AASHTO M331-17 pdf free download

AASHTO M331-17 pdf free download.Smoothness of Pavement in Weigh-in-Motion (WIM) Systems.
4.1.4. In addition to the initial calculations of the WIM scale roughness index for WIM scale location acceptance, the pavement smoothness of each existing WIM scale shall be verified every two years. Profile records shall be collected and indices recalculated every two years to ensure that the scale remains likely to produce load estimates that meet the functional performance requirements ofASTM El318.
4.1.5. In specifying a location for a WIM scale with more than one sensor on a single wheel track (typical with piezoelectric WIM equipment), the position of the scale shall be defined as the location of the downstream sensor. The WIM scale roughness index is to be referenced to this point.
4.1.6. Under certain conditions, jointed concrete pavement surfaces may exhibit significant changes in roughness due to variations in the temperatures of the pavement. Profile records of these pavements shall be taken at least twice, at times that correspond to approximate extremes of pavement (not air) temperature gradient that are likely to be experienced at the candidate location. The location for a WIM scale shall be chosen so that the WIM scale roughness index calculated from either of these profile records does not exceed the limits.
4.2. Summary of’Practice—Test methods for evaluating the smoothness of pavement in an existing WIM system are presented herein. These procedures are applicable for determining a WIM scale roughness index level that would indicate that a WIM scale is likely to produce acceptable levels of weighing error as defined in Table 1. The smoothness tests require the collection of longitudinal profile data with a sampling rate of 25 mm [1 in.] or less and otherwise in accordance with R 57. Computer analysis of these profiles serves to calculate the WIM scale roughness index that will be compared to acceptable threshold values.
4.3. Significance and Use—The WIM scale roughness index was developed in a correlation of calculated roughness values to WIM scale error for a large-scale study of pitch-plane simulations of 3S2 (five-axle tractor-semitrailers) vehicles. The index was further verified in a study of simulations of WIM scale errors associated with three-axle single-unit trucks. Subsequently, the index was refined using the same set of pitch-plane simulations on several existing WIM site profiles. This correlation allows the indexes to be used to determine whether the WIM system pavement smoothness is sufficient to achieve weight measurements of 3S2 trucks and three-axle single-unit trucks that fall within ASTM error tolerance levels. The calculation of WIM scale roughness index values that fall within those that correlate to the scale measurement tolerances specified in Table 1 means that the scale is very likely to produce an acceptable level of weighing error.
4.5. Interpretation of Results- -Table 2 shows the upper threshold value indices for Types I and II WIM scales in evaluating the smoothness of the pavement after a WIM scale installation. The upper threshold value of the index is that above which a WIM system is very likely to produce an unacceptable level of weighing error.AASHTO M331-17 pdf download.