bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and Application of a Vehicle Procurement Model for Rural Fleet Asset Management
Authors: Davenport Nathan S. , Anderson Michael D. , Farrington Phillip A.
Published: May 2018

Advanced asset management systems have emerged as important tools in the management, maintenance, and procurement of vehicles for transit fleet operators. Effective design and use of an asset management system can increase productivity, enhance public perception, and provide a consistent basis for decision making and planning. This paper documents the design and application of a vehicle procurement model in an asset management system created for the Alabama Department of Transportation to manage vehicles purchased and operated through the Section 5311 federal grant program. The vehicle procurement model predicts future vehicle serviceability, or condition rating, by using a combination of factors, including service area socioeconomic data and vehicle usage data. Application of the system helps transportation professionals estimate the overall fleet quality, identify vehicles that will need to be replaced each year, aid in the management of vehicles, and provide a basis for predicting future funding and budgetary needs.
Use of Planning Support Software in Transit Services
Authors: Peng Zhong-Ren , Hawks Sarah , West Kate
Published: May 2018

Many U.S. transit agencies have been using planning support software to assist in daily planning, operation, and customer services. However, the literature is not clear about the extent to which transit agencies are using planning support software programs for daily activities. To determine the state of the practice in the use of planning support software in the U.S. transit agencies, a survey was conducted. The survey found that the use of planning support software confirms the general trend in the use of information technology: that is, its use is directly related to the size of the transit agencies. Larger transit agencies tend to use more planning support software, while small agencies do not use that much. Probably one of the most important findings is that many smaller transit agencies consider the purchase and use of planning support software in transit planning, operation, and marketing as unnecessary, especially given the difficulties in obtaining funding, training staff, and hiring and retaining technical support personnel. However, those difficulties are mainly caused by constraints in budgeting and technical staffing issues rather than the undesirability of or the unproved or unrealized benefits related to the use of planning support.
Creating Intelligent, Coordinated Transit
Authors: Espinosa Judith M. , Holm Eric F. , White Mary E.
Published: May 2018

New Mexico is among the first states in the United States to develop, implement, and deploy contactless, smart card technology in a rural area. The Alliance for Transportation Research Institute, working with the New Mexico Department of Transportation's Public Transportation Programs Bureau, developed the Intelligent, Coordinated Transit (ICTransit) smart card technology and the Client, Referral, Ridership, and Financial Tracking (CRRAFT) software. The U.S. Department of Transportation's FTA–FHWA Joint Program Office provided federal funding for the project. The ICTransit smart card functions as a universal use electronic fare card, enabling passengers to transfer between transit providers to access jobs, education, and health care beyond their local rural communities. ICTransit's Global Positioning System receiver and Pocket PC capture the time and location that passengers board and exit the vehicle and the passenger miles traveled on the vehicle. The CRRAFT software system for express scheduling, automatic generation of monthly financial reports, and onboard tracking of ridership provides increased efficiency in rural areas. The ICTransit system with CRRAFT can overcome barriers to coordinated interagency transportation and provide increased access and mobility to all, but especially to those underserved by public transportation. ICTransit with CRRAFT can empower states to build coordinated transportation networks that provide safe and seamless movement of people and enhance the quality of life.
Framework for Testing Innovative Transportation Solutions
Authors: Shaheen Susan A. , Novick Linda
Published: May 2018

Transit accounts for just 2% of total travel in the United States. One reason for low ridership is limited access; many individuals either live or work too far from a transit station to make its use practical. In developing transit connectivity solutions, researchers often employ a range of study instruments, such as stated-preference surveys, focus groups, and pilot programs. To gain better understanding of response to one innovative transit solution, several research tools were applied, including a longitudinal survey, a field test, and a pilot program. The innovation examined was a commuter carsharing model, called CarLink, which linked short-term rental vehicles to transit and employment centers. Over several years, researchers explored user response to the CarLink concept, a field operational test (CarLink I), a pilot program (CarLink II), and a commercial operation (the pilot was turned over to Flexcar in summer 2002). This multistage approach provided an opportunity for researchers to learn and adapt as each phase progressed. In this paper, the authors outline the CarLink model, technology, and early lessons learned; describe CarLink II operational understanding; provide a synopsis of the pilot program transition; and offer recommendations for future model development.
Assessing the Potential Extent of Carsharing
Authors: Schuster Thomas D. , Byrne John , Corbett James , Schreuder Yda
Published: May 2018

