A framework for assessing the consequences of deferred or hastened highway asset interventions

Application of a treatment at appropriate time is indeed a critical issue in highway asset management. A treatment that is applied too early (hastened) or too late (deferred) has consequences in terms of the agency cost, facility performance and cost-effectiveness. This research uses basic concepts in costing and effectiveness analysis to develop a methodology for quantifying the consequences of mistimed highway preservation interventions. Through a case study on pavement preservation, demonstrating the practical application of the methodology, it is observed that the consequences of hastened or deferred interventions can differ across asset classes as well as across intervention types: the consequent life-cycle cost increases and performance losses are more severe for non-interstate highways compared with interstate highways, and are more severe for maintenance compared with light rehabilitation. Recognising that in the practical world, the timing of interventions need not be at the optimal levels, the paper goes on to show how an agency could use the developed methodology to establish acceptable ranges of intervention timing and introduce flexibility in its preservation schedules by establishing the earliest and the latest times for applying an intervention in order to avoid undue penalties in terms of cost and effectiveness.     

Effect of Neural Network Topology on Flexible Pavement Cracking Prediction

Pavement surface cracking has long been considered an important criterion for maintenance intervention because of its detrimental effects on pavement performance. Once initiated, cracking increases in severity and extent and allows water to penetrate the pavement. The water weakens the unbound layers and consequently accelerates the rate of pavement deterioration. Cracking prediction and its control are thus key components in determining the timing and cost of pavement maintenance. A neural network–based model is presented in this paper for predicting flexible pavement cracking. One-, two-, and three-hidden-layer backpropagation neural network (BPNN) topologies are investigated and their cracking-prediction performances compared. Based on the analysis, it is concluded that for the same optimal number of processing elements, a one-hidden-layer BPNN topology may be sufficient in achieving satisfactory results in cracking prediction; increasing the number of layers may not add any significant benefit to the performance of the model.     

PROJECT-LEVEL EVALUATION OF HIGHWAY MAINTENANCE USING STATE INCREMENT DYNAMIC PROGRAMMING

This paper presents a project-level evaluation of highway maintenance options using the state increment life-cycle cost analysis method. The case study utilizes pavement management data specific to the New York State Thruway Authority (NYSTA). The study demonstrates that the state increment method can be used at the project-level to: (1) assess the effect of treatments on pavement condition and remaining life, (2) determine the optimal time and condition for various treatments using stochastic dynamic programming, (3) evaluate the effects of uncertainty in pavement performance, (4) rank alternatives for each state based on life-cycle cost, and (5) provide remaining life estimates. Based on the case study results, a reasonable probabilistic representation for the pavement state transitions is selected and the condition-treatment matching rules are suitably modified. It is concluded that the presented comprehensive project-level evaluation of highway maintenance has helped adjust and validate the modeling information used in decision making.     

Optimal Reconstruction Periods for Stochastically Deteriorating Infrastructures

Abstract:   In this article we address the problem of identifying the optimal period between reconstructions, also called reconstruction periods, for an infrastructure system whose performance deteriorates stochastically over time. Performance may refer to the physical condition, such as pavement or bridge condition. We first demonstrate that for any stochastic deterioration process and reconstruction period, the long-term cost-effectiveness, defined as the ratio of the total non-monetary benefit to the total monetary cost across several reconstruction periods, is simply the ratio of the expected benefit to the expected cost up to the first reconstruction, assuming that reconstructions bring the facility back to the new state. We then select four popular mathematical forms of facility performance and present methods to determine the optimal reconstruction periods. The reconstruction cost is assumed to satisfy a certain specified structure.     

Algorithm for Spatial Clustering of Pavement Segments

Abstract:   An algorithm is developed to enable the Georgia Department of Transportation (GDOT) to determine pavement preservation project termini by analyzing segment-level pavement condition rating. This article formulates a new spatial search model for determining appropriate pavement preservation project termini. A spatial clustering algorithm using fuzzy c-mean clustering is developed to minimize the rating variation in each cluster (project) of pavement segments while considering minimal project scope (i.e., length) and cost, initial setup cost, and barriers, such as bridges. A case study using the actual roadway and pavement condition data in fiscal year 2005 on Georgia State Route 10 shows that the proposed algorithm can identify more appropriate segment clustering scheme, than the historical project termini. The benefits of using the developed algorithm are summarized, and recommendations for future research are discussed.     

