Dynamic Response Solution in Transient State of Viscoelastic Road under Moving Load and Its Application

In order to study the dynamic response of an asphalt road, a dynamic model of the road under a moving load is proposed, in which the viscoelastic characteristics of the base and pavement are all considered, the pavement is regarded as an infinite beam on a Kelvin viscoelastic base. By using Green’s functions, Laplace transforms, and Fourier transforms, the analytical solution in transient is deduced. As the viscosity of the pavement is included in the model, the analytical solution can be used to investigate more of the factors that affect the dynamic response, such as vehicle speed, temperature, and road material properties. Using this analytical solution, some numerical calculations are given to illustrate the effects of vehicles’ speeds and different damping on the deflection with the displacement.     

Van Der Waals Force and Asphalt Concrete Strength and Cracking

Van der Waals force between neutral molecules is employed to characterize the interaction among molecules in asphalt cement. Several important consequences emerge from the consideration. The brittle strength of the asphalt binder is shown to be linked to the well depth of the Van der Waals potential and the mesoscopic cracks present within the asphalt binder. Moreover, the elastic modulus of asphalt binder is analytically related to the potential well depth. The strength of the asphalt concrete (AC) is estimated by considering aggregate surface characteristics and the adhesion strength between asphaltenes or resins and molecules of aggregates. These predictions can help design asphalt concrete pavement. Formulas for predicting the binder strength and the interfacial breaking strength between aggregates and binders are derived. These results are supported by reported data. Furthermore, an analytic expression for the strength of AC is given at temperature below the AC glass transition point.     

沥青配比与焦炭质量之间的关系

 为了提高焦炭强度及粒度，利用40 kg试验焦炉研究了不同沥青添加方式（型煤中添加或直接添加）以及不同沥青添加比例对配煤焦炭质量的影响。研究结果表明，将沥青按照6%的比例配入型煤，随着型煤配比的逐步增加，焦炭的强度和粒度均明显改善，且与沥青比例存在很好的相关性；当配入30%比例的型煤时，型煤中沥青的配比与焦炭质量也存在较高的相关性；直接配加1.8%沥青比将同比例沥青加入型煤可得到冷强度和粒度组成更优的焦炭，但焦炭的热强度稍差。     

Development of a New Structural Model with Prism and Strip Elements for Pavements on Steel Bridge Decks

A new structural model for pavements on steel bridge decks (SLPE) is developed. In this model, a prism element and a strip element represent the pavement and steel bridge deck, respectively. A newly developed link element models the insulation layer that bonds the pavement to the steel deck plate. The SLPE model is verified by calculations that simulate a simply supported square plate and an actual pavement on a bridge deck. Furthermore, the model is expanded to deal with dynamic problems that consider the viscosity of asphalt materials.     

Rate-Type Model for Bituminous Mixtures and Its Application to Sand Asphalt

A variety of hot mix asphalt mixtures are used in highway and runway pavement construction. Each mixture caters to specific needs. Mixtures differ from one another in the type and percentage of aggregates and asphalt used, and their response can be markedly different, and thus there is a need to develop constitutive models that can differentiate between the different kinds of mixtures. In this paper, we outline a general procedure for the constitutive modeling of bituminous mixtures. We illustrate the efficacy of this approach by means of an application to sand asphalt. The governing equations for this special problem reduce to a stiff nonlinear ordinary differential equation and this is solved numerically using Gear’s method. We compare the results of the predictions of the model that we have developed with the compressive creep experiments carried out by Wood and Goetz on a typical sand asphalt mixture and find them to be in good agreement.     

Construction Management of a Small-Scale Accelerated Pavement Testing Facility

Research in accelerated pavement testing (APT) facilities has traditionally focused on the pavement performance such as rutting and fatigue cracking, but documentation on construction management and information of the actual pavement construction quality is limited. There are typically four critical factors that need to be considered to achieve the best possible outcome in construction: cost, schedule, construction process, and quality control, and management. With the objective of developing guidelines for planning and executing construction of a small-scale APT facility, this paper presents a case study documenting and evaluating the construction process and construction management efforts of two sensor-instrumented hot mix asphalt pavement test sections built in a small-scale APT facility. The focus of the experiment was to study bottom-up fatigue cracking of the flexible pavement structure. The presented information and lessons learned serve as a template and guide for agencies pursuing this type of research and pavement construction.     

