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22 Quality Control/Quality Assurance of AASHTO DARWin Analyzed Data Used by 21% of survey respondents (Appendix B, Question The Long-Term Pavement Performance Program Manual 59), DARWin automates the processes in the 1993 AASHTO for Falling Weight Deflectometer Measurements (Schmalzer Guide for the Design of Pavement Structures. Version 3.1, 2006) lists the software data checks required. These data the most recent version, is designed for 32-bit versions of checks are discussed in greater detail in chapter four: Windows operating systems. Back-calculation is based on a mathematical iteration. As inputs, the program accepts Roll-off Dynatest version 20, KUAB, and PDDX files, but it cannot Nondecreasing deflections use Dynatest version 25 files ("AASHTOWare DARWin Overflow Product Features" 2005). Load variation--set to 18 kN + 0.02X (4,000 lbf + 0.02X), where X represents successive drop loads Carl Bro RoSy DESIGN for Roads Deflection variation--set to 2m + 0.01X (0.0787 mils + 0.01X), where X represents successive mea- Based on a fast Fourier transformation algorithm, Carl Bro's sured deflections RoSy DESIGN software calculates pavement layer stresses and strains in a 32-bit Windows environment. Additionally, FWD data should be processed onsite using FWDCon- RoSy DESIGN is able to link backcalculated data to a geo- vert and FWDScan (Schmalzer 2006). Once at the office for spatial database. The program is compatible with "data from processing, the data are subjected to a variety of software any FWD equipment" ("Carl Bro RoSy DESIGN Product and correction algorithms. Data Sheet" 2006). Despite its availability with all Carl Bro FWDs, no SHAs reported using RoSy DESIGN (Appendix Other Findings B, Question 59). In the early 1960s, California began measuring pavement Dynatest ELMOD deflections using a device of its own design. Known as the California Traveling Deflectometer, the device exerted A plurality of SHAs surveyed reported that Dynatest's a simulated 80 kN (18,000 lbf) single-axle force, while a ELMOD (an acronym for Evaluation of Layer Moduli and Benkelman Beam measured the resulting deflections. This Overlay Design) is their FWD analysis package of choice. unique device is a fundamental standard by which Califor- Used by 21% of survey respondents, ELMOD is currently nia compares all other nondestructive pavement deflection at version five. Back-calculation is based on a mathematical testing devices. While using the Caltrans flexible pavement iteration, and the user may choose between the finite-ele- rehabilitation design method, deflections are correlated to ment, linear elastic theory or a nonlinear subgrade algo- the California Deflectometer. Additionally, FWD data are rithm by means of add-ons. The program operates in a 32-bit correlated to a standardized reference FWD load, FWDref, Windows environment. ELMOD 5 is able to read Dynatest which transmits a 40 kN (9,000 lbf) load to a loading plate versions 9, 10, 20, and 25 files, as well as Microsoft Access 305 mm (12 in.) in diameter. The correlation function is database files generated by Dynatest WinFWD. illustrated in Eq. (2), KUAB ERIDA (2) For FWD data analysis, KUAB provides the ERIDA soft- where D (CD) is the California Deflectometer equivalent ware package. KUAB's pavement analysis software is com- deflection and D (FWDref) represents deflections measured patible with Dynatest FWD equipment ("Pavement Analysis by the reference FWD. Additionally, any FWDs must pos- Software" 2003). The program supports KUAB's FWD for- sess a valid calibration certificate issued by an FWD calibra- mat, Unicode text files, and PDDX files. Despite its compat- tion center ("California Test 356 . . ." 2004). ibility and possible bundling with KUAB FWDs, no SHAs reported using ERIDA for data analysis (Appendix B, Ques- tion 59). Data Analysis Software MODCOMP FWD manufacturers bundle their own software with the FWDs they sell, but each software package is available for Currently in version 6, MODCOMP was reported as the data separate purchase. The following sections describe the vari- analysis package of choice by two SHAs. The program sup- ous software packages available. ports linear and nonlinear modeling criteria (Stubstad et al. 2000). MODCOMP is freely available and was developed by