5.14 Wheel loads

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Let us assume that the contact area of a tire is 40× 20 cm and that the load

it carries is 50 kN. If the slab thickness is 60 cm then at the midsurface the

load carrying area has widened to 100 × 80 cm; see Fig. 5.43.

Figure 5.44 gives an impression of how an FE program resolves six such

wheel loads representing a heavy truck traversing a hinged rectangular slab

into a series of line loads that push and pull at the slab; see Fig. 5.44. The

bending moments (see Fig. 5.45) instead give the impression that the slab

carries the original wheel loads.

The elements are conforming square elements based on the shape functions

in (5.17). The element size is 50 cm which means—if the load distribution in

the lesser direction of the tire is neglected—that the equivalent nodal force at

the node directly under the tire is 25 kN and that the two neighboring nodes

carry a load of 12.5 kN.

5.15 Circular slabs 461

Fig. 5.43. Wheel load

line moments. Shown here are

forces, ↑ = tensile forces

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