Hamburg Wheel-Track Test Equipment Requirements and Improvements to AASHTO T 324 (2016) / Chapter Skim
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9 • Impression measurement system; • Temperature measurement and control system; • Wheel dimensions; • Wheel loads; • Specimen and track length; and • Data collection and reporting. Other factors within the current standard were also analyzed to accommodate any changes and new recommendations as needed.
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10 (a) Overall setup (b)
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11 1. The video file was split into individual image frames.
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12 Figure 3 Wheel position as a function of time 3.3.2 Impression Measurement System Section 5.3 of the AASHTO T 324 specification requires that an LVDT be used to measure the impression of the wheel as it tracks over the specimen. It further specifies that the LVDT have a minimum range of 20 mm (0.8 in.)
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13 Figure 4 Metal specimen for verifying locations of deformation readings During the course of the study, the research team fabricated a new metal specimen with a longer curved track length to avoid the problem of the wheel "climbing out" of the track. The machine drawing of this metal specimen and the analytical solution of the wheel and metalspecimen interaction is presented in Appendix C
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14 The calibration of the impression measurement systems from the vendors were verified as described in the instruction manuals provided with the machines. Next, the aluminum specimen was installed in each of the machines to verify that the readings were being recorded at exactly the locations specified by the vendors.
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15 (b) Recording deformation readings along the curvature (ruler shown for scale)
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16 Figure 7 Curvature of the metal specimen recorded by machine LVDT connected to data acquisition system 3.3.3 Temperature Control System The temperature control system comprises a water tank, heater(s) , temperature sensor(s)
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17 Figure 8 Temperature sensor locations 3.3.4 Wheel Dimensions The thickness and diameter of the wheels from the different manufacturers were measured. A digital caliper was used for this task.
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18 3.3.5 Wheel Loads Section 5.1 of AASHTO T-324 specifies the load on the wheel is 703 ± 4.5 N (158 ± 1.0 lbs.)
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19 Figure 11 Specimen mold (reproduced from AASHTO T 324) 3.3.7 Free Circulating Water on Mounting System Sections 5.5 and 5.6 of AASHTO T-324 requires that the specimen mounting system (slab or cylinder)
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20 (a) Measurement procedure (b)
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