wind guidance note -reva

5/27/2018 Wind Guidance Note -RevA

1/11

LiftingIndustry Standards

Engineers Guidance NoteDynamic Wind Loadings Mobile CranesAuthor: The Crane Industry Council Australia Rev. ADate: 09/01/2014


2/11

Page 2 of 11 LiftingIndustry Standards

Table of Contents

1. Purpose ..................................................................................................................................... 3

2. Background ............................................................................................................................... 3

3. Measuring Wind Speed ............................................................................................................ 3

4. Further Information ................................................................................................................... 3

5. Allowable Wind Surface Area to Load ratio ............................................................................ 4

6. Allowable Wind Surface Area................................................................................................... 4

7. Dynamic Wind Pressure ........................................................................................................... 4

7.1. Wind pressure for given wind speeds ................................................................................ 5

8. Surface Area.............................................................................................................................. 6

8.1. Load Surface Area ............................................................................................................. 6

8.2. Drag Coefficient ................................................................................................................. 6

8.3. Wind Surface Area ............................................................................................................. 8

9. Permissible Wind Speed .......................................................................................................... 9

9.1. Permissible Wind Pressure ................................................................................................ 9

9.2. Permissible Wind Speed .................................................................................................... 9

9.3. Wind Force ........................................................................................................................ 910. Simplified calculation charts ................................................................................................. 10

Disclaimer and Copyright

This CICA Engineers GuidanceNote has been compiled for general information only, is not to be considered as a substitute forprofessional advice, and should not be treated as an exhaustive statement on the subject. The Crane Industry Council of Australia (CICA)accepts no responsibility for the accuracy, completeness or currency of the material included in this CICA Engineers Guidance Note.

Users of this CICA Engineers Guidance Note are encouraged to obtain professional advice and to exercise their own skill and care inrelation to any of its material.

CICA disclaims any and all liability or responsibility for any loss or damages arising out of any use of, or reliance on, this CICA EngineersGuidance Note.

This CICA Engineers Guidance Note is copyright. Readers may use and reproduce this material in an unaltered form only for non-commercial use within their own organisation. Apart from any use permitted under the Copyright Act 1968, all other rights are reserved.


3/11


1. Purpose

To provide assistance for mobile crane users in determining reduced permissible wind speeds basedon load surface area in accordance with design standards and manufacturer load charts. This willassist in determining safe operating conditions for the mobile crane.

2. Background

A mobile crane is subject to wind speed limitations during lifting, erection, dismantling, and also whenout-of-service.

The default Loadchartwindspeed for cranes designed to AS1418.5-2002 Clause 3.3.2 is 10 m/sbut typical values vary from 9-16 m/s and may be as high as 20 m/s. The Load chart wind speedvaries on manufacturers specifications and may be dependent on boom length &/or sequence. Somemanufacturers also permit higher wind speeds if the Load chart capacityis reduced in accordance

with their specific calculations or tables.

Most manufacturers and design standards clearly state appropriate limitations; however crane usersmust be aware that the wind speed nominated on the load chart during lifting is normally calculatedfor a given Wind Surface Area.

In summary, this is due to loads of different surface areas producing different loads to the crane andin particular side load to the boom. Examples loads of the same mass producing different windrelated loads to the crane could be formwork shutters compared to an electric motor.

Dynamic Loading due to wind pressure is a function of wind speed. As can be seen in the DynamicWind Pressuresection increased load from higher wind speeds is squared (i.e. twice the wind speedmeans four times the wind pressure).

3. Measuring Wind Speed

It should be noted that the wind speed can vary between ground level and the boom tip or load height.The use of anemometers attached to a pendulum arrangement on a boom tip can be an excellentmeans to assess the conditions.

4. Further Information

This guidance note contains summary information only and further information and a listing of CICA

recognised Crane Engineers is available by contacting the Crane Industry Council of Australia:

Contact details

Postal address PO Box 136, Mount Waverley, Victoria, 3149

Street address Unit 10, 18-22 Lexia Place, Mulgrave, Victoria, 3170

Telephone +61 3 9501 0078

Fax +61 3 9501 0083

Email [email protected]

Website www.cica.com.au
http://c/Users/Engineer/AppData/Local/Microsoft/Windows/Temporary%20Internet%20Files/Content.Outlook/VGMWJTRR/[email protected]://c/Users/Engineer/AppData/Local/Microsoft/Windows/Temporary%20Internet%20Files/Content.Outlook/VGMWJTRR/www.cica.com.auhttp://c/Users/Engineer/AppData/Local/Microsoft/Windows/Temporary%20Internet%20Files/Content.Outlook/VGMWJTRR/www.cica.com.auhttp://c/Users/Engineer/AppData/Local/Microsoft/Windows/Temporary%20Internet%20Files/Content.Outlook/VGMWJTRR/[email protected]


4/11


5. Allowable Wind Surface Area to Load ratio

Many Manufacturers nominate an allowable Wind Surface Area to Loadratio, normally given in m2/tonne, within their load chart or operators manual. The load to be lifted needs to be compared to thisratio and either the Wind Surface Areakept below this value or the maximum permissible windspeed reduced.

