Guidelines for Dowel Alignment in Concrete Pavements (2009) / Chapter Skim
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Pages 15-33
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From page 15... ...
The vertical translation distribution of the dowel bars within each nominal thickness is shown in Table 3.1. When absolute values are considered, the average vertical depth deviation for all projects is 0.46 in.
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From page 16... ...
8 9 10 11 12 # of Projects 3 7 11 26 5 # of Dowel Bars 1036 4847 7321 9529 2388 Dowel Diameter, in. 3 X 1.25 4 X 1.25; 3 X 1.5 3 X 1.25; 8 X 1.5 2 X 1.25; 24 X 1.5 5 X 1.5 Construction 3 Basket 2 Basket; 5 DBI 1 Basket; 10 DBI 20 Basket; 6 DBI 3 Basket; 2 DBI Average Depth, in.
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From page 17... ...
that apparently did not result from dowel misalignment but 17 8 9 10 11 12 Projects 3 7 11 26 5 Dowel Bars 1036 4847 7321 9529 2388 Dowel Diameter, in. 3 X 1.25 4 X 1.25; 3 X 1.5 3 X 1.25; 8 X 1.5 2 X 1.25; 24 X 1.5 5 X 1.5 Construction 3 Basket 2 Basket; 5 DBI 1 Basket; 10 DBI 20 Basket; 6 DBI 3 Basket; 2 DBI Average Depth, in.
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From page 18... ...
Examples of these analyses for transverse cracking and joint faulting are presented here. Appendix B provides more detail on the analysis for these distresses and joint opening.
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From page 19... ...
There was no statistical difference in average vertical translation, average longitudinal translation, or average vertical tilt between joints that are adjacent to slabs exhibiting transverse cracking and joints adjacent to intact slabs. However, there was a statistically significant difference between the two groups with respect to horizontal skew.
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From page 20... ...
. The joints with higher average vertical tilts had higher levels of average faulting.
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From page 21... ...
Figure 3.6 shows the pullout force versus relative dowel and displacement for two aligned dowels (to illustrate the variability in pullout force) and for a dowel with 3 in.
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From page 22... ...
Shear capacity is defined as the load at which the concrete around the dowel experiences shear failure. Shear stiffness is defined as the relationship between changes in shear force in relation to changes in relative dowel displacement.
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From page 23... ...
When comparing the shear force versus relative dowel displacements for an aligned dowel to that for a dowel with reduced embedment length, a dowel with reduced concrete cover, and a dowel with both reduced embedment length and reduced concrete cover, a compounding effect of misalignments is observed. The decrease in concrete cover results in a large decrease in ultimate shear capacity with little loss of shear stiffness while the reduction in embedment results in modest losses of both shear capacity and stiffness.
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From page 24... ...
. Table 3.5 gives the ultimate shear capacities for different levels of longitudinal translation, concrete covers, vertical tilt, and dowel diameter.
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From page 25... ...
However, because the MEPDG faulting model assumes the same diameter for all dowels, a single equivalent dowel diameter that accounts for all dowels needs to be estimated. Finite element modeling shows that the LTE of the joint is affected by misalignment of the dowel in the wheel path approximately as much as the combined effect of the same level of misalignments for all of the other dowels in the joint (see Table 3.6)
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From page 26... ...
. The relationship between the reduction in normalized shear capacity and the reduction in dowel diameter from d0 to d is presented as follows: Thus, the adjustment factor for concrete cover rcc can be presented as follows: r d d DSC d cc = = − 0 0 1 1 9628 Δ (11)
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From page 27... ...
Even if spalling is not visible, the ability of the dowel to transfer the load will be diminished. Figure 3.16 presents the calculated dowel diameter adjustment factors versus vertical translation for combinations of PCC thickness and dowel r CC CC CCcc = − − ∗( )
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From page 28... ...
Thus, any combination of dowel misalignment that results in a LTE equal to or greater than the nominal LTE will not affect the pavement performance; rotations that result in less than the nominal LTE will have adverse effects on the joint performance. Table 3.8 gives the nominal load transfer efficiencies obtained from the finite element slab model for various dowel diameters; lower LTE is obtained for smaller dowel diameters.
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From page 29... ...
3.4.1.4 Faulting Prediction After computing the adjustment factors for all misalignment types, the equivalent diameter for the doweled joint should be computed using Equation 4. The effect of dowel misalignment on the reduction of pavement life with respect to faulting and/or the reduction in predicted faulting reliability then can be determined using the MEPDG faulting model.
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From page 30... ...
The following procedure is suggested for analyzing the effects of dowel misalignment on the performance of a uniform pavement project: 1. Use dowel alignment measurements to calculate the equivalent dowel diameter in each joint of the pavement project using the procedure described in Section 3.4.1.
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From page 31... ...
[175 mm] , the adjustment factor for the longitudinal translation and related reduction in embedment length is calculated using Equation 6 as follows: 3.5.1.2 Vertical Translation (Low Concrete Cover)
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From page 32... ...
for the joint is obtained by multiplying the original dowel diameter (d0) by the adjustment factors for concrete cover, embedment length, vertical tilt, and horizontal skew as follows: Since the concrete cover for each dowel was greater than the minimum required concrete cover, no further reduction of the equivalent dowel diameter is needed.
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From page 33... ...
Predicted IRI for the as-designed pavement project.
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