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Publication Number: FHWA-RD-03-088
Date: November 2003

Introduction to The LTPP Information Management System (IMS)

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The Pavement Monitoring (MON) module contains photographic distress, manual distress, transverse profile distortion (ruts), longitudinal profile, deflection, friction, and drainage data .

9.1 PHOTOGRAPHIC AND MANUAL DISTRESS

Data stored in the MON_DIS tables provide a measure of pavement surface condition, including the amount and severity of cracking, patching and potholes, existence of surface deformation, joint defects, and other types of surface defects. Data on the transverse profile and rut-related distresses are stored in other tables.

Initially, visual interpretation of high-resolution 35-mm (1.38-inch) photographic images of the pavement surface was the primary means used to obtain the surface distress data. A national distress data collection contractor was hired to take the field measurements and interpret the images. The images provided a photographic record that can be reviewed and reinterpreted in the future. Circa 1994, the frequency of the distress surveys conducted by manual inspection of test sections by LTPP regional contractors in the field increased.

To create a distress time history, data users are often faced with combining distresses from photographic and manual data collection methods. The limitations of each method of data collection must be recognized in interpreting combined data sets, particularly when illogical time series trends exist.

The guidelines for distress data collection are contained in the Distress Identification Manual for the LTPP project.

9.1.1 MON_DIS Tables

Most of the distress data tables have names beginning with MON_DIS. The one exception is the MON_DROP_SEP table that contains shoulder dropoff and separation information.

MON_DIS_AC_REV: This table contains distress survey information obtained by manual inspection in the field for pavements with AC surfaces.

LTPP Database Tip!

Transverse cracks can include cracks caused by low temperature or reflection cracking types of mechanisms. Since the LTPP program does not classify cracks by these distress mechanisms, users must make these interpretations. Hand-drawn distress maps, 35-mm (1.38-inch) photographs, and maps of distress surveys conducted prior to overlay may be useful in identifying these types of cracking mechanisms.

MON_DIS_CRCP_REV: This table contains distress survey information obtained by manual inspection in the field for continuously reinforced PCC pavements.

MON_DIS_JPCC_REV: This table contains distress survey information obtained by manual inspection in the field for jointed PCC pavements.

MON_DIS_PADIAS_AC: This table contains distress survey information for AC-surfaced pavements interpreted from 35-mm (1.38-inch) black-and-white photographs using an early version of the PADIAS software for data collected prior to April 1992. Work is underway to reinterpret the film with version 4.2 of the PADIAS software and store the information in the MON_DIS_PADIAS42_AC table.

MON_DIS_PADIAS42_AC: This table contains distress survey information for AC-surfaced pavements interpreted from 35-mm (1.38-inch) black-and-white photographs using version 4.2 of the PADIAS software.

MON_DIS_ PADIAS_CRCP: This table contains distress survey information for continuously reinforced PCC pavements interpreted from 35-mm (1.38-inch) black-and-white photographs using an early version of the PADIAS software for data collected prior to May 1991. Work is underway to reinterpret the film with version 4.2 of the PADIAS software and store the information in the MON_DIS_PADIAS42_CRCP table.

MON_DIS_PADIAS42_CRCP: This table contains distress survey information for continuously reinforced PCC pavements interpreted from 35-mm (1.38-inch) black-and-white photographs using version 4.2 of the PADIAS software.

MON_DIS_ PADIAS_JPCC: This table contains distress survey information for jointed PCC pavements interpreted from 35-mm (1.38-inch) black-and-white photographs using an early version of the PADIAS software for data collected prior to May 1992. Work is underway to reinterpret the film with version 4.2 of the PADIAS software and store the information in the MON_DIS_PADIAS42_JPCC table.

MON_DIS_PADIAS42_JPCC: This table contains distress survey information for jointed PCC pavements interpreted from 35-mm (1.38-inch) black-and-white photographs using version 4.2 of the PADIAS software.

MON_DIS_JPCC_FAULT: This table contains manual measurements of fault height on individual joints and cracks taken using a Georgia-style faultmeter.

