Justin Smith

I believe you are referring to imperfections etc when deigning the falsework. The new DR AS 3610.2 addresses this. It is currently out for public draft. Z36 (mentioned above) is a great design hand book but was published 7 years ago and will need a some updates when it comes to falsework design. The proposed  new formwork standard has a dedicated falsework section.

Public draft period for DR AS 3610.2 closes 06/04/2021

The problem with scaffold is that in order to design it properly, you are doing a very advanced analysis. I'm self taught, in-so-far as I have tested scaffold systems and then altered the design software input to mimic the behavior of the scaffold. 

To answer your question, I have never come across any design guides for scaffold design at an advanced engineering level. 

I tend to use falsework design journals articles and standards as it is the same as scaffold in structure (but much less load applied in scaffold). 

I have not found a rich vein in scaffold design journal articles, the ones that I have seen are mainly focused on wind design. 

For engineering design I recommend the classic structural beam element software packages (Microstran, Spacegas etc). But you must have the ability to use in-member axial and rotational springs. Any of the big boy advanced FEA software, such as Stand7, can do it as well, just a bit more complex. I would use the more advanced FEA for R&D of scaffold systems. 

I would keep having those arguments. The wind load is only appropriate for when installing hoarding on Mars... 

I don't know what members were on the code committee that put together AS 4687 but my experience of code committees, especially for minor codes that don't attract academics specialised in the relevant industry results in codes that support the suppliers of the product in the given industry. 

Wow... artisans... I would not describe the laborers installing backprops as that!

However, there is no way to practically measure how much preload is in a prop short of using load cells or strain gauges - which are a long way from practical. 

Live load is detailed in AS1576.1

Common loads are:

Light duty - 225kg/bay - typically general access only. 

Medium duty - 450kg/bay - the most commonly specified. 

Heavy duty - 675kg/bay - used for demolition, formwork protection, heavy construction like laying blocks. 

No, not from the airport authorities. 

They just sent out a drone to make sure we did not exceed height and sent the fine in the mail if we did exceed height...

Reo cages are truly horrible to model. 

The number one thing is to model the bars off set from each other or your model will develop too much stiffness. Also model the wire ties as pins. I also carry out tests of the wire tie connections for the particular steel fixer where possible so that some sort of number can be assigned to the ties. You cannot rely on the wire ties for direct structural reliability, but you cannot ignore them either - or you will end up with a very impractical design. 

I never worry about the displacement as long as the bars remain elastic. It is amazing how large the displacement can get before you start to yield the bars. I highly recommend going to site and watching a reo lift. It will show you what you can get away with in term of deflection and how accurate your modelling is. 

The big killer for reo cages is the joint strength. Failures on site that I have observed have been distortion/yielding of the 'church' bars (top lifters) owing to inadequate bracing and bar capacity and the welds/wire ties snapping owing to lifting chains binding and applying massive shear loads that were not allowed for. 

Good luck with reo cage lift design - do not under estimate it!

The draft for public comment AS3610.2:2021 has just been released!!!!!🥳

There is no ability in the Australian scaffold industry at this stage to monitor scaffold reuse. The equipment is reused constantly and is discontinued when it can no longer be serviced. Fatigue is not an issue. But the scaffold becomes bent over time and joints are essentially smashed out of shape due to the hammering they take when being done-up and released. 

Badly bent equipment, especially if in direct compression, must be replaced or reinforced if seen during a site inspection. For engineering I would recommend L/300 out of straight (the allowance for tube in AS3610). Obviously the capacity of the tube must be down graded as steel designed to AS4100 is L/1000. 

AS3610: 1995 has always had the requirement for a 1.3 (30%) increase in FW loads when designing for the strength limit state. AS3610.2 2021 DRAFT also has the requirement for 1.3 LF. This is over and above the 1.25 continuity requirements for a 2 span support. 

The 1.3 factor is essentially an adjustment between limit state and permissive stress and also based on field studies that showed loads were +/- 30-40% of what was predicted by area tributary methods for determining leg loads. The main reason is for timbers spanning over a support owing to small gaps between jacks and headers. Note that the factor does not need to be applied for single span systems (single joist span and single header span as is the case with most modular systems).