基于能量法的路面不平整度评价

分析了IRI和PSD两种路面平整度评价指标的弊端,建立四分之一车辆模型,推导了IRI的计算公式,并根据随机振动理论得出了IRI和PSD二者之间的关系,研究还指出,以后的路面不平整度研究的方向应该是在PSD的基础上,综合考虑人-车-路三方面的因素,从而实现人-车-路的和谐.     

Pavement Smoothness Prediction Based on Fuzzy and Gray Theories

Abstract: Pavement smoothness has been recognized as one of the measures of pavement performance. In the Mechanistic‐Empirical Pavement Design Guide (MEPDG), pavement smoothness indicated by the International Roughness Index (IRI) was predicted based on various distresses using traditional regression analysis approaches. Recognizing the limitations of linear regression method, a Gray Theory‐based technique was previously proposed by the authors for the development of pavement smoothness prediction models. In this article, instead of using the conventional least squares method to determine the coefficients for gray prediction models, fuzzy regression method is proposed to solve this gray problem. With pavement IRI and distresses data exported from the Long Term Pavement Performance (LTPP) database, Fuzzy and Gray Model (FGM)‐based smoothness predictions are established using influencing factors similar to those in MEPDG. Based on the comparisons among results originated from MEPDG models, conventional GM models, FGM models, and actual LTPP data, it is shown that the Gray Theory‐based prediction methods with fuzzy regression for estimating model coefficients provide promising results and are useful for modeling pavement performance.     

水泥混凝土路面预防性养护技术研究

从路况标准、预养护对策选择和最佳预养护时机确定3个方面出发,对水泥混凝土路面预养护技术进行系统研究。以路面状况指数和行驶质量指数为指标,确定了水泥混凝土路面的预养护路况标准;以现有水泥路面养护措施为基础,综合考虑交通和路面状况等因素的影响,建立了水泥混凝土路面预养护对策矩阵;采用费用效益分析法,以效益费用比为指标,建立了最佳预养护时机的确定方法。     

高速公路沥青路面全寿命经济分析

为了进一步提高公路建设的投资效益,在分析高速公路沥青路面耐久性和寿命周期关系的基础上,建立了沥青路面全寿命周期费用模型,该模型综合考虑了投资方案的初始修建费、未来的养护维修费、用户费用和寿命期内的其它相关费用。介绍了沥青路面全寿命经济分析的方法,讨论了全寿命经济分析过程中需要重点考虑的两个问题——沥青路面使用性能衰变的预测和维修时机、策略的选择,并对两种不同结构类型的沥青路面进行了实例分析。本文的研究可以为当前新形势下的公路建设项目投资决策和运营管理提供参考。     

大面积广场沥青路面的施工

上海通用汽车研发中心(广德)项目道路工程动态广场沥青路面的设计对平整度要求高。根据大面积广场沥青路面施工难点,结合工程实际,从原材料要求、配合比设计、机械设备的保障、施工过程等方面进行控制,确保工程质量达到国际平整度指数(IRI)的设计要求。广场3层沥青路面摊铺采用"井"字形错缝施工。采用大吨位双钢轮压路机静压,取得了满意的效果。     

Optimal Strategies for Highway Pavement Management in Developing Countries

Highway pavement design in developing countries is usually based on standards borrowed from industrialized countries. However, it may not be economically feasible to use these high design standards in developing countries, because of significant differences in socioeconomic conditions. Using the World Bank's highway design and maintenance standards model (HDM-III), this paper investigates optimal pavement design and its relationship with the developmental stage of a country. Optimal pavement design can be defined as that which minimizes total transport costs to society, which comprise the sum of agency costs and road user costs. Basic data for the analysis were derived from Chinese conditions, and appropriate adjustments were made to model five classes of hypothetical countries in different developmental stages. It is shown that the optimal trade-off between initial expenditure on construction and subsequent maintenance depends on the developmental stage of an economy. The same high design standards that are suitable for industrialized countries may not be economically justified in developing countries. Developing countries should start with modest pavements and then spend more on maintenance afterwards, which is an overdue, neglected priority today.     