冲击碾压、橡胶沥青及应力吸收层组合技术在公路工程中的应用研究

分析了冲击碾压的作用机理、橡胶沥青的生成机理及应力吸收层应用性能.基于\     

Constructability and Economics of FRP Reinforcement Cages for Concrete Beams

This paper presents a quantitative economic analysis and a qualitative constructability analysis of three-dimensional fiber-reinforced plastic (FRP) reinforcement cages for concrete beams. Material, labor, and life-cycle costs are provided, and construction practice aspects are discussed. The results of the analyses indicate that prefabricated FRP cages can offer benefits to the construction industry. Although the initial costs of the FRP materials are likely to be higher than those of steel rebar, there is a significant potential for cost savings due to reduced maintenance and labor costs, as a result of the corrosion resistance of the FRP and the increased construction productivity. When direct life-cycle costs are considered, FRP reinforcements already constitute, in many cases, an economically competitive alternative to conventional steel reinforcement in adverse environments. If, in addition, the indirect cost savings as well as quality and safety issues are considered, the FRP reinforcement may be even more competitive.     

Cost-Effectiveness Evaluation of Warranty Pavement Projects

Warranty contracts are expected to enhance product quality and service life at lower life-cycle cost. Recognizing that such benefits could be offset by the generally higher costs of warranties, an assessment of the relative cost-effectiveness of warranty contracts compared to their traditional counterparts is currently of great interest. Using pavement data from Indiana, this paper evaluates the costs, effectiveness, and cost-effectiveness of warranty and traditional contracts. Effectiveness was measured in terms of pavement condition and treatment service life. The paper determined that the warranty contracts generally had higher agency costs but produced pavements with superior condition and service life, and lower construction periods and work-zone user costs, compared to their traditional counterparts. Over a 5-year period, the warranty contracts were found to be 27–30% less cost-effective than their traditional counterparts. Over the long term, the warranty contracts were found to be 70–90% more cost-effective on the basis of service life and 58–65% more cost-effective on the basis of both service life and pavement condition. The study results suggest that the higher long-term cost-effectiveness of warranty contracts is more perceptible when both cost and effectiveness are viewed over the entire life of the pavement treatment and when both agency and user cost are used in the cost analysis. The paper discusses certain aspects of such comparative evaluation studies that could lead to biased inferences and calls for careful screening of warranty and traditional contracts for such studies.     

Evaluation of Full-Depth Asphalt Pavement Construction Using X-Ray Computed Tomography and Ground Penetrating Radar

In the past few years, a number of full-depth or perpetual pavements have been designed and constructed in the State of Texas. A study was conducted to examine the quality of the compaction of the thick asphalt layers within these pavements using advanced forensic tools such as X-ray computed tomography (X-ray CT) and ground penetrating radar (GPR). The GPR is a nondestructive tool for evaluating the uniformity of density in pavements at highway speed. X-ray CT is a laboratory tool that is used to conduct detailed analysis of air void distribution and uniformity in asphalt pavement cores. This paper presents the results of analyzing one of the perpetual pavements constructed in State Highway 114 (SH-114). In this project, two different structural asphalt pavement sections were placed, one included a 1?in. (25.4 mm) stone filled (SF) Superpave mix and the other included a traditional dense graded Type B material. The dense graded Type B material was found to be uniformly compacted. However, major compaction problems were identified with the coarse SF Superpave mix. The poor compaction and associated high percent air vsoids were found to permit moisture infiltration, which could potentially lead to rapid pavement deterioration. The analysis showed very good agreement between the GPR and X-ray CT results and demonstrated the efficiency of using GPR and X-ray CT in the evaluation of asphalt pavement compaction.     

基于全生命周期的绿色公路建设分析

深度分析了国内外交通行业碳排放清单及碳排放因子目录,结合中国交通行业特点,基于现有的公路工程估算指标及中国传统交通行业施工机械设备台班单价计算表,总结归纳符合中国交通行业特点的碳排放因子数据. 基于归因全生命周期评价方法（ALCA）,采用“自下而上”的公路工程碳排放计量思路,将公路工程项目建设期内工程活动分为分项工程–分部工程–单位工程,建立了公路工程建设期碳排放数据库及碳排放测算模型. 在此基础上,利用MATLAB搭建了公路工程碳排放智能估算软件并对国内两段支线高速公路的路面工程碳排放进行了估算分析,实现了仅通过公路里程量、工程方量和公路等级等信息即可快速估算并统计碳排放量,同时能够智能溯源各阶段碳排放要素并定位碳排放大户,为交通行业节能减排提供数据和理论基础. 分析显示,在路面工程中,稳定土基层和沥青路面面层的碳排放主导整体碳排放量,占据了99.6%以上,其中,以C32.5水泥为主的材料占据了75%左右的碳排放.     

