Assessment of the reliability of operated sections of highways

The structural failure of a flexible pavement occurs when the accumulated fatigue damage produced by all the vehicles that have passed over each section exceeds a certain threshold. For this reason, the service life of pavement can be predicted in terms of the damage caused by the passage of a single standard axle and the expected evolution of traffic intensity (measured in equivalent standard axles) over time. In turn, the damage caused by the passage of an axle depends on the vertical load exerted by the wheels on the pavement surface, as given by the technical standard in application, and the depths and mechanical characteristics of the layers that compose the pavement section. In all standards currently in application, the unevenness of the road surface is disregarded. Therefore, no dynamic effects are taken into consideration and the vertical load is simply given in terms of the static weight carried by the standard axle. However, it is obvious that the road profile deteriorates over time, and it has been shown that the increase in the pavement roughness, when considered, gives rise to important dynamic effects that may lead to a dramatic fall in the expected structural service life. In this paper, we present a mathematical formulation for the fatigue analysis of flexible pavements that includes the effects of dynamic axle loading. A pavement deterioration model simulates the sustained growth of the IRI (International Roughness Index) over time. Time is discretized in successive time steps. For each time step, a road surface generation model provides a profile that renders the adequate value of the IRI. A QHV (Quarter Heavy Vehicle) model provides the dynamic amplification function for the loads exerted on the road surface along a virtual ride. This function is conveniently averaged, what gives the value of the so-called effective dynamic load amplification factor (DLA); this is the ratio between the effective dynamic loading and the static loading at each time step. Finally, the damage caused by the passage of the standard axle can be evaluated in terms of the dynamic loading. The product of this damage times the number of equivalent standard axles gives the total fatigue damage produced in the time step. The accumulated fatigue damage at each moment is easily computed by just adding up the damage produced in all the previous time steps. The formulation has been implemented in the software DMSA (Dynamic & Maintenance Simulation App). This tool has been specifically developed for the evaluation of projects in applications for financing submitted to the European Investment Bank (EIB). DMSA allows for quantifying the expected structural service life of the pavement taking into account both the rise of the dynamic axle loads exerted by the traffic as the road profile deteriorates over time and the different preventive maintenance strategies to be taken into consideration.

The importance of high initial smoothness on newly constructed or rehabilitated pavement facilities has been identified by many researchers and recognized by many road agencies. Pavements with high initial smoothness display retarded roughness progression and, therefore, longer service lives. In Ontario, Canada, the Ministry of Transportation (MTO) implemented a bonus/penalty system for smoothness in the mid-1990s. Initially based on the profile index and scallops (i.e., bumps) measured with a California Profilograph, the specification is now based on the International Roughness Index analyzed locally (for bumps) and over regular intervals. The potential bonus for high initial smoothness in Ontario is considerable, as is the potential penalty for excessive roughness. Furthermore, the ability to correct areas of excessive roughness after placement is greatly limited by the MTO because the public does not wish to observe a new pavement surface being “damaged” by a milling machine. Given such, contractors are proactively requesting smoothness testing on base pavement layers so that areas of excessive roughness can be addressed prior to the placement of the surface layer. However, once the smoothness of the base layer is determined, the contractor must decide whether areas of excessive roughness will be sufficiently smoothed by the surface hot mix asphalt (HMA) layer or whether milling is first required (at additional cost). In addition to a brief overview of the Ontario smoothness specification, this paper presents the change in pavement smoothness with increasing HMA layers measured at a select project location in order to identify how much additional smoothing a contractor should anticipate. Of particular interest is the change in smoothness from an in-place recycled layer to a base HMA layer and, finally, a surface HMA layer. The results will allow contractors to optimize pavement smoothness (and their associated bonus) while minimizing costly corrective milling.