For cranes designed to EN1300 this value is typically 1.2 m2/tonne (unless otherwise specified by themanufacturer). It should be noted however different manufacturers specify different allowable windareas. Another common allowable wind area for hydraulic boom cranes is:

( ) 6. Allowable Wind Surface Area

The AllowableWind Surface Area can be calculated as follows:

Example: If a load chart or operators manual nominates a total Allowable Wind Surface Areaof 1.2m2/ tonne and the chart capacity is 10 tonne a load with a Wind Surface Areaof 12 m2can be safelylifted at the Load chart wind speed.

If the Wind Surface Area of a load is less than total allowable no further calculations need to bemade. However if the Wind Surface Area of a load is greater than total allowable further calculationsneed to be made to determine the Permissible Wind Speed.

7. Dynamic Wind Pressure

Dynamic Wind Pressureis a quasi-static measure of the pressure being exerted by wind on a loadcalculated as follows:

Where

Example


5/11


7.1. Wind pressure for given wind speeds

Wind speed

Dynamic pressure

( )

8 40

10 63

12 90

14 123

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14

DynamicWindPressure(N/m2)

Wind Speed (m/s)

Wind pressure


6/11


8. Surface Area

The total Wind Surface Areaof a load must be calculated to determine the effect the Dynamic WindPressurewill have on the load. This is calculated by multiplying the Load Surface Areaby the DragCoefficient.

8.1. Load Surface Area

The Load Surface Areais the net area of a load projected to the horizontal. This should becalculated taking into account the worst case, assuming that the wind blows from the mostunfavourable direction. Anything considered a load to the crane, including rigging, must be taken intoaccount.

Example

20 foot container

8.2. Drag Coefficient

The Drag Coefficient is a dimensionless measure of a shapesresistance to wind pressure. Thetable below gives values for common shapes. Further drag coefficients are given in AS1170.2-2011.

When in doubt the manufacturer of the load or engineer should be called upon to provide a dragcoefficient.


7/11


Profiles, angles, box sections (small) f/b Cd

50 1.9040 1.70

30 1.6520 1.6010 1.355 1.30

Tubes f/b Cd

dV < 4.645 m2/s

whereV = wind speed, m/sd = diameter, m

50 1.10

40 1.00

30 0.95

20 0.90

10 0.80

5 0.75

dV 4.645 m2/s 50 0.8040 0.7530 0.7020 0.7010 0.655 0.60

Large box sections over 350 mm square& 250 mm x 450 mm rectangular

f/b Cd

40 2.2030 2.1020 1.9510 1.755 1.55

40 1.930 1.8520 1.7510 1.555 1.4

40 1.430 1.3520 1.3010 1.205 1.00

40 1.0030 1.0020 0.9010 0.905 0.80

Flat plates f/b Cd

80 2.0060 1.8540 1.7520 1.5015 1.4010 1.305 1.20


8/11


Wire rope 1.20

Latticed frames

Cd

Single frames, wind normal toface (use shielding factorformultiple frames)

Profiles, angles,box sections,plates

0.05 1.950.10 1.900.20 1.750.30 1.600.40 1.450.50 1.45

Tubular members dV < 4.645 m2/s 0.05 1.30

0.10 1.250.20 1.200.30 1.100.40 1.05

0.50 1.05dV 4.645 m2/s 0.80

Assembled frames, square or triangular, wind normal to face CdSquare frames ofprofiles, angles,box sections,plates


9/11


9. Permissible Wind Speed

If the Wind Surface Areacalculated is greater than the Manufacturers nominated a Wind SurfaceArea / Loadratiothe Permissible Wind Speedmust be reduced to create the equivalent total loadto the crane.

9.1. Permissible Wind Pressure

The Permissible Wind Pressureis calculated as follows:

Example: Using previous values, crane 10 tonne capacity and 12 m/s Load chart wind speed:

9.2. Permissible Wind Speed

The Permissible Wind Speed can now be determined:

Example: Using previous values

This resultant permissible wind speed should be compared against the maximum operable windspeed nominated by a manufacturer for the required crane configuration.

The manufacturers maximum limit should never be exceeded.

9.3. Wind Force

The Dynamic Wind Pressureand Wind Surface Areacan also be used to calculate the WindForce, F, as a result of the wind is calculated as;

Using the previous example of 20 foot container with 8.8 m/s wind speed:

This can be checked against the force from theAllowable Wind Surface Area to Load ratio.


10/11


10. Simplified calculation charts

Reduced allowable wind speeds based on 9 m/s load chart wind speed

Load

(T

e)

Load surface area with drag coefficient (m2)

Reduced allowable wind speeds based on 11 m/s load chart wind speed

Load

(Te)



11/11


Reduced allowable wind speeds based on 12.8 m/s load chart wind speed

Load

(Te)

Load surface area with drag coefficient (m

2

)

Reduced allowable wind speeds based on 14.3 m/s load chart wind speed

Load

(Te)


wind guidance note -reva

Documents

wind speeds

wind force

permissible wind pressure

permissible wind speed

allowable wind surface

wind guidance note reva

dynamic wind pressure

cica engineers guidance