Modeling Measured 3D Tire Contact Stresses in a Viscoelastic FE Pavement Model

Three‐dimensional (3D) contact stresses occurring between the road surface and the tire that were measured with the South African Vehicle Road Surface Pressure Transducer Array (VRSPTA) device under a moving wheel are transformed to a corresponding force/stress pattern representing the actual contact stress state under the tire by means of a software program. In combination with a dynamic load function such force patterns derived from these Stress‐in‐Motion (SIM) measurements with the VRSPTA device are used to introduce a more advanced load representation of the tire‐pavement interface into a three‐dimensional (3D) finite element (FE) model. Further, a method is presented to derive viscoelastic material properties of asphalt concrete (AC) mixes from dynamic frequency sweep shear (FS‐S) tests of lab specimens or field cores that can be used to define material behavior of the AC layers in the 3D FE pavement model. Linear elastic layered theory is utilized to validate the results of the FE computations in order to demonstrate that the FE method can successfully be used to include SIM measurements for more advanced analysis and design of pavements. First results of the 3D FE simulation of a load circle of the Heavy Vehicle Simulator (HVS) during accelerated pavement testing of a pavement test section are presented. These results encourage employment of the FE pavement model for further simulation work to assess the rutting potential of AC mixes in combination with different tire types and loading situations.     

Neural Network–Based Intelligent Compaction Analyzer for Estimating Compaction Quality of Hot Asphalt Mixes

Continuous real-time estimating of compaction quality during the construction of a hot mix asphalt (HMA) pavement is addressed in this paper. The densification of asphalt pavements during construction usually is accomplished by using vibratory compactors. During compaction, the compactor and the asphalt mat form a coupled system whose dynamics are influenced by the changing stiffness of the mat. The measured vibrations of the compactor along with process parameters such as lift thickness, mix type, mix temperature, and compaction pressure can be used to predict the asphalt mat density. Contrary to existing techniques in the literature in which a model is developed to fit experimental data and to predict mat density, a neural network-based approach is adopted that is model-free and uses pattern-recognition techniques to estimate density. The neural network is designed to read the entire frequency spectrum of roller vibrations and to classify these vibrations into different levels. The intelligent asphalt compaction analyzer (IACA) is then trained to convert these vibration levels into a “number” indicative of the asphalt mat density at a given location. This two-step process eliminates the need for regression analysis and produces more accurate density measurements than those reported elsewhere in the literature. Compaction studies of HMA mixes on a stiff subgrade indicate that the changes in the vibration characteristics of the roller are attributable to an increased compaction of the HMA base. The results also show that, with the neural network working as a classifier, the IACA can estimate the density continuously, and in real time, with accuracy levels adequate for quality control in the field.     

Computer Model for Life-Cycle Cost Analysis of Roadway Pavements

This paper describes the development of a computer model that performs life-cycle cost analysis (LCCA) of roadway pavements, analyzing the cost of both the agency and the user. Agency costs are a function of the type of rehabilitation, restoration, resurfacing, or reconstruction (i.e., 4R) treatment applicable to each pavement type, given its surface distress and structural condition. The cost of each treatment is calculated from the unit prices specified for the activities involved and the roadway geometry. User costs include vehicle operating and nonvehicle operating costs, which are a function of pavement roughness, as well as user delay costs, which are a function of lane closure practice. User benefits are calculated as savings in user costs due to reduction in pavement roughness from its current state to that of a new pavement. At the roadway network level, sections are flagged for analysis in decreasing benefit-cost order, whereby the cost of the most capital-intensive 4R treatment is considered. Sections flagged at the network level are carried forward to the project level analysis. The project level analysis allocates the available budget among the sections selected to maximize user benefits over the analysis period. The software package implementing this methodology, called pavement investment decisions (PID) is generic; that is, it allows customizing through a series of input screens to fit the pavement management database and practices of any state Department of Transportation (DOT).     

ZrO2悬浮液性能研究

采用乙醇为溶剂，PVB为分散剂和粘结剂，对固相的质量分数为55％的ZrO2悬浮液的制备和性能进行了研究。通过测定悬浮液的粘度和最终沉降体积，确定最佳分散剂含量。悬浮液的制备分两个阶段：第一阶段，悬浮液由ZrO2粉、乙醇和质量分数为0．7％的PVB(分散剂)组成，球磨24h，目的是打开颗粒团聚体和润湿粉料；第二阶段，主要是使悬浮液与粘结剂的混合，分别加入不同量的PⅦ(粘结剂)，球磨24h。结果表明，分散剂含量为粉体质量的0．7％时，能使ZrO2粉末得到良好的分散；当粘结剂含量少于6％时，在涂层坯体过程中容易出现裂纹；而粘结剂含量高于6％时，悬浮液中含有较多的气泡。加入0．7％分散剂和6％粘结剂，可以获得粘度适中、悬浮稳定的ZrO2悬浮液。     

