Friction in AS

[Florian Dieterle]

Friction is a common topic in temporary works as often temporary stages are relying on friction and a positive connection ignoring friction would result in an design that is inefficient and could create additional risks during the operation. 

Guidance in Australian Standards (AS) on friction coefficients is limited and in this thread we could discuss different references. Friction from laboratory test are often difficult to translate into real world values due to site conditions being humid, greasy, dusty and variability in surface preparation. 

 

[Florian Dieterle]

AS 5100.4 Bridge bearings in Table 10.1 defines friction coefficients for Bridge bearings, which is relevant to temporary bearings as well such as heavy falsework, temporary sledges and sliding systems. 

This table defines 50% friction coefficient between Steel and concrete with a reduction factor of 0.6, resulting in a friction coefficient of 0.6x50%=30%. Debonding agent/formoil or a very smooth cast surface should be avoided to keep this assumption valid.

For steel to steel interfaces, the friction coefficient depends largely on the surface treatment of the steel but up to 30% friction can be justified. 

[Evan Field]

We use british standard BS 5975 code of practice for temporary works as it contains a much more comprehensive list of friction co-efficients 

[Richard Czeizler]

AS3600:2018 table 8.4.3 describes coefficents of friction for concrete to concrete in the context of logitudinal shear in composite beams. Ignoring the the cohesion factor, do we think these values are reliable for other contexts? i.e. lateral loads on precast slabs that do not yet have a positive connection to the PC beam.

[Shane Groom]

There are also some values in the National Transport Commission Load Restraint Guide.

Load Restraint Guide | National Transport Commission (ntc.gov.au)

I believe these values can be used as guidance in absence of actual testing.  

[Florian Dieterle]

Thanks for the interesting references. @Shane Groom, yes, especially for transportation, it is often important to have realistic (not too conservative) friction values. Special rubbers (such as Regupol) can be used and perform well even when wet.