Members of carsharing organizations reduce both the number of vehicles owned and vehicle miles traveled (VMT). Given these benefits at the individual level, carsharing may interest policy makers as another tool to address the negative environmental, economic, and social consequences of automobile dependence. However, the aggregate effects of carsharing must be estimated before sound policy decisions can be made. This paper describes a Monte Carlo simulation of the economic decision to own or share a vehicle on the basis of major cost components and past vehicle use. The simulation estimates the percentage of vehicles that would be cheaper to share than own. In Baltimore, Maryland, this result ranged from 4.2% under a traditional neighborhood carsharing model to 14.8% in a commuter-based carsharing model. Sensitivity analyses identified travel time and VMT as the most important economic factors, which likely incorporate other factors such as transit access and environmental attitudes. Because travel behavior, not ownership cost, drives the economic carsharing decision, the model hypothesizes that there will be increasing marginal societal benefits from policies that promote carsharing. The model can be applied to any geographic area and can be used to assess carsharing impacts of various policies that change the economics of owning or driving an auto. These results indicate that carsharing can become prevalent enough to be considered an important policy tool.
Travel Effects of a Suburban Commuter Carsharing Service
Authors: Shaheen Susan A. , Rodier Caroline J.
Published: May 2018

Since 1998, carsharing organizations in the United States have experienced exponential membership growth, but to date there have been only a few evaluations of their effects on travel. Using the results of focus groups, interviews, and surveys, this paper examines the change in travel among members of CarLink–-a carsharing model in the San Francisco Bay Area, California, with explicit links to transit and suburban employment–-after approximately 1 year of participation. The demographic and attitudinal analyses of CarLink members indicated that the typical member ( a) was more likely than an average Bay Area resident to be highly educated, in an upper income bracket, and professionally employed and ( b) displayed sensitivity to congestion, willingness to try new experiences, and environmental concern. Some of the more important commuter travel effects of the CarLink programs included an increase in rail transit use by 23 percentage points in CarLink I and II; a reduction in driving without passengers by 44 and 23 percentage points in CarLink I and II, respectively; a reduction in average vehicle miles traveled by 23 mi in CarLink II and by 18 mi in CarLink I; an increase in travel time and a reduction in travel stress; a reduction in vehicle ownership by almost 6% in CarLink II; and reduced parking demand at participating train stations and among member businesses. The CarLink travel results are compared with those of neighborhood carsharing models in the United States and Europe.
Improving California's Bay Area Rapid Transit District Connectivity and Access with Segway Human Transporter and Other Low-Speed Mobility Devices
Authors: Shaheen Susan A. , Rodier Caroline J. , Eaken Amanda M.
Published: May 2018

To evaluate the potential for low-speed modes to improve transit access, the EasyConnect field test will offer shared-use Segway Human Transporters (HT), electric bicycles, and bicycles linked to a Bay Area Rapid Transit District station and surrounding employment centers in California. Because of safety concerns, research was conducted to understand the risks associated with these modes and potential risk factors. A review of the safety literature indicates that user error is the major cause of low-speed mode crashes, and significant risk factors are poor surface conditions and obstructions to drivers’ vision. As a result, an extensive training program and carefully selected routes have been included in the field test. The regulatory and legislative history of the HT is chronicled to understand how concerns about its interaction with pedestrians have produced legislation that includes specific safety requirements. The low-speed modes used in this project will be equipped with safety devices, and participants will be required to wear helmets. The survey results of 13 HT implementation projects provide insight into potential advantages and challenges to the field test. Results of interviews and meetings with field test stakeholders are presented with a discussion of their influence on the field test design. Finally, conclusions and future project steps are discussed.
Prediction Model of Bus Arrival Time for Real-Time Applications
Authors: Jeong Ranhee , Rilett Laurence R.
Published: May 2018

Advanced traveler information systems (ATIS) are one component of intelligent transportation systems (ITS), and a major component of ATIS is travel time information. Automatic vehicle location (AVL) systems, which are a part of ITS, have been adopted by many transit agencies to track their vehicles and to predict travel time in real time. Because of the complexity involved, there is no universally adopted approach for this latter application, and research is needed in this area. The objectives of the research in this paper are to develop a model to predict bus arrival time using AVL data and apply the model for real-time applications. The test bed was a bus route located in Houston, Texas, and the travel time prediction model considered schedule adherence, traffic congestion, and dwell times. A historical data-based model, regression models, and artificial neural network (ANN) models were used to predict bus arrival time. It was found that ANN models outperformed both the historical data-based model and the regression model in terms of prediction accuracy. It was also found that the ANN models can be used for real-time applications.
Application of New Technology Product Research to New Suburban Commute System Design and Validation
Authors: Raney Steve
Published: May 2018

To provide improved alternatives to suburban solo commuting, a technologically intensive door-to-door mobility service was designed for suburban commutes, with special emphasis on addressing attitudinal and psychological barriers. A literature review, expert opinion, and a geographic information system journey-to-work analysis influenced the initial conceptualization. Concepts were then iteratively refined through interview research. The final system concept was validated with stated preference surveys employing gap analysis to measure the importance of barriers and the effectiveness of proposed solutions. An elaborate eight-step, assembly-line survey protocol was employed and featured immersive, virtual reality–based respondent stimuli (information acceleration), full disclosure of psychological barriers, and customized door-to-door commute comparisons. Original contributions include two aspects: a unique combination of varied product research techniques for the design and demand forecasting of futuristic transportation systems and rich anecdotal descriptions of technology worker commute psychology.
Assessing Transit Level of Service along Travel Corridors
Authors: Xin Yaping , Fu Liping , Saccomanno Frank F.
Published: May 2018

This paper describes a case study of applying the recent edition of the Transit Capacity and Quality of Service Manual (TCQSM) to evaluate the quality of transit service on several travel corridors in an urbanized area. The study focuses mainly on four level-of-service (LOS) measures: service frequency, hours of service, service coverage, and transit–auto travel time. Assumptions are introduced to extend these measures, which are intended for a particular element of a transit system–-such as stops and route segments–-so that they become applicable for measuring the quality of transit service of travel corridors. An extensive case analysis indicates that all LOS measures are sensitive to various transit planning variables and can be easily calculated with readily available data. The research has also identified a range of issues with the current TCQSM methodology.
Evaluating Interior and Door Configurations of Rail Vehicles by Using Variable Loading Densities
Authors: Lau Samuel W.
Published: May 2018

As many U.S. metropolitan areas expect unprecedented growth in population and travel in the next 20 to 30 years, rail transit agencies are faced with the challenges of replacing their aging fleets and procuring new vehicles to keep up with ridership increases. As funds become increasingly scarce, many operators are exploring ways of increasing car capacity by considering interior configurations (to maximize loading efficiency) and door configurations (to minimize the effect of increased loads on station dwell times). Few studies address the design and evaluation of interior and door configurations as a system. Typically, seating configurations are designed separately from door configurations. Furthermore, interior configuration evaluations or maximum vehicle loading quoted by car manufacturers assume a uniform loading density applied throughout the car. Loading on transit vehicles, however, varies greatly within a car. This affects practical vehicle capacity and its impact controlling dwell time at the busiest door. The San Francisco Bay Area Rapid Transit District, a heavy rail rapid transit system in California, recently conducted an evaluation of interior and door configurations based on a methodology that used variable loading densities and resulting impact on door loads for dwell time estimation. Variable loading density is more realistic in simulating actual passenger loading experience. This research shows that depending on the interior and door configuration, applying uniform loading density may misrepresent actual car capacity and door loads and thus waste valuable resources or underestimate actual needs.
Estimation of Transit Reliability Level-of-Service Based on Automatic Vehicle Location Data
Authors: Camus Roberto , Longo Giovanni , Macorini Cristina
Published: May 2018

This paper concerns transit quality of service and focuses on reliability. Starting from automated vehicle location (AVL) data collected in a case study, the advantages and limitations of the Transit Capacity and Quality of Service Manual (TCQSM) method for level-of-service (LOS) estimation are discussed. In particular, this method is clear, simple, and easy to use, but sometimes it may lead to inconsistent LOS estimations for three reasons. First, it does not consider the amount of delay but considers only the number of trips that are late. Second, it does not adequately address the effect of early departures on users. Finally, it introduces a fixed tolerance (3 min in advance and 5 min late) around the schedule to consider the trip on time. A new service measure called weighted delay index is proposed; it allows these limitations to be overcome. In this paper, a methodology for its estimation is presented, and new LOS ranges and thresholds for reliability are proposed. Both the TCQSM method and the proposed one have been applied to four routes of the Trieste transit network in Italy. The basic data have been collected through the AVL system during the peak hours of a month. The results have been compared with reference to real data, and it appears that the proposed approach could lead to more graduated LOS estimation because of the higher number of parameters introduced in the new transit service measure.
Methodologies for Evaluation of Effective Slab Width
Authors: Chiewanichakorn Methee , Aref Amjad J. , Chen Stuart S. , Ahn Il-Sang
Published: May 2018

A composite section is made up of a steel girder and concrete slab connected by shear connectors. The shear lag phenomenon usually takes place in such a section and results in underestimation of stresses and strains at the web-to-flange intersections of the girder. With the introduction of the concept of effective slab width, the actual width can be replaced by an appropriate reduced slab width. The classical effective slab width definition does not take into account the strain variation through the slab thickness. More sophisticated definitions are introduced and used with finite element analyses. The method of finite element modeling is discussed, and the model is successfully verified with experimental results. Parametric study is conducted to investigate the effective slab width for both positive and negative moment sections. The effective slab width is computed and compared with the current AASHTO load and resistance factor design (LRFD) specifications. The results demonstrate that full width can be used as the effective slab width in the design and analysis in most cases for the design and analysis of both positive and negative moment sections. The current AASHTO LRFD specifications are found to be conservative for configurations with widely spaced girders, especially in negative moment sections.
Fatigue Strength and Evaluation of Double–Mast Arm Cantilevered Sign Structures
Authors: Li Xuejun , Whalen Timothy M. , Bowman Mark D.
Published: May 2018

Double–mast arm cantilevered sign structures are widely used in Indiana and in many other states. Because of the large sign area and relatively high flexibility, wind loading on these sign structures occasionally produces significant stress cycles. Cracking caused by fatigue damage may occur at several critical spots on the sign structures. An analytical investigation of the fatigue lives of the critical details in double–mast arm sign structures is discussed in this paper. An analytical procedure is introduced, and wind load selection and simulation are explained. Finite element models based on a prototype double–mast arm sign structure are described, and dynamic analyses and fatigue life results are presented. It was found that the post-to–base plate socket weld connection was the most critical detail and that variations in the fatigue life occurred because of differences in the wind environment at various sites.
Review of Steel Bridges with Fracture-Critical Elements
Authors: Dexter Robert J. , Connor Robert J. , Mahmoud Hussam
Published: May 2018

This paper presents findings of NCHRP Synthesis Project 35-08 that gathered available information on bridges with fracture-critical members (FCM) from the literature, from a survey of bridge owners and consultant inspectors, and from targeted interviews. In the 1970s, material, design, fabrication, shop inspection, and in-service inspection requirements were improved for steel bridges in general. Special provisions for FCM were then implemented, mainly in reaction to bridge collapses. These requirements transformed the industry and the design of modern bridges so that fatigue and fracture are rare in bridges built in the past 20 years. There is a hidden initial cost in some cases because more expensive superstructure designs are being used than necessary to maintain an acceptable reliability level because of restrictions or more subtle prejudice against bridges with FCM. The major impact on life-cycle costs is the additional mandate for hands-on in-service inspection of FCM. There are also varying definitions of “fracture critical,” and consequently there is wide disagreement in classifying different types of superstructures as fracture critical. Numerous bridges have had a full-depth fracture of a fracture-critical girder and did not collapse, usually because of the alternative load-carrying mechanism of catenary action of the deck under large rotations at the fracture. The capacity of damaged superstructures (with FCM removed from the analysis) may be predicted with refined three-dimensional analysis. However, there is a strong need to clarify the assumptions, load cases and factors, and dynamic effects in these analyses. This paper reports on results of this study.
Prefabricated Bridge Elements and Systems in Japan and Europe
Authors: Russell Henry G. , Ralls Mary Lou , Tang Benjamin M.
Published: May 2018

In April 2004, a scanning tour of Japan, the Netherlands, Belgium, Germany, and France was made to obtain information about bridge construction methods being used to minimize traffic disruption, improve work zone safety, minimize environmental impact, improve constructibility, increase quality, and lower life-cycle costs. From information obtained from the tour, 10 technologies were identified for further consideration and possible implementation into U.S. practices. These included two technologies that allow bridges to be built off site and then moved to their final location in a short time, three superstructure systems and four deck systems that facilitate faster and safer construction, and one substructure system. The two technologies for moving bridges were self-propelled modular transporters and other moving systems, including skidding or sliding, incremental launching, floating, rotating, and lifting of bridges into place. The superstructure systems included a precast concrete deck system known as the Poutre Dalle system, the use of partial-depth concrete decks prefabricated on steel or concrete beams, and U-shaped precast concrete segments with transverse ribs. The deck systems involved full-depth prefabricated concrete decks, special cast-in-place closure joint details, hybrid steel–concrete deck systems, and a multiple-level corrosion protection system. The substructure system consisted of stay-in-place precast concrete panels that serve as both formwork and structural elements for solid and hollow bridge piers.
Assessment and Risk Ranking of Conventionally Reinforced Concrete Bridges for Shear
Authors: Higgins Christopher , Daniels Theresa K. , Rosowsky David V. , Miller Thomas H. , Yim Solomon C.
Published: May 2018

Large numbers of conventionally reinforced concrete bridges remaining in service are lightly reinforced for shear. State-of-the-art assessment of these bridges for shear requires consideration of shear and moment interaction. An assessment and risk-ranking methodology is proposed that incorporates moment–shear interaction. From analyses of vehicle loads on indeterminate bridge models, maximum moment and maximum shear are not coincident at intermediate support locations. Determining the critical combination of shear and moment requires evaluation of envelope values from shear–moment load histories for comparison with capacity curves. Capacity of the sections is determined by using AASHTO modified compression field theory, and statistical understrength is based on experimental test results. Comparison of the load effects and capacity is demonstrated for an in-service bridge to determine the reliability index (measure of relative risk) at sections along a girder. The reliability index can be used to establish rational load restrictions on the basis of a target reliability index for the inventory. The index can also be used for comparison between components and populations of conventionally reinforced concrete bridges for risk ranking. Ranking based on relative reliability indexes permits bridge engineers and managers to prioritize the bridges for repair or replacement.
Prestress Loss Measurements in Missouri's First Fully Instrumented High-Performance Concrete Bridge
Authors: Yang Yumin , Myers John J.
Published: May 2018

Prestress losses have a direct impact on concrete stress development and deflection behavior of highway bridge members. A poor estimate of prestress losses can result in a structure in which allowable stresses are exceeded or camber and deflection behavior is poorly predicted, such that the serviceability of a structure may be adversely affected. This paper reports the prestress losses observed throughout fabrication, shipment, erection, and the first 2 years of service for the first high-performance superstructure concrete bridge in Missouri. The prestress losses investigated included prerelease losses, elastic shortening losses, relaxation losses, creep losses, and shrinkage losses. Results from the study were compared with eight commonly used loss estimate models for total prestress losses, including AASHTO and Prestressed Concrete Institute methods. Recommendations were proposed by the authors for the most appropriate methodology to use to predict prestress losses in high-strength concrete girders accurately.
Connections between Simply Supported Concrete Beams Made Continuous
Authors: Dimmerling Amy , Miller Richard A. , Castrodale Reid , Mirmiran Amir , Hastak Makarand , Baseheart T. Michael
Published: May 2018

Precast bridge girders can be made continuous for live loads with the provision of a moment connection over the supports. NCHRP Project 12–53 examined methods for making this type of moment connection. This is usually done by placing negative moment reinforcement in a cast-in-place deck over the support and by placing a diaphragm between the girder ends. To counteract positive moments caused by creep and shrinkage, positive moment connections are often provided at the girder ends. An experimental study of the strength of six different positive moment details, involving either extended strand or extended bar, was conducted. The results showed that all details had sufficient strength. Details using additional stirrups in the diaphragm were found to have increased ductility, and the use of horizontal web bars increased capacity. Two full-size specimens were tested to determine the level of continuity after cracking occurs at the joints. One of these specimens was also monitored for several months to determine the effects of creep, shrinkage, and temperature on the connections. It was found that expansion and contraction of the deck caused by heat of hydration and changes in ambient temperature greatly affected the system. However, an anticipated formation of negative moment caused by differential shrinkage did not occur. Even when the positive moment connection was near failure, the system maintained 70% continuity even when cracked. The system was also found to have adequate negative moment capacity.
Dynamic Test and Analysis of Curved Steel Box Girder Bridges
Authors: Huang Dongzhou
Published: May 2018

This paper presents experimental and analytical impact factors for two existing curved steel box girder bridges. A Florida Department of Transportation test truck with a total weight of 468.8 kN applied the dynamic loading. The truck speed was incrementally increased from crawl to design speed. To evaluate the test results, the truck was simulated as a nonlinear vehicle model with 15 degrees of freedom. The bridge deck surface was assumed to be good and was simulated as a random process. Test and analytical results show that the impact factors of torsion are normally less than 30%, as are the impact factors of bending moment for bridges with span lengths less than 39 m. The impact factors of vertical shear are generally less than 15%, as are the impact factors of bending moment for bridges with span lengths greater than 50 m. The current AASHTO Guide Specifications for Horizontally Curved Highway Bridges appears to overestimate the dynamic loading of curved steel box girder bridges, especially for bridges with span lengths greater than 50 m. The research results are instructive and applicable to both bridge design and bridge load rating.
Performance of Lightly Confined Reinforced Concrete Columns in Long-Duration Subduction Zone Earthquakes
Authors: Stapleton Seth E. , McDaniel Cole C. , Cofer William F. , McLean David I.
Published: May 2018

The main goals of this research were to evaluate typical 1950s and 1960s as-built bridge columns in western Washington State in large subduction zone earthquakes and to investigate the dependency of failure mechanisms on loading history. Eight displacement histories were applied to eight nominally identical, half-scale, circular reinforced concrete columns expected to respond primarily in flexure (flexure-dominated). The main design deficiencies were a short longitudinal reinforcement lap splice at the base of the column (35 db) and inadequate transverse reinforcement. Test results showed that the failure mode of reinforced concrete columns was controlled by the column loading history. Three distinct failure mechanisms were observed for columns with an aspect ratio of approximately 4.2, assuming symmetric, double-curvature behavior. Large initial displacements greater than six times the effective yield displacement (Δ y) were likely to result in shear failures. Columns experiencing many displacements less than 4Δ y were likely to fail because of longitudinal reinforcement buckling. Columns subjected to several displacement excursions less than 4Δ y followed by an excursion greater than 6Δ y were likely to fail by longitudinal reinforcement slipping within the splice region. Despite the deficiencies present in circular reinforced concrete bridge columns built before 1975 in western Washington State, this study showed that flexure-dominated columns with a 35 db lap splice in multiple-column bent, three-or four-span bridges were not likely to experience significant damage in the predicted Cascadia Subduction Zone earthquake. However, other components of the bridge need to be assessed to determine whether the global bridge response is acceptable under the predicted Cascadia Subduction Zone earthquake.
Seismic Retrofitting of Outrigger Knee Joints
Authors: Shattarat Nasim K. , McLean David I.
Published: May 2018

Experimental tests were conducted on one-third-scale outrigger knee joint specimens to define the vulnerabilities of existing outrigger bents under seismic in-plane loading and to develop appropriate retrofit measures to address the identified vulnerabilities. The specimens incorporated deficiencies present in the outrigger knee joints in the WA-99 Spokane Street overcrossing in western Washington State. The as-built specimens exhibited poor behavior with failure at low ductility levels because of shear distress and reinforcement bond failures within the joint. Threshold principal tension stress values describing the expected condition of the joints were established and compared with values obtained by other researchers. Elbow-shaped circular steel jacketing around the joint and beam region was used to retrofit the as-built specimens. The retrofitted specimens formed a plastic hinge in a gap introduced at the top of the column with improved ductility and energy dissipation capacities when compared to the behavior of similar as-built specimens. Retrofitted outrigger knee joint systems can be expected to achieve ductility levels of at least 5 as well as drift capacities exceeding 6%.
Pressuremeter Investigation for Mass Rapid Transit in Bangkok, Thailand
Authors: Prust Richard E. , Davies John , Hu Shuang
Published: May 2018

The 20-km (12.5-mi) mass rapid transit underground railway system in central Bangkok, Thailand, recently opened for passengers. During construction, the project was divided into two separate civil design–build contracts: the northern section, comprising approximately 10 km (6.2 mi) of twin bored tunnels, and nine stations constructed within slurry walls by adopting top-down techniques. A crucial part of the design of the underground structures was the selection of appropriate design parameters for the slurry walls. The contractor was responsible for ground-related issues and carried out a detailed site investigation to confirm the ground conditions and define soil parameters for the design of the underground structures. The site investigation comprised 40 conventional wash-bored borings and six self-boring pressuremeter tests. This paper describes the site investigation that was carried out for the project and the ground conditions that were encountered, with particular focus on the use of the self-boring pressuremeter to estimate the soil strength, stiffness, and in situ pressure for use in design of the slurry walls. The paper discusses the various methods used to interpret the data and compares the parameters derived from the pressuremeter to those derived from other methods and from back-analysis of the behavior of the wall during construction. It is concluded that in the conditions in Bangkok, the pressuremeter testing provided higher strength and stiffness values than determined from other methods and that these parameters were subsequently borne out by the behavior of the underground structures.
Stress Crack Resistance of Corrugated High-Density Polyethylene Pipes in Different Test Environments and Temperatures
Authors: Hsuan Y. Grace , Zhang Jingyu
Published: May 2018

Corrugated high-density polyethylene (HDPE) pipe 36 in. (900 mm) in diameter was evaluated for its stress crack resistance with the notched constant ligament stress test (ASTM F 2136). Test specimens were taken directly from the pipe liner to include the processing effects. In addition to the standard test condition of 10% Igepal solution at 50°C, tests were performed in water and air at temperatures of 60°, 70°, and 80°C. The test data were analyzed with the ISO 9080 method to define the transition point and ductile-to-brittle curve. The results indicate that the 10% Igepal solution greatly accelerates the stress cracking process, whereas the stress cracking behavior in water and in air is aggressive and practically the same. Activation energies in both ductile and brittle portions of the curve are in general agreement with the literature for HDPE resins. The results indicate that the rate processing method is an accurate model with which to extrapolate data from elevated test temperatures to lower service temperatures. However, Popelar's shift method tends to overestimate the failure times.
Evaluation of the Effect of Lime Modification on the Dynamic Modulus Stiffness of Hot-Mix Asphalt
Authors: Bari Javed , Witczak Matthew W.
Published: May 2018

Hydrated lime is often used as a mineral filler or antistripping additive in hot-mix asphalt (HMA). Many agencies across North America require the use of lime in all HMA mixtures being placed on high-volume roadways. Despite this wide use of lime, its effects on the HMA mixture dynamic modulus (E*) stiffness have rarely been evaluated. The new mechanistic–empirical (M-E) pavement design guide, Guide for Mechanistic–Empirical Design of New and Rehabilitated Pavement Structures, developed under NCHRP Project 1–37A uses E* as the primary material property of asphalt mixtures for the HMA characterization. A comprehensive study was completed at Arizona State University to assess the effect of lime addition on the E* stiffness of HMA mixtures. The study demonstrated that the standard test and design methodologies of the new M-E pavement design guide could be used effectively for lime-modified HMA mixes. With these methodologies, hydrated lime was found to increase the E* of HMA mixtures by 17% to 65% across the range of mixtures, lime contents, and temperature, with an overall average of 25% increase found from 17 mixture–lime percentage combinations across six different HMA mixes. This paper also outlines a provisional protocol for evaluating the E* master curve for lime-modified HMA mixtures using any of the three hierarchical levels found in the new NCHRP Project 1–37A pavement design guide.
Mechanistic and Volumetric Properties of Asphalt Mixtures with Recycled Asphalt Pavement
Authors: Daniel Jo Sias , Lachance Aaron
Published: May 2018

This research examines how the addition of recycled asphalt pavement (RAP) changes the volumetric and mechanistic properties of asphalt mixtures. A Superpave® 19-mm mixture containing 0% RAP was the control for evaluating properties of mixes containing 15%, 25%, and 40% RAP. Two types of RAP were evaluated: a processed RAP and an unprocessed RAP (grindings). Testing included dynamic modulus in tension and compression, creep compliance in compression, and creep flow in compression. Dynamic modulus and creep compliance master curves were constructed with the use of the time–temperature superposition principle to describe the behavior of each mix over a range of temperatures. The voids in mineral aggregate (VMA) and voids filled with asphalt (VFA) of the RAP mixtures increased at the 25% and 40% levels, and there was also an influence of preheating time on the volumetric properties. The dynamic modulus of the processed RAP mixtures increased from the control to 15% RAP level, but the 25% and 40% RAP mixtures had dynamic modulus curves similar to that of the control mixture in both tension and compression. The creep compliance curves showed similar trends. A combination of gradation, asphalt content, and volumetric properties is likely the cause of these trends.
Laboratory Investigation of Mixing Hot-Mix Asphalt with Reclaimed Asphalt Pavement
Authors: Huang Baoshan , Li Guoqiang , Vukosavljevic Dragan , Shu Xiang , Egan Brian K.
Published: May 2018

This paper presents a laboratory study in which the blending process of reclaimed asphalt pavement (RAP) with virgin mixture was analyzed through controlled experiments. One type of screened RAP was blended with virgin (new) coarse aggregate at different percentages. A blended mixture containing 20% of screened RAP was subjected to staged extraction and recovery. The result from this experiment indicated that only a small portion of aged asphalt in RAP actually participated in the remixing process; other portions formed a stiff coating around RAP aggregates, and RAP functionally acted as “composite black rock.” The resulting composite layered structure was desirable to improve the performance of the hot-mix asphalt mixture.
Test for the Presence of Asphalt Antistripping Additive
Authors: Maupin G. W.
Published: May 2018

A small device available commercially uses litmus paper and a spectro-photometer to analyze vapors from hot liquid asphalt binders and mixtures to determine the percentage of antistripping additive present. Approximately 60 five-point additive content–color index count regressions were performed on binders and mixtures to determine how well the device measured additive content. The regressions basically fit the quadratic format used by the manufacturer in the recommended calibration process. The regressions were best when the litmus color index count was calculated by subtracting the initial count of the blank strip from the final count after exposure from the mixtures. Changes to the instrument software and testing temperature were necessary as the investigation progressed to accommodate different grades of binders. After the planned testing was completed, some retesting of the binders was performed with the use of modified equipment and procedures. The changes appeared to improve the consistency of the results. Test results with mixtures were less accurate than for binders; however, if the vapor trap is modified as described, the accuracy for mixtures should be improved substantially. Because the test can be performed quickly, it would be possible to perform multiple tests on a sample. Multiple tests would increase the confidence of the test results.
Comparison of Thin-Lift Hot-Mix Asphalt Surface Course Mixes in New Jersey
Authors: Bennert Thomas , Fee Frank , Sheehy Eileen , Jumikis Andris , Sauber Robert
Published: May 2018

