Study of Long-Term Pavement Performance (LTPP): Pavement Deflections
Chapter 2. LTPP Data Screened and Reviewed
Data Request
The level E FWD load-deflection data (Data Release 9.0, November
23, 1998) were requested and received when this project began in
1998. Included with this requested information were up-to-date FWD
loads and deflections, along with all pertinent ancillary FWD data.
All data were then processed as described below.
Data Organization for Screening and Processing
The data obtained from the database were organized for detailed
analyses. Specifically, the largest volume of LTPP data in the
database, the FWD load-deflection data from the “*.M06” data
tables, was reorganized as follows:
- Each level E load-deflection data record was retrieved from the
database tables in comma-delimited format, with four directories
(i.e., one *.M06 subdirectory for each of the four LTPP regions).
For each regional *.M06 file, the data were reorganized into
“sections” and “dates of test” while retaining the original format
(comma delimited, columns A through W or 1 through 23).
- For each LTPP region, subdirectories were then created using a
six-character section identification name, with the first two
characters being the State number and the last four being the LTPP
section identification number. For example, an analysis
subdirectory in Region 4 called “040122” denotes State #04
(Arizona) and LTPP section #0122 (Specific Pavement Studies
(SPS)–1, section 22). In this report, an individual test section
(for instance, section 040122) may also be referred to as section
04–0122.
- For each subdirectory identifying the LTPP section, a series of
“day” files then were generated. The file names correspond to the
date of test at that section, using a six-digit file name in
“yymmdd” format. For example, one of the files under subdirectory
040122 is 930726, which contains the load-deflection data records
from Arizona’s SPS section #0122, tested on July 26, 1993.
- All subsequent data processing began with the above-outlined
file format for the FWD load-deflection data. All other ancillary
FWD data were left in the format in which it was received, as the
size of the remaining database data files was small enough to
manage on a personal computer (PC) for use in a standard
spreadsheet program.
Individual FWD instruments, or machines, are identified by
serial number (SN). Thus FWD SN #129 refers to the FWD with the
serial number 129. In this report, serial number is sometimes
referred to as unit. Thus FWD SN #129 is also identified as unit
#129.
The pre-autumn 1998 comma-delimited structure of each line of
load-deflection data, as recorded in the database at level E, is
shown in table 1.
Table 1. Format of FWD load-deflection records from the
pre-autumn 1998 database.
FWD Load-Deflection Records (Data
Lines) |
|
Data Structure in the
Database |
Contents of Data Fields |
Field |
Max. # of Characters |
Units |
LTPP section
identification number |
A |
4 |
String |
State
number |
B |
2 |
Integer |
Construction
number |
C |
1 |
Integer |
Date of
test |
D |
9 |
yymmdd |
Time of test
(24-hour clock) |
E |
4 |
String |
FWD SN (FWD
serial number) |
F |
8 |
String |
Station
number |
G |
6 |
Floating.1 |
Lane
designation |
H |
2 |
String |
Drop sequence
number |
I |
2 |
Integer |
Drop
height |
J |
1 |
String |
Peak load plate
pressure (kilonewtons) |
K |
4 |
Integer |
Whole history
stored offline? |
L |
1 |
String |
#1 deflection
sensor reading (µm) |
M |
4 |
Integer |
#2 deflection
sensor reading (µm) |
N |
4 |
Integer |
#3 deflection
sensor reading (µm) |
O |
4 |
Integer |
#4 deflection
sensor reading (µm) |
P |
4 |
Integer |
#5 deflection
sensor reading (µm) |
Q |
4 |
Integer |
#6 deflection
sensor reading (µm) |
R |
4 |
Integer |
#7 deflection
sensor reading (µm) |
S |
4 |
Integer |
(Not used) |
T |
0 |
Empty |
(Not used) |
U |
0 |
Empty |
(Not used) |
V |
0 |
Empty |
Data quality
level |
W |
1 |
String |