SANS 517:2009 Light Steel Frame Building

7/26/2019 SANS 517:2009 Light Steel Frame Building

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ISBN 978-0-626-23463-8SANS 517:2009

Edition 1

SOUTH AFRICAN NATIONAL STANDARD

Light steel frame building

Published by SABS Standards Division1 Dr Lategan Road Groenkloof Private Bag X191 Pretoria 0001Tel: +27 12 428 7911 Fax: +27 12 344 1568

www.sabs.co.zaSABS

Copyright protected. This standard was downloaded on 2011-04-04 10:20 by Mr. John Anderson (Private).

Single-user license only; copying and networking prohibited.


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SANS 517:2009Edition 1

Table of changes

Change No. Date Scope

Foreword

This South African standard was approved by National Committee SABS SC 59F, Constructionstandards Steel and aluminium structures, in accordance with procedures of the SABS StandardsDivision, in compliance with annex 3 of the WTO/TBT agreement.

This document was published in November2009.

Reference is made in 4.1 and 6.1 to the "relevant national legislation". In South Africa this meansthe National Building Regulations and Building Standards Act, 1977 (Act No. 103 of 1977).

Reference is made in 5.12.2 to the relevant national legislation. In South Africa this means theOccupational Health and Safety Act, 1993 (Act No. 85 of 1993).

Reference is made in 8.2.1 to the relevant national body. In South Africa this means theEngineering Council of South Africa (ECSA), or the South African Council for National ScientificProfessions (SACNASP).

Annexes A, B and C are for information only.

IntroductionThe Southern African Light Steel Frame Building Association (SASFA) was formed as a division ofthe SA Institute of Steel Construction by a group of interested companies to coordinate thesystematic development of this new industry and to ensure quality throughout the value chain. Oneof the major tasks identified was to establish this standard for light steel frame building.




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Contents

Page

Foreword

Introduction

1 Scope .................................................................................................................................. 3

2 Normative references .......................................................................................................... 4

3 Definitions and symbols....................................................................................................... 63.1 Definitions ................................................................................................................... 63.2 Symbols ...................................................................................................................... 19

4 Materials .............................................................................................................................. 204.1 General ....................................................................................................................... 204.2 Steel . .......................................................................................................................... 204.3 Fasteners ................................................................................................................... 204.4 Interior lining of walls and ceilings ............................................................................. 204.5 Exterior cladding of walls (excluding masonry) .......................................................... 214.6 Masonry for exterior cladding of walls and foundation walls ...................................... 214.7 Thermal and acoustic insulation ................................................................................ 214.8 Damp proof courses ................................................................................................... 214.9 Wall ties and fixings ................................................................................................... 214.10 Sheathing to prevent racking ..................................................................................... 214.11 Vapour permeable membranes ................................................................................. 214.12 Reinforced concrete ................................................................................................... 224.13 Holding down devices ................................................................................................ 22

4.14 Floors ......................................................................................................................... 22

5 Steel structure ..................................................................................................................... 225.1 Basis for design .......................................................................................................... 225.2 Resistances of structural elements and connections ................................................. 235.3 Design actions ............................................................................................................ 235.4 Design criteria ............................................................................................................ 335.5 Methods of assessment of resistances ...................................................................... 335.6 Roof members ............................................................................................................ 345.7 Wall elements ............................................................................................................. 375.8 Floor members ........................................................................................................... 435.9 Connections ............................................................................................................... 465.10 Bracing ....................................................................................................................... 475.11 Testing ........................................................................................................................ 505.12 Construction of the steel frame .................................................................................. 515.13 Tolerances ................................................................................................................. 525.14 Durability and corrosion ............................................................................................. 565.15 Support of wall cupboards and fittings ....................................................................... 585.16 Earthing ...................................................................................................................... 58

6 Walls, roofs and suspended floors ...................................................................................... 586.1 Scope ......................................................................................................................... 586.2 General Requirements ............................................................................................... 596.3 Exterior walls .............................................................................................................. 636.4 Internal walls .............................................................................................................. 706.5 Roofs and ceilings....................................................................................................... 736.6 Suspended floors ........................................................................................................ 78




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Light steel frame building

1 Scope

This standard establishes rules and requirements for the design, fabrication and construction of

buildings with light steel frames, clad and insulated with appropriate materials, including the walls,roofs, floors, and foundations of such buildings.

This standard applies to buildings which do not exceed the geometric limitations given in figure 1.

This standard does not cover doors, windows, services, finishes or other elements of buildings thatare either not peculiar to light steel frame buildings or do not have a direct interface with the steelframe.

Dimensions in metres

W = widthL = length

Figure 1 Geometric limitations




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2 Normative references

2.1 Standards

The following referenced documents are relevant for the application of this document. For datedreferences, only the edition cited applies. For undated references, the latest edition of thereferenced document (including any amendments) applies. Information on currently valid nationaland international standards can be obtained from the SABS Standards Division.

AS 2870.1, Residential slabs and footings Construction.

ASTM D 7033, Standard practice for establishing design capacities for oriented strand board (OSB)wood-based structural-use panels.

ASTM E 1677, Standard specification for an air retarder (AR) material or system for low-rise framedbuilding walls.

ISO 11997-2, Paints and varnishes Determination of resistance to cyclic corrosion conditions Part 2: Wet (salt fog)/dry/humidity/UV light.

SANS 204-2, Energy efficiency in buildings Part 2: The application of the energy efficiencyrequirements for buildings with natural environmental control.

SANS 227, Burnt clay masonry units.

SANS 248, Bituminous damp-proof courses.

SANS 266, Gypsum plasterboard.

SANS 457-2, Wooden poles, droppers, guardrail posts and spacer blocks Part 2: Softwoodspecies.

SANS 457-3 (SABS 457-3), Wooden poles, droppers, guardrail posts and spacer blocks Part 3:Hardwood species.

SANS 675, Zinc-coated fencing wire.

SANS 803, Fibre-cement boards.

SANS 952 (SABS 952), Polyolefin film for damp-proofing and waterproofing in buildings.

SANS 1200 DM, Standardized specification for civil engineering construction Section DM:Earthworks (roads, subgrade).

SANS 1200 M, Standardized specification for civil engineering construction Section M: Roads(general).

SANS 1273 (SABS 1273), Fastness for roof and wall coverings in the form of sheeting.

SANS 1381-1, Materials for thermal insulation of buildings Part 1: Fibre thermal insulation mats.

SANS 1381-4, Materials for thermal insulation of buildings Part 4: Reflective foil laminates (rolls,sheets and sections).

SANS 1381-6 (SABS 1381-6), Materials for thermal insulation of buildings Part 6: Cellulose loosefill thermal insulation material.




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SANS 1383, Rigid urethane and isocyanurate foams for use in thermal insulation.

SANS 1700 (all parts), Fasteners.

SANS 3575/ISO 3575, Continuous hot-dip zinc-coated carbon steel sheet of commercial anddrawing qualities.

SANS 4998/ISO 4998, Continuous hot-dip zinc-coated carbon steel sheet of structural quality.

SANS 7253/ISO 7253, Paints and varnishes Determination of resistance to neutral spray (fog).

SANS 9364 /ISO 9364, Continuous hot-dip aluminium/zinc-coated steel sheet of commercial,drawing and structural qualities.

SANS 10005, The preservative treatment of timber.

SANS 10043, The installation of wood laminate flooring.

SANS 10100-1 (SABS 0100-1), The structural use of concrete Part 1: Design.

SANS 10100-2 (SABS 0100-2), The structural use of concrete Part 2: Materials and execution ofwork.

SANS 10124, The application of soil insecticides for the protection of buildings.

SANS 10142-1,The wiring of premises Part 1: Low-voltage installations.

