Wheel Patch Definition

The wheel patch definition dialog is accessed from the “Generate Static Vehicle Load” dialog and allows the user to specify that each vehicle wheel load should be represented by a series of grid point loads in a rectangular patch. This will only affect the analysis if the patch size is large compared to the panel size of the grillage. The patch size will generally be determined from loading code requirements for the contact area of the wheel with the road surface and the spread of load down to the neutral axis.

Definition

Axle Number

The user selects the axle number to define.

Contact Area

The length of the contact area along the length of the vehicle and the width of the contact area across the width of the vehicle.

Spread to Neutral Axis

The amount by which the surface patch has spread before the load reaches the neutral axis of the beam elements. This forms a uniform width border around the contact patch, giving a patch length of contact area length plus twice spread and a patch width of contact area width plus twice spread.

Number of Point Loads

This allows the user to influence the number of point loads to be used to represent the wheel patch. Unless the patch will cover several panels of the grillage, requesting more than 4 point loads across the width of a patch is unlikely to affect the results.