Point / Distrubuted / Imposed Loads 1

[promaxaccess]

New to this site and not a structural engineer, so please bear with me if i use terms out of context.
I work with powered access platforms (cherry pickers etc.) and wish to produce a sheet or fact file to quickly and easily define or describe the difference in point and imposed loads on a structure. The reason being, that i contantly get asked for the POINT load in Kgs /m2 load for a machine? the customer etc. obviously looks at a floor design and sees the load capacity in KGS /m2 but does not see the effects of point loads, distributed loads or relationship to the structural strength of the structure underneath. I.E a platform can have a high weight, travel on crawler tracks and then support itself on extended stabilisers. A machine with a greater weight giving a more evenly distributed load than a lighter machine with a `whippy` boom causing `bounce` loads on the stabiliser legs and feet. - any ideas anyone?

 

[dbuzz]

I think some of your terminology may be confused.

Imposed actions are 'live loads' such as those due to use, occupancy, wind, earthquake etc. Permanent actions are 'dead loads' such as those due to gravity. Imposed and permanent actions can both take the form of point or distributed loads.

Point loads are those applied over a very small length or area and idealised in analysis and calculations as occurring at a single point. Units are kN, lbf, kips, etc.

Distributed loads are those applied over a length or an area. Units are kN/m, lbf/ft, etc. or kPa, psf, etc.

In your case the actions from the equipment will be applied as point loads at the wheels or outriggers. Whenever I've checked a floor for a forklift or crane the data is always presented as gross vehcile weight and maximum operating weight together with a table of wheel/outrigger loads for the two cases.

 

[promaxaccess]

Thanks dbuzz,
Sorry for any confusion caused by use of terminology. Your answer appears to confirm how is was thinking - in that the total weight of the machine is required to prove the load capacity of the structure or support etc. while the loads under wheels or stabiliser legs must be known or shown to assess the floor or slab for potential `punch through` - would this usually be required as a load or load/area. The reason i ask is that i recently had a machine refused into a building because the floor (block paved) had a design load shown as 5Kn/m2 but public transport (buses) weighing approx. 10000Kgs on two axles were allowed to travel over this area. Our machine weighs only 3000Kgs and has a leg spead of 4mts X 4mts.