Guidelines for Dowel Alignment in Concrete Pavements (2009) / Chapter Skim
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From page 2... ...
However, because concrete cover describes the distance between the dowel and slab surface, it also reflects the vertical positions of the dowel and its vertical translations. 2.1.3 Current Specifications Different states have adopted different requirements for dowel bar tolerances with respect to longitudinal and vertical translation, horizontal skew, and vertical tilt (see Table 2.1)
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. Vertical Tilt Horizontal Skew LongitudinalTranslation Vertical Translation Agency in.
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The standard pullout test data typically are presented as a plot of pullout force versus dowel horizontal displacement. The results of such tests have been used to calibrate a finite element model (Khazanovich et al., 2001)
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Thus, if higher bearing stresses were observed for reduced dowel diameters and also observed for joints with misaligned dowels, levels of dowel misalignment could be equated to reduced dowel diameters when bearing stress is considered. Cracking models relate PCC pavement longitudinal bending stresses developed at mid-slab with the percentage of cracked slabs.
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model was adapted for roughness prediction. 2.3 Research Approach The following section describes the approach used in conducting field and laboratory tests, analytical modeling, and developing performance predication models for JPCP with misaligned dowels.
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2.3.2.2 Test Procedure The dowel pullout testing was conducted after the test beams had been water-cured for 7 days. Because concrete pavement can experience contraction and shrinkage within several hours after concrete setting, the 7-day curing time was selected to ensure uniformity of the test beams.
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Each dowel was tested individually by pulling it vertically with respect to the concrete beam, in a displacementcontrolled mode until the concrete surrounding the dowel failed. During the testing, the shear pull force and displacements of the dowel and concrete were recorded continuously.
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measures the displacement of the metal angle above the dowel, giving a measure of absolute dowel displacement. LVDT2 measures the displacement at the edge of the concrete beam closest to the dowel, LVDT3 measures the beam displacement 2 in.[51 mm]
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From page 10... ...
, the dowel exhibits additional displacements with respect to the concrete beam surface. The relative dowel displacement can be computed as: where ∂rel = the dowel displacement due to the compression of the concrete around dowel; ∂calc = the calculated rigid body displacement; and ∂meas = the dowel displacement measured by LVDT1.
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From page 11... ...
In the lab, shear testing always was conducted after the pullout testing to model the effect of joint opening prior to wheel loading. In a similar manner, the finite element beam model was set up to apply the pullout test prior to applying the shear pull test, therefore accounting for damage in the concrete beam.
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From page 12... ...
By comparing the results of the shear-pull tests to those of the ABAQUS model, rational parameters were established for the dowel-concrete interaction model. Figure 2.13 shows the shear force versus relative displacements for an aligned dowel tested in the laboratory and for a simulated dowel using ABAQUS.
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From page 13... ...
The equivalent dowel diameter concept postulates that, with regard to joint faulting, a joint with misaligned dowels behaves as a joint with aligned dowels with a diameter, deq, as defined by the following equation: where remb = the adjustment factor for a reduction in embedment length; rcc = the adjustment factor for a reduction in concrete cover; rvt = the adjustment factor for vertical tilt; rhs = the adjustment factor for horizontal skew; and d0 = the nominal dowel diameter. The adjustment factors can have values ranging from 0 to 1, where the value is inversely related to the level of misalignment.
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From page 14... ...
The MEPDG IRI model considers changes in ride quality over time as a degradation of the initial smoothness due to transverse cracking, spalling, faulting, and pavement site conditions. The general equation for the IRI model is presented below to illustrate the compound effect of predicted transverse cracking, spalling, and faulting on prediction of pavement ride quality (AASHTO, 2008)
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