SANS 10106, The installation, maintenance, repairs and replacement of domestic solar waterheating systems.

SANS 10160 (SABS 0160), The general procedures and loadings to be adopted in the design ofbuildings.

SANS 10161 (SABS 0161), The design of foundations for buildings.

SANS 10162-1, The structural use of steel Part 1: Limit-state design of hot-rolled steelwork.

SANS 10162-2 (SABS 0162-2), The structural use of steel Part 2: Limit-states design of cold-formed steelwork.

SANS 10177-2, Fire testing of materials, components and elements used in buildings Part 2: Fireresistance test for building elements.

SANS 10249, Masonry walling.

SANS 10252-1, Water supply and drainage for buildings Part 1: Water supply installations forbuildings.

SANS 10252-2 (SABS 0252-2), Water supply and drainage for buildings Part 2: Drainageinstallations for buildings.

SANS 10254, The installation, maintenance, replacement and repair of fixed electric storage waterheating systems.

SANS 10400 (SABS 0400), The application of the National Building Regulations.

TRH 14,Guidelines for road construction materials.




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2.2 Other publications

NHBRC (National Home Builders Registration Council, RSA), Home Building Manual, Parts 1 3.

Agrment Board of South Africa, Booklet B1, Performance criteria and minimum requirements forthe assessment of innovative methods of construction.

3 Definitions and symbols

For the purposes of this document, the following definitions and symbols apply.

3.1 Definitions

3.1.1acceptable

acceptable to the authority administering this standard, or to the parties concluding the purchasecontract, as relevant

3.1.2acoustic insulationinsulation material installed to reduce the transmittance of sound from one side of the insulation tothe other

3.1.3air infiltrationair movement through a material, component or an assembly into a building

3.1.4

balconiesexternal areas, at least one metre above ground level

3.1.5beamhorizontal structural member that supports vertical loads and is subject to flexural stresses

3.1.6bearersub-floor beam supporting the floor joists (see figures 2 and 7)

3.1.7bottom wall plate

bottom platemember running along the bottom of a wall frame and resting directly on a foundation wall,foundation beam or floor slab (see figures 2 and 4)

3.1.8bracingdiagonal members, or diaphragms, that resist lateral movement of members or racking forces (orboth), (see figures 2, 9 and 10)

3.1.9branderingmember fixed to roof trusses or rafters to support the ceiling (see figure 3), and which does notapply to suspended ceilings




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3.1.10brick veneersingle leaf non-load-bearing brick wall serving as exterior cladding

3.1.11building envelopeexterior skin of a building, consisting of the floor, external walls, ceiling under roof overhangs, androof cladding

3.1.12bulk insulationmineral or synthetic fibre wool in rolls which are available in different densities and thicknesses

NOTE Referred to as bats when cut to length.

3.1.13

category 1 buildingbuilding which

a) is designated as being a class A3, A4, F2, G1, H2, H3 and H4 occupancy (see SANS 10400),

b) has no basements,

c) has a maximum length between intersecting walls or members providing lateral support of 6,0 m,and

d) has a floor area not exceeding 80 m2

3.1.14

chordtop (rafter) or bottom member of a truss (see figures 2 and 3)

3.1.15competent personperson who is qualified, by virtue of his education, training, experience and contextual knowledge,to make a determination regarding the performance of a building or part thereof in relation to afunctional regulation

3.1.16crawl spacegap between a suspended ground floor and the underlying ground, to allow for inspection andmaintenance of structural members supporting the floor

3.1.17domestic dwellingbuilding used for residential purposes, consisting of one or more dwelling units

3.1.18energy efficiencymeasure of the minimisation of the need to use energy for heating and cooling of buildings

3.1.19expansion jointdiscontinuation between elements, such as wall panels, to allow for relative movement betweenadjoining elements and to prevent stresses arising in the elements from such differential

movements




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3.1.20exterior wallwall forming part of the building envelope, and which is normally load-bearing

3.1.21external wall claddingweather resistant external skin of a building, fixed to the light steel frame

NOTE External wall cladding may consist of a single leaf of brickwork (veneer), weather resistant boards orreinforced plaster.

3.1.22fibre cement boardcomposite material made of cement, sand and cellulose or synthetic fibres (or both)

3.1.23fire ratingshortest period for which a building element or building component will comply with therequirements for stability, integrity and insulation (see 4.1)

3.1.24fire resistanceability of a composite floor, wall or ceiling assembly to remain stable when exposed to heatgenerated by fire

3.1.25floor joistbeam that directly supports the flooring (see figures 2 and 7)

3.1.26

glass woolmaterial made from glass, spun into fibre-like structure

NOTE Available in different densities (kilogram per cubic metre) for use as insulation.

3.1.27gypsum boardboard with a gypsum plaster core with an envelope of two layers of paper

NOTE Gypsum board can be specified to be fire resistant or water resistant.

3.1.28insulation

building fabric installed in wall and roof cavities, or attached to steel framing elements or claddingmaterials, to provide resistance against heat or sound transfer (or both), between rooms ordwellings

NOTE The insulation specified for category 1 buildings does not comply with the insulation requirement ofSANS 204-2. It was included to allow for low cost buildings.

3.1.29internal liningcladding of an internal wall, the inner face of an external wall or a ceiling that provides a neat finish,fire resistance to the light steel structure and part of the insulation

3.1.30jack studvertical member in a wall frame below or above a window or door opening (see figure 2)




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3.1.31jamb studstud located beside an opening in a wall frame such as a window or door opening (see figures 2, 5

and 6)

3.1.32light steel frame buildingbuildings in which the load-bearing structure, comprising the wall framing, columns, beams, trusses,panels or any combination of these, consists of assemblies of thin-walled cold-formed steel sections

3.1.33lintelhorizontal member in a wall frame spanning over an opening (see figures 2, 5 and 6)

3.1.34nogging

horizontal restraining member fixed between studs in a wall frame (see figures 2 and 4)

3.1.35non-load-bearing wallswall that is not required to carry gravity or wind loads (see figure 8)

3.1.36notchinglocalised removal of material from a steel element that involves cutting away a flange of the elementor a portion thereof

3.1.37open web joist

parallel-chord truss that supports concentrated or distributed loads, such as floor joists, rafters in aroof and lintels (see figures 5 and 6)

3.1.38purlinmember fixed to roof trusses or rafters to support roof sheeting (see figure 3)

3.1.39rackingin-plane distortion of a framing module such as a wall or a roof, involving movement of the toprelative to the bottom, in the plane of the module

3.1.40

reflective insulationmaterial with a reflective surface such as a reflective foil laminate capable of reducing radiant heatflow due to its high reflectivity and low emissivity

3.1.41roof battenmember fixed to roof trusses or rafters to support roof tiles (see figure 3)

3.1.42R-valuemeasure of resistance to heat flow of a material or composite element, including the effects of anyair spaces or reflective surfaces (or both)

NOTE The higher the R-value, the better the ability of the material or composite element to resist the flow ofheat through it. R-values are expressed using the units, m2K/W.




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3.1.43sheathingrigid board fastened directly to the wall studs to provide support for exterior cladding material, to

lend structural support to the light steel frame members or to enhance the insulation of exteriorwalls

3.1.44sheet insulationinsulation materials in (rigid) sheet form

NOTE Sheet insulation is available in different densities and thicknesses, with or without reflective surfaces.

3.1.45sound insulationmeasures taken to reduce the transfer of sound through a composite wall or floor assembly(see 3.1.2)

3.1.46spacingunless otherwise specified, the centre-to-centre distance between studs, joists, bearers, trusses,battens, purlins or other elements

3.1.47spanunless otherwise specified, the centre-to-centre distance between the supports of a beam, truss,

joist, purlin, batten, rafter or roof

3.1.48stone wool

material made from stone or slag, spun into fibre-like structure

NOTE Available in different densities (expressed using the units, kg/m3) for use as insulation.

