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5 Background This chapter provides background, the study objectives and scope, a definition of full-scale accelerated pavement testing (f-sAPT), a summary of the perceived impacts and benefits of f-sAPT, a review of previous syntheses, and a summary of the questionnaire responses from f-sAPT stakeholders. The focus of this synthesis is f-sAPT. Much of the source material refers to accelerated pavement testing (APT) in general, and the convention followed in the synthesis is to use the term f-sAPT for all references to APT, except where the reference is specifically not related to full-scale work, and where it would then be indicated as such. The aim of this NCHRP synthesis is to collate and ana- lyze the research conducted in the area of f-sAPT from 2000 to 2011. NCHRP Synthesis 235 (Metcalf 1996) and NCHRP Synthesis 325 (Hugo and Epps Martin 2004) reported on information pertaining to APT projects until early 2000. Since then, f-sAPT programs in the United States and abroad have expanded and research findings have been published on a wide range of topics. More than 30 f-sAPT programs are currently active in the United States and internationally. There have been three international conferences dedicated solely to APTâ1999 Reno (Nevada), 2004 Minneapolis (Minnesota), and 2008 Madrid (Spain), with the 4th International Confer- ence on Accelerated Pavement Testing planned for 2012 in Davis (California). Presentations and publications stemming from TRB annual meetings, other conferences, and journals have also added to the increase in APT research findings. It is clear that f-sAPT research has generated significant findings, and that the application of these findings has expanded into the broad field of pavement engineering. The f-sAPT narrative over the last decade is well-defined through a focus on the keynote addresses and syntheses of the three International APT conferences held since 1999 (Mahoney 1999; Hugo 1999, 2004; Prozzi et al. 2007; Dawson 2008). Mahoney (1999) posed a number of questions on the impact and applications of APT relating to technology, cost, products and value to customers, and international collaboration. Expec- tations for the future of APT were identified as: ⢠Improved analytical data analysis techniques; ⢠More APT devices in service; ⢠New and improved non-destructive testing equipment complementing APT; ⢠Improved practices (design procedures, specifications, etc.) resulting from APT; ⢠More services and options from the private sector; ⢠Increased use of the Internet for a variety of pavements and APT activities; and ⢠Formation of APT consortia. Hugo (1999) identified the reasons for success for long-term/mature APT programs as part of a multifaceted effort that includes an extensive laboratory program and a cooperative approach that results in rapid and extensive implementation. Technical similarities between the various APT programs include the validation of design procedures, consideration of material performance, consideration of alternative or marginal materials, and measurement and instrumentation. It is acknowledged that APT is an expen- sive tool that must support the management of pavement infrastructure. Partnering and cooperation to ensure eco- nomic use of APT is important and the achievements of APT in evaluation of both traditional and new materials and their properties should be published and marketed. Supple- mental tools for APT have become useful and indeed valu- able as diagnostic tools in their own right. On a technologi- cal level, it is important that the incorporation of improved understanding of loading conditions be supported. The improved modeling of all pavement response modes to enable a better link between APT and long-term pavement performance and real life should be a focus area. Data need to be consolidated and utilized for design and management purposes. The necessity for and power of laboratory material testing in conjunction with APT is well-documented and guidelines are emerging and should be maintained. APT could serve as a proving ground for newly developed mod- els over the full spectrum of pavement engineering. Envi- ronmental conditions for tests need to be improved and understood. The level of application of models in day-to- day pavement design and analysis should drive the level of sophistication. The need to move from elastic layer theory to more sophisticated finite element models (FEMs), also accounting for visco-elastic and nonlinear response, was highlighted. Hugo (2004) opened the 2nd APT conference by not- ing that the overall goal of APT programs is to improve chapter one IntroductIon
