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Load transfer devices such a dowels and longitudinal reinforcement can be very effective provided the stiffness of the concrete surrounding the bar is of sufficient strength, stiffness and durability.

 

Load transfer is considered to be a function of relative vertical movement under loading at joint/crack. Relative movement can be written as a function of (3):

 

   

 

where

 

Pd            the load on steel dowel/bar as a result of wheel loading (kN),

dia            steel diameter (mm), and

E1           stiffness of the concrete (MPa).

 

The stiffness or bearing capacity of the concrete surrounding the steel bar is directly related to the cube strength of the concrete and this is discussed in more detail under properties of the concrete slab.

 

For the design of dowels bars please use the figures as discussed under load transfer.

 

The steel spacing for Continuously Reinforced (CR) pavements is optimized by using the computer program. Steel spacing is adjusted until an average crack spacing of between 1.5 m and 2.0 m is obtained. For Ultra-Thin Continuously Reinforced (UT) which is steel-fibre reinforced, longitudinal bars are normally spaced at less than 100 mm, to obtain a desirable crack spacing of less than 0.5 m.

 

In the Ultra-Thin Reinforced pavement without steel fibres close crack spacing (about 0.5 m) develops at an early stage in spite of the relatively low steel content.