3.1.49structural steelall steel which forms part of the structure, including the roof construction, wall frame construction,floor and ceiling supports

3.1.50studsvertical members of the light steel wall frame

NOTE Studs could be load-bearing, or not (see figures 2 and 4).

3.1.51subfloorlower layer of timber, concrete or fibre cement flooring to which the bottom wall plate and wearingsurface is attached

3.1.52suspended floorfloor supported by beams or columns

3.1.53tenancy-separating wall/floor

wall or floor that separates one residential unit from another




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3.1.54thermal breakair gap or layer of insulating material between two building components to reduce the transfer of

heat by conduction

3.1 55thermal efficiencyability of a composite building component or assembly (floor, wall, ceiling or roof) to resist heattransfer

3.1.56top wall platemember running along the top of a wall frame (see figures 2 and 4)

3.1.57TRH

technical recommendations for highways

3.1.58trusslatticed frame supporting the roof and ceiling over the full width of the domestic dwelling (seefigures 2 and 3)

3.1.59uncontrolled air flowunintended movement of air into or through a room or a building

3.1.60vapour permeable membrane

membrane installed to prevent or minimise the ingress of moisture and uncontrolled air flow, andallow the passage of vapour

3.1.61wall tiebracket or wire connecting brick veneer cladding to the steel frame

3.1.62weatherproofingmeasures taken to prevent the ingress of moisture and to minimise uncontrolled air flow

3.1.63web member

element of a truss or open web joist other than the top and bottom chord (see figures 2 and 3)




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Figure 2 Typical framing




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a) Typical roof truss assembly

b) Typical panel roof assembly

Figure 3 Typical roof assemblies




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Stud spacing

Lowerstorey

Studheight

Lower storeytop plate

Lower storeybottom plate

Lower storeycommon stud

Floor joistspacing

Rafter / Truss

spacing

Upperorsinglestorey

Studheight

Upper or single

Storey top plate

Upper or singlestorey bottom plate

Upper or singlestorey common stud

Nogging

Drg.740g

Figure 4 Components of a typical wall assembly




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Lintel

Sill trimmer

Lintel

span

Jamb stud

Floor joistspacing

Drg.740i

Figure 6 Lower storey lintel




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Figure 7 Components of typical floor frame

Load-bearing ornon-load-bearing wallparallel to floor joist

Load-bearing ornon-load-bearing wallperpendicular tofloor joist

Drg.740k

Figure 8 Typical wall arrangement




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Roof bracing

Drg.740l

Figure 9 Typical roof bracing

'K' brace

Double diagonalmetal strap brace

Sheet brace(FC sheet,hardboard, plywoodor steel)

Drg.740m

Figure 10 Typical wall bracing systems




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3.2 Symbols

A summed area supported by a structural member

cp resultant coefficient for internal and external wind pressure

cpe coefficient for external wind pressure

cpi coefficient for internal wind pressure

cr terrain roughness factor

d distance between points

G permanent load (own weight of building)

H height

L span or length

qk uniformly distributed imposed load

Qk concentrated imposed load

qp peak wind pressure

s spacing of elements

vb basic wind speed

w wind pressure

W wind load

Wr wind load on roof

Ww wind load on wall

W(down) downward-acting wind load

W(up) upward-acting wind load

roof slope

deflection

air density




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4 Materials

4.1 General

Materials that have been proven to meet the requirements of the relevant national legislation (seeforeword), if used appropriately in combination with other materials, and installed to an acceptablequality of workmanship, are listed as being acceptable in this section. Other materials andcombinations of materials may be used if information derived from authoritative sources can beprovided to demonstrate that the requirements of the relevant national legislation (see foreword) aremet in all respects.

A building element or building component shall comply with the requirements for stability, integrityand insulation when tested in accordance with the relevant provisions of SANS 10177-2.

4.2 Steel

Steel, either hot rolled or cold formed, used for the structures of light steel frame buildings, shallcomply with the requirements of an internationally recognised standard and shall have a coating atleast equivalent in corrosion resistance and robustness to 200 g/m

2 galvanising (Z200) or a

150 g/m2aluminium-zinc coating (AZ150).

Light structural steel members shall be manufactured using the prescribed steel strength grade (forexample, 300 MPa or 550 MPa minimum yield strength) in accordance with the design specification.The material shall comply with the requirements of SANS 3575 or SANS 4998 (or both), orSANS 9364.

All steel used shall have sufficient formability to allow the cold forming of profiles without anycracking of the steel substrate.

Steel elements shall comply with the dimensional and straightness tolerances given in 5.13.1.

4.3 Fasteners

Fasteners, connectors and fixing methods for the steel structure shall comply with

a) SANS 1700 (all parts) for bolts, nuts and screws (self drilling or self tapping (or both)), asrelevant,

b) the manufacturers recommendations, supported by international standards,

c) specifications for clinching or other mechanical means of fastening as recommended by the

manufacturer, supported by international standards or specifications.

Carbon steel fasteners shall be coated with a zinc or inorganic coating (or both) to provide corrosionprotection similar, under the prevailing conditions, to the metallic coated steel sheet used for thelight steel cold-formed sections (for example coating designation Z275). (See 5.14.)

4.4 Interior lining of walls and ceilings

The materials shall comply with

a) SANS 266 for gypsum plasterboard, and

b) SANS 803 for fibre cement board (subject to fire rating requirements).




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4.5 Exterior cladding of walls (excluding masonry)


a) SANS 803 for fibre cement board, and

b) SANS 3575 or SANS 4998 for galvanised steel sheet.

4.6 Masonry for exterior cladding of walls and foundation walls


a) SANS 227 for clay bricks, and

b) SANS 10249 for cement blocks.

4.7 Thermal and acoustic insulation


a) SANS 1381-1 for fibre thermal insulation mats,

b) SANS 1381-6 for loose fill thermal insulation,

c) SANS 1381-4 for reflective foil laminates,

d) acceptable flame retardant grade expanded or extruded polystyrene, and

e) SANS 1383 for rigid polyurethane foam and poly-isocyanurate.

4.8 Damp proof courses


a) SANS 248 for bituminous damp-proof courses, and

b) SANS 952 for polyolefin film.

4.9 Wall ties and fixings


a) SANS 675 for galvanised wire, and

b) SANS 4998, SANS 3575 or SANS 9364 for zinc or aluminium-zinc coated steel strap.

4.10 Sheathing to prevent racking

The material shall comply with ASTM D 7033 for orientated strand board (OSB).

4.11 Vapour permeable membranes

The material shall comply with ASTM E 677 for air retarder material or system for framed building

walls.




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4.12 Reinforced concrete

The material shall comply with SANS 10100-2 for reinforced concrete.

4.13 Holding down devices


a) SANS 3575 for brackets and washers made from galvanised steel sheet, with minimum coatingdesignation Z200, and

b) SANS 9364 for brackets and washers made from aluminium-zinc coated material, with minimumcoating designation AZ150.

4.14 Floors


a) SANS 803 for fibre cement boards,

b) ASTM D 7033 for OSB board (structural), and

c) SANS 10100-2 for structural concrete.

5 Steel structure

5.1 Basis for design

5.1.1 General

The structure shall resist all the loads the building will be subjected to, including loads deriving fromits own mass. However, the lateral support provided to steel elements by the non-structuralelements of the building, such as the wall or roof cladding or the ceilings, may be taken into accountin the design of these elements, provided that it can be demonstrated that the non-structuralelements have adequate strength for lending such support, and that the steel structure will not besubjected to loads its elements cannot resist without such lateral support while the non-structuralelements are, for whatever reason, not in position.

A clear path shall be discernable for every force, from where the force acts to the foundations, andall members and connections along this path shall have adequate strength and stiffness to resistthe forces generated in them without failure, or deflections that exceed the maximum deflections

specified in this standard.

The system effect as described in annex B may be taken into account in the design of systems ofbeams or other bending elements with crossing members that can distribute load between thebeams.

5.1.2 Durability

The design criteria are based on the assumption that the materials used and their installation andmaintenance will ensure that components fulfil their intended structural function for the intended lifeof the structure. (See 5.14.)




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5.2 Resistances of structural elements and connections

5.2.1 Design standard

Cold-formed steel components shall be designed to meet the requirements of SANS 10162-2,except where expressly specified differently in this standard. Hot-rolled steelwork shall be designedto comply with the requirements of SANS 10162-1.

5.2.2 Design properties

The yield stress and ultimate strength of the steel shall, except for steel with a minimum yield stressof 550 MPa, be taken as the listed yield stress and ultimate tensile strength for that grade of steel inthe applicable standard (see 4.2). The yield stress and ultimate strength of any steel for which themechanical properties cannot be proved by means of a mill test certificate shall not be taken ashigher than 200 MPa and 365 MPa, respectively.

Steel with a minimum yield stress of 550 MPa and of elongation less than 8 % may not be used inbase metal thicknesses exceeding 0,90 mm. For such steel in base metal thicknesses of not lessthan 0,60 mm, the yield stress and tensile strength shall both be taken as 495 MPa, while for basemetal thicknesses less than 0,60 mm the yield stress and tensile strength shall both be taken as410 MPa. The properties of the steel may be determined as described in SANS 10162-2.

It is customary in South Africa to refer to the coated thickness of galvanised steel sheet as thethickness of the sheet. As the coating does not add to the strength of the material, designers shallwork with the base metal thickness as the thickness, determined as follows:

Bt = Ct 0,04 mm

where

Bt is the base metal thickness, expressed in millimetres;

Ct is the coated metal thickness expressed in millimetres.

The dimensions of a steel section shall be taken as the specified dimensions, which shall be usedto derive the section properties.

Due allowance shall be made for holes, cutaways and other ways in which the strength of anelement may be impaired, including holes made during or after erection in the structure toaccommodate services, in accordance with 5.7.1 and 5.8.2.1 and 7.2.

5.3 Design actions5.3.1 General

Structural design actions and combinations of actions, in general, shall be in accordance withSANS 10160. The simplified actions described in 5.3.2 to 5.3.4 (inclusive), may be used whereappropriate.

Construction loads may become critical on some components of an unfinished building and in suchcases shall be accounted for in the design.

Where loads other than those specified in 5.3 (such as snow loads, seismic loads, or loadcombination(s) containing such loads) are applicable, they shall be accounted for in the design.




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5.3.2 Imposed loads for domestic dwellings

For the design of domestic dwellings as defined in 3.1.17, the following characteristic imposed loads

may be used, with the uniformly distributed load and the concentrated load not necessarilyoccurring simultaneously:

a) For roofs, not accessible except for normal maintenance:

Uniformly distributed load (qk): 0,5 kPa for contributory areas < 3 m2;

0,25 kPa for contributory areas >15 m2; interpolate in-between;

Concentrated load (Qk): 1,0 kN applied anywhere.

b) For general floor areas:

Uniformly distributed load (qk): 1,5 kPa, but if the area Asupported by a single column, wall,

beam or girder exceeds 20 m

2

;

A

qk3,1

0,3 + 1,5 0,75 kPa=

Concentrated load (Qk): 1,5 kN.

c) Balconies and roofs used for floor type activities 1,0 m or more above ground:

Uniformly distributed load (qk): 4,0 kPa;


d) Lateral horizontal loads applied to balustrades on balconies:

Uniformly distributed load: 0,5 kN/m applied at the top of the balustrade;

Concentrated load: 1,0 kN applied at the top of the balustrade.

5.3.3 Wind loads

5.3.3.1 General

The wind loads used in the design of buildings meeting the geometric limitations of figure 1 may becalculated in accordance with 5.3.3.2 and 5.3.3.3.

5.3.3.2 Peak wind speed pressure

The peak wind speed pressure qp,expressed in kilopascals shall be determined using equation (1).

q c v2

p r b,0

1. (1,4

2 000= ) (1)




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Longitude Degrees

Figure 11 Geographic regions related to wind speeds

LatitudeDegrees




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5.3.3.3 Wind pressure on surfaces

5.3.3.3.1 General

Wind load on structures and structural elements shall be determined taking into account thesimultaneous action of external and internal wind pressures.

The net pressure on a wall, roof or other element is the difference between the pressures on theopposite surfaces taking due account of their signs. Pressure directed towards the surface is takenas positive, and suction, directed away from the surface, is taken as negative.

5.3.3.3.2 Internal wind pressure

For a building without a wall with a dominant opening, the internal pressure coefficient cpi shall betaken as +0,2 or 0,3, whichever causes the more severe loading in combination with theappropriate external wind pressure.

For a building with a dominant opening in the windward wall, the internal pressure coefficient cpishall be taken as +0,75. If this dominant opening can be assumed to be closed during stormconditions, the internal pressure coefficient cpi may be taken as +0,6.

A wall shall be regarded as containing a dominant opening if the area of its openings is at leasttwice the sum of the area of openings and leakages in the remaining exterior walls of the building.

The wind pressure, w (expressed in kilopascals), on walls and ceilings in the building shall bedetermined using equation (2) and the appropriate internal pressure coefficient cpi, as definedabove.

w = qpcpi (2)

where

qp is the peak wind speed pressure, in accordance with 5.3.3.2;

cpi is the pressure coefficient for the internal pressure.

5.3.3.3.3 External wind pressure on walls

The external pressure coefficients cpe for buildings and parts of buildings depend on the size of theloaded areaA, which is the tributary area of the structure that produces the wind action effect in thestructural component to be calculated. The external pressure coefficientsare given for loaded areasof 1 m

2 and 10 m

2 in the tables for the appropriate building configurations as cpe,1, for local

coefficients, andcpe,10, for overall coefficients, respectively.

Values for cpe,1are intended for the design of small elements and fixings with an area per elementof 1 m

2or less, such as cladding or roofing elements. Values for cpe,10may be used for the design of

the overall load bearing structure of buildings.

The external pressure coefficients cpe for the walls of a building with a rectangular plan shall beobtained from figure 12. The definition of the zones on the walls of the building is given in figure 12.

The external wind pressure we(measured in kilopascal) on the vertical walls of the building shall bedetermined using equation (3) and the appropriate external pressure coefficients as defined infigure 12.

we = qpcpe (3)




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where

qp is the peak wind speed pressure;

cpe is the pressure coefficient for the external pressure.

b = plan dimension of the building perpendicular to the wind directiond = plan dimension of the building along the wind directione = 0,2 or 0,4h, whichever is the smaller

h = eaves height of the building

Plan view of rectangular building

1 2 3 4 5

Zone

A B C D

Valuesof external pressure coefficientCoefficient

cpe

cpe,1 1,4 1,1 +1,0 0,5

cpe,10 1,2 0,8 +0,8 0,5

Figure 12 Key for vertical walls of rectangular plan buildings

5.3.3.3.4 Resultant wind pressure

The resultant wind pressure w on walls or roofs is the sum of the internal and external windpressures, and shall be calculated using equation (4) and the appropriate internal and externalpressure coefficients as defined figure 12.

W = qp (Cpe + Cpi) (4)

where qp, cpiand cpeare as defined for equations (2) and (3).




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The external wind pressure coefficient for mono-pitched roofs shall be obtained from table 2.

The wind pressure, w(expressed in kilopascals), on the mono-pitched roof of the building shall be

determined using equation (4) and the appropriate external and internal pressure coefficients asdefined in table 2.

Table 2 External pressure coefficient cpe for mono-pitched roofs

1 2 3 4 5 6 7

Local coefficient Overall coefficient

Cpe,1 Cpe,10

Wind direction

0or 180 90 0or 180 90

Roof pitch

Zone

degrees E (edge) F G (edge) E (edge) F G (edge)5 2,0 1,2 2,0 1,3 0,8 1,8

ora 0,0 0,0 0,0 0,0

15 2,0 1,2 2,5 1,3 0,9 1,9

ora 0,2 0,2 0,2 0,2

30 1,5 0,8 2,0 0,8 1,0 1,5

ora 0,7 0,4 0,7 0,4

45 0,7 0,5 2,0 0,7 1,0 1,4

ora 0,7 0,6 0,7 0,6

a At wind direction of = 0 the pressure changes rapidly between positive and negative

values around a pitch angle of

, accordingly both positive and negative values aregiven. For such roofs, two cases should be considered: one with all positive values, andone with all negative values. Positive and negative values cannot act in combination onthe same face.

5.3.3.3.7 External wind pressure on duo-pitched roofs

The roof, including protruding parts, shall be divided into zones as shown in figure 15.

The external wind pressure coefficients for the duo-pitched roofs shall be obtained from table 3.




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Table 3 External pressure coefficients cpefor duo-pitched roofs

1 2 3 4 5 6 7 8 9 10 11

Local coefficient Overall coefficient

Cpe,1 Cpe,10

Wind direction

0or 180 90 0or 180 90

Roof pitch

Zone

degrees G (edge) H J K (edge) L G (edge) H J K (edge) L

5 2,0 1,2 0,6 2,0 1,2 1,2 0,6 0,6 1,3 0,7

ora 0,0 0,0 0,2 0,0 0,0 0,2

15 1,5 0,3 1,5 2,0 1,2 0,8 0,3 1,0 1,3 0,6

ora 0,2 0,2 0,0 0,2 0,2 0,0

30 1,5 0,2 0,5 2,0 1,2 0,5 0,2 0,5 1,4 0,8

ora 0,7 0,4 0,0 0,7 0,4 0,0

45 0,0 0,0 0,3 2,0 1,2 0,0 0,0 0,3 1,4 0,9

ora 0,7 0,6 0,0 0,7 0,6 0,0

a For the across wind situation the pressure changes rapidly between positive and negative values on

the windward face depending on the roof pitch , accordingly both positive and negative values aregiven. For such roofs, four loading cases shall be considered, where the largest or smallest values ofall areas G and H are combined with the largest or smallest value in area J. Positive and negativevalues cannot act in combination on the same face.

The wind pressure w (expressed in kilopascals), on the duo-pitched roof building shall bedetermined using equation (4) in 5.3.3.3.4 and the appropriate external and internal pressurecoefficients as defined in 5.3.3.3.2 and 5.3.3.3.7.

5.3.3.3.8 Local wind pressure at corners of roofs

The local external pressure coefficient for the square extending for 2 m in both directionshorizontally from the corners of a roof shall be taken as 2,9. This pressure coefficient shall be usedin conjunction with the pressure on the underside of the roof for the design of purlins, battens andsheeting and their fixings in this area.

5.3.4 Actions during construction

Critical loads and combinations of loads during construction may be different from those for thecomplete structure. These include:

a) Imposed load arising from the stacking of construction materials.

b) Imposed load arising from people working on the incomplete frame.

c) The wind load during construction may be based on a design wind speed with a mean returnperiod of 10 years. The wind load effects on the incomplete structure may be different from thaton the complete structure, for example, supported walls may become free standing walls duringconstruction, or roof sheeting in the internal zone of a roof could become edge sheeting, andtherefore need temporary bracing.

d) Unbalanced loads arising during construction.




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e) Loads on roofs during construction:

uniformly distributed load (qk): 0,50 kPa for contributory areas < 3,0 m2, or 0,25 kPa for

contributory areas > 15 m2

, with linear interpolation in-between;


5.4 Design criteria

5.4.1 Strength and stability

The building as a whole, and its parts, shall be designed to prevent overturning, uplift, sliding orexcessive settlement, as well as failure of either the steel elements or the non-structural materialsby collapse, tearing, unacceptable cracking or local deformations.

The design load for the ultimate limit state shall be that combination of (factored) loads which

produce the most adverse effect on the building. For domestic dwellings as defined inclause 3.1.17, the design loads may be determined from, but not limited to, the loads and loadcombinations given in 5.6 to 5.8 (inclusive).

NOTE Only combinations of actions usually deemed as potentially critical have been included in the designcriteria in sections 5.6 to 5.8 (inclusive). SANS 10160 provides further information for other situations.

5.4.2 Serviceability

The design criteria for serviceability shall be taken from, but not limited to, the criteria given insections 5.6 to 5.8 (inclusive).

NOTE The design criteria have been determined on the basis of experience. The serviceability limits are

intended to provide satisfactory service for typical situations. SANS 10160 provides further guidelines for othersituations.

5.5 Methods of assessment of resistances

5.5.1 General

The assessment of the resistance to loads of a structural element or structural assembly shall becarried out by one of the following methods:

a) calculation;

b) testing; or

c) combination of calculation and testing.

5.5.2 Calculations

Calculations shall be based on appropriate structural models for the ultimate or serviceability limitstates under consideration. The method of structural analysis shall take into account equilibrium,stability and geometric compatibility. The combinations of loads shall include all appropriatecombinations outlined in this document. The design properties for steel shall be in accordancewith 5.2.2. The design capacities of steel elements shall be determined in accordance withSANS 10162-1 or SANS 10162-2.




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Table 5 Serviceability response limits Trusses and rafters

1 2 3 4 5

Issue of concernServiceability

parameterFactored

loadLimit of

responseApplication

Visual sagging Mid-span deflection () 1,1 Gk L/300 Truss top chord or rafter

Cracking of ceiling Mid-span deflection () Qk d/250 Truss bottom chord orceiling joist

Deflection underimposed load

Mid-span deflection () 1,0 Qkor1,0 qk

d/200 or

L/250, whicheveris less

Truss or rafter

Deflection underwind load

Mid-span deflection () 0,6 Wk L/150 Truss or rafter

Undulation of roof Differential mid-span

deflection ()

1,1 Gk s/150

(< 4 mm)

Differential deflection

between adjacenttrusses or rafters

d = distance between nodal points, expressed in millimetres

s = spacing between trusses

L = span of truss or rafter, expressed in millimetres

Gk, Qk, qkand Wk = as in 5.6.2.1

NOTE For cantilevers, the limit of response may be taken as twice that of the mid-span deflection whereLis the projection of the cantilever.

5.6.4 Ceiling brandering

5.6.4.1 Design for strength

The load combinations used for the determination of the design load effects for strength are:

0,9 Gk + 1,3 Wk(up)

1,2 Gk + 1,3 Wk(down)

where

Gk are the permanent loads of the brandering, ceiling and insulation;

Wk is the wind load resulting from internal pressure, from 5.3.3.

NOTE Brandering need not be designed to resist imposed loads, on the assumption that nobody will beallowed to stand on the brandering.

5.6.4.2 Design for serviceability

For satisfactory performance under each issue of concern, the calculated value of the parameterunder the nominated load shall be kept within the limiting value of the response, as shown intable 6.




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5.7.2 Load-bearing wall studs

5.7.2.1 General

Load-bearing wall studs include

a) common studs that support the vertical loads applied to the top wall plate by rafters, trusses andceiling joists, and horizontal loads due to wind,

b) jamb studs that are provided on each side of an opening to support loads from the lintel over theopening as well as the horizontal wind load across the width of the opening, and

c) studs supporting concentrated loads, which are installed in addition to common studs (or jambstuds) to carry concentrated vertical loads arising from principal roof or floor supportingmembers.

Load-bearing wall studs shall be designed to carry the tension or compression loads from supportedfloors or roofs, and also to carry horizontal wall loads, and to transfer these loads to the top andbottom wall supports.

Wind load effects on studs include a combination of axial loads from wind pressure on roofs anduniformly distributed lateral loads from wind pressure on walls.

5.7.2.2 External load-bearing wall studs for a single storey or upper storey of a two storeyconstruction

5.7.2.2.1 Design for strength

The load combinations for the determination of the design load effects for the strength of wall studs

are:

1,2 Gk + 1,6 qk

1,2 Gk + 1,6 Qk

1,2 Gk + 1,3 (Wkw + Wkr(down))

0,9 Gk + 1,3 (Wkw + Wkr(up))

where

Gk is the self weight of the roof, including roof structure, roof cladding, roof battens,

ceiling battens, ceiling, services and roof insulation if appropriate;

qk and Qk are the imposed loads on the roof;

Wkw is the wind load normal to the wall;

Wkr is the wind load on the roof.

NOTE Wall studs may also be subject to additional axial forces if they are part of the bracing systemresisting racking forces.

NOTE Guidance for the determination of weights can be found in annex A.




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5.7.2.2.2 Design for serviceability

For satisfactory performance under each issue of concern, the calculated value of the parameter

under the nominated load shall be kept within the limiting value of the response in table 7.

Table 7 Serviceability response limits External walls, single or upper storey

1 2 3 4 5


parameterLoad

Limit ofresponse

Application

Discernable movement Mid-height deflection () 0,6 Wkw H/150(< 20 mm)

Face loading

Impact Mid-height deflection () Q H/200(< 12 mm)

Soft body impact on wall

Wkw = wind load normal to wall

Q = 0,7 kN

H = height of the stud, expressed in millimetres

5.7.2.3 External load-bearing wall studs for the lower storey of a two storey construction

5.7.2.3.1 Design for strength

The load combinations used for the determination of the design load effects for the strength of wallstuds are:

1,2 Gk + 1,6 Qk

1,2 Gk + 1,6 qk

1,2 Gk + 1,3 (Wkw + Wkr(down))

0,9 Gk + 1,3 (Wkw + Wkr(up))

where

Gk is the self weight, of the roof, including the roof structure, roof cladding, roofbattens, ceiling battens, ceiling, upper storey walls, upper storey floor, services androof insulation, if appropriate;

qk and Qk are the imposed loads on the roof and upper storey floor;

Wkw is the wind load normal to the wall;

Wkr is the wind load on the roof.

NOTE Guidance for the determination of weights can be found in annex A.

5.7.2.3.2 Design for serviceability

For satisfactory performance under each issue of concern, the calculated value of the parameterunder the nominated load shall be kept within the limiting value of the response in table 8.




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Table 8 Serviceability response limits External walls, lower of two storeys

1 2 3 4 5


parameterLoad

Limit ofresponse

Application

Discernable movement Mid-height deflection () 0,6 W H/150(< 20 mm)

Face loading

Impact Mid-height deflection () Q H/200(< 12 mm)

Soft body impact on wall

H = height of lower storey

W = either Wkwor Wkrin 5.7.2.3.1

Q = 0,7 kN

NOTE Jamb studs may warrant specific serviceability criteria to counteract the closing and slammingof doors. Brittle lining materials, such as ceramic tiles, may require special consideration forserviceability. Brick veneer should not be considered as a brittle cladding material under this definition.

5.7.2.4 Internal load-bearing wall studs

Design criteria for internal load-bearing wall studs are similar in principle to external load-bearingwall studs. Wind load normal to the wall is limited to differential pressure between the wall faces andmay be taken as 0,3 qpwhere qpis obtained from 5.3.3.2.

5.7.3 Non load-bearing studs

5.7.3.1 General

Non-load-bearing studs are defined here as wall studs that are not required to carry gravity loads,other than their own self-weight. These studs are, however, expected to carry any lateral loads suchas wind loads, impact loads or internal pressures they may be subjected to and shall be designedaccordingly.

The top wall plate of a non load-bearing wall shall be laterally supported.

Joints shall be made in non-load-bearing walls where they cross movement joints in the mainstructure.

Care shall be taken to ensure that non-load-bearing studs do not become load-bearing because ofdeflection of a floor above it. This can be achieved by measures similar in concept to those depictedin figure 16. The finishes shall be detailed so as not to be damaged by the resulting movements.




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where

Gk is the weight of the complete roof, upper storey walls and floor, including the

ceiling;

qk and Qk are the imposed loads on the roof and upper storey floor;

Wkr is the wind load on the roof;

Wkw is the wind load normal to the wall.

NOTE Guidance on the determination of weights can be found in annex A.


For satisfactory performance under each issue of concern, the calculated value of the parameter

under the nominated load shall be kept within the relevant limiting value of the response, as shownin table 9.

Table 9 Serviceability response limits for wall plates and lintels

1 2 3 4 5


parameterLoad

Limit ofresponse

Application

Wall plates

Sagging or wind uplift Mid-span deflection () Gkor

0,9G + 0,6 Wkr(up)

L/200(< 3 mm)

Relevant Gkfor upperstorey and lowerstorey top plates

LintelsSagging Mid-span deflection () Gk L/300

(< 10 mm)

Relevant Gkfor upperstorey lintel

Wind uplift Mid-span deflection () 0,9 Gk + 0,6 Wkr(up) L/200

5.7.6 Wall bracing

Wall bracing shall be designed in accordance with 5.10.3.

5.8 Floor members

5.8.1 General

All floor members including floor joists, bearers and flooring shall be designed to act together as astructural unit to transfer all the loads imposed on the roof, walls and floors to appropriate supports.In addition, the floor assembly is expected to act as a diaphragm to transmit the horizontal shearaction effects arising from wind actions.

5.8.2 Floor joists and bearers

5.8.2.1 General

Floor joists are designed mainly to support floor loads. Floor bearers are designed to support the

floor joists (see figure 7).




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Drg.740x

Figure 18 Overlapping joists

5.8.2.2 Design for strength

The combinations of loads used for the determination of the design load effects for floor joists orbearers are:

1,2 Gk + 1,6 qk

1,2 Gk + 1,6 Qk

where

Gk are the permanent combined loads supported by joists or bearers;

Qk and qk are the imposed loads as in 5.3.2.

The load effects of concentrated loads shall be considered where appropriate.

NOTE Guidance on the determination of weights can be found in annex A.

Where a joist or bearer is subjected to a point load deriving from a stud standing on it, it shall be

designed to resist the load resulting from that combination of loading that causes the load to be amaximum.


For satisfactory performance under each issue of concern, the calculated value of each parameterunder the nominated load shall be kept within the appropriate limiting value of the response asshown in table 10.




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Table 10 Serviceability response limits Floors

1 2 3 4 5

Issue ofconcern

Serviceabilityparameter

Load Limit of response Application

Noticeable sag Mid-span deflection () qk L/450

Gk + qk L/35015 mm

Normal floorsystem

Vibration Mid-span deflection () Gk + 0,2qk 5 mm

1,0 kN Span

m mm

Dynamicperformanceof floor

3,53,84,2

1,71,61,5

Load shared among 2 to3 joists for chipboard orplywood floor, and 3 to5 joists for concrete orbuilt-up acoustic floor

4,6

5,36,2

1,4

1,31,2

NOTE 1 Alternatively, a dynamic analysis can be performed with a loading of G + 0,2qkfor which theresponse limit is that the frequency should exceed 8 Hz.

NOTE 2 Mid-span deflection refers to the total floor system deflection.

NOTE 3 Limit of response for a cantilever may be taken as half of the values given above.

5.8.3 Floor and sub-floor bracing

Floor and sub-floor bracing and their connections shall be designed in accordance with 5.10.4.1and 5.10.4.2.

5.9 Connections

5.9.1 General

Connection elements include connection components (frame anchors, brackets, straps, plates,parts of members to be connected) and connectors (welds, bolts, screws, rivets, clinches, nails,structural adhesives).

5.9.2 Design criteria

Connection components and connectors shall be designed to satisfy the following:

a) Connection elements shall be capable of resisting design load effects arising in the connectionas the result of the design load effects in the connecting members and their supports.

b) Deformations at the connection shall be within the acceptable limits.

c) Appropriate allowance shall be made for any eccentricity at the connection.

d) Appropriate allowance shall be made for any local effects at the connections (for example, stressconcentration and local buckling).

e) The uplift forces due to wind load shall be assessed and adequate tie-down shall be provided toresist these forces.

f) The strength and serviceability of the connection shall be assessed by computation usingSANS 10162-2, if applicable, or by prototype testing in accordance with 5.11, or by information

supplied by the manufacturer, provided that proof can be provided that such information is basedon a comprehensive testing programme.




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i) The racking strength of the system shall be established by either full size prototype testing or bya rational analysis. Connection details shall be designed to resist the forces specified in 5.3 orSANS 10160.

j) The braced panels shall be effectively attached to the roof and floor structures.

Figure 19 Typical distribution of bracing walls

5.10.4 Suspended floor bracing

5.10.4.1 General

Suspended floors shall be designed to form a rigid plate that can provide lateral support to the wallsand ensure that the shape in the plan of the building is maintained under all loading conditions. Ifthe strength of the flooring is not adequate for resisting the forces acting on it and transmitting theforces to the wall or sub-floor bracing, or the rigidity is not sufficient for resisting deformation,

bracing in the plane of the floor shall be provided.

5.10.4.2 Floor joists or bearers

Floor joists rely on the floor decking to provide lateral restraint. Similarly, bearers rely on floor joiststo provide lateral restraint.

If the span of floor joists or bearers consisting of lipped channels or -shaped channels exceeds4 m, the joists should be secured against rolling at points along their length not further than 3 mapart by bridging as shown in figure 20, or by another effective method.

All joists and bearers shall be secured against toppling or rolling at all supports.




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5.11.3 Establishment of design values for a specific product using prototype testing

5.11.3.1 General

When the design resistance Rd, for a specific product is established by prototype testing of thatproduct the following conditions shall be satisfied:

a) the minimum number of tests shall be 3;

b) the design value Rdshall satisfy:

Rd(Rmin./kt)

where

Rmin. is the minimum value of the test results;

kt is the sampling factor as given in table 11.

NOTE The condition of the product under test should be the same as the condition of the product in use.

Table 11 Sampling factor kt

1 2 3 4 5 6 7

Coefficient of variation of structural characteristics

kscNumber oftest units

5 % 10 % 15 % 20 % 25 % 30 %

3 1,15 1,33 1,56 1,83 2,16 2,564 1,15 1,30 1,50 1,74 2,03 2,37

5 1,13 1,28 1,46 1,67 1,93 2,23

10 1,10 1,21 1,34 1,49 1,66 1,85

100 1,00 1,00 1,00 1,00 1,00 1,00

5.11.3.2 Interpolation of values obtained by prototype testing

When prototype testing is conducted for a range of a specific parameter (for example span), toestablish design values for a specific product in accordance with 5.11.3.1, it is permissible tointerpolate the obtained results for that parameter provided that there is no change in structural

behaviour (for example no change in collapse mode) within the interpolating range.

No extrapolation of test values is permitted.

5.12 Construction of the steel frame

5.12.1 Introduction

Buildings can be highly vulnerable during construction. An incomplete building is still required to besafe for the people on site. The actions that need to be taken depend on the method ofconstruction.




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5.12.2 Factors to be considered during construction

The following factors shall be considered:

a) The partially complete structure may be subjected to a variety of loadings (see 5.3.4).

b) Regulatory safety requirements for workers in accordance with the relevant national legislation(see foreword).

c) Provision of scaffolding and barriers, particularly those that rely on the building frame for support.

d) Temporary bracing and tie-down during the installation of permanent bracing and tie-down.Particular care should be taken to provide adequate temporary bracing for the lower storey ofmulti-storey construction where racking loads are significantly higher than those in single storeybuildings.

5.13 Tolerances5.13.1 Manufacturing and assembly tolerances

5.13.1.1 Sections

The tolerances for cold-formed sections shall be determined such that the relevant actual sectionalproperties differ by not more than 5 % from the design section properties.

5.13.1.2 Length

The length of a component shall not deviate from its specified length by more than 2 mm.

5.13.1.3 Straightness

A component that is specified to be straight, shall not deviate about any axis from a straight linedrawn between the end points by more than L/1000 or 6,0 mm, whichever is less.

5.13.1.4 Assembly

Assembled wall panels shall each not deviate from the specified dimension by more than:

Length: +2, 4 mm;

Height: 2 mm.

The height of assembled roof trusses may not deviate by more than 10 mm from the specified

dimension.

5.13.2 Installation tolerances

5.13.2.1 Attachment to supporting structure

For load-bearing walls (including shear panels), gaps between the bottom plate and the concreteslab greater than 3 mm shall be packed with load-bearing shims under each stud. For non-load-bearing walls, gaps greater than 3 mm shall be packed with load-bearing shims or grouted at jambstuds and points where the bottom plate is fastened to the slab. Where the gap under the bottomplate exceeds 10 mm the space between the bottom plate and the slab shall be filled with groutafter installation of the shims.

For the attachment of floor joists, bearers, trusses and rafters to walls, where the gap exceeds3 mm, the gap shall be packed with load-bearing shims.




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5.13.2.2.5 Flatness of walls for installation of linings

The flatness of an individual wall that is to be lined shall be such that when a 1,8 m long straight

edge is placed parallel to the wall face, the maximum deviation from the straight edge does notexceed 3 mm over 90 % of the area, and does not exceed 4 mm over the remaining area.

5.13.2.3 Trusses, rafters, ceiling joists and floor members

5.13.2.3.1 Position

Trusses, rafters, ceiling joists and floor members shall be positioned within 20 mm from theirspecified position.

5.13.2.3.2 Straightness

Trusses, rafters, ceiling joists and floor members shall be installed so that they will not deviate from

a straight line by more than L/500 where Lis the length of the member (see figure 23).

The difference in the level of points on adjacent members that are intended to be on the same levelshall not exceed 1/150 of the spacing of the members or 6 mm, whichever is less.

L = length of member

Figure 23 Straightness of members

5.13.2.3.3 Plumb

Out of plumb at any point along the length of the truss from top to bottom, shall not exceed h/100unless the trusses are specifically designed to be installed out of plumb (see figure 24).




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Figure 25 Vertical alignment of members

5.14 Durability and corrosion

5.14.1 Steel structure

Steel covered by wall or roof cladding, or surrounded by sub-floor walling, and not within 500 m ofthe sea, as well as steel that is not covered by cladding or surrounded by sub-floor walling, and notwithin 10 km of the sea or within a heavy industrial area, shall be continuous hot-dip galvanisedsheeting with minimum coating class Z200, or a coating with corrosion resistance at least equivalentto 100 g/m

2galvanising, per side. An appropriate higher level of corrosion protection is required for

steel structures located closer to the sea or within heavy industrially polluted areas.

Wherever galvanised steel has been welded or cut by flame, the affected areas shall be paintedwith a zinc-rich paint having at least 85 % of zinc in the dry film.

5.14.2 Fasteners

5.14.2.1 The minimum specification for corrosion protection of fasteners is supplied in table 12.




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Table 12 Corrosion protection requirements for fasteners

1 2 3 4 5

Coating

classcApplication Location in building

Ease of

accessa Atmosphere

b

min.

Difficult Inland C2Inside building envelope

Difficult Aggressive C2

Easy Inland C2Steel wall frames

Outside building envelopeEasy Aggressive C3

Difficult Inland C2Ventilated roof cavity


Difficult Inland C2Trusses

Unventilated roof cavity


Difficult Inland C2Wall frame anchors Inside building envelope


Easy Inland C2External cladding Outside building envelope

Easy Aggressive C3

wet rooms'Easy Internal Regular

condensation C2Internal lining, ceilings

all other rooms Easy Internal Dry C1

Easy Inland C2d

Roofing Outside building envelopeEasy Aggressive C3

d

a

For inspection and maintenance.

b Aggressive: Marine environment (500 m to 10 km from the sea), or industrially polluted

atmospheres. Inland: All other environments.

c Coating class defines the corrosion resistance requirements. (See 5.14.2.2.)

d Subject to requirements of SANS 1273.

5.14.2.2 Test for compliance with coating class requirements: Screws shall be driven into agalvanized sheet of at least 15 mm thickness, then removed and mounted on an inert material fortesting. The significant surface (i.e. head and un-driven shank) shall be evaluated. Salt fog testsshall be made in accordance with SANS 7253, with an additional 240 hours of UV exposure beforethis for fasteners with organic coatings. The UV requirements shall be in accordance with

ISO 11997-2, as follows:

a) Lamps and wavelength: UVB 313/280 nm

b) Cycle: 4 h UV/60 C, 4 h condensation/50 C

For C1 after exposure for 72 h, C2 after 240 h, and C3 after 1 000 h, no more than 5 % of thesignificant exposed surface shall show red rust and there shall be no blistering of the coating.

5.14.2.3 Fasteners of the coating types in table 13 comply with the test requirements for therespective coating classes.




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Table 13 Corrosion protection requirements for fasteners

1 2 3

Minimum coatingthicknessCoating class Coating type

m

C1 Electroplated zinc 4

Electroplated zinc 12

Mechanically plated zinca 17C2

Mechanically plated tin-zinc (20 % Sn, bal Zn)a 12

Electroplated zinc 30

Mechanically plated zinca 40

Mechanically plated tin-zinc (20 % Sn, bal Zn)a 25

C3

Hot-dip galvanized 30a The porosity of mechanically plated coatings requires microscopic examination of a

cross section through the coating, at 500 magnification. It shall be carried out over asuitable flat surface on the head of the fastener. No continuous through thicknessporosity shall be evident.

5.14.2.4 Fasteners not inside the building envelope and not washed by rain (for example underoverhangs) in marine and industrial environments, require additional protection against corrosion,such as organic coatings.

5.14.2.5 Fasteners or the packaging (or both) should be acceptably marked to show compliance.

5.14.2.6 Manufacturers of rivets should provide evidence that rivets, once installed, have durabilityrequired by the design, i.e. life expectancy equivalent to that of the materials being connected andcompatibility with those materials.

5.15 Support of wall cupboards and fittings

Noggings or other structural elements of sufficient strength shall be provided as required to supportfittings such as kitchen cupboards or sanitary fittings and taps.

5.16 Earthing

The steel frame shall be properly electrically earthed to comply with SANS 10142-1.

6 Walls, roofs and suspended floors

6.1 Scope

The requirements of this section cover the cladding, insulation, waterproofing and other materialsattached to or installed between the elements of the steel frame. Windows, doors and otherinstallations for ventilation such as, natural lighting are excluded. Specific information is provided fordomestic dwellings. All buildings shall be designed to meet the requirements of the relevant nationallegislation (see foreword) for such buildings, and any additional applicable requirements.




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6.2 General requirements

6.2.1 Damp and weatherproofing

Roofs, floors and external walls shall prevent the ingress of moisture from outside the buildingenvelope that can affect the health or comfort of occupants.

6.2.2 Durability

The building shall, with appropriate maintenance, be able to survive for its design life.

6.2.3 Energy efficiency

6.2.3.1 General

The building shall facilitate, through its thermal performance, the efficient use of energy for artificialheating or cooling, while providing an acceptable indoor environment for its occupants or theprocesses conducted in the building.

A number of factors impact on the thermal efficiency of a building, such as roof colour, orientation ofthe building, area and type of glazing, shading for windows, sealing against uncontrolled air flowand insulation of walls, ceilings and floors (see SANS 204-2). Only the limitation of uncontrolled airflow and insulation are addressed in this standard.

South Africa has been divided into six climate zones (see figure 26). The recommended R-valuesbelow are based on the climatic conditions in each zone.

6.2.3.2 External walls

In order to meet the requirement of 6.2.3.1, the external walls of a domestic dwelling shall meet thethermal insulation requirements in table 14. Where a garage is attached to a domestic dwelling,either the outer wall of the garage, or the wall separating the garage from the domestic dwelling,shall meet the requirements in table 14.




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Figure 26 Map of climate zones in South Africa

Table 14 Minimum required R-value (m2k/w)) of thermal

insulation for external walls of domestic dwellings

1 2 3

Climate zone

1, 4 or 6 2, 3 or 5

Required R-value

Building

(m2K/W)

Category 1 buildings 0,32 1,14

All other buildings 2,20 1,90

NOTE The climate zones for South Africa aredefined in figure 26.

6.2.3.3 Roofs and ceilings

The combination of roof and ceiling insulation of a domestic dwelling shall meet the thermalinsulation requirements in table 15.




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Table 15 Minimum required R-value (m2K/W) of thermal

insulation for roofs and ceilings of domestic dwellings

1 2 3 4 5 6 7

Climate zone

1 2 3 4 5 6

Direction of heat flow

Upwards UpwardsUp- and

downwardsUpwards Downwards Upwards

Required R-value

Building

m2K/W

Category 1 buildings 2,22 1,92 1,62 2,22 1,62 2,10

Other buildings 3,70 3,20 2,70 3,70 2,70 3,50

NOTE 1 The climate zones for South Africa are defined in figure 26.

NOTE 2 The required R-values and the direction of heat flow assume that a domestic dwelling willhave a greater degree of occupancy during the night than during the day.

6.2.3.4 Floors

6.2.3.4.1 With the exception of climate zone 5, a concrete slab-on-ground shall have insulationinstalled around the vertical edge of its perimeter which shall

a) have an R-value of not less than 1,0,

b) be water resistant in order to retain its thermal insulation properties,

c) be continuous from the adjacent finished ground level

1) to a depth of not less than 300 mm, and

2) for the full depth of the vertical edge of the concrete slab-on-ground,

d) with an in-slab heating system, shall be insulated underneath the slab with insulation having aR-value of not less than 1,0.

6.2.3.4.2 With the exception of climate zone 5, a suspended floor that is part of a buildingsenvelope shall have insulation installed

a) for climate zones 1 and 2, with a partially or completely unenclosed exterior perimeter, whichshall achieve a R-value of 1,5,

b) for climate zones 3, 4 and 6, with a partially or completely unenclosed exterior perimeter, whichshall achieve a R-value of 1,0.

c) with an in-slab heating system, around the vertical edge of its perimeter and underneath the slab,having a R-value of not less than 1,0.

d) The insulation shall be water resistant in order to retain its thermal insulation properties.




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6.2.4 Acoustic insulation

The acoustic insulation in a building shall ensure that its occupants can use it for its normal

purposes without being unduly disturbed by noise coming from adjacent rooms or from outside, orbeing concern

Documents

SANS 517:2009 Light Steel Frame Building