Shade Sail Design Guidelines

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Shade Sail Design Guidelines
Publication: Greenline Group Pty Ltd
Shade sail design guidelines:
The purpose of this document is to provide the ‘layman’ of shade sail design in-depth
guidelines and knowledge to design shade sails that work, look good and provide value
for money.
It is typically aimed at schools, councils, builders and architects completing small to
medium shade sails for government and private projects. It doesn’t cover in detail any
highly specialised structures like large tensile membrane structures, car park structures or
membrane facades.
Shade sails are a great way of covering large areas in an attractive, functional and
economical manner. When designed and built properly, they are a long term, permanent
solution. There are several frequently raised questions and it would be best to address
these first:
Q
Are shade sails temporary structures?
No. While a shade sail can be removed if needed, the structures are typically
A
designed to be a permanent fixture and are engineered to withstand the same wind &
storms as the surrounding buildings. A properly designed and certified structure that
is correctly maintained will not ‘blow away’ or ‘fall down’ under any normal storm. Life
expectancy on a shade structure is typically 15+ years.
Q
Do you have many problems with vandals?
A
No. Structures are designed to be vandal resistant. While a determined vandal can
damage almost anything, the intent is to make the structures too hard to vandalise so the
vandals go elsewhere. This is achieved with minimum height clearances and anti-vandal
climbing devices on columns, fire retardant shade cloth and smart column location.
GREENLINE
GROUP
This picture is for illustrative purposes only. The design may vary slightly to suit the landscape.
Job:
Drawn:
Generic Shade structure Sails
3 BALL PL WAGGA WAGGA NSW 2650 FREECALL: 1800 044 200 PH: (02) 6938 1000 FAX: (02) 6938 1001 E: [email protected]
Apvd:
FP
GJN
Date:
Dwg#
21/09/2012
02
Job #
GD-09-37
© COPYRIGHT - GREENLINE GROUP PTY LTD
GREENLINE
GROUP
This picture is for illustrative purposes only. The design may vary slightly to suit the landscape.
Job:
Drawn:
Generic Shade structure Sails
Apvd:
3 BALL PL WAGGA WAGGA NSW 2650 FREECALL: 1800 044 200 PH: (02) 6938 1000 FAX: (02) 6938 1001 E: [email protected]
FP
GJN
Date:
Dwg#
21/09/2012
02
Job #
GD-09-37
© COPYRIGHT - GREENLINE GROUP PTY LTD
Publication: Greenline Group Pty Ltd
Design Standards:
Unfortunately there are very few national and international standards which
directly apply to shade sails. There are a number of Australian Standards and
sections of the National Construction Code (NCC) which apply to projects
and Greenline advises that a professional i.e. building certifier or architect,
be involved to identify and ensure compliance with all standards and codes.
Some of the common standards and codes are:
Shade specific & general construction
•
AS 1170 - structural design actions
•
AS 3600 - concrete structures
•
AS 3610 - formwork for concrete
•
AS 1671 - steel reinforcing materials
•
AS 1554 - structural steel welding
•
AS 1627 - metal finishing
•
AS 4100 - steel structures
•
AS 4174 - synthetic shadecloth
•
AS 2001 - methods of test for textiles
•
AS 1530 - methods of fire tests on building materials, components and structures
Carpark
•
AS 2890 - facilities
Lighting
•
AS 3000 - electrical installations
Playgrounds & parks
•
AS 4685 - playground equipment
•
AS 4486 - playgrounds & playground equipment
Publication: Greenline Group Pty Ltd
There are a number of key design criteria to consider when specifying or building a
shade sail structure:
•
Engineering
•
Steelwork selection & heights
•
Steelwork detailing
•
Coverage of area
•
Size of sails
•
Heights of sails
Area usage
A key item to define is the purpose of the structure:
•
What area is to be covered?
•
What times of the day/year to be covered/not covered
Sometimes it can be uneconomical to cover a full playground for all daylight hours (eg.
8am to 4pm) as the shadow from the shade sails moves drastically across the ground
throughout the day and covering a 100m² area might require a shade 3 or 4 times
the size to provide continuous shade. Consideration should also be given to adjoining
buildings/trees which can provide shade in the area.
Overshadowing of adjoining properties/areas should also be considered.
Column location
Shade sails designs should consider column location. Shade sails do not have to have
a regular or symmetrical plan area, but there are certain limits as to how irregular a
structure could be. When designing structures, try to keep the length of the sail to not
more than 70% larger than the width. Keep the larger diagonals to within 200% of the
shorter diagonals. Typical minimum/maximum spans are as follows:
Material
Light/residential duty shadecloth (>320gsm)
Medium shadecloth (320 – 370gsm)
Heavy shadecloth (370 – 400gsm)
Minimum
4m
6m
8m
Maximum
7m
14m
20m
Publication: Greenline Group Pty Ltd
Column Location:
When placing columns, consider usage of the area and surrounding structures &
buildings – key items to consider:
•
Fall zones of playground equipment
•
Pedestrian flow
•
Services ie: sewer, power, water, data below ground, & power lines above the ground (contact DBYD 1100)
Proximity to retaining walls, trenches etc
•
Posts clear of path.
Sails situated to provide best
cover from western sun



Playground covered with
no posts in fall zone.
Existing lighting, services &
flora considered in design


Posts located
away from path
areas

Publication: Greenline Group Pty Ltd
Sail Heights:
Sail heights
Shade sails require minimum ‘height difference’ or ‘fall’ across the sail
to maintain tension and look good. Typically a four post shade sail has
two high & two low points diametrically opposed to create a ‘saddle’ or
‘hypar’ (hyperbolic paraboloid) shape.
A ‘skillion’ shape can work, but exerts greater forces onto the columns
and does not maintain tension as well.
A typical guide for minimum height difference is:
Minimum height difference (m) = longest diagonal (m) ÷ 7
Height
Difference
Clearance
Height
View A
Span
View A
Low
na
l
High
High
Di
ag
o
Lo
na
ng
l
es
t
Di
ag
o
Low
High
Square Sail
Low
Low
High
Odd shape sail
(See also example on next page.)
Publication: Greenline Group Pty Ltd
Attention should be paid to the height of the infrastructure below and adjoining the proposed shade
sail. Special consideration should be given to playground equipment and climbing equipment
that the sail remains out of reach of the users. There are no standards for clearance above structure
(except the NCC which states all structures should provide greater than 2100mm head height) but
Greenline recommends the following minimum clearances.
Items being covered
Open area
ie: courtyard, pool, footpath
Playground equipment
Basketball courts etc
Caryards, fuel stations, areas
accessible by trucks
Low vandalism area
3.0m at lowest point
3.0 at lowest point
3.5m at lowest point
2.5m above platforms and acces- 2.5m above all playground
sible areas
equipment
1.0m above non-accessible turrets
& roofs etc
4.5m at the lowest point unless compliance with international
basketball standards is required
4.5m at the lowest point
Top of Turrent: Low Points: HIgh Points: 10,000
High
High
Low
4.0m high
4.0m high
6.0m high
4000
10,000
2000
Low
High vandalism area
3.5m at lowest point
Publication: Greenline Group Pty Ltd
Low point faces west
or north west to block
hot afternoon sun.
Low
High
High point faces north
east. This allows morning
sun into the area.
High
Low

N
Steelwork Selection & Detailing:
Selection of the right type of columns is critical to the final appearance and longevity of
the structure. CHS columns are the most common and work the best.

CHS round columns

RHS Rectangular
columns

UB (universal beam)
Not ideal due to
sharp corners.

PFC (parrallel flanged
channel) Not used due
to insufficient strength.
Publication: Greenline Group Pty Ltd

Pull of sail

Columns:
Columns are typically installed on a lean (or rake). This is for both aesthetics
and functionality. Shade structures are designed using high deflection analysis
software. Columns are designed to deflect (bend) within a given allowance as per
structural designs. This means that columns installed plumb have the capacity to
deflect inwards, giving the appearance of ‘falling over’. While this is not the case,
deflection is not noticeable when columns are installed with a slight lean.
Force on column
(Deflection is exaggerated)


Raked columns
Plumb columns






Columns typically are installed with between 2.5° and 5° of lean. Columns are
leaned away from the direction of pull, which is typically the approximate centre
of the sail.
Publication: Greenline Group Pty Ltd
Column detail:
It is important that columns have welded caps and lugs to prevent moisture
entering the column and rusting it out.

Welded caps and
lugs prevent moisture
entering the column.

Knock-on caps and
eyebolts let moisture
into the column.
Footing detail:
Shade sails typically have wet-set foundations. If base-plated
designs are used, ensure that the baseplate and hold-down
bolts are concealed well below the finished ground level
(generally 150mm below). See also ‘footing types’ for more
info.
Column protective coatings
There are three main types of protective coatings used on shade structure steelwork:
1.
Powdercoat
2.
Hot dip galvanising
3.
Two-pack paint
Feature
Cost
Durability
Vandal resistant
Colour choice
Process
Powdercoat
Economical
Good
Available
Large choice
Steel is sand blasted,
coated with zinc-rich
primecoat, powdercoated,
then baked
Common Brands Dulux, Interpon
Hot Dip Galvanising
Economical
Good
Good
Galv only
Steel is dipped in an acid
bath or sandblasted then
dipped in the zinc bath
-
Two-Pack Paint
Expensive
Great
Available
Large choice
Steel is sandblasted then
coated with a zinc rich
primer, a mid coat and a
top coat
Dulux
Publication: Greenline Group Pty Ltd
Force on post


