Stiffness characterisation of full-scale airfield test pavements using computational intelligence techniques

The falling weight deflectometer (FWD) is a non-destructive test equipment used to assess the structural condition of highway and airfield pavement systems and to determine the moduli of pavement layers. The backcalculated moduli are not only good pavement layer condition indicators but are also necessary inputs for conducting mechanistic based pavement structural analysis. In this study, artificial neural networks (ANNs)-based backcalculation models were employed to rapidly and accurately predict flexible airport pavement layer moduli from realistic FWD deflection basins acquired at the U.S. Federal Aviation Administration's National Airport Pavement Test Facility (NAPTF). The uniformity characteristics of NAPTF flexible pavements were successfully mapped using the ANN predictions.     

Uncertainty analysis in structural number determination in flexible pavement design—a convex model approach

The AASHTO Guide for Design of Pavement Structures uses a structural number as one of the major inputs for flexible pavement thickness design. Previous studies have shown that the layer coefficients, which are a component of the structural number, have variability. The use of these values without a strong consideration of their variability can influence the overall determination of the structural number, hence, the thickness of the pavement. This paper proposes to use convex models as a tool for addressing the variability and uncertainty in the structural number determination. The convex models provide a completely non-probabilistic representation of uncertainty. The uncertainty is treated as unknown-but-bounded. The approach is illustrated by an example.     

Effects of overlay designs on reliability of flexible pavements

Management of flexible pavements requires timely application of preventive maintenance and rehabilitation actions such as overlays. These actions are an integral part of a design strategy that minimises the use of recourses over the pavement's life-cycle. The objective of this paper is to develop a reliability model for flexible pavements that accounts for the effects of overlay designs. In this paper, the pavement responses are determined by the linear theory of elasticity for the system of pavement layers, while the pavement reliability is represented as a series system of two failure criteria: fatigue cracking and rutting. To illustrate the developed model, a numerical study is presented. Sensitivity and importance measures are computed for the parameters and the random variables included in the limit state functions. The sensitivity measures suggest that the initial asphalt layer thickness and the sub-grade stiffness are the critical predictors of the pavement performance after application of a structural overlay.     

Pavement performance assessment using a cost‐effective wireless accelerometer system

Pavement condition monitoring is required to identify pavements in need of maintenance or rehabilitation. Early identification of reduction in pavement's structural resistance and improving the structural resistance by minor repairs can lead to significantly lower maintenance costs for transportation agencies. In this study, a cost‐effective wireless sensor that can be embedded in the road to measure the transient vibrations due to different applied loads was tested to determine its effectiveness in terms of pavement displacement measurements. Test results show that the vibration sensor, combined with the algorithms, can be embedded in new or existing pavements and used as an accurate wireless displacement sensor. The low cost of the sensor system allows the use of these sensors at high densities for monitoring the performance of an entire road network. Outputs from the developed system can be directly used to evaluate the condition and performance of pavement structure (increasing displacement over time indicating increasing pavement damage). In addition, displacement data from the system can be used to backcalculate pavement layer stiffnesses, which can be used to predict long‐term performance of the pavement structure. Reduction in pavement layer stiffness over time can be used to determine long‐term damage accumulation.     

级配碎石层在2种典型路面结构中的计算分析

以长沙市武广片区道路试验段为依托工程,通过理论分析和3D有限元数值分析、工程应用与后期跟踪检测相结合等技术手段,对级配碎石层应用于2种典型道路路面结构(柔性结构和倒装结构)的性能差异进行了研究。利用大型有限元分析软件ABAQUS建立路面结构的3D模型,充分考虑了级配碎石层的弹塑性,对柔性结构、倒装结构在单次平面均布矩形荷载作用下的力学响应进行了分析;通过变化级配碎石层的回弹模量和厚度,对2种路面结构的力学指标峰值进行了敏感性分析。试验段检测结果表明,采用3D有限元模型分析路面结构能较真实地反映路面结构的实际力学响应。     

Evaluating long-term benefits of geosynthetics in flexible pavements built over weak subgrades by finite element and Mechanistic-Empirical analyses

Finite element (FE) models were developed to evaluate the benefits of geosynthetic reinforcement in flexible pavements built over weak subgrades. The parametric study was conducted to evaluate the effect of different variables such as base thickness, geosynthetic type, geosynthetic stiffness, and double-geogrid layers. FE analyses were performed for 100 load cycles, and the permanent deformation (PD) was used to calibrate the empirical parameters in MEPDG equations for each layer, which were used to extrapolate PD data for the service life of pavements. The PD curves for unreinforced and similar reinforced sections were used to evaluate the Traffic Benefit Ratios (TBR) at different rut depths. The results showed that the inclusion of one geogrid/geotextile layer at the base-subgrade interface could significantly reduce pavement rutting. The use of geogrid is more effective than geotextile in reducing pavement rutting. The derived TBR values range from 1.91 to 8.9 for one geogrid layer and from 1.71 to 5.92 for one geotextile layer. The TBR values increase with increasing the rutting depth and geosynthetic stiffness. The TBR value demonstrates an optimum at a base thickness of 10 in. The results demonstrated the superior benefits of using double geogrid layers compared to single-layer cases.     