LTPP Database Tip!

The MON_DIS_JPCC_FAULT table contains information on the location of joints and cracks on jointed PCC pavements. This information can be useful in interpreting FWD load-transfer measurements and profile data.

MON_DIS_JPCC_FAULT_SECT: This table contains test section summary statistics for fault measurements taken on a test section on the same monitoring day. Fault-height values that are null or are less than -1 are excluded from the section statistics calculations.

MON_DROP_SEP: This table contains lane-to-shoulder dropoff measurements for AC-surfaced pavements. It also contains lane-to-shoulder dropoff and lane-to-shoulder separation measurements for PCC pavements.

9.2 TRANSVERSE PROFILE DISTORTION

The bulk of the data from which users can obtain information on test section rutting is based on interpretation of transverse profile measurements . These data are stored in tables whose names begin with MON_T_PROF. Early in the program, rut-depth measurements were made using a 1.2-m (4-ft) straightedge reference. These measurements were primarily taken on SPS-3 test sections, although such measurements on other test sections varied by LTPP region. These data are stored in the MON_RUT_DEPTH_POINT table. Transverse profile measurements have been chosen by the LTPP program over 1.2-m (4-ft) straightedge measurements because research has shown that, in many instances, wheel-path depressions are wider than 1.2 m (4-ft).

Text Box: Elevation Figure 4. Illustration of how transverse profile measurements are normalized to lane edges. Graph. This is a Cartesian coordinate plot. The abscissa is labeled distance from the outside lane edge and is demarcated in 1-foot units, beginning at zero and ending at 12.  The ordinate is elevation and is demarcated in 0.2-inch units, starting at zero and ending at 1.2. Three lines are plotted on the graph.  A solid line labeled "True Profile" starts at coordinates (0, 0).  It consists of a series of straight line segments at various angles, and ends at coordinates (12, 0.8). The dashed line labeled "Reference Datum" is a straight line connecting the coordinates (0, 0) and (12, 0.8).  The third line is a solid line labeled as "Normalized Profile" and "Normalized to Datum," which starts at coordinates (0, 0), consists of a series of straight line segments similar in profile to the lane labeled "True Profile," and ends at coordinates (12, 0). Two numbers appear at the top of the graph. The first number is 501682, directly under it is the number 1 plus symbol 00.

Figure 4. Illustration of how transverse profile measurements are normalized to lane edges.

Transverse profile measurements are taken using photographic and manual techniques. The photographic technique results in non-uniform spacing between profile points. The manual technique uses uniform 0.305-m (1-foot) spacing between profile points. As illustrated in figure 4, the transverse elevations are adjusted to a reference line through the endpoints so that the elevations of the endpoints are zero.

The LTPP regional offices are responsible for collecting manual transverse profile data for their region. The national data collection contractor that takes the photographic distress measurements also takes the photographic transverse profile measurements . Measurements are typically taken at 15.25-m (50-ft) intervals.

To obtain rutting information, the transverse profile shapes must be interpreted. This interpretation was performed under one of the LTPP-sponsored data analysis efforts. The results of these computations are stored in the MON_T_PROF_INDEX_POINT and MON_T_PROF_INDEX_SECTION tables. The values in the POINT table are those computed for each measurement location, while the summary statistics for all measurements on a test section are stored in the SECTION table.

A variety of transverse profile distortion indices, which can be used to characterize rutting, are stored in the MON_T_PROF_ INDEX table. Quantification of rutting is complex; it is much more difficult than may be apparent to a casual observer. While the LTPP program has not yet developed indices that capture all aspects of rut characterization, two important measures of rut depth are based on a 1.83-m (6-ft) straightedge and lane-width wireline reference.

The straightedge rut-depth method is based on positioning the straightedge at various locations in each half of the lane until the maximum displacement from the bottom of the straightedge to the top of the pavement surface is found. As shown in figure 5, at each measurement location, three surface profile distortion indices are computed for each half of the lane. These include maximum depth, offset from lane edge to the point of maximum depth, and depression width.