Evaluation of Four Permeable Pavement Sites in Eastern North Carolina for Runoff Reduction and Water Quality Impacts

Four permeable pavement applications in North Carolina’s Coastal Plain were constructed and monitored to determine their effectiveness of reducing runoff quantity and improving water quality. Sites were either constructed of permeable interlocking concrete pavers (2), porous concrete (1), or concrete grid pavers (1). One site of each pavement type was monitored for runoff reduction for periods ranging from 10 to 26 months. Measured runoff depths from rainfall events over 50?mm were used to determine permeable pavement equivalent curve numbers for the sites, which ranged from 45 to 85. Only the two permeable interlocking concrete pavement (PICP) sites were monitored for water quality. Runoff and exfiltrate samples were intended to be collected, in addition to runoff monitoring, from the Swansboro PICP site. However, no runoff was produced during this study from the Swansboro PICP site for rainfall events up to 88?mm. From exfiltrate concentrations, nutrient retention was estimated to be 3.4 and 0.4?kg/ha/year for total nitrogen and total phosphorus, respectively. For the Goldsboro PICP site, water quality of asphalt runoff and PICP exfiltrate were compared. Analysis of water quality samples from the second site determined that concentrations of total Kjeldahl nitrogen, ammonia, total phosphorus, and zinc were significantly (p ? 0.05) lower in permeable pavement exfiltrate than asphalt runoff.     

Analysis of Life-Cycle Maintenance Strategies for Concrete Bridge Decks

This paper presents the development of a project-level decision support tool for ranking maintenance scenarios for concrete bridge decks deteriorated as a result of chloride-induced corrosion. The approach is based on a mechanistic deterioration model and a probabilistic life-cycle cost analysis. The analysis includes agency and user costs of alternative maintenance scenarios and considers uncertainties in the agency cost and the corrosion rate in the deterioration model. The tool presented in this paper can be used to find the optimal condition index of a given bridge deck that minimizes life-cycle cost. Based on the results obtained on three existing bridge decks, it is shown that the total life-cycle cost (user cost plus agency cost) is a nonlinear function of the maximum tolerable condition of the deck, Sm, and that for a practical range of Sm, the relationship between total life-cycle cost and Sm is convex.     

Field Trial for Asphalt Pavements Reinforced with Geosynthetics and Behavior of Glass-Fiber Grids

This paper presents details of a large field trial and some observations conducted to evaluate the practical efficiencies of geosynthetically reinforced asphalt pavements in Shanxi Province, China. Three glass-fiber grids (LB2000 II, TGG-8080, GGA 2021), one plastic grid (Tensar AR1), two geotextiles (nonwoven needle-punched and nonwoven heat-bonded), and one geocomposite (Tensar AR-G) application were selected for evaluation. These geosynthetics were installed in the interface between new asphalt pavement layers (APL) and new cement-stabilized gravel–sand base courses coated by emulsified asphalt or within new APL in the reconstruction of asphalt pavement sections (Program I), or in the interface between old APL and new overlay layers in the asphalt overlay pavement sections (Program II). In each program, reinforced sections with different geosynthetics were compared with each other and with nonreinforced sections to determine relative performance. Inspections after construction showed that the integrated damage ratio and deflection in the pavement sections reinforced with glass–fiber grids were less than other pavement sections. Furthermore, after about 4?years of service, glass-fiber grids were dug out and no breaking and node movement were discovered. Nevertheless, observations indicated that geosynthetics may not be effective, if bearing capacity of the base course/subgrade is inadequate, or if the overlay thickness is too thin, or if preconstruction repair of distressed old pavement is incomplete.     

Normalizing Behavior of Unsaturated Granular Pavement Materials

One of the important components of a flexible pavement structure is granular material layers. Unsaturated granular pavement materials (UGPMs) in these layers influence stresses and strains throughout the pavement structure, and have a large effect on asphalt concrete fatigue and pavement rutting (two of the primary failure mechanisms for flexible pavements). The behavior of UGPMs is dependent on water content, but this effect has been traditionally difficult to quantify using either empirical or mechanistic methods. This paper presents a practical mechanistic framework for determining the behavior of UGPMs within the range of water contents, densities, and stress states likely to be encountered under field conditions. Both soil suction and generated pore pressures are determined and compared to confinement under typical field loading conditions. The framework utilizes a simple soil suction model that has three density-independent parameters, and can be determined using conventional triaxial equipment that is available in many pavement engineering laboratories.