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Cyclonic Area D esign M anual

Cyclonic Area D esign M anualSte el Roofing and Walling

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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

values.

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

consideration.

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.

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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

steel.

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

requirements.

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

projects.

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

detail.

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 . , , . . . , , . . , , . . . , , . . , , . . , , . . . , , .

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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

hemishpere.

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

numer