The BCA does not clearly define and distinguish between walls, partitions, balustrades, guard rails, hand rails and barriers.
AS1170.1 gives top edge loads for barriers. Applying a load to the top edge of a barrier of any height is not considered appropriate: the line load needs applying at a height appropriate to the nature of the loading.
AS1657 sets the maximum height for a guard rail at 1100mm. Depending on their orientation to a barrier; a person’s body contact with a barrier is likely somewhere between waist height and shoulder height. A look at anthropometric data indicates that 95th percentile shoulder height is 1528mm for men and 1440mm for women. No data readily available for waist height, but hand knuckle height when standing has 95th percentile values of 837mm for men and 787mm for women, this is lower than the waist but higher than the knee.
Barrier heights in the codes do not consider the situation of people in a crowd climbing on each others shoulders. The loads applied at the upper levels of a barrier are therefore expected to be less than can be applied at lower levels. It is also to be noted that humans can push with greater force than they can pull, therefore for a barrier placed at a free edge, expect outward load to be greater than inward load.
Where high barriers are used the top edge is neither suitable for use as a hand rail nor a guard rail, as it is too high, and a separate hand rail would be required.
It is therefore considered barriers higher than 1100mm should only be designed for the top edge line loads applied at a height no higher than 1100mm. For barriers (panels/plates) higher than 1100mm the panel should be considered as infill and loading should be the higher of the AS1170.1 barrier infill load and the BCA requirements for walls of light weight construction (0.25kPa).
If a guard rail is provided then further consideration should be given to only applying 0.25kPa above the rail, and the higher barrier infill load below.