CHAPTER 5 CONCRETE PAVEMENTS - TU Delft

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Figure 5.10: Influence chart of Pickett and Ray for the bending moment along the slab edge. 175
The equations 5.5 and 5.6 and figure 5.10 are valid for the calculation of flexural tensile stresses due to traffic loadings in a single concrete slab. However, in reality a plain concrete pavement consists of a number of concrete slabs with joints between them. The load transfer in these joints is dependent on the joint width (which depends on the slab length), the amount of traffic and the type of joint construction (which means: aggregate interlock, ty bars and dowel bars). Teller and Sutherland have defined the total load transfer in a joint as follows (11): W = 2w u 100 (5.8) wl + wu where: W = joint efficiency (%) related to deflections wl = deflection (mm) at the joint edge of the loaded concrete slab wu = deflection (mm) at the joint edge of the unloaded concrete slab In joints of plain concrete pavements without dowel bars the joint efficiency W decreases from 70-90% just after construction to 10-30% at long term due to the polishing effect of the repeated traffic loadings on the concrete of the joint sides. In structural design calculations for these joints without dowel bars the safe value W = 0% (i.e. a free edge) generally is used. In joints with dowel bars at long term there remains a joint efficiency W of 50-60%. Similar to equation 5.8, however, the joint efficiency can also be defined as (12): W ' = 100 σ l 2 σ u + σ u Where: W ‘ = joint efficiency (%) related to flexural stresses in the concrete slab σl = flexural tensile stress (N/mm 2 ) at the joint edge of the loaded concrete slab σu = flexural tensile stress (N/mm 2 ) at the joint edge of the unloaded concrete slab The joint efficiency W ‘ with respect to flexural stresses appears to be (much) smaller than the joint efficiency W with respect to deflections, as is illustrated in figure 5.11. (5.9) Figure 5.11: Flexural stresses related to deflections for doweled concrete slabs (12). 176
Page 1 and 2: CHAPTER 5 CONCRETE PAVEMENTS 160
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CHAPTER 5 CONCRETE PAVEMENTS - TU Delft

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