Scaffold Calculations
Prior to erecting any Scaffold, it is necessary to determine the expected loads on the proposed Scaffold this informs what "Duty Rating" of Scaffold must be used, this and the working height not only determines the quantity of Scaffold but also the expected "Dead Load", the capacity of the supporting surface to support the expected Scaffolds combined Loads is also considered, this is known as "Bearing Capacity", all of which is used to determine support requirements such as minimum size of Soleplate that is required to sufficiently support the Scaffold on the supporting surface.
Scaffold Quantity
The Method for Calculating Scaffold Quantities required for a Job will vary depending on job specific details such as;
Is the site is sloping or level
Is scaffold required around the whole perimeter of the structure or only some of the structure
Doe's the Job require one "Work Platform" or is more than one required
What width of Platform will be used
Are "Hop Ups" required, at what height will the "Work Platform" be
Are "Ladder Beams" required to Span across openings
and the list goes on.
But the Basic principals are that the number of "Bays" that are required around a structure is calculated using the "Into Over" method, while the amount of components is more subjective and based on variables such as, Height and Number of Work Platforms, and Length of each "Run" of Scaffold Bays, these Calculations are made easier by drawing a "Sketch Plan" of the Scaffold and each Run of "Bays" calculated separately as follows;
The Number of Screwjacks may be simply counted off the "Sketch Plan"
The Number "Standards" is calculated by first determining the total Lineal metres of "Standard" required then making up the total Lineal metres with a combination of different Lengths of Standard (it is necessary to have combinations of different lengths of "Standard" as Joins in "Standards" must be staggered)
Transoms and Ledgers must generally be no greater than 2.000m apart (vertically), additional Transoms and Ledgers will be required where used for "Handrail" and "Midrail"
The Number of Planks will depend on the width of "Work platform" and the Number of Platforms including Hop Ups
The Number of "End Braces" will depend on the Height of the Scaffold and the number of ends to be Braced
The number of "Face Braces" will depend on the Height and Number of Bays per Run of the Scaffold
So as you can see, it take a good understanding of Scaffold components and Job requirements to calculate Scaffold Quantities
Is the site is sloping or level
Is scaffold required around the whole perimeter of the structure or only some of the structure
Doe's the Job require one "Work Platform" or is more than one required
What width of Platform will be used
Are "Hop Ups" required, at what height will the "Work Platform" be
Are "Ladder Beams" required to Span across openings
and the list goes on.
But the Basic principals are that the number of "Bays" that are required around a structure is calculated using the "Into Over" method, while the amount of components is more subjective and based on variables such as, Height and Number of Work Platforms, and Length of each "Run" of Scaffold Bays, these Calculations are made easier by drawing a "Sketch Plan" of the Scaffold and each Run of "Bays" calculated separately as follows;
The Number of Screwjacks may be simply counted off the "Sketch Plan"
The Number "Standards" is calculated by first determining the total Lineal metres of "Standard" required then making up the total Lineal metres with a combination of different Lengths of Standard (it is necessary to have combinations of different lengths of "Standard" as Joins in "Standards" must be staggered)
Transoms and Ledgers must generally be no greater than 2.000m apart (vertically), additional Transoms and Ledgers will be required where used for "Handrail" and "Midrail"
The Number of Planks will depend on the width of "Work platform" and the Number of Platforms including Hop Ups
The Number of "End Braces" will depend on the Height of the Scaffold and the number of ends to be Braced
The number of "Face Braces" will depend on the Height and Number of Bays per Run of the Scaffold
So as you can see, it take a good understanding of Scaffold components and Job requirements to calculate Scaffold Quantities
Bearing Capacity
Bearing Capacity of the Foundations is determined by a Geotechnical Engineer, this is done prior to Construction activities ,and is given in Kilopascals, however to make the appropriate calculations Kilopascals (Kpa) must be converted to Kilograms per square metre (Kg's/m2).
mastertradeskills.com has developed calculators such as the "Kpa to Kg's/m2 Converter" (below) which is available for Free for you to check your "Kpa to Kg's/m2" conversion. mastertradeskills.com's "Soleplate Length Calculator" is available on the Scaffold Soleplate Calculations page (Premium Content) 

Soleplate Length
Calculating the Correct size of a Soleplate is essentially determining the size of the area that a soleplate needs to be to support the load that will be on the Soleplate for the site specific conditions (Bearing Capacity), each Soleplate is calculated separately as each Soleplate will support different Loads (Typically the worst case scenario is calculated so that the Largest Soleplate is used Throughout, however this can be an inefficient use of materials) , the Soleplate area is divided by the width of the Soleplate to determine the length that the Soleplate needs to be, but first the "Total Load" needs to be determined, the "Total Load" is a combination of the "Dead Load" which is the sum of the "portions" of all the Scaffold Components that are being supported by that individual Soleplate, and the "Live Load" which is the "portion" of the "Live Load Duty Rating" for each "Work Platform" that is being supported by the Soleplate, the "Total load" is then divided by the sites Bearing Capacity to determine the minimum amount of area that the Soleplate needs to be.
The Formula for Calculating Soleplate length can be found in section 8.3 of A.S.4576, these Calculations should only be carried out by a "Competent" person, as some Soleplates will fall under the Special Design criteria, and errors can be catastrophic. The advice in relation to Scaffold on mastertradeskills.com is intended specifically for scaffold no greater than 4 metres to the highest "Work Platform" and/or not requiring a Licence 
The Soleplate Length Calculator is available on the Scaffold Quantity Premium Content page (Purchase Premium page Now)

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