Force on post
Force on
footing




Force on
footing
Footing types:
A bored pier is the most common method for
shade structure foundations in eastern Australia.
A bored pier footing relies on the lateral strength
of the soil to counter the moment forces applied
onto it.
Bored piers can be impractical in sandy soil
(low cohesion of the soil makes the sides of the
footing ‘cave in’) or rocky sites (too hard to dig) .
These sites can call for pad style footings, which
typically require significantly more concrete
than piers.
Pier Footing
Pad Footing
A geotechnical report can be conducted to determine the soil type and best footing type. Other items to
pay attention to are water table (a high water table can cause problems with excavation) or highly reactive
soils (soils that move a lot with changes in moisture level).
Pier Footing
YES
Possibly
Probably not
Probably not
Clay
Rock
Sand
High water table
Pad footing
YES
YES
YES
YES
Shade sail detailing:
 
Closed end sling
‘D’ shackle

 

Welded lugs
Hook end turnbuckle
Eyebolt in column

Publication: Greenline Group Pty Ltd
Shadecloth detailing:
Shade sails should be manufactured from a commercial
grade shadecloth. There are a number of good brands
available; Greenline recommends the following:
Parasol Protex – excellent shade mesh for small to medium
structures (up to 200m² per cover); available in 10 fire
retardant colours. UVR block of between 88.7% and 94.4%.
Nominal 325gsm. 10 year UV warranty.
Architec 400 – excellent shade mesh for medium to large
structures, available in 11 colours. UVR block of between
87.7% and 96.0%. Nominal 400gsm. 12 year UV warranty
UVR block requirements:
The only standard calling for minimum UVR block applies to
childcare centres and it calls for minimum 94% UVR block.
The small difference in UVR block between colours doesn’t
make any difference in performance and is not noticeable
to users of the area. Most shade cloths are tested untensioned anyway and will open up slightly once installed.
Fire Retardant:
Most shade cloths have some degree of fire retardancy. The
test is conducted under AS 1530 part 2 and part 3. The
actual standard does not have a ‘pass’ or a ‘fail’ but just is a
recognised method of determining the fire retardancy level
of a particular shade cloth.
Note: ‘Fire Retardant’ shade cloth means that the cloth
shouldn’t burn without a heat source. The cloth will still melt
when a flame is applied, but shouldn’t continue to burn
once the flame is withdrawn. Obviously if you have a bush
fire going through the area, the sail is still going to burn
down!
Parasol Protex
Publication: Greenline Group Pty Ltd
(which is considered fire retardant) has the following properties:
AS 1530.2
Flammability index 19 (range 0 – 100)
Spread factor 16/14 (range 0 – 40)
Ignitability index 13 (range of 0 – 20)
AS 1530.3
Spread of flame index 8 (range of 0 – 10)
It is important that sails are sewn with UV stabilised PTFE thread. ‘Standard’ cotton
threads are not UV stabilised and can deteriorate quickly.
Sails need to be designed and manufactured to take the loads applied onto them,
including specialised seams and ‘doublers’ or double thickness fabric reinforcing.
Parasol Protex Colours
Parasol Protex Colours:
Architec 400
Polyfab
Colours
POLYFX®
COMSHADE®
ARCHITEC 400®
Orange
Berry
Lemon/Yellow
Grape
Lime
Porcelain
Cappuccino
Café Noir
Sandstone
Rust
Copper
Merlot
Aquamarine
Navy Blue
Black
Slate
Blue Gum
Platinum
Light Green
Midnight Green
Colour Disclaimer: For technical reasons connected with colour reproduction, the colours shown may not be an exact representation of the actual product.
POLYFAB’S
INTERNATIONAL
DISTRIBUTION
Contact us for a distributer nearest you.
Publication: Greenline Group Pty Ltd
Need help with your next shade structure design?
Greenline specialise in providing innovative solutions to Councils for
maximising shade in public space. For a unique design suited to your
application, give one of the team a call.
FREE CALL: 1800 044 200
Ph: 02 6938 1000
Fax: 02 6938 1001
Email: [email protected]
www.greenline.com.au
Note:
Information in this publication is subject to copyright and is intended as a guide only. Greenline cannot take any responcibility for
any loss or damage arising out of use of the information supplied herein.
GREENLINE GROUP PTY LTD, 3 Ball Place, WAGGA WAGGA, NSW 2650
P: 02 6938 1000 F: 02 6938 1001 FREE CALL: 1800 044 200 E: [email protected]