The use of thin-lift hot-mix asphalt (HMA) surface course mixes has gained wide acceptance in the United States as a means of improving ride quality and safety. Generally, these materials are classified as having an open-graded and gap-graded aggregate skeleton, nominal aggregate sizes of 12.5 mm or less, and higher than normal asphalt binder contents and are placed in thicknesses of less than 1 in. (25 mm). The use of the thin-lift materials has been found to improve wet-weather driving conditions, reduce traffic noise associated with the tire–pavement interface, and improve ride quality measurements. Typically, thin-lift HMA surface course mixes found in New Jersey consist of open-graded friction courses and Novachip, with a few roadway sections using microsurfacing and stone-mastic asphalt. Each of these material types is evaluated to provide an assessment of their ride quality and safety. These thin-lift materials are compared with in-service dense-graded asphalt mixes and portland cement concrete (PCC). PCC pavements have three different surface conditions: no treatment, transverse tined, and diamond grind. To establish performance comparisons between the different surface courses, noise measurements using the close proximity method, wet-skid resistance, and ride quality data consisting of the ride quality index and international roughness index were used. The performance information, along with current costs associated with the materials and construction, can provide a means of establishing the cost-effectiveness for the use of these surface treatments under specific situational conditions.
Advanced Testing and Characterization of Interlayer Shear Resistance
Authors: Canestrari Francesco , Ferrotti Gilda , Partl Manfred N. , Santagata Ezio
Published: May 2018

The performance of multilayered pavement systems depends strongly on interlayer bonding. To guarantee good bonding, tack coats (also called bond coats) are usually applied at various interfaces during pavement construction or overlay. The effectiveness of the tack coat can be assessed with the use of several devices arranged by different laboratories to evaluate interlayer shear resistance. This paper shows how interlayer shear resistance may be evaluated through the Ancona shear testing research and analysis (ASTRA) device. ASTRA results, expressed in units of maximum interlayer shear stress (τpeak), highlight the effects of various influence parameters such as type of interface treatment, curing time, procedure of specimen preparation, temperature, and applied normal load. Moreover, this paper compares the τpeak results obtained by two different shear test devices: the ASTRA tester designed and developed in the Polytechnic University of Marche (Italy) and the layer-parallel direct shear tester created by the Swiss Federal Laboratories for Materials Testing and Research. The two test methods provide different but comparable results showing the same ranking of shear resistance for different interface treatments.
Raveling of Asphaltic Mixes Due to Water Damage
Authors: Kringos N. , Scarpas A.
Published: May 2018

Open-graded asphalt mixes are often used for wearing surfaces of roads exposed to large amounts of rainfall throughout the year. The high permeability of the mix guarantees fast drainage of the water away from the surface and thus increases road safety. However, the large amounts of water that flow through the asphalt have a negative effect on the material characteristics of the mastic and cause debonding of the aggregates from the mastic, called raveling. To understand and quantify the physical processes and the mechanics leading to raveling, an extensive experimental and analytical investigation is being undertaken at Delft University of Technology in the Netherlands. One goal of the investigation is the development of the finite element tool RoAM (raveling of asphalt mixes), which is capable of simulating the gradual development of damage throughout asphalt mixes due to water infiltration. Desorption, diffusion, and dispersion are included as fundamental processes. This paper shows the results of a computational analysis to identify the impact of the different water damage phenomena and presents results of a sensitivity study of the relevant parameters. From the computational analyses it is concluded that simulation of water damage in asphaltic mixes is possible if the desorption characteristics as well as the diffusion and dispersion coefficients can be determined.
Estimating Results of a Proposed Simple Performance Test for Hot-Mix Asphalt from Superpave Gyratory Compactor Results
Authors: Faheem Ahmed F. , Bahia Hussain U. , Ajideh Hossein
Published: May 2018

This study intended to use the Superpave® gyratory compactor (SGC) as a basis for estimating the stability of asphalt mixtures as a surrogate for proposed method for the simple performance test. Several asphalt mixtures were produced with varying aggregate sources, asphalt contents, and gradations. Every mixture was compacted with the SGC and evaluated with the repeated compression test procedure for rutting measurements recommended by NCHRP Project 9–19 and the AASHTO 2002 pavement design manual to evaluate whether the results from the SGC can be related to the rutting of mixtures. Densification curves produced by the SGC were used to determine the volumetric properties besides the calculation of the traffic densification index (TDI), which represents the densification experienced by traffic loading during pavement service life. The traffic force index (TFI) was also calculated with a special accessory added to the SGC during compaction (the pressure distributor analyzer). The TFI represents the work done by the traffic to densify the mixture. Results from the mixture rutting tests were used to estimate the flow number (FN). The FN, an important mixture property, is shown to have a strong correlation to the TFI. The TFI was also found to be strongly correlated with the TDI and gives an opportunity to estimate the mixture resistance to compaction forces with the use of its volumetric behavior. The main finding of the study is that the SGC appears to give information that can be used to characterize the stability of the mixtures. Such information could be used as an initial screening criterion to select mixtures for various traffic levels.