The lane-width wireline rut indices are based on anchoring an imaginary wireline at each lane edge. The wire reference connects any peak elevation point that extends above the lane edges with straight lines. The wireline reference method is illustrated in figure 6. The same type of pavement surface profile distortion indices as those for the straightedge are also computed.

Figure 5 illustrates an idealized transverse pavement profile. In each lane half, depth is determine as the distance from the bottom of a 1.8-m straight edge, offset is the distance from the lane edge to the depth measurement, and depression width is the distance between the contact points between the straight edge and the pavement surface.

Figure 5. Illustration of LTPP transverse pavement distortion indices based on 1.8-m (6-ft) straightedge reference. Distortion indices are computed for each half of the lane, including depth, offset to point of maximum depth, and depression width.


Figure six illustrates an idealized transverse profile with an imaginary wire line stretched crossed it and attached at the lane edges. In each lane half, the depths are the distance from the wire line reference to the pavement surface, depression width is the distance between the contact points between the wireline reference and pavement surface, and the offsets are the distance from the lane edge to the points were the depths are measured.  

Figure 6. Illustration of LTPP transverse pavement distortion indices based on lane-width wireline reference. Distortion indices are computed for each half of the lane, including depth, offset, and depression width.

The reason these indices are referred to as transverse profile distortion indices is that the location of the maximum depth is not constrained to the wheel path. Rutting is defined as a longitudinal depression in the wheel path. The algorithm was constrained only to each half of the lane.

LTPP Database Tip!

Transverse profile statistics, based on the photographic measurement method, are available for PCC-surfaced pavements. This is an interesting data source for those interested in ruts on PCC-surfaced pavements. Manual transverse profile measurements on PCC surfaces are not taken. In 2001, the LTPP program stopped the photographic interpretation of transverse profile measurements on PCC pavements.

9.2.1 MON_T_PROF Tables

The relational structure of the MON_T_PROF tables is shown in figure 7.

MON_T_PROF_MASTER: This table contains information on the general characteristics of transverse profile measurement data, including date, measurement device, number of profiles measured, and measurement width. This is the parent table for all other tables stored in the MON_T_PROF_* submodule. One record is created in this table for each set of transverse profile measurements on a test section. The content of the DEVICE_CODE field in MON_T_PROF_MASTER indicates the type of measurement. A value of "P" indicates a photographic measurement; "D" indicates a manual dipstick measurement.

MON_T_PROF_DEV_CONFIG: This table contains information on equipment configuration settings used to capture, digitize, and interpret transverse profile measurements using the photographic and manual dipstick measurement methods. Note that transverse profile measurements based on the photographic method are obtained at the same time as the photographs for the film-based distress interpretations.

 

Figure seven shows that the MASTER table is linked to both the DEV_CONFIG and PROFILE tables. The PROFILE table is linked to the INDEX_POINT table. INDEX_POINT table is linked to the INDEX_SECTION table. Figure 7. Relational structure among tables in the MON_T_PROF module. Flowchart. This figure consists of text boxes connected with one-sided arrows. In the upper left side of the figure, the box labeled Master has an arrow pointing directly to the right at a box labeled DEV_Config. An arrow also points straight down from the Master box to a box labeled Profile.  An arrow points straight down from the Profile box to a box labeled Index_Point.  A horizontal arrow from Index_Point points to the right at a box labeled Index_Section. MON_T_PROF_PROFILE: This table contains edge-normalized transverse profile data. Up to 30 x-y points on the transverse profile are stored in this table. Field names starting with X represent the offset from the outside lane edge; those names starting with Y are the elevation of the point relative to the outside-edge starting point.

MON_T_PROF_INDEX_POINT: This table contains transverse profile distortion indices for each longitudinal measurement location.

MON_T_PROF_INDEX_SECTION: This table contains summary statistics for the transverse profile distortion statistics stored in the MON_T_PROF_INDEX_POINT table.

9.2.2 MON_RUT_DEPTH_POINT Table

The MON_RUT_DEