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Cyclonic Design Manual

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  • 8/12/2019 Cyclonic Design Manual



    Cyclonic Area D esign M anual

    Cyclonic Area D esign M anualSte el Roofing and Walling

  • 8/12/2019 Cyclonic Design Manual



    Contents and introductionContents

    Introd uction . . . . . . . . . . . . . . . . . .2

    Full Support of BlueSco pe

    Lysaght . . . . . . . . . . . . . . . . . . . . . .3

    Tropical C yclones a nd Wind fo rces

    on Buildings . . . . . . . . . . . . . . . . . .4

    Loca l Pressure Areas . . . . . . . . . . .5

    Test ing o f Roo fing & Wa lling

    Profiles . . . . . . . . . . . . . . . . . . . . . .6

    Selection Tab les . . . . . . . . . . . . .7-8

    Installation Details . . . . . . . . . . .9-10

    Wind Classificat ion . . . . . . . . . . . .11

    Topo g raphic Classificat ion . . . . . .12

    De sig n Tab les . . . . . . . . . . . . .13-15

    Please note:

    The d at a co nta ined in this manual

    wa s estab lished b y tests using

    BlueScope Lysaght roofing and

    walling products. It cannot beassumed to app ly to seemingly

    similar p roducts from ot her

    manufacturers, and BlueScope

    Lysag ht w ill not b e he ld responsible

    for the st ructural integ rity o f any

    structure designed using this data

    and products not of BlueScope

    Lysag hts manufact ure.

    Engineers should take note, this

    document is a limited edition

    interim reprint of our earlier design

    guide, and table values arepermissible values, not limit state


    Northern Australia, a s with ot her

    tropical areas, is prone to be

    affected by tropical cyclones.

    Because o f the nat ure o f cyclones

    and the wind speeds associated

    with them, the de sig n of b uildings

    locat ed in cyclone p rone a rea s and,

    in particular, the fixing of building

    components requires special


    Cyclone Tracy, which de stroye d

    Darwin on December 25, 1974,

    drew a ttention to the larg ely

    unrecog nised fa ct that the

    performance of sma ll building s is as

    important, perhaps even more

    important, tha n the pe rformance of

    large ones. It a lso d emonstrated

    that, even when human safety was

    not so crucial (loss of life due to

    building damage was very small in

    relation to t he tota l da mag e), the

    socio-eco nomic cost o f such

    damage justifies placing high

    priority on the safety aspects of

    small buildings as well.

    One aspect of cottage building

    which wa s g raphically illustrated by

    Cyclone Tracy w as t he importa nce

    of the roof fixing and the fixing of

    its suppo rts. Flying de bris was t he

    cause of many broken window s

    which allowed a build-up of

    pressure inside . The resulting

    upward force on the roof was

    responsible for numerous instance s

    of whole roof structures being

    blown o ff.

    Therefore, it is not eno ugh to simply

    ensure the strength of roof fixing.

    Rather, it is nece ssary that all

    connections of building components

    be a deq uate to withstand the

    expected uplift forces.

    This ma nual, produced by

    BlueScope Lysaght, is a supplement

    to, a nd should b e used w ith, the

    BlueScope Lysaght Roofing and

    Walling Installat ion Ma nual.

    It was prepared to assist architects,

    engineers and builders in the

    correct spe cificat ion a nd installat ion

    of BlueSco pe Lysag ht roofing and

    wa lling prod ucts in cyclonic area s.

  • 8/12/2019 Cyclonic Design Manual



    The full support ofBlueScope LysaghtAt BlueScope Lysaght, we have a

    trad ition of q uality to live up t o - atradition that g oes b ack over 130

    years to w hen the orig inal John

    Lysaght be g an supplying steel

    roofing t o Australia.

    Ever since we began manufacturing

    in Australia, we have branded our

    products with a symbol of quality.

    Its a trad ition we still follow to da y.

    All our roofing products are

    branded with our company name,

    the base metal thickness of the

    steel, the yeild stress, the applicable

    Australian sta ndard and the a mountof protective coa ting per squa re

    metre for ZINCALUME or COLORBOND


    So look for the BlueScope Lysaght

    edge markings when you buy - its

    your assurance o f q uality.

    Our reputat ion fo r qua lity, howe ver,

    g oes b eyond just providing the b est

    prod ucts at comp et itive p rices. It is

    also based on our aim of providing

    a b ette r service than you can ge t

    anywhere e lse.

    This Cyclonic Area De sign Ma nual is

    just one example of a rang e of

    te chnical lite rature tha t is

    recognised as being the most

    comprehensive in the business. Any

    of our brochures are available free,

    on req uest, at BlueScope Lysaght

    Sales O ffices.

    We provide a te chnical ad visory

    service fo r all of o ur custome rs as

    well, where our engineers are

    always available to discuss new

    applications for our roofing andwa lling p rod ucts. They w ill make

    suggestions and advise on

    specifications. In short, they will

    wo rk with you to de velop t he be st

    way to meet your design


    And o n top of that , there is the

    special Warranty, ob ta inab le from

    our offices simply by asking.

    At BlueScope Lysaght, were so

    confide nt we ma ke the b est q uality

    steel roofing and walling products inAustralia, w e ca n g uarantee t hem,

    in writing , for up to 25 years on

    your comme rcial a nd industrial


    Simply by a sking for it a t a ny of o ur

    offices, youll get a copy of our

    wa rranty, which you can e xamine in


    Youll find tha t it b ac ks our

    products performance with all the

    strengt h of o ur 130 years expertise

    and experience, providing the

    prod uct is installed in acco rdance

    with o ur specificat ions.

    G eneral Prod ucts Performance

    Warranty . , , . . . , , . . , , . . . , , . . , , . . , , . . . , , .

  • 8/12/2019 Cyclonic Design Manual



    Tropical cyclones andwind forces on buildingsTropical cyclones

    Tropical cyclone s a re w arm c oredwind systems w hich affect t he

    coa stal reg ions of Northern

    Australia. They a re formed ove r

    warm tropical waters, where the

    temperature must be >27C when

    severe ba rometric d epressions

    occur. Hig h speed winds b low

    spirally inward from all sides to form

    a roughly circular core or eye which

    can rang e in size up to ab out 50km

    in diameter. Overall, a cyclonic wind

    system can have a diameter as large

    as 650km.The sp iralling a ction is caused b y the

    earths rotation and is clockwise in

    the southern hemisphere, a nti-

    clockwise in the northern


    Air draw n into the e ye o f a cyclone

    is carried vertically by convection

    and a pumping action generated by

    high a ltitud e w ind s. This core a ctivity

    extends up to 12km ab ove the sea.

    The a ir rising in the co re o f the

    cyclone carries with it substantial

    amounts of water vapour which

    condenses to form heavy cloud and

    rain in the area of maximum wind

    force around the core.

    The cond ensing w at er vap our

    releases vast amounts of heat

    energy w hich is expend ed enlarg ing

    the system. As cyclones extract t heir

    energy from the warm water, they

    d issipa te fairly q uickly o n rea ching

    land, b ut often not b efore doing

    tremendous damag e.

    Cyclones ususally move at speed s ofbe tw een 2 and 15 m/sec and

    be cause o f their size, high w ind

    speed s can last for many hours.

    These winds a re of a cyclic nature,

    causing sugnificant dyna mic forces

    on building components.

    These cyclic forces ca n ind uce

    fatigue in roofing mate rials, their

    supports and fixings; fa tigue which

    ofte n limits the performance o f a

    component or system. In addition,

    beca use o f the rotation of the w ind

    system, the wind direction at apa rticular po int ca n chang e 180 as

    the cyclone passes. This requiresthat building designs should nottake shielding into account unlessit is roughly equal on all sides.

    Wind Forces on Buildings

    Wind creat es a number of forces onbo th internal and e xternal surfaces

    of a building; fo rces w hich must be

    considered when d esig ning or

    selecting clad ding mat erials, their

    fastene rs and supports. These fo rces

    produce b oth p ositive pressure and

    negative pressure (suction) and their

    mag nitude is affected by the

    velocity of the wind and the

    buildings deg ree of e xposure a nd

    config uration. The resulta nt

    pressures are calculated using AS

    1170 Part 2, 1989 SAA LoadingCode - Wind Forces.

    In cyclonic areas, particular note

    should be taken of the effects of

    internal pressures o n roof a nd wa ll

    clad ding and the importance of local

    pressure areas.

    Flying debris is a significant problem

    in tropical cyclones and there are


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