Fuzzy logic modeling of deflection behavior against dynamic loading in flexible pavements

Flexible pavements are especially affected by moving vehicles. As a result of the moving vehicles, the pavement starts to deteriorate. For the determination of the structural capacity of the pavement, non-destructive testing equipments are used. These are mainly Benkelman beam, Dynaflect and falling weight deflectometer (FWD). In such a process, the most important thing is to analyze the collected data. In general, linear elastic theory and finite element method are used for this purpose. Since linear elastic theory and finite element method are time consuming, a fuzzy logic approach is used for the elimination of this drawback during the course of this study. Results indicate that the fuzzy logic approach can be used for the modeling of the deflection behavior against dynamic vehicle loading for flexible pavements. The fuzzy model is able to predict the deflection behavior against dynamical loading. The new approach can capture the non-linearity of surface deflection behavior.     

Airfield pavement deterioration assessment using stress-dependent neural network models

In this study, an artificial neural network (ANN)-based approach was employed to backcalculate the asphalt concrete and non-linear stress-dependent subgrade moduli from non-destructive test (NDT) data acquired at the Federal Aviation Administration's National Airport Pavement Test Facility (NAPTF) during full-scale traffic testing. The ANN models were trained with results from an axisymmetric finite element pavement structural model. Using the ANN-predicted moduli based on the NDT test results, the relative severity effects of simulated Boeing 777 (B777) and Boeing 747 (B747) aircraft gear trafficking on the structural deterioration of NAPTF flexible pavement test sections were characterized. The results indicate the potential of using lower force amplitude NDT test data for routine airport pavement structural evaluation, as long as they generate sufficient deflections for reliable data acquisition. Therefore, NDT tests that employ force amplitudes at prototypical aircraft loading may not be necessary to evaluate airport pavements.     

半刚性基层沥青路面耐久性对设计影响分析

利用JTG D50—2006《公路沥青路面设计规范》中路面各结构层层底拉应力验算公式和BISAR3.0设计分析软件,对半刚性基层沥青路面疲劳寿命及影响因素进行了分析。分析结果表明,延长路面使用寿命的关键是增加半刚性基层和底基层的疲劳寿命,减小在行车荷载作用下的半刚性基层和底基层层底的拉应力。这可通过增加路面各结构层厚度和土基模量等措施获得,而其中增加底基层厚度和土基模量是既经济又有效的措施。     

Pavement sustainability index for highway infrastructures: A case study of Maryland

Pavement deterioration creates conditions that undermine their performances, which gives rise to the need for maintenance and rehabilitation. This paper develops a mathematical multi-linear regression analysis (MLRA) model to determine a pavement sustainability index (PSTI) as dependent variable for flexible pavements in Maryland. Four categories of pavement performance evaluation indicators are subdivided into seven pavement condition indices and analyzed as independent variables for each section of pavement. Data are collected from five different roadways using field evaluations and existing database. Results indicate that coefficient of determination (R²) is correlated and significant, R² = 0.959. Of the seven independent variables, present serviceability index (PSI) is the most significant with a coefficient value of 0.032, present serviceability rating (PSR) coefficient value= 0.028, and international roughness index (IRI) coefficient value= ?0.001. Increasing each unit value of coefficients for PSI and PSR would increase the value of PSTI; thereby providing a more sustainable pavement infrastructure; which explains the significance of the model and why IRI will most likely impact environmental, economic and social values.     

考虑层间状态的沥青路面温度与荷载耦合行为分析

沥青路面是典型的层状体系,层间黏结状态的好差直接影响到路面的使用性能.采用三维非线性有限元软件ABAQUS,同时考虑沥青混合料的劲度模量随温度变化的特性,数值模拟计算了沥青路面在不同温度场状况下分别与水平及竖向荷载耦合作用的关键力学响应,分析各响应指标随层间接触状态变化的特性.研究结果表明由于接触模型作用机理的不同,其关键力学指标响应要比连续模型下的大;除路表竖向变形大小几乎与层间接触状态无关外,其他指标在低温状况下,层间接触条件变化对其影响较小,而在高温状况下,特别当层间接触摩擦系数μ＜0.6时影响很大,尤其对基层、底基层的最大拉应力及面层的最大剪应力影响显著.研究成果为科学解释沥青路面在不同环境温度与车辆荷载综合作用下的破损特征与行为机理提供了有力依据,为改善层问黏结条件有利于提高路面整体性能提供了理论支撑.     