Asphalt concrete (AC) pavement is one of the most important infrastructures that involve multiple layers of different materials subjected to non-uniform traffic loadings and varying environmental conditions. The repetitive traffic loadings that the road experiences during its service life, combined with temperature fluctuations, cause rutting, fatigue and other forms of deteriorations, which ultimately degrade the performance and durability of pavement structures. Both traffic volume and loads are increasing from year to year with rapid rate. The various categories of vehicles with different performance and operational characteristics contribute to pavement distresses. The dynamic load generated by heavy vehicles is considered as the primary cause of road structural damage and contribute the greater portion of the deterioration of AC pavements. Besides, the influence of temperature, which varies with time and along the pavement depth, makes an ever-changing temperature field. Extreme low daily temperature during winter and high temperature and solar radiation during summer cause thermal cracking and permanent deformation, respectively. The temperature gradient down to the depth has a direct influence on the properties of the AC structures, and hence, affects the response of a pavement while subjected to load. Estimation and prediction of the maximum distresses likely to happen within the pavement layer is vital for proper design of the pavement. Constitutive modeling of the deformation behavior of AC enables to evaluate the deterioration progress. On the other hand, better understanding of materials behaviors and structural responses of asphalt concrete in combination with of load-stress-strain computation tools, allows for optimization of asphalt pavement thickness and material choice. Until recently, AC pavements have been designed to serve for about 20-25 years, however, it has been observed that some roads have been serving for more than 40 years without the need for structural rehabilitation. Such phenomenon has strengthened the issue of prolonged service life of road pavements to be remained as a key concern for road industries for the past several years. In this research, the response of asphalt concrete has been evaluated by employing the ABAQUS finite element model. In order to take into account the effect of temperature on materials properties as well as to determine the deformation progress of a pavement under different temperature and loading conditions, a rut prediction model is developed. Various parameters critically influencing the accumulation of permanent deformation are evaluated by the Burger-material-based model developed by the Author. The FE analyses mainly have focused on the stress-strain state of AC pavement with varying loading conditions, structural geometry and material properties. The analysis showed keeping structural geometry, loading condition and other material parameters constant, an increase the E-moduli of the binder twice yields 4.9% and 14.3% reduction in vertical stresses developed at the mid-depth of the binder and base layers, respectively and increasing the same by forth fold yields as well 11.1% and 27.6% in these layers. However, there is a slight increase in stress in the wearing layer, in both cases. This holds true as well in case of increasing the E-moduli of the base course, there are increase in stresses developed on both wearing and binder courses. The FE analyses show that critical shear stresses are developed within the binder layer. It has been observed that the magnitude of the vertical stress in the wearing course is independent of the wheel configuration, however, the overlapping of stresses is gradually pronounced in the binder course. The analyses reveal that the subbase and subgrade layers suffer greatly due to the influence of the overlapping of stresses developed by dual/multiple wheels. The vertical stress developed at the top layers of the asphalt concrete is one of the major contributors for rut formation on this layer. Of course the rate of rut formation is a function of the frequency of such load application, materials properties and other external factors such as temperature. A Burger-based rutting model has been developed which can predict the accumulation of permanent deformation throughout the service life of a pavement with varying traffic load spectrum and annual and daily temperature variations. The model takes into account the hourly, daily and annual variations of the traffic, the expected traffic wheel loads and operating speed. At the same time, the time variation of temperature across the pavement depth are evaluated and associated with the material properties of the structure layers. It has been found that the higher the viscous component of the material the better the serviceability of the road without undergoing excessive deformation. Higher growth rate accelerates deformation. In addition, the structural geometries have an important contribution for the reduction of the over all permanent deformation of a pavement. It is recommended to work further on development of fatigue and other forms of damage prediction model under various loading spectrum and temperature ranges and integrate together for full scale analysis of AC pavements.

With the rapid development of economy, heavy load traffic has become the major transportation challenge for the expressway, in addition, it is the key factor influencing the service life of pavement. Based on characteristic investigation and analysis of heavy load traffic on Beijing-Shanghai Expressway (Hebei province section), accumulative equivalent axles which the pavement structure actually bear under the heavy load traffic action at different conditions are discussed. The service life of the asphalt pavement under heavy load traffic is estimated and evaluated in several aspects such as the road surface deflection, tensile stress of semi-rigid base and subbase, the road ultimate load. At last, the rationality of available measures to control the overload and overrun is analyzed and evaluated. The result shows that as overload and overrun traffic on expressway become more serious, and the error of axle load conversion in original road structural design under heavy load traffic, accumulative equivalent axles which the road surface actually bear increase greatly, therefore the internal structure stress of the road increases substantially, then early damage of asphalt pavements occurs and the service life of asphalt pavement is cut, which causes a great economic loss. For these reasons, some suggestions and measures to control vehicles of overload are provided. Keyword: heavy load traffic; Asphalt Concrete Pavement; equivalent axles; service life; controlling measure

In a bid to ensure cost-effective highway construction practices, highway agencies constantly seek ways to accelerate project design and delivery through implementation of innovative contracting and procurement practices. The concept of warranties, which is one of such promising practices, involves a shift of the burden of construction quality control, product performance and product maintenance from the owner to the contractor. As such, warranty projects are expected to enhance product quality and service life, and ultimately, reduced life-cycle cost. The expected benefits of warranty projects, however, could be offset by their historically higher construction costs. It is therefore necessary to evaluate the costs and benefits of warranty contracts vis-à-vis traditional contracts so that the more cost-effective practice can be identified. The present study reviewed the state of warranty practice in highway pavement construction in Indiana and elsewhere, collects data on warranty and traditional contracts, and carried out statistical analyses to evaluate the relative costs, effectiveness and cost-effectiveness of these two alternative contracting practices. Effectiveness was measured in terms of average pavement condition and pavement service life, and costs were expressed in annualized costs per lane-mile. All costs were adjusted for inflation and economy of scale. The study confirmed that the warranty contracts generally have higher agency costs than traditional contracts, but produced pavements that were superior to their traditional counterparts in terms in average pavement condition (rutting, cracking and roughness) and service life. It was determined that the typical projected treatment life of warranty contract pavement was 25 years while similar traditional contract pavements had a service life of 15 years. Also, the average construction period and resulting workzone user costs were lower for warranty contract pavements. The medium-term cost-effectiveness analysis showed that when the analysis is carried out over a relatively short period of 5-years (the typical warranty period), the warranty pavement contracts are not as cost-effective as their traditional counterparts. However, the long-term cost-effectiveness analysis (which used treatment service life as the analysis period) clearly indicated that the warranty contracts are generally more cost-effective than traditional contracts. The study results suggest that the superiority of warranty projects over traditional projects is more discernible when both cost and effectiveness are viewed over the entire life of the pavement treatment.

The investigation of the pavement performance under dynamically increased wheel loads combines approaches about the modelling of axle assemblies, the simulation of the dynamic wheel loads due to longitudinal unevenness as well as the estimation of the impact on the service life of pavements. The focus in this work is laid on the determination of distress and service life of rigid pavements under dynamic wheel loads using a recently introduced and for the purpose of this study adopted mechanistic-empirical design method for rigid pavements. The results show a good correlation between the assessed Weighted Longitudinal Profile (WLP) (as an indicator for longitudinal unevenness) and the theoretical service life of rigid pavements. Based on that correlation a rating scheme for longitudinal unevenness is introduced. It allows the classification of the unevennes of roads in a five-grade system depending on the WLP and the definition of limiting values for the longitudinal unevenness.

Pavement service life is an important factor that affects both the whole life cost and carbon footprint of a pavement. The service life of a pavement is affected by several different parameters which can be broadly classified into climate conditions, binder and mixture properties, pavement design, workmanship, and maintenance strategies. The current practice for determining service life of pavements involves the use of pavement design tools, which are used while constructing a new pavement or performing a reconstruction/resurfacing or pavement maintenance. In addition, field measurements using ground penetration radar, falling weight deflectometer, traffic speed deflectometer, and other techniques are also used to assess the condition of an existing pavement. The information from these measurements is then combined with pavement design software to predict potential pavement service life. The accuracy of the predicted pavement service life is affected by the associated uncertainties in the parameters that affect pavement life. The following paper presents various approaches that could be potentially used to determine the associated uncertainties in the estimation of pavement service life. The various uncertainty quantification techniques have been applied to a specific design, and the outcomes are discussed in this paper. The Monte Carlo simulation method, a system-level uncertainty quantification technique, can estimate a probabilistic pavement service life. The other uncertainty quantification schemes are software specific and provide probabilistic life factors by assumed statistical distributions. Hence, the Monte Carlo simulation technique could be one potential method that can be used for estimating a generalized pavement service utilizing predictions from various design software.

Estimating the effects of influential factors on pavement service life is an important, but difficult task for highway agencies. In this study, by specifying pavement condition rating (PCR) of 70 as the terminal pavement status, survival curves were developed based on historical PCR data using Cox Proportional Hazards method. Further, the estimated service lives are obtained from these survival curves. As an example, the survival data of asphalt overlays on flexible pavements in Ohio were analyzed for this study. The effects of influential factors such as structure thickness, climate, traffic loading, and pavement conditions prior to repair on pavement service life were addressed. The results showed that the Cox Proportional Hazards model is applicable in estimating the effects of influential factors on pavement service life. The service life obtained from this study can be used to assist with pavement rehabilitation decision-making, overlay design, and budget allocation.

In New York State, cold in-place recycling (CIPR) is one of a series of asphalt pavement rehabilitation options designed to extend the pavement service life. Recycling pavements with CIPR can decrease energy consumption and can reduce the environmental burden and cost associated with asphalt pavement rehabilitation. However, one drawback to increased use of CIPR has been uncertainty about expected service life and factors that affect long-term CIPR performance. These uncertainties generally limit the use of CIPR to low-volume pavements to minimize the exposure of CIPR-rehabilitated pavements to aggressive traffic conditions. A study examined the effect on service life of CIPR pavements in New York State of daily traffic, truck traffic, base thickness, base-plus-subbase thickness (total pavement thickness), geographical pavement location (environment and climate), and the condition of the pavement before CIPR rehabilitation. Data used in the analysis were compiled from the 2008 New York State Department of Transportation Pavement Management Group Highway Sufficiency Ratings Database, which represented 163 CIPR projects covering a pavement distance of 756 mi. CIPR rehabilitation can be expected to increase the service life of pavements, on average, by approximately 11 years. When CIPR is used on higher-trafficked (better-designed) pavements that have thicker supporting bases and subbases, its performance will benefit from thicker bases and the service life of the pavement will be extended.

Concrete Pavement Restoration (CPR) techniques were applied on a 30 mile stretch of I-65 between SR-114 and US-231 at Crown Point, in Indiana, in 1985. At the time of rehabilitation, some typical functional and structural distresses were developed. The distresses included comer, diagonal, longitudinal and transverse cracking and faulted, spalled and broken joints. The deteriorated surface resulted in a rough ride and a low skid resistance with potential slippery problems. Three types of full depth patches (dowelled, inverted T, and inverted T with a middle dowelled joint) were constructed to replace sections of severe pavement breakups. Partial depth patches were placed to repair minor surface distresses. Cracks were routed and sealed, and joints were refaced to inhibit intrusion of water. Diamond grinding was employed to restore the smooth riding quality and to increase the skid resistance, as well as to remove faulting at joints and cracks. This study evaluated the impact of the CPR techniques on pavement condition and performance. The three types of full depth patches were still functioning well after five years in service. However, the dowelled full depth patch had lower load transfer coefficients than the inverted T full depth patches. The middle contraction joint installed on inverted T patches did not function as desired, and therefore its use should be discontinued. The partial depth patches performed poorly and required continuous maintenance throughout the study period. Diamond grinding greatly reduced the roughness and moderately increased the wet skid resistance of the concrete pavement. The quick reduction of the wet skid resistance after rehabilitation limited the service life to 5 to 6 years. The concrete pavement continued to deteriorate after rehabilitation and the amount of concrete defects have been increasing at a significant rate. However, most of the defects were in the low severity category and the pavement was still structurally sound by the end of this study. A life cycle cost analysis indicated that CPR was more cost effective than an asphalt overlay for this project even though CPR gained a service life that is shorter than the typical service life of an asphalt overlay. This study indicated that the cost of CPR and the service life of a pavement after rehabilitation are determined not only by the success of CPR techniques, but also by the condition and remaining service life of the original pavement at the time of rehabilitation. Therefore, it is strongly recommended that adequate condition evaluation and cost analysis be performed before rehabilitation to determine the feasibility of CPR.