6 performance and economics of pavements. To achieve this APT is used to simulate behavior of an equivalent in-service pavement under conventional traffic and prevailing environ- mental conditions. In the process, knowledge is gained over the full spectrum of pavement engineering. Closer linkage is still required between pavement management systems (PMS), in-service highways, and long-term monitoring (LTM) programs. Careful formulation and execution of new APT studies with due regard to the impact of the extensive vol- ume of significant findings from completed APT studies is required. Better national and international collaboration is also required. [Improvement of the understanding and quantifica- tion of environmental effects through specifically structured studies based on what is already known.] Many reports of application of significant APT-related findings leading to increased pavement quality and performance life are available and should be communicated in a well-structured manner to executive decision makers to ensure sustainability of APT as a field of pavement engineering. Prozzi et al. (2007) focused on the long standing link between APT and the history of pavement design and high- lighted the close relationship between TRB and APT and the importance of international collaboration in transportation research. The differences between APT and LTM, long-term effects, the need for improved modeling, and showing the taxpayers the benefits of what is done were highlighted. The importance of international collaboration, the low political profile of APT, and the need for a focus on efficient, safe, sustainable roads was emphasized. Roads agencies identi- fied the major needs as upgrading of the transportation sys- tem, accurate performance predictions, focus on marginal materials, and the performance of rehabilitated pavements, while emphasizing international collaboration. The importance of conducting pre-project benefitâcost ratio (BCR) analyses to define goals and to communicate with the public (âaddress tomorrowâs problems not todayâsâ) is highlighted. Materials producers see new responsibilities, new global environmen- tal challenges, and availability of private-sector funding for APT as the most important issues. A summary synthesis indi- cated that: ⢠APT covers all major pavement response modes, materials, and pavement types; ⢠APT needs advance modeling and quantitative methods to be beneficial to practitioners; ⢠APT pays off through producing significant savings in pavement life-cycle costs, and ⢠Opportunities exist for private funding and international collaboration. Based on the keynotes and syntheses the importance of technical research excellence to enable the most economical use of scarce natural resources to enable a sustainable trans- portation network supported by international cooperation is visible through f-sAPT over the last decade. defInItIon of full-Scale accelerated Pavement teStIng Metcalf (1996) defined f-sAPT as âthe controlled application of a prototype wheel loading, at or above the appropriate legal load limit to a prototype or actual, layered, structural pavement system to determine pavement response and performance under a controlled, accelerated, accumulation of damage in a com- pressed time period. The acceleration of damage is achieved by increased repetitions, modified loading conditions, imposed climatic conditions (e.g., temperature and/or moisture), the use of thinner pavements with a decreased structural capacity and thus shorter design lives, or a combination of these factors. Full-scale construction by conventional plant and processes is necessary so that real world conditions are modeled.â Saeed and Hall (2003) stated the definition of APT to be âthe appli- cation of wheel loads to specially constructed or in-service pavements to determine pavement response and performance under a controlled and accelerated accumulation of damage in a short period of time.â Hugo and Epps (2004) stated that âFor this report, accel- erated pavement testing was defined as the controlled applica- tion of wheel loading to pavement structures for the purpose of simulating the effects of long-term in-service loading con- ditions in a compressed time period.â They defined the scope of NCHRP Synthesis 325 as âdesigned to capture significant findings from full-scale APT, which is defined as the applica- tion of wheel loading, close to or above the legal load limit(s) to a prototype or actual, layered, structural pavement system (Metcalf 1996). The intent of the APT is to determine pave- ment response and performance under a controlled, acceler- ated accumulation of damage in a compressed time period. Accordingly, full-scale test tracks and roads; for example, the Minnesota Road Research Project (MnROAD) were included. However, experimental road sections such as those from the LTPP [Long-Term Pavement Performance] studies were excluded, except where they form an integrated part of an APT program.â The minutes of the TRB Full-Scale Accelerated Pavement Testing Committee [AFD40 (2)] (January 2005) state, âIt is decided by all attendees that APT facilities include only those that test pavement structures and not individual pavement layers. Therefore, the Hamburg Wheel tester and the Asphalt Pavement Analyzer are not considered APT facilitiesâ (Appendix B, Minutes AFD40 meeting, January 11, 2005). Following this line of reporting this synthesis therefore also focuses on full-scale APT as originally defined by Metcalf (1996). Study oBjectIve The specific objective of this synthesis is to expand on the foundation provided in NCHRP Syntheses 325 and 235 on f-sAPT by adding information generated between 2000 and
7 2011, and identify gaps in knowledge and future research needs for f-sAPT. Study ScoPe The study scope incorporates information on all aspects of f-sAPT since 2000. In this regard, the following topics are specifically included: ⢠Evaluation of the operational f-sAPT programs ⢠Discussion of material-related issues as researched through f-sAPT ⢠Discussion on pavement structure-related research using f-sAPT ⢠Application of f-sAPT in the evaluation and validation of new Mechanistic-Empirical (M-E) pavement design methods ⢠Identification of the future needs and focus of f-sAPT. Research and development conducted outside the focus period (pre-2000) are excluded from this synthesis. This work has been covered extensively in the previous syntheses. The inadequate information on some topics, as well as the lack of discussion on early developments by various f-sAPT programs in this synthesis, is the result of this limited period focus. For an understanding of developments in f-sAPT it is thus strongly suggested that the various syntheses on f-sAPT and relevant NCHRP reports be read as a series of documents, and vital developments will be missed if the focus is only on selected documents. It is also important to appreciate that the synthesis is based on published information. There is always work underway on many novel developments that readers may expect to be covered in the synthesis, but that is missing; if such research has not yet been published it would not be covered in this synthesis. ImPactS and BenefItS of accelerated Pavement teStIng The purpose of f-sAPT is to provide a more cost-efficient answer to questions regarding pavement and materials response and performance. The major topics that can be answered cost- effectively using f-sAPT include (Harvey 2008): ⢠Identification and highlighting of deficiencies in current practices ⢠Evaluation of materials, designs, materials specifi- cations, or construction standards before full-scale implementation ⢠Comparison between alternatives for materials, designs, materials specifications, or construction standards under controlled conditions ⢠Assessment of the impact of changes in vehicle tech- nology on pavement performance ⢠Development of insight regarding pavement mechanics and damage mechanisms and validation and calibration of models for pavement analysis and design. Over the last decade more knowledge and responsibil- ity is moving from the road authority to the road contractor. F-sAPT offers the potential for reducing the risks of using new and innovative materials in pavements, but only if it is well-coordinated with laboratory work, field testing, and computer modeling as it provides a link between laboratory tests and long-term pavement performance. F-sAPT typically fills the gap between the uncertainty of the design model and the real, long-term pavement performance. New materials or concepts can be tested under heavy traffic and an equivalent of approximately 15 years of traffic within a short period. F-sAPT provides a good tool for the determi- nation of the effects of special vehicles with complex loading configurations such as the Boeing 777 (specifically with the advent of airfield-loading scaled f-sAPT). The impacts of f-sAPT can thus be observed in improved understanding of pavement behavior in general and pavement performance in particularly (Beuving 2008). Summary of PrevIouS SyntheSeS Three major documents have been prepared on APT since 1996 of which two are syntheses (Metcalf 1996; Hugo and Epps Martin 2004) and one is an NCHRP report (Saeed and Hall 2003). The major trends and outcomes of these documents are summarized to form the basis of the current synthesis. It was deemed important to use these as the starting point for this project, as various issues have already been investigated, evaluated, and sufficiently covered in the previous studies. Highlights from these reports are used to indicate trends and to define the major topics and contents for this document. Major information that did not change over the last decade is summarized in this chapter and not repeated elsewhere. The trends and planned future applications identified in the previous synthesis (Hugo and Epps Martin) are addressed to evaluate to what extent these occurred. Details on specific issues are addressed further in upcoming chapters. metcalf (1996) Metcalf (1996) identified the increasing pressures to effec- tively and economically manage the road systems across all countries within a context of increasing numbers of vehicles and applied loads, requiring continuing efforts to understand and improve the design, construction, maintenance, and rehabilitation technologies for pavements and provision of robust evidence for the regulation of traffic loadings as the basis for f-sAPT. The basis for the traditional pavement design procedures and the understanding of the behavior of layered systems is an historic attempt to physically model pavement response under load with the aim of understanding
8 pavements so that their performance under increased traffic loads can be predicted accurately within an environment of constrained funding for infrastructure and the demand for cost-effective rehabilitation of pavements that have reached or exceeded their original design life. The main goal of f-sAPT is to help develop a methodol- ogy to allow for exploration of new pavement configurations with controlled traffic load parameters that can accumulate damage faster than the anticipated growth of or changes in vehicle technology, with control of nontraffic load factors such as material variability and environmental variation. The first laboratory studies used static loads on pavement materials within a tank to measure the strains and deformations in a partial simulation of a road pavement. This evolved to using repeated loading on multilayer pavements and the use of rolling wheel loading to better simulate the traffic. The next evolution entailed the use of full-scale loads on plates or wheel assemblies applied with static or repeated load systems. Con- struction of test roads over which a load was provided by ordinary vehicles driven repeatedly over the pavement and at about the same time followed. Full-scale test tracks appeared where fully loaded wheel assemblies were running on circular or linear full-size pavement sections. Four basic f-sAPT methods were identified; test roads, circular tracks, linear tracks, and pulse or static loading. Close correlation between results from the different facilities was viewed as unlikely because of the different operational prin- ciples. Limitations in terms of the effect of the combination of environmental factors and time are acknowledged. Although traffic load can be more closely controlled, varied, and mea- sured, the full-load spectra have not yet been applied to test pavements. The primary application of f-sAPT is viewed as an empirical comparison of different pavement configurations, materials, and loading configurations. The secondary appli- cation is viewed as the validation of theoretical pavement response and material behavior models. The application of f-sAPT for determining load equivalencies of different tires, wheel assemblies, and axle groups yielded load factors for use in design and demonstrated that such factors are also dependent on pavement configuration. Early f-sAPT experiments led to major benefits in validating and calibrating theoretical models of pavement behavior, while f-sAPT allowed for further refinement of these models and supported the development of performance models. Initial f-sAPT applications focused on assessment of full- scale pavement configuration and material performance and response to full-scale loads with an emphasis on goal-specific results. The limited provision of the major influence of environmental factors on pavements simulated in f-sAPT is acknowledged, with temperature effects being partially con- trolled. The effects of environmental change, moisture and temperature variation, and curing or aging of materials still exist and these can only be addressed to a limited extent using existing f-sAPT facilities. It was determined that a future strategy should incorporate a strategic approach to pavement research wherever possible and attempt to better coordinate the various f-sAPT programs so that each can build on the experiences of the others; building on improved models of pavement response with compatible material behavior and pavement performance criteria so that the results can be applied across a number of programs. Improvements in instrumentation enabled strain, deflection, and deformation measurements to be possible in accordance with theoretical predictions on pavement tests while tempera- ture can be measured and the effects incorporated in analyses. Moisture changes were less well determined. The literature on the costs and benefits of f-sAPT were still very limited, although the benefits were regarded as substan- tial and effective. Specific benefits are visible in terms of improved design procedures and life estimates; validation of existing, new, nontraditional, and modified materials usage under a range of loading conditions; development and evalu- ation of rehabilitation techniques; improved understanding of the theory of road pavements and general increased confi- dence in pavement designs. The few BCRs calculated ranged between 1.2 and 11.6. Application of f-sAPT results is evident in terms of improved pavement design procedures, modifications of design cata- logues, development and validation of mechanistic pavement and overlay design, and an improved understanding of exist- ing and innovative material behavior. Load-related phenom- ena using aircraft load effects, super single tires, multi-wheel axle groups, and suspension dynamics are being considered as part of research actions. The development of theoretical models has been limited to relatively few facilities, with most concentrating on shorter-term, empirically based, comparative evaluations of materials and pavement layer configurations. Although f-sAPT is viewed as costly, the following pos- sible alternatives provide justification for f-sAPT programs: ⢠Waiting for results to accumulate at a low rate under actual traffic; ⢠Potential cost of failures under actual traffic; ⢠Lack of control of major experimental, traffic, and envi- ronmental variables; and ⢠Difficulties in extrapolating results to other than local applications. The cooperative nature of f-sAPT was already evident with programs selecting appropriate approaches to its par- ticular circumstances within a broader strategy for pavement research. As it was recognized that no device was ideal for all tasks, a number of different philosophies were embodied in the different international facilities. The expectation of advances in telecommunications to facilitate a better link between international f-sAPT programs was evident, with the newly
9 formed TRB Committee on Full-Scale and Accelerated Test- ing (AFD40) expected to bring f-sAPT experts together to share ideas. Major international research programs with the focus on in-service performance monitoring were developed where f-sAPT, laboratory materials characterization, and mechanistic models of pavement behavior were combined to better understand road pavement performance. The primary requirement of f-sAPT programs is to be part of a coherent pavement research strategy as a component of an integrated program of laboratory materials characteriza- tion, f-sAPT, and long-term monitoring (LTM) within which the laboratory program could focus on characterization of materials for use in mechanistic design procedures to be used confidently in the field to refine existing designs and generate new ones. F-sAPT studies should support credible pavement response and performance data that can be used to validate the laboratory materials and theoretical models of pavements in advance of ever-increasing traffic demands and changing vehicle designs. Specific needs for further study included: ⢠Load rate dependency of pavement and material response and performance ⢠Effects of construction and maintenance factors ⢠Extent and effects of environmental changes ⢠Dynamic traffic load parameters. Saeed and hall (2003) The increased use of f-sAPT by highway agencies as a means of evaluating potential construction materials, pavement designs, and other pavement-related features was identified. This research was concerned with APT where full-scale wheel loads are applied to full pavement structures by machines or vehicles in a test facility, at a test track, or on an in-service pavement. The research focused on identification and develop- ment of definitions of data elements associated with APT and recommendation of guidelines for data collection, storage, and retrieval. The data guidelines developed delineate data elements related to APT and their definitions, describe infor- mation on state-of-the-art data storage and retrieval systems, provide recommendations and specifications for a database, and propose data collection frequencies. The various data elements were categorized as follows: ⢠Administrative (details of a particular APT facility or study/experiment being conducted at the facility). ⢠Load application (wheel loadings applied to test pave- ment and the characteristics of the applied loads). ⢠Pavement description (pavement type, construction, and geometric details). ⢠Material characterization (material type, composition, stiffness, strength, and test methods). ⢠Environmental conditions (primarily temperature and moisture data affecting external and internal pavement conditions). ⢠Pavement response (deflections, stresses, or strains mea- sured at the pavement surface and within the pavement structure when subjected to a given load or changes in temperature and moisture). ⢠Pavement performance (various types of pavement sur- face distress, smoothness, and longitudinal and transverse profiles). Data can be collected manually, semi-automatically, or automatically. Electronic text files and spreadsheets are used for small data amounts, whereas dedicated databases were mostly used for large quantities of data. Storage capacity, cost, performance, reliability, and manageability are considered when selecting a data storage and retrieval system. The cooperative nature of APT was demonstrated with APT operators indicating a willingness to share data gener- ated at their facility with other APT operators and researchers. However, nonuniformity in climatic conditions, pavement materials, and construction practices were considered a hindrance to cooperative use of data. They recommended that existing facilities should make their databases more compatible with the proposed guidelines, and new facilities should adopt these guidelines to facilitate use of data among APT facilities, researchers, and other interested parties, which could generate maximum benefits from APT studies. hugo and epps martin (2004) In NCHRP Synthesis 325, Hugo and Epps Martin (2004) focused on programs operational during the period from 1984 to 2004, identifying 28 active programs of which 15 were located in the United States. The development of a new gen- eration of test devices that incorporated partial or full environ- mental control was specifically noted. They stated that APT has been instrumental in validating and refining agency structural design guidelines and improvements in structural design by the insight gained on the effect of the following factors on pavement performance: ⢠Interaction between structural composition and material characteristics, ⢠Importance of bond between layers and the quantifica- tion of the effect, ⢠Influence of concrete slab configuration, ⢠Influence of support under concrete slabs, and ⢠Influence of water on performance and related failure mechanisms. It was shown that APT was useful for answering questions relating to the use of new materials, composite materials, and materials with complex physical characteristics. It further served as a tool for the confirmation and validation of labo- ratory test procedures. APT has become an important tool for developing and evaluating pavement models and assists in answering questions related to rehabilitation, construction, and
10 maintenance. Economic gains as a result of APT were calcu- lated with BCRs varying from 1 to greater than 20. Ancillary artifacts such as the improved understanding of tireâpavement interaction and its effect on performance have been developed within APT environments, and provided a quantitative basis for communicating issues around pavement performance with decision makers. They concluded that APT had served as a means of improv- ing performance and economics of pavements and improved the understanding of the factors that affect pavement per- formance through its ability to explore a wide variety of struc- tural compositions and configurations; simulate mechanisms, conditions, and processes through loading and environment; test and characterize materials; and analyze and understand response and performance. International cooperation was highlighted with an under- standing between the TRB A2B09 committee on APT and the Cooperation for Science and Technology (COST) 347 committee, which focused on as much exchange of informa- tion as possible, and was viewed as paving the way for the European APT programs to share their knowledge in the 2004 survey. The cooperative and collaborative nature of APT was evident from the synthesis, and it was stated that by prudent use of the available information and collaborative research efforts APT programs could advance pavement knowledge more rapidly through planned replication of tests to improve the reliability of findings and establish confidence limits. Specific issues identified for potential collaborative efforts included: ⢠Tracking the performance of in-service pavements that have been tested in APT programs, ⢠Closer correlation with in-service pavement evaluation and long-term pavement monitoring and related PMS programs, ⢠Improvement of the quantification of the environmental impact on APT performance, ⢠Advancement in the understanding of vehicleâpavement interaction to enhance pavement performance prediction, and ⢠The prudent use of the available information to improve the reliability of findings. The application of international APT facilities in supporting warranty contracts and improved management of pavement infrastructure was evident. It appears as if the U.S. APT pro- grams entered a phase of development that should provide the tools, technology, and practices that will enable them to be well prepared for a similar situation. With the trend toward privatization and partnering, the results of APT studies are no longer naturally in the public domain, often slowing down the technology transfer through conferences and publications. In general, APT activities throughout the world have become more linked and this is enhancing exchange of data and information. avaIlaBle InformatIon The information available for this synthesis consisted of responses to an extensive on-line web questionnaire; informa- tion obtained from journal and conference papers published from 2000 to 2011 (published by May 2011); discussions with interested and affected parties regarding f-sAPT, and meeting minutes and presentations of the TRB Full-Scale Accelerated Pavement Testing (AFD40) committee as avail- able on the AFD40 website. This chapter provides a summary of collected information, whereas details on the various topics are provided in chapters two through seven. The approach taken in this synthesis around the citation of specific models and equations is to generally refrain from highlighting specific models and equations that are limited to specific testing and materials conditions and that can be mis- interpreted if the full background to the study is not available. The approach used provides a narrative description of such equations and models and refers the reader to the original reference to appreciate the context and specific details regard- ing aspects such as the pavement structure, environment, and load condition. Information in chapters two through seven are provided in chronological order under appropriate subheadings. Generally, this allows for the development of more detailed research on specific topics over time. Cited references are typically stated at the beginning of relevant paragraphs to ease the reading process. Where appropriate and important for an improved understanding of the information, the state or country of origin of the information is provided. All abbreviations and acronyms are noted at the first instance in each chapter to enable independent study of separate chapters without refer- ence to all previous chapters. Questionnaire analysis The questionnaire was developed and hosted in an online for- mat to which potential respondents were invited. Responses were captured automatically and downloaded and analyzed once all invited and interested respondents completed the ques- tionnaire. Respondents included f-sAPT owners and operators, APT specialists (not necessarily owners or operators), and U.S. state departments of transportation (DOTs) representatives. The full questionnaire is provided in Appendix A, with the list of parties contacted for responses in Appendix B. Details on each of the f-sAPT programs identified are in web-only Appen- dix C, while the detailed questionnaire feedback is summarized in web-only Appendix D. General feedback from the ques- tionnaire is provided in this chapter, with details on each of the specific topics provided in chapters two to through seven. Feedback from the various respondents ranged in detail from the minimum to complete and detailed information and references. To keep a balanced approach in the synthesis most data were summarized in the main body of the synthesis
11 with appropriate expanded information shown in the relevant appendix. Where comparative information was not available for the majority of the respondent programs (i.e., funding levels of f-sAPT activities) it has been excluded in the body of the report to prevent incorrect conclusions from being formed based on a very limited data sample. journal and conference literature Journal and conference proceedings from 2000 to 2011 have been sourced for papers covering f-sAPT topics. It has become increasingly more common for conferences to host dedicated f-sAPT sessions in their programs. A number of the papers touch on more than one specific topic, whereas there are also cases where more than one paper covers the same set of tests or developments from different perspec- tives. The approach used in the synthesis limits the use of specific references to the main topic of the paper and com- bines references on a specific topic where appropriate. Most of the citations on a specific topic are provided in chronologi- cal order. References not specifically cited are included in the Bibliography. discussions with affected Parties Discussions were held throughout the project with various affected stakeholders regarding the contents supplied for the synthesis. Where the information was of a supporting or explanatory nature to the published information, these discussions are not separately referenced. Where additional information was supplied through such discussions, and no published reference existed, the source is identified as such. trB full-Scale accelerated Pavement testing (afd40) minutes and Presentations The TRB Full-Scale Accelerated Pavement Testing committee (AFD40) started as a task force (A2B09); currently, it func- tions as a full committee and tracks presentations and papers linked to its activities through an active website and commu- nication with members (http://www3.uta.edu/faculty/sroman/ AFD40). The public domain information from this committee has been incorporated into the synthesis where appropriate and cited as such. QueStIonnaIre feedBack Summary This section contains a summary of Section 2 of the question- naire, which covered general perceptions regarding f-sAPT. The detailed information gleaned from the questionnaires is used in the various chapters of the synthesis. Where respon- dents provided information in the questionnaire that could not be substantiated with an official reference, the questionnaire responses and Appendix D are cited as a reference. The questionnaire targeted three groups of respondents. First, a group of specialists who have worked in the field of f-sAPT and are not actively involved was used to ensure that âolderâ knowledge is not lost (five respondents). Second, all 50 U.S. state DOTs were invited to participate through invitations sent to the staff responsible for pave- ments in accordance with the AASHTO Subcommittee on Design membership list (http://design.transportation.org/ Pages/Directory.aspx, accessed May 4, 2011) of December 2009. As shown in Appendix A, the first question after the biographical information allows the respondent the option to immediately indicate whether or not they are interested in completing the survey (no interest in APT activities from the respondent/state). Thirty-eight responses were received from U.S. state DOTs indicating that 32 states were interested in APT and 6 were not. Third, 43 known U.S. and international operators and owners of f-sAPT devices were invited to respond to the questionnaire. This is an increase of 15 over the number iden- tified in the Hugo and Epps Martin synthesis (2004), although only 29 of these programs responded and completed the ques- tionnaire in various levels of detail. Where details were not supplied by programs through the questionnaire, details of the programs have been identified through papers and web- sites and added to the synthesis. The total number of respon- dents in tables and graphs do not always add up to the total number of respondents for the survey, as some respondents did not answer all survey questions. A total of 72 unique responses were obtained from the com- bination of U.S. state DOTs, specialists, and APT programs. Fifty-six (77%) of the respondents viewed the importance of f-sAPT as high, with 13 viewing it as medium and only 3 holding the view that the importance is low. The major roles seen for f-sAPT are pavement structure and basic materials research, while commercial evaluation of products is deemed as playing a smaller role (Figure 1). Thirty-nine respondents viewed the future of f-sAPT as a normal part of operations and increasing (Figure 2). The major benefits of f-sAPT are viewed as improved structural and material design methods, performance modeling, and evaluation of novel materials and structures (Figure 3). rePort Structure The synthesis starts with the introduction and general proj- ect background, incorporating the general perceptions of respondents to the questionnaire. Chapter two focuses on the current f-sAPT programs and associations, as well as equip- ment and sensors typically used. In chapter three issues around pavement materials and pavement structure research are cov- ered, while chapter four focuses on the interaction of loads and the environment. Chapter five evaluates modeling and analysis of data, and chapter six discusses benefits (economi- cal and others) of f-sAPT. Chapter seven reviews expected
12 0 10 Pa ve me nt str uc tur e r es ea rch Ba sic m ate ria l re se arc h Tra ffic lo ad ing Ev alu ate re ha bili tat ion op tio ns Ev alu ate sp ec ific ap plic ati on iss ue s Fu nd am en tal re se arc h (l ong ter m) De ve lop me nt of gu ide line s Pa ram ete r re se arc h (t em per atu re, etc ) Ac ad em ic f oc us ed re se arc h Co mm erc ial eva lua tion s Oth er 20 30 40 50 60 70 N um be r o f r e sp o n de nt s FIGURE 1 Anticipated roles of f-sAPT according to respondents. 0 5 10 15 20 25 30 35 40 45 Normal part of operation as required Growing Replace f-sAPT with simulations and advanced computer analyses Other N um be r o f r es po nd en ts FIGURE 2 Perceptions regarding the future of f-sAPT.
13 future developments and incorporates the major conclusions of the synthesis. Full references are provided together with a Bibliography. The appendices provide detailed information obtained from the questionnaire. chaPter Summary Chapter one focused on the background to the synthesis and provides the historical introduction through a timeline dis- cussion of previous synthesis documents and the keynote addresses of the first three international APT conferences. It provides the definition used for f-sAPT as well as the ori- gin of the information used in the synthesis. It explains the focus period of the synthesis and the importance of viewing the various f-sAPT syntheses and NCHRP documents as an ongoing and complementary series of references. Finally, it provides background on the surveyed respondents, the number of respondents providing inputs to the synthesis, and sum- marizes these responses on general perceptions regarding the roles, benefits, and future of f-sAPT. 0 10 Im pro ve d s tru ctu ral de sig n m eth od s Im pro ve d m ate ria l d es ign m eth od s Ev alu ati on of no ve l m ate ria ls / str uct ure s Im pro ve d p erf orm an ce m od elin g De ve lop m en t o f p er for m an ce - re lat ed spe cifi ca tio ns Ma ter ial da tab as es Be tte r u nd ers tan din g o f va ria bili ty Im pro ve d p av em en t m an ag em en t Wa rra nty co ntr ac ts Oth er 20 30 40 50 60 70 N um be r o f r es po nd en ts FIGURE 3 Perceptions regarding the benefits of f-sAPT.