Spatiotemporal matching method for tracking pavement distress using high-frequency detection data

Various algorithms based on deep learning have achieved promising results in pavement distress detection. However, the detected distresses are not tracked throughout the life cycle. In long-term application scenarios, pavement distresses may take on different forms due to image acquisition mode, distress development, and environmental change, which make tracking distresses a tough question. We present in this study a spatiotemporal matching method based on high-frequency real pavement distress datasets. Pavement distresses of fixed routes were collected 30 times over 5 months, and distresses with spatiotemporal information were obtained at time series. We apply image rectification, stitching and distress class, and bounding box generation algorithms for pre-processing to align the collected images to the same-detail level and angle. A four-step spatiotemporal matching module is designed, including global positioning system (GPS) filtering, class filtering, relative position filtering, and distress feature filtering. The results reveal that the comprehensive rank-3 hit rate of the matching method reaches 88.73%, and the method is robust to environmental factors, which helps show performance decay of distresses and the effect of maintenance operations. It is concluded that the spatiotemporal matching method is convenient to operate, and it lays the foundation for an agency to track distress evolution and make timely treatment of distresses in the life cycle.     

超重荷载对沥青路面的影响分析

主要分析了某一超重荷载(约1 900 t)对沥青路面的影响。文章内容包括超重荷载下路面结构分析及超重荷载运输的费用分配。路面结构分析采用三维有限元法和层状弹性理论程序并结合摩尔-库伦屈服准则进行。超重荷载运输的费用分配则根据超重荷载相对于标准荷载对路面损坏的影响并结合路面大修所需费用进行预计。     

Reliability‐Based Optimization Models for Scheduling Pavement Rehabilitation

Abstract: Deteriorating pavements require timely application of rehabilitation actions. This article presents reliability‐based optimization models for scheduling rehabilitation actions for flexible pavements. The pavement reliability and the effect of rehabilitation actions are modeled using parametric fragility curves based on simulated pavement responses. Three models are presented: MIN‐C, a model that minimizes the cost where the target reliability is set as a constraint; MAX‐R, a model that maximizes the cumulative life‐cycle reliability where the budget is set as a constraint; and minimize cost and maximize reliability (MINMAX), a multi‐objective model that determines Pareto optimal solutions to reliability‐cost trade‐off. As the multi‐objective optimization model is nonlinear and nonconvex, the solution approach is based on a multi‐objective genetic algorithm (MOGA). The results from a numerical example show that the developed optimization model can be used efficiently in determining optimal rehabilitation strategies and cost‐reliability trade‐offs.     

沥青混凝土路面的质量控制

介绍了沥青路面的病害及其病害产生的危害,分析了沥青混凝土路面病害产生的原因,从设计、施工和路面维护三个方面阐述了保证沥青混凝土路面工程质量的措施,以延长沥青路面的使用寿命,提高道路的投资效益。     

Trend Curve Optimal Control Model for Optimizing Pavement Maintenance Strategies Consisting of Various Treatments

Abstract: Most literature on pavement maintenance optimization for the case of continuous time assumes only one type of maintenance treatment, such as overlay, to be applicable and demonstrates solution procedures with simple cases of limited scopes. However, as overlays may not always be appropriate, depending on traffic loading/pavement situations, the objective of this article is to propose an optimization approach based on the trend curve optimal control model, to obtain optimal strategies possibly consisting of overlay, resealing, and reconstruction. The applicability of the solution procedure is demonstrated with several cases representing a variety of traffic loading/pavement situations. The solutions indicate that an optimal maintenance strategy can consist of multiple types of treatments depending on the situation, illustrating the versatility of the proposed procedure.     

Effect of Performance Model Accuracy on Optimal Pavement Design

In the first part of this paper, an analysis of the data collected during the American Association of State Highway Officials (AASHO) road test, based on probabilistic duration modeling techniques, is presented. Duration techniques enable the stochastic nature of pavement failure time to be evaluated as well as censored data to be incorporated in the statistical estimation of the model parameters. The second part of this paper presents the use of economic optimization principles for determining the optimal design of flexible pavements. We study the effect of deterioration model accuracy on optimal design and lifecycle costs by comparing three models. The first is a simple regression model developed by the AASHO, which forms the basis of design standards in use today. The second is a regression model that was developed with the same AASHO data set, but that includes a correction for data censoring. The third model is the probabilistic model developed in the first part of this paper. The results show that the AASHO model, when used as an input to lifecycle cost minimization, produces a pavement structural number that is lower than that produced by using the other two deterioration models. This results in shorter pavement lives and higher costs due to more frequent resurfacing. The savings in lifecycle cost accrued by using optimal structural number are shown to be quite significant, offering a sound basis for revising current design practices.     