Specifics of calculating required strength of highway pavements

A stated goal of governments in addressing climate warming and to transition to a low carbon future by the end of this century is to increase the proportion of energy supplied by alternative sources. For the hydrocarbon processing industry, the question of stranded assets will become significant as these alternative energy sources become more prevalent. Existing equipment will need to operate to the end of its useful life and new equipment may need to be avoided. In particular, coker drums are very expensive investments due to their size, materials and number required in the delayed coker unit of a processing facility. Because of the severe service environment in which coke drums operate, the service life of a drum is not well established. Long term reliability of coker drums is impacted by thermo-mechanical damage mechanisms associated with self constraint of the drum shell and skirt during the formation of hot and cold temperature spots and patches. By assessing the imposed thermomechanical strains, a more precise determination of drum fatigue may be made, allowing better estimation of service life. This service life may be estimated for newly fabricated drums and those drums with shell damage, such as bulging. Service life determination is of practical importance for operators since it provides a more realistic estimate of operational life as compared to the normally referenced Code design life. An accurate estimation of drum service life has not been available in the industry to date due to a number of deficiencies and conservatisms in the current calculation practices. Insight into the causal damage mechanism provides opportunities in identifying alternatives in design, material selection, fabrication, inspection, and maintenance for operating this equipment to a practical and optimal target service life.

Abstract
 In Yemen, farmers and people living along the roads are suffering from the lack of utilization of rainwater runoff from road surface & surrounding area and road water structures. The objectives of this research is to optimize the benefits of Road Rainwater Harvesting (RRWH) to the beneficiaries during road design, construction and operation & maintenance; to suggest a technical outlines; to induce the awareness of road’s engineers on the importance of Integrated Water Harvesting Management (IWHM), in addition to discussing the Environmental and Social Impact Assessment (ESIA). The research approach focused on conducting field visits and applying a reconnaissance survey to document the current and potential road rainwater structures along the pilot section of 24 km as part of Sana’a – Al-Hodiedah road between Al- Masajed village and Sooq Al-Aman; Designing and applying questionnaires and interviews for farmers & beneficiaries, and road engineers. The SPSS software program was used to analyze the collected data. From the conducted interviews along the road, it was revealed that almost all the stakeholders have land adjacent to the roadside, and their farms are irrigated from rainwater collected from road structures. All inhabitants considered water floods running from/on the road surface and structures as their rights, and it is distributed at the moment according to the field’s water rights which exist before the road construction. The research found that almost all farmers considered the water from roads as contaminated water. The source of contamination comes from residual oil on the road, diesel, oil from oil shops and suspended soil particles. On the other hand, according to the road engineer’s questionnaire, the concept of water harvesting, groundwater recharge and water for irrigation from road surface and road structures were not considered during design. In addition, the results obtained showed that water-harvesting techniques in the pilot road section is in the form of farmers’initiatives implemented by directing water to their farms for irrigation. The study conclude applying RRWH to protect the road sections from erosion and damage; increase the availability and utilization of water in the areas nearby roads; minimize the erosion of landscape especially in mountainous areas as well as in road embankments; improve the stabilization of the road slopes; and maintain esthetic value of landscape nearby roads. It is recommended that road drainage structure should be located in a proper place to avoid conflicts among farmers and fulfill their water rights. To avoid soil and water contamination by oil, grease and fuel from vehicles along the road, the research recommends that oil workshops should be implemented and forced to collect and recycle oil instead of disposing it on the road surface. RRWH is recommended to be applied to mitigate the damage of terraces during the heavy runoff. The study urges the joint efforts from all stakeholders and road engineers to apply the suggested technical outline in this paper by including rainwater harvesting from roads as part of road design, implementation and maintenance.
 Keywords: rainwater harvesting, road design, culverts, engineers,stakeholders, farmers, ESIA, Yemen, social and economic benefits.

Abstract
 In Yemen, farmers and people living along the roads are suffering from the lack of utilization of rainwater runoff from road surface & surrounding area and road water structures. The objectives of this research is to optimize the benefits of Road Rainwater Harvesting (RRWH) to the beneficiaries during road design, construction and operation & maintenance; to suggest a technical outlines; to induce the awareness of road’s engineers on the importance of Integrated Water Harvesting Management (IWHM), in addition to discussing the Environmental and Social Impact Assessment (ESIA). The research approach focused on conducting field visits and applying a reconnaissance survey to document the current and potential road rainwater structures along the pilot section of 24 km as part of Sana’a – Al-Hodiedah road between Al- Masajed village and Sooq Al-Aman; Designing and applying questionnaires and interviews for farmers & beneficiaries, and road engineers. The SPSS software program was used to analyze the collected data. From the conducted interviews along the road, it was revealed that almost all the stakeholders have land adjacent to the roadside, and their farms are irrigated from rainwater collected from road structures. All inhabitants considered water floods running from/on the road surface and structures as their rights, and it is distributed at the moment according to the field’s water rights which exist before the road construction. The research found that almost all farmers considered the water from roads as contaminated water. The source of contamination comes from residual oil on the road, diesel, oil from oil shops and suspended soil particles. On the other hand, according to the road engineer’s questionnaire, the concept of water harvesting, groundwater recharge and water for irrigation from road surface and road structures were not considered during design. In addition, the results obtained showed that water-harvesting techniques in the pilot road section is in the form of farmers’initiatives implemented by directing water to their farms for irrigation. The study conclude applying RRWH to protect the road sections from erosion and damage; increase the availability and utilization of water in the areas nearby roads; minimize the erosion of landscape especially in mountainous areas as well as in road embankments; improve the stabilization of the road slopes; and maintain esthetic value of landscape nearby roads. It is recommended that road drainage structure should be located in a proper place to avoid conflicts among farmers and fulfill their water rights. To avoid soil and water contamination by oil, grease and fuel from vehicles along the road, the research recommends that oil workshops should be implemented and forced to collect and recycle oil instead of disposing it on the road surface. RRWH is recommended to be applied to mitigate the damage of terraces during the heavy runoff. The study urges the joint efforts from all stakeholders and road engineers to apply the suggested technical outline in this paper by including rainwater harvesting from roads as part of road design, implementation and maintenance.
 Keywords: rainwater harvesting, road design, culverts, engineers,stakeholders, farmers, ESIA, Yemen, social and economic benefits.

PURPOSES : The purpose of this study is to analyze the service life of expressway pavement based on both traffic volumes and use of deicing chemicals. METHODS : A database was built using expressway rehabilitation history information from over the last decade. In order to estimate the service life of expressway pavement, various analysis methods were considered, and a decision was made to perform analysis using a method based on an accumulated rehabilitation ratio. The service life of expressway pavement was then analyzed by classifying the scale of traffic volume and extent of de-icing chemicals used. RESULTS : The service life of PMA and SMA ranged from 7.8 to 10.6 years and from 9.9 to 12.0 years, respectively. The service life of JCP ranged from 16.0 to 22.2 years, and the service life of CRCP was 33.5 years on average. Results of assessing service life according to traffic volumes and de-icing chemicals showed that the lower the traffic volumes were, the greater the service life of PMA and JCP, and the less that de-icing chemicals were applied, the greater the service life of JCP. CONCLUSIONS : The dependence of expressway pavement service life on traffic volumes and de-icing chemicals makes it possible to apply LCCA for regional maintenance plans and cost-effective selection of expressway pavement type.