Uncertainties in determining the responses of reinforced flexible pavements using in-situ tests

A 225m long full-scale testing lane was constructed at a local road in Australia to evaluate the performance of the flexible pavements over a weak soft subgrade. The pavements were reinforced with three types of geosynthetic products: High-density polyethylene (HDPE) geogrid, HDPE geocomposite and fibreglass geocomposite. The road was divided into 15 sections with different configurations such as the thickness of the base course, reinforcement types and locations, and base course materials. A series of in-situ tests were conducted on each section to compare the behaviour of the pavement structures, such as the moduli of the subgrade, base course and asphalt layer. The comparison shows that there is a large variation in the properties of the structures and great uncertainties in determining the properties even within the sections with the same configuration. When the base course is weaker, the FWD tests may be able to detect the effect of the reinforcements below the asphalt seal layer. Smaller plates are recommended when determining the modulus of thinner base course layers using FWD or LWD tests to minimize the influences from the subgrade.     

沥青路面预防养护时机的选择

指出了沥青路面预防性养护对维持良好的路面性能具有重要意义,而预防性养护的效果与养护时机和措施的选取密切相关,对预防性养护时机的选取方法进行了分析,并针对商开高速公路病害情况,确定了最佳预防性养护时机与预防性养护措施。     

路面管理理论与方法的研究进展及趋势

路面是交通基础设施的主要组成部分,路面管理是公路资产管理的重要内容。论文全面回顾了国际国内近年来路面管理领域的最新研究进展,主要包括路面管理过程中路面状况评价、路面性能预测,以及管理策略优化的常用方法、指标及模型,对比分析了人工神经网络、模糊逻辑和遗传算法等人工智能技术在路面管理中的应用;并对路面管理的发展趋势——公路资产管理这一热点问题进行了探讨。     

An Expert System to Evaluate Concrete Pavements

"Pavement Expert" is an expert system developed to aid in the evaluation of concrete pavements. The system is operational on an IBM microcomputer. It guides the engineer through the evaluation procedure, ensures that it is carried out adequately, and that it can be independently repeated by other engineers. "Pavement Expert" operates in two modes: dialogue and data rogging modes. The dialogue mode is controlled by a Savoir shell which controls the dialogue between the user and the system. The system makes decisions "intelligently" concerning the length of the section to evaluate, extent and severity of the observed distresses, and calculates and stores the final indices. The data logging mode acts as an intelligent data logger recording specific observed distresses. This information is presented graphically on the screen, allowing for alterations to be made. The system consists of five stages ranging from identifying the road to providing a full report on the general condition of the pavement.     

Thiopave改性沥青路面力学响应研究

基于Thiopave改性沥青路面良好的高低温稳定性,采用有限元软件对典型半刚性基层沥青面层进行计算,得到不同沥青面层层底力学响应,并对计算结果进行对比研究,得到的主要结论如下：Thiopave沥青路面层底弯拉应力显著大于SBS沥青及基质沥青路面,路表轮隙中心处弯沉值小于SBS沥青及基质沥青路面;随着SEAM掺量的增加,...     

沥青路面水损害及其防治措施的研究

我国沥青路面在高速公路中得到广泛使用,针对沥青路面水损害问题,分析了水损坏现象和产生机理。在水损害产生的原因的基础上,从不同角度分析水对沥青路面产生水损害的影响,并通过对设置排水层的路面结构和没有设置排水层的沥青路面结构进行损伤对比分析,提出了高速公路沥青路面抗水损害的有效措施。     

某城市道路刚性组合式路面水损害分析及防水技术

某城市道路刚性组合式路面出现了龟裂、沉陷、松散、坑洞、补块损坏等水损害现象,主要与路面结构不合理、施工质量不佳、养护不当等因素有关。介绍了该城市道路改造工程中采用的小空隙率沥青混合料面层、铺设SBR改性乳化沥青稀浆封层、设置胶粉改性沥青防水防裂层、级配碎石排水层等综合防水技术。     

水泥混凝土路面板模量反算的一种新方法--惰性弯沉法

路面结构层模量反算方法有多种,但都因反算解的唯一性问题而使反算结果误差太大.为了提高反算精度,本文提出了"惰性点"的概念.发现在混凝土路面的弯沉盆上,存在一个其弯沉值几乎不随面层模量变化而改变的点,该点即被定义为惰性点.该点的发现,为唯一确定路面结构层模量提供了理论基础.     

基于沥青路面功能性能的预防性养护时机指标

路面预防性养护是国内外近年来研究的热点,路面预防性养护对维持良好的路面性能具有重要的意义。预防性养护的成功与否及其效益与进行预防性养护的时机密切相关,然而对于预防性养护的时机目前国内外还没有很好的解决办法。文章从预防性养护的作用出发,结合我国公路事业发展的现状,提出了基于沥青路面功能性能的预防性养护指标体系:路面沥青老化指标、路面渗水系数、路面行车安全性指标、平整度和路面状况指数(PCI) ,以及获取这些指标需要进一步解决的关键问题。