Aggregate and disaggregate statistical evaluation of the performance-based effectiveness of long-term pavement performance specific pavement study-5 (LTPP SPS-5) flexible pavement rehabilitation treatments

Engineers continually seek effective techniques for preserving highway infrastructure. Using data from the specific pavement study#5 of the long-term pavement performance (LTPP) programme's western region, this article evaluated the performance of eight flexible pavement rehabilitation treatments. Aggregate and disaggregate post-treatment performance models were developed for each treatment. Effectiveness was measured in the short term (roughness reduction) and long term (estimated treatment service life and area bounded by the performance curve (ABP)). The results showed that compared to 2-inch treatments, 5-inch treatments were on average more effective in terms of the following measures: 47% (estimated service life) and 35% (ABP) depending on the level of surface preparation, mix type and initial pavement condition. Also, relative to minimal surface preparation, intensive surface preparation generally yielded greater effectiveness: 25% (estimated service life) and 49% (ABP) depending on added thickness, mix type and initial pavement condition. Compared to recycled mix treatments, virgin mix was marginally more effective. Finally, compared to pavements treated in poor condition, those treated in good condition were significantly more effective. Treatment effectiveness models were developed for predicting the expected effectiveness of future treatments on the basis of attributes such as treatment type, added layer thickness, level of surface preparation and mix type.     

A Markov‐Based Road Maintenance Optimization Model Considering User Costs

User costs of different maintenance actions need to be assessed in road maintenance as well as the maintenance costs. The vehicle operating cost (VOC) and the travel delay cost are two major components of the user costs associated with road maintenance actions. This article simplifies the general calculation models of these two user cost components and develops a multiobjective Markov‐based model to minimize both maintenance cost and user cost subject to a number of constraints including the average annual budget limit and the performance requirement. The road deterioration process is modeled as a discrete‐time Markov process, the states of road performance are defined in terms of the road roughness, and the state transition probabilities are estimated considering the effects of deterioration and maintenance actions. An example is provided to illustrate the use of the proposed road maintenance optimization model. The results show that the optimal road maintenance plan obtained from the model is practical to implement and is cost‐effective compared with the periodical road maintenance plan. The results also indicate that the maintenance cost and the user cost are competitive. When maintenance works are carried out more frequently, the life‐cycle maintenance costs will increase while the life‐cycle user costs will decrease. This is because the VOC contributes the most amount of the user cost and its change has a contrary trend to the change of the maintenance cost over time.     

Modelling of volatile organic compounds emission from dry building materials

A numerical and an analytical model were developed to predict the volatile organic compound (VOC) emission rate from dry building materials. Both models consider the mass diffusion process within the material and the mass convection and diffusion processes in the boundary layer. All the parameters, the mass diffusion coefficient of the material, the material/air partition coefficient, and the mass transfer coefficient of the air can be either found in the literature or calculated using known principles.

The predictions of the models were validated at two levels: with experimental results from the specially designed test and with predictions made by a CFD model. The results indicated that there was generally good agreement between the model predictions, the experimental results, and the CFD results. The analytical and numerical models then were used to investigate the impact of air velocity on emission rates from dry building materials. Results showed that the impact of air velocity on the VOC emission rate increased as the VOC diffusion coefficient of the material increased. For the material with a diffusion coefficient >10⁻¹⁰ m²/s, the VOC emission rate increased as the velocity increased; air velocity had significant effect on the VOC emission. For the material with a VOC diffusion coefficient <10⁻¹⁰ m²/s, the VOC emission rate increased as the velocity increased only in the short-term; <24 h. In the medium to long-term time range, the VOC emission rate decreased slightly as the air velocity increased; velocity did not have much impact on these materials. Furthermore, the study also found that the VOC concentration distribution within the material; the VOC emission rate and the VOC concentration in the air were linearly proportional to the initial concentration. However, the normalized emitted mass was not a function of the initial concentration: it was a function of the properties of the VOC and the material.