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30 In a technology brief by IDOT's BMPR, specific uses of AC overlay, were developed at YONA Engineering Con- FWD data were listed. On rigid pavements, the brief lists sulting & Management in Israel. This method reduces SNeff the following uses ("Pavement Technology Advisory . . ." calculations into five equations. Previously, SNeff determi- 2005): nation was done through an empirical process developed by AASHTO. Deflection basins measured by FWDs form Locating areas of poor support beneath jointed con- the first step in the YONAPAVE process. The area under a crete pavements plot of FWD deflections versus distance forms the basis for Determining load transfer across transverse and longi- a characteristic length 10 equation, whose value is then car- tudinal joints ried through a calculation of subgrade modulus of elasticity Estimating subgrade and pavement layer elastic moduli Esg. SNeff can then be determined from the 10 and Esg values. values (E1, E2, etc.) The SNeff values generated by the YONAPAVE process cor- Developing cost-effective maintenance and rehabili respond "in generally good agreement" with values calcu- tation alternatives lated by the MODULUS or AASHTO NDT interpretation approach (Hoffman 2003). On flexible pavements, the IDOT brief lists the following uses ("Pavement Technology Advisory . . ." 2005): To accomplish the elimination of spring load restric- tions by 2002, the Alaska DOT and Public Facilities (Alaska Determining the structural adequacy of a pavement DOT&PF) conducted FWD tests on all roads where spring and identify causes of failure load restrictions had been practiced. In all cases, recommen- Determining uniformity of support along a project and dations were made for AC overlays on the existing AC pave- identify weak areas ments based on the FWD data (Bush and Tohme 2003). Estimating subgrade and pavement layer elastic moduli values (E1, E2, etc.) Developing cost-effective maintenance and rehabili CASE 3. JOINT SEALING EVALUATION tation alternatives The Concrete Pavement Technology Program Task 9 research When conditions warrant, California's PCC roadways study, Cost-Effectiveness of Sealing Transverse Contraction may be rehabilitated by replacing individual slabs. These Joints in Concrete Pavements (Hall et al. 2004), utilizes slabs, which must measure at least 3.6 m (12 ft) in width and FWD analysis of joint load transfer and voids to analyze the 2 m (6.6 ft) in length, are considered good candidates for performance of PCC pavements with sealed and unsealed replacement if a visual inspection shows two or more corner joints. According to the authors, the study is expected to breaks; if they contain "third-stage cracking," segments that answer the following questions: move relative to each other, longitudinal or transverse cracks wider than 13 mm (0.5 in.), or cracks with 150 mm (6 in.) or What are the effects on long-term performance of more of spalling; or if they are no longer supported because unsealed transverse joints in concrete pavements with of settlement, base failure, or excessive curling. Once a visual different pavement cross sections and slab dimensions, inspection is done, the guidelines recommend FWD usage, traffic levels, and climatic conditions? along with drainage analysis and coring, to determine pave- What are the effects of different transverse joint seal- ment condition ("Slab Replacement Guidelines" 2004). ant materials and configurations on the long-term per- formance of concrete pavement in various climatic The New York State DOT (NYSDOT) evaluates pave- conditions (climatic zones)? ment structural capacity using FWD, but not on the project Is sealing transverse contraction joints cost-effective level. Additionally, tests are done only in the following situa- for different pavement designs and materials over a tions (Comprehensive Pavement Design Manual 2000): range of climatic zones and traffic levels (Hall et al. 2004)? Deflection survey of 50 statewide sites as a part of pavement performance monitoring program Deflection survey of 48 statewide sites as part of a CASE 4. Pavement Management Systems SUPERPAVE performance monitoring program Determination of load transfer efficiencies at joints and Several states include FWD data in their PMSs. For exam- cracks of PCC pavements ple, Nebraska's PMS stores FWD data that are collected by Determination of the appropriateness and effectiveness the Materials and Research Division. These data are used for of cracking and seating, and rubblizing operations "structural capacity analysis, evaluation of existing subgrade strength, and overlay analysis." Deflection test locations and The YONAPAVE algorithms for evaluating the effective frequency will vary according to project conditions (State of structural number (SNeff ), and thereby the thickness of an Nebraska Pavement Management Systems 2007).