parapet and other
2
cantilever walls except retaining Normal to 1.00walls flat surface
3
Exterior and interior ornamen- Anylations and appendages direction 1.00
Towers, tanks plus contents,
c1limlleys, smokesr~cks. and Any
4 penthouses - all when connect- direction 0.20(1)
ed to or forming part of
a
building
S Tank plus contents when resting Any
on the ground
I
direction 0.10
6
I
Floors and roofs acting as dia- AnyI
phragms(2) direction 0.10Connections for exterior and
in-I
terior walls and elements except Any
7 those forming part of the main direction
I
2.00I
structural system as defined in
l
Table 4.1.7.A.
I
Notes to Table 4.1.7.B.:
(1) When "-"ID of any bulldine is equal to or ereater than I to I, Increase value by
t)o per cent.
(2) Floors and roofs aetiq &8 diaphral1DB sball be desiped for a minimum foree eorr .. eponding to the value of Cp of 10 per eent applied to loade tributary from that _tore)' unlesa a /l1'eater force F s 18 asaigned to the Iud under eonsideraUon &8 per
Clause -1,1.7.1.(5) (a).
(b) The overturning moment Ms at any level r shall be multiplied by 1:1: where
Is
=
I+
(I-I) (hz''',,)3
The incremental change..~ in the design overturning moments, in the
storey under consideration, shan be distributed to the various resisting
elements in the same proportion as the distribution of sbears in the resisting system. Where other vertical members are provided which are capable of partially resisting the overturning moments a redistribution may be made to these. memben if framing memben of suffici~nt
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(8) (a) Torsional eccentricities about the vertical axis of the building shall be computed in all storeys. Tbe..design eccentricity shall be taken to be
l.S times the computed eccentricity, increased by an accidental eccen-tricity equal to O.OS times the plan dimension in the direction of the computed eccentricity considered.
(b) Where the total torsional eccentricity determined according to Clause (a) exceeds 2S per cent of the pIan dimension measured parallel to the eccentricity, either:
(i) a dynamic analysis shall be carried out, or
(li) the effects of torsion in the statical analysis shall be doubled.
(9) A building having setbacks wherein each plan dimension of the tower is at least 7S per cent of the corresponding dimension of the structural system of the lower part may be considered as a uniform building without setbacks for the purpose of determining the seismic forces.
For other conditions of setbacks, the tower shall be designed as
a
separate structure using the larger of the seismic coefficients at the base of the tower determined by considering the tower as either a separate structure for its own height, or as a part of the over-all structure.4.1.7.2.(1) Lateral deflections or drift of a stor~y relative to its adjacent storeys shall be considered in accordance with accepted practice.
(2) All portions of the structure shall be designed to act as an integral unit in resisting horizontal forces unless separated by a distance sufficient to avoid contact under deflection from seismic action. Adjacent structures shall be
separated to prevent pounding due to earthquakes.
(3) The nonstructural components shall be detailed so as not to transfer to the structural system any forces unaccounted for in the design. Any inter-action of rigid elements such as walls and the structural system shall be
examined to show that the capacity of the structural system is not impaired by the action or failure of the rigid elements.
(4) Except where the seismic regional factor R is zero, pile footings of every building or structure shall be interconnected continuously by ties in at least two directions, designed to carry by tension or compression a horizontal force equal to 10 per cent of the larger pile cap loading, unless it can be demonstrated that equivalent restraints can be provided by other means. 4.1.7.3.(1) Except as provided in Sentences (2) and (3) buildings in Zones I, 2 and 3 more than 200 ft (61 m) in height shall have ductile moment-resisting space frames capable of resisting not less than 2S per cent of the required seismic force for the structure as a whole.
(2) Other structural concepts may be approved by the authority having jurisdiction when evidence is provided that the structure can withstand the appropriate design earthquake with ductility and energy absorptive capacity equivalent to that provided in Sentence (1).
(3) Buildings more than 200 ft (61 m) in height in seismic Zone 1 may have concrete shear walls in lieu of ductile moment~resisting space frames if
these walls are designed with special provisions required for their ductile behaviour.
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loads on railings Impact and vibrations Horizontal crane loadsSUBSECTION 4.1.8. OTHER EFFECTS
4.1.8.1. The minimum design loads on a railing which guards a drop of more than 18 in. (457 mm) are:
Horizontal load
(a) 150-lb per lineal foot (2188 N/m) applied horizontally at the top of the railing for all occupancies except those provided for in Clause (b),
(b) a 125-lb (556 N) single point load applied horizontally at any location at the top of the railing for occupancies where crowding by many peo-ple is very improbable, such as industrial catwalk areas.
Vertical load
(c) 100-lb per lineal foot (1459 N/m) applied vertically at the top of the railing and acting separately from the horizontal load provided for in Clauses (a) and (b).
4.1.8.2. Grandstands and any building used for assembly purposes to accom-modate large numbers of people at one time shall be designed to resist all inertia sway forces produced by the use and occupancy of the building or structure. The inertia force shall be not less than 20 lb per lineal foot
(292 N/m) of seat parallel to each row of seats or 10 lb per lineal foot
(146 N/m) of seat perpendicular to each row of seats.
4.1.8.3. The minimum design load due to equipment, machinery, or other objects or persons that may produce impact, is the total of the- weight of the equipment or machinery plus its maximum lifting capacity, or the appropriate live load, multiplied by an appropriate factor listed in Table 4.1.8.A. Where dynamic effects such as resonance and fatigue are likely to be important as a result of vibration of equipment or machinery, a dynamic analysis shall be carried out.
Table 4.1.8.A.
Forming Part of Article 4.1.8.3.
Impact Due to Factor
Operation of motor driven cranes 1.25
Operation of hand driven cranes 1.10
Live loads on hanger supported floors and
stairs 1.33
Operation of elevators See CSA Standard B 44,
1966, Item 2.6.2.
Column 1 Column 2
4.1.8.4. The minimum horizontal design loads on crane runway rails are: (a) the lateral force which shall be
(i) for power-operated crane trolleys, 20 per cent, and for hand operated trolleys, 10 per cent, of the sum of the weights of the lifted loads and of the crane trolley excluding other parts of the crane,
(H) applied at the top of the rail, one-half on each side of the runway and
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NATIONAL
BUILDING
CODE
OF
CANADA
1970
PART 4 DESIGN
SECTION 4.2
FOUNDATIONS
TABLE OF CONTENTS
Subsection 4.2.1. General... 159
Subsection 4.2.2. Materials Used in Foundations. . . . . . .. 164
Subsection 4.2.3. Design Considerations ... . .. 165
Subsection 4.2.4. Footings, Rafts and Foundation Walls. .. 167
Subsection 4.2.5.
Piles . . . 169
Subsection 4.2.6.
Piers and Caissons ... 174
Subsection 4.2.7. Special Foundations . . . .. ... 175
Subsection 4.2.8. Excavating, Placing and Filling ... , 175
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SECTION 4.2 FOUNDATIONS
SUBSECTION 4.2.1. GENERAL
Application
U.l.L(l) This Section applies to the design of foundation systems for the
foJ1owing:
(a) all buildings used for the following occupancieJ
(i) Group A. Assembly Occupancies
(ii) Group B.lnstitutiollai Occupancies
(iii) Group
F,
Division 1, High Ha:.ard Industrial Occupancies(b) all buildings exceeding 6000 sq ft (558 m:.!) in building area or exceed-ing 3 storeys in height used for the f01lowing occupancies
(i) Group C, Residelltial Occupancies
(ii) Group D, Business and Personal Services Occupancies (iii) Group E. Mercantile Occupancies
(iv) Group F, Divisions 2 and 3, Medium and Low Ha::'llrd Ifldlwrial
Occupancies, and
(c) all buildings of smalJer size than in (b),
(i) whose foulldations are erected in fill, very loose sand, very loose sand and gravel, soft till, very soft clay, soft clay, and clay shale,
(ii) whose superstructures are of metal frame, or reinforced concrete construction,
(iii) where unusual loading or thermal conditions exist, or (iv) supported on piles.
(2) For buildings not listed in Sentence (1) requirements for design will be found in Part 9 of this Bylaw.
(3) Requirements for the control of groundwater around spaces formed below grade are given in the appropriate articles set forth in Part 9 of this Bylaw.
Definitions
4.2.1.2. Words that appear in italics are defined in Part 2 of this Bylaw. Nomenclatul'e
4.2.1.3. Soil is that portion of the earth's crust which is fragmentary, or such that some individual particles of a dried sample may be readily separated by
agitation in water; it includes boulders. cobbles, gravel, sand, silt, clay and organic
mauer.
402.1.4.(1) A cohesionless soil identified as:
(a) "graver is a soil consisting of particles smaller than 3 in, (76 mm). but retained on a No.4 sieve, and
(b) "sand" is a soil consisting of particles passing a No.4 sieve but retained on a No. 200 sieve.
(2) "Sands" are further subdivided as follows:
(a) "coarse sand" is a soil consisting of particles pas.~ing a No.4 sieve but retained on a No. 10 sieve,
(b) "medium sand" is a soil consisting of particles passing a No. 10 sieve but retained on a No. 40 sieve, and
(e) "fine sand" is a soil consisting of particles passing a No. 40 sieve but
retained on a No. 200 sieve.
159
SoU,
Cohesionles5 soil. gravel and sandCopyright
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Cobbles and boulders Density of cohesionless soil Cohesive soil, silt and clay Consistencies of cohesive soils(3) Particles identified as:
(a) "cobbles" are rock fragments whose greatest dimensions are between 3 (76 mm) and 8 in. (203 mm), and
(b) "boulders" are rock fragments whose greatest dimensions exceed 8 in. (203 mm).
4.2.1.5.(1) A cohesionless soil described as
(a) "dense" requires 30 or more blows per foot in a penetration test, (b) "compact" requires between 10 and 30 blows per foot in a penetration
test,
( c) "loose" requires between 4 and 10 blows per foot in a penetration test, and
(d) "very loose" requires fewer than 4 blows per foot in a penetration test where the test is carried out in accordance with CSA A119.1-1960, "Code for Split-Barrel Sampling of Soils."
(2) Where it is not possible to conduct a penetratioD test, a cohesionless soil may be described as
(a) "dense" if it is not possible for a man of average weight to push a wooden picket more than 1 Y.z in. (38 mm) into the soil, and
(b) "loose" if it is possible for a man of average weight to push a wooden picket 8 in. (203 mm) or more into the soil.
(3) The picket referred to in Sentence (2) is 2 in. by 2 in. (51 mm by 51 mm) dimensions, bevelled at 45° on all sides at one end to form a point. 4.2.1.6. A cohesive soil identified as
(a) "silt" is a soil
(i) the particles of which are not visible to the naked eye,
(ii) dry lumps of which are easHy powdered by the fingers,
(iii) that, after shaking a small saturated pat vigorously in the hand, exhibits a wet shiny surface that disappears rapidly when the pat is subsequently squeezed, and
(iv) that does not shine when moist and stroked with a knife. (b) "clay" is a soil
(i) the particles of which are not visible to the naked eye, (ii) dry lumps of which are not easily powdered by the fingers,
(iii) that, after shaking a small saturated pat vigorously in the hand, does not exhibit a wet shiny surface, and
(iv) that shines when moist and stroked with a knife.
4.2.1.7. The consistencies of cohesive soils can be identified according to the description given in Table 4.2.1.A. and may be related to the approximate undrained shear strengths as indicated.
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I I0:
Table 4.2.1.A.Forming Part of Article 4.2.1.7.
Approximate
Consistency Description undrained shear
strength "very stiff" is of a type impossible to indent Over 2000 psf
with the thumb but readily in-dented with the thumbnail,
"stiff" is of a type difficult to indent 1000 to 2000 psf with the thumb; with difficulty it
can be remoulded by hand,
"firm" is of a type that can be indented 500 to 1000 psf by moderate thumb pressure,
"soft" is of a type that can be pene- 250 to 500 psf trated several inches with the
thumb,
"very soft" is of a type that can easily be less than 250 psf penetrated several inches by the
fist
Column 1 Column 2 Column 3
4.2.1.8. Organic soils and soils other than those identified in Articles 4.2.1.4. to 4.2.1.7. shall require special investigations to determine suitable design properties.
4.2.1.9. In this Section a soil or rock identified as
(a) "clay-shale" is fine-grained, finely laminated, will swell on wetting, and will disintegrate on its first drying and wetting cycle,
(b) "till" is of glacial origin, unsorted and heterogeneous and can contain a range of particle sizes including boulders, cobbles, gravel, sands, silts and clays and can exist at any relative density or consistency, and (c) "cemented sand and gravel" is a mixture of sand and gravel or boulders
thoroughly cemented together as a hard layer which will not soften in its natural bed when wet.
4.2.1.10.(1) Rock is that portion of the earth's crust which is consolidated, coherent and relatively hard, and is a naturally formed mass of mineral mat-ter which cannot be readily broken by the hands.
(2) Rocks vary from "hard" through "medium hard" to "soft,"
(a) "hard" means rock comparable to concrete with a compressive strength greater than 6000 psi (41,370 kN/m2),
(b) "medium hard" means rock comparable to concrete with a compressive strength greater than 2500 psi (17,238 kN 1m2), and
( c) "soft" rock is comparable to brick masonry with a compressive strength greater than 500 psi (3,448 kN/m2 ).
