Investigating the Relationship of As-Constructed Asphalt Pavement Air Voids to Pavement Performance (2021) / Chapter Skim
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Pages 178-183
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178 Table 18 Summary of All Analysis Methods Performance Characteristic Pavement Type Analysis Method 1 Analysis Method 2 Analysis Method 3 Rutting New 57% met expectation 21% contradict Approximate R2 = 0.31 nominally contradict Predicted R2 = 0.46 nominally met Rehabilitation 67% met expectation 0% contradict Approximate R2 = 0.16 minimally contradict Predicted R2 = 0.47 no influence Fatigue Cracking New 82% met expectation 9% contradict Approximate R2 = 0.41 significantly met Predicted R2 = 0.62 mixed expectation Rehabilitation 40% met expectation 30% contradict Approximate R2 = 0.35 nominally met Predicted R2 = 0.46 significantly met Thermal Cracking New 42% met expectation 50% contradict Approximate R2 = 0.38 nominally met Predicted R2 = 0.36 no influence Rehabilitation 50% met expectation 50% contradict Approximate R2 = 0.32 nominally met Predicted R2 = 0.30 nominally met Ride New 54% met expectation 38% contradict Approximate R2 = 0.24 nominally met Predicted R2 = 0.19 nominally met Rehabilitation 25% met expectation 42% contradict Approximate R2 = 0.21 nominally met Predicted R2 = 0.39 nominally met Met expectation – lower as-constructed air voids improved pavement performance Contradicted – higher as-constructed air voids improved pavement performance Approximate R2 – applied to models that used quintile regression to fit the median Predicted R2 – applied to ANN model prediction using test data Regional Analysis Approach This section of the User Guide provides an agency with recommendations on the process to perform this analysis with data from the agency's dataset. Many of the recommendations reflect lessons learned by the research team as the NCHRP study progressed.
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From page 179... ...
179 Analysis Method 1 Subgroup Scatter Plots This analysis approach divides the agency's pavement network into subgroups with common climate, traffic, and pavement structure such that the performance of the pavement sections within a subgroup is expected to be similar. The climate conditions within the agency's boundaries will determine how many climate zones are needed.
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180 curve, so if performance was only measured every 2 years, the performance period is 12 years. For Analysis Method 1, each performance characteristic is represented by a single value of condition (inches of rutting)
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181 that distress reaches a critical value. For example, rutting measured over time or the year in which thermal cracking first appears.
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182 Analysis Method 3 ANN Models This section describes how to assess the effect of as-constructed AV on pavement performance by ANN models. The ANN approach is a computer based adaptive information processing technique that allows for establishing correlations between the input variables Xi and the output variables Yj through the inter-connected neurons (i.e., weight factors, wji)
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From page 183... ...
183 Step 4 – Apply the ANN Processing Technique. Once the training and validation datasets are assembled and the ANN architecture is defined, the ANN process uses transfer functions, a back propagation method to minimize the mean squared error with the training dataset, and a learning algorithm to adjust the neuron weight factors all programmed using the Matlab software.
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