U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000


Skip to content
Facebook iconYouTube iconTwitter iconFlickr iconLinkedInInstagram

Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations

 
REPORT
This report is an archived publication and may contain dated technical, contact, and link information
Back to Publication List        
Publication Number:  FHWA-HRT-14-088    Date:  March 2015
Publication Number: FHWA-HRT-14-088
Date: March 2015

 

Long-Term Pavement Performance Ohio SPS-1 and SPS-2 Dynamic Load Response Data Processing

7. DLR TRACE ISSUES

Some dubious sensor trace patterns were encountered in the processing of the Ohio SPS-1 and SPS-2 DLR data. For example, some sensor traces exhibited a flat unresponsive pattern. Other sensor traces indicated the mislabeling of a transverse strain gauge as a longitudinal strain gauge.

OHIO SPS-1 TRACE ISSUES

LVDT Trace Pattern Issue

All of the LVDTs were buried deep in the subgrade or close to the interface between the subgrade and the base layer in the Ohio test sections. Thus, LVDT traces should not contain any trace valleys (no tensile strains) but only peaks (compressive strains). However, the LVDT3 sensor for tests J2A, J2C, J2D, J2E, J2F, and J2G (test section 390102) showed a trace pattern similar to a longitudinal strain gauge trace that assumes valleys. Figure 16 shows LVDT3 trace in test J2A with a trace pattern similar to a longitudinal strain gauge trace.

This graph shows the transverse linear variable differential transformer (LVDT)-3 test J2A run 5 longitudinal strain gauge trace that assumes valleys. The x-axis shows time and ranges from 0 to 4 s. The y-axis shows inches and ranges from -0.002 to 0.014 inches. The plot has three peaks ranging from 0.011 to 0.013 inch and several minor valleys ranging from -0.001 to -0.002 inch in the range of approximately 1.25 to 1.75 s.
Figure 16. Graph. Transverse LVDT3 longitudinal strain gauge trace that assumes valleys

Strain Gauge Trace Pattern Issue

Strain gauge sensors Dyn10 and Dyn11 for tests J2A, J2C, J2D, J2E, J2F, and J2G in test section 390102 showed a flat unresponsive trace pattern. The assumption was that the sensors were not connected properly. Figure 17 shows flat strain gauge sensor Dyn10 trace in test J2A.

This graph shows results from an unresponsive strain gauge trace from Dyn10 test J2A run 5. The x-axis shows time and ranges from 0 to 4 s. The y-axis shows microstrain and has one coordinate label, which is -3.638ï‚´10-12 microstrains that is repeated throughout the length of the y-axis. The plot shows a horizontal line.
Figure 17. Graph. Unresponsive strain gauge trace

Longitudinal strain gauges are expected to assume trace valleys, whereas transverse strain gauges are not. However, longitudinal strain gauge sensor Dyn17 for tests J8A, J8D, J8E, and J8G (test section 390108) showed a trace pattern that, if flipped, is similar to a transverse strain gauge trace that assumed no valleys. Figure 18 shows the longitudinal Dyn17 strain gauge trace in test J8A exhibiting an upside down transverse strain gauge trace pattern.

This graph shows a longitudinal Dyn17 strain gauge trace for test J8A run 4 exhibiting an upside down transverse pattern. The x-axis shows time and ranges from 0 to 4 s. The y-axis shows microstrain and ranges from -50 to 10 microstrains. The plot has three valleys ranging from -25 to -49 microstrains in the range of approximately 1.6 to 2.25 s, with the deepest valley being the third one around -49 microstrains.
Figure 18. Graph. Longitudinal Dyn17 strain gauge trace exhibiting an upside down transverse pattern

The LVDT3 and Dyn17 strain gauge sensors for test sections 390102 and 390108 may have been mislabeled inadvertently. The data collection dates match for tests in both test sections. For example, the data collection date for tests J2A (LVDT3) and J8A (Dyn17) were the same. Similarly, data collection dates for tests J2D, J2E, and J2G (LVDT3) were the same as for tests J8D, J8E, and J8G (Dyn17), respectively.

The peak data information contained in Ohio truck peak (TruckPeak.txt) file was unclear. The data have peak values recorded for the same sensor number and run number but at different sensor locations. Table 18 shows sample truck peak data for test section 390102 strain gauge sensor Dyn12 run 1. The column labeled "X" represents the estimated position of the front-axle at the time when the peak occurred. Specifically, it is the X-coordinate measured from the southernmost deep LVDT in the AC sections. The column labeled "Peak Value" shows the recorded front-axle peak values. The actual location of strain gauge sensor Dyn12 from the measured southernmost deep LVDT in the AC sections was 192 inches (X = 192 inches), but the truck peak data showed multiple sensor locations (X values). Also, the peak value of 411.40 µe at X = 194.7 inches closely matched the first peak value extracted from the DLR data process, which was 433.04 µe at X = 192 inches.

Table 18. Sample Ohio SPS-1 truck peak data for test J2F.

Series

Subseries

Run

Section

Sensor Name

Sensor Number

X (inches)

Peak Value
( µe)

2

F

1

390102

Dyn

12

30.0

-118.60

2

F

1

390102

Dyn

12

55.8

758.00

2

F

1

390102

Dyn

12

71.0

-203.30

2

F

1

390102

Dyn

12

120.1

5.03

2

F

1

390102

Dyn

12

171.5

-57.61

2

F

1

390102

Dyn

12

194.7

411.40

2

F

1

390102

Dyn

12

209.9

-114.10

 

The beginning offset, ending offset, and range values for strain gauges, LVDTs, and PCs obtained from the DLR raw traces did not match the beginning and ending offset and range values in SDR 22.0.(6) Per the technical support service contractor's recommendations, the beginning offset, ending offset, and range columns were removed and do not show up in SDR 27.0.(1)

OHIO SPS-2 TRACE ISSUES

The DLR SPS-2 data information was reviewed for data discrepancies before processing. Data information included the SPS-2 TCS raw data, the OU data, SDR 22.0 DLR data, and information from Evaluation of Pavement Performance on DEL 23.(12) Site visits A, B, and C of SPS-2 tests J1, J5, J8, and J12 (test sections 390201, 390205, 390208, and 390212, respectively) were inconsistent with SPS-2 subseries H, I, and J of the OU file. In contrast, site visits A through G of SPS-1 tests J2, J4, J8, and J10 (test sections 390102, 390104, 390108, and 390110, respectively), had matching subseries in the OU data file. The data collection dates of the SPS-2 test section visits A, B, and C, however, matched subseries H, I, and J, respectively, of the OU data file. Since subseries A through G had already been used for SPS-1, the assumption is that OU assigned H, I, and J in place of A, B, and C for SPS-2. Also, the wheelpath offset values in SDR 22.0 for SPS-2 were populated from subseries H, I, and J of the data file for test sections A, B, and C, respectively. Table 19 shows the inconsistencies between the SPS-2 test section visits and the OU subseries.

Table 19 . Ohio SPS-2 inconsistencies between test section visits and subseries.

Raw Ohio-TCS Data

Test Truck
Series from
Sargand et al. (12)

OU Data

Test Job

No. of Files/Runs

Test Date

Subseries

Start Time for
Run 1*

J1A

28

8/12/1996

2

H

15:15:00

J1B

26

8/13/1996

2

I

11:00:00

J1C

14

8/14/1996

2

J

10:11:00

J5A

29

8/12/1996

2

H

15:15:00

J5B

26

8/13/1996

2

I

11:00:00

J5C

14

8/14/1996

2

J

10:11:00

J5J1M

18

7/29/1997

4

M

13:10:00

J5J1N

18

7/30/1997

4

N

10:20:00

J5J1O

18

7/30/1997

4

O

13:32:00

J5J1P

18

8/06/1997

4

P

07:18:00

J8A

26

8/12/1996

2

H

15:15:00

J8B

27

8/13/1996

2

I

11:00:00

J8C

17

8/14/1996

2

J

10:11:00

J8S3M

18

7/29/1997

4

M

13:10:00

J8S3N

18

7/30/1997

4

N

10:20:00

J8S3O

18

7/30/1997

4

O

13:32:00

J8S3P

18

8/06/1997

4

P

07:18:00

J12A

4

8/12/1996

2

H

15:15:00

J12B

27

8/13/1996

2

I

11:00:00

J12C

14

8/14/1996

2

J

10:11:00

J12J10M

18

7/29/1997

4

M

13:10:00

J12J10N

18

7/30/1997

4

N

10:20:00

J12J10O

18

7/30/1997

4

O

13:32:00

J12J10P

17

8/06/1997

4

P

07:18:00

*The dates of the runs in this column are the same as the test dates listed in column 3.
Note: Test truck series 2 and 4 were used for Ohio SPS-2.

 

SPS-2 DLR sensors LVDT5 and LVDT6 were unresponsive for all tests; LVDT5 and LVDT6 records all had zero values.

The ASCII files for SPS-2 tests J5J1M, J5J1N, J5J1O, J5J1P, J8S3M, J8S3N, J8S3O, J8S3P, J12J10M, J12J10N, J12J10O, and J12J10P had 32 LVDT sensors (LVDT1 through LVDT32). The other tests (J1A, J1B, J1C, J5A, J5B, J5C, J8A, J8B, J8C, J12A, J12B, and J12C) had only 16 LVDT sensors (LVDT1 through LVDT16). The DLR study team processed only the first 16 LVDTs (LVDT1 through LVDT16) based on information present in the OU EmbeddedSensor.txt file, which showed only the first 16 LVDTs.

Table 20 shows strain gauge sensors for each SPS-2 test that had time history data. For example, test J1A had eight strain gauge sensors of which only four sensors (Dyn1, Dyn4, Dyn5, and Dyn8) had time history data. The other strain gauge sensors (Dyn2, Dyn3, Dyn6, and Dyn7) did not have time history data.

Table 20 . Strain gauge sensors with time history data for each test.

Test Job

Test Section

Strain Gauge Sensors that have Time History Data

J1A

390201

Dyn1, Dyn4, Dyn5, and Dyn8

J1B

390201

Dyn1, Dyn4, Dyn5, and Dyn8

J1C

390201

Dyn1, Dyn2, Dyn7, and Dyn8

J5A

390205

Dyn1, Dyn4, Dyn5, and Dyn8

J5B

390205

Dyn1, Dyn2, Dyn7, and Dyn8

J5C

390205

Dyn1, Dyn2, Dyn7, and Dyn8

J8A

390208

Dyn1, Dyn4, Dyn5, and Dyn8

J8B

390208

Dyn1, Dyn2, Dyn7, and Dyn8

J8C

390208

Dyn1, Dyn2, Dyn7, and Dyn8

J12A

390212

Dyn1, Dyn4, Dyn5, and Dyn8

J12B

390212

Dyn1, Dyn2, Dyn7, and Dyn8

J12C

390212

Dyn1, Dyn2, Dyn7, and Dyn8

J5J1M

390205

Dyn1, Dyn2, Dyn7, and Dyn8

J5J1N

390205

Dyn1, Dyn2, Dyn7, and Dyn8

J5J1O

390205

Dyn1, Dyn2, Dyn7, and Dyn8

J5J1P

390205

Dyn1, Dyn2, Dyn7, and Dyn8

J8S3M

390208

Dyn1, Dyn2, Dyn7, and Dyn8

J8S3N

390208

Dyn1, Dyn2, Dyn7, and Dyn8

J8S3O

390208

Dyn1, Dyn2, Dyn7, and Dyn8

J8S3P

390208

Dyn1, Dyn2, Dyn7, and Dyn8

J12J10M

390212

Dyn1, Dyn2, Dyn7, and Dyn8

J12J10N

390212

Dyn1, Dyn2, Dyn7, and Dyn8

J12J10O

390212

Dyn1, Dyn2, Dyn7, and Dyn8

J12J10P

390212

Dyn1, Dyn2, Dyn7, and Dyn8

Note: All Ohio SPS-2 test sections had eight strain gauge sensors deployed.

 

Table 21 shows multiple peak values for Dyn1 run 1. Based on the Embeddedsensor.txt file, the location of the Dyn1 sensor was 84 inches from the southernmost first LVDT (the coordinate reference point), so the first peak value of -22.07 was compared to the smooth first peak values extracted from SPS-2.

Table 21 . Sample Ohio SPS-2 truck peak data for test J1A.

Series

Subseries

Run

Section

Sensor Name

Senor Number

X (inches)

Peak Value
(
µe)

2

H

1

390201

Dyn

1

18.6

3.00

2

H

1

390201

Dyn

1

82.3

-22.07

2

H

1

390201

Dyn

1

153.9

11.14

2

H

1

390201

Dyn

1

222.0

-44.72

2

H

1

390201

Dyn

1

311.9

4.95

Note: Subseries "H" infers "A." Please see the second bullet under Ohio SPS-2 data issues in chapter 10.

 

In table 22, Dyn8 strain gauge from test J5J1P runs 1-10 collected at 499.964 Hz on August 6, 1997, had significantly larger raw strain values compared to other SPS-2 strain gauge values, which were mostly less than 100 µe. Thus, further investigation is needed for this strain gauge.

Table 22 . Raw Dyn8 strain gauge values of test J5J1P.

State Code

SHRPID

Run Number

Minimum Strain Raw Value ( µe)

Maximum Strain Raw Value ( µe)

39

0205

1

19,939.61

19,974.62

39

0205

2

20,024.00

20,058.39

39

0205

3

19,990.25

20,027.13

39

0205

4

20,066.51

20,097.77

39

0205

5

20,164.66

20,200.29

39

0205

6

20,224.04

20,257.80

39

0205

7

20,269.05

20,307.19

39

0205

8

20,340.94

20,372.82

39

0205

9

20,386.58

20,422.21

39

0205

10

20,458.47

20,483.47

The first 500 trace data points were used to average a gain adjustment factor for SPS-2 data. On average, each SPS-2 time history dataset contains close to 7,000 data points, whereas each SPS-1 time history dataset contains about 5,000 data points. Due to significant noise in the SPS-2 data, the first 500 data points may not be enough. For future research, the first 700 data points should be used to determine a gain adjustment factor for SPS-2 data, where 700 is approximately 10 percent of each SPS-2 time history dataset.

As with the SPS-1 data, the SPS-2 beginning offset, ending offset, and range values for strain gauges and LVDTs obtained from the DLR raw traces did not match the beginning and ending offset and range values in SDR 22.0. Per the technical support service contractor's recommendations, the beginning offset, ending offset, and range columns were removed and did not show up in SDR 27.0.

 

Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000
Turner-Fairbank Highway Research Center | 6300 Georgetown Pike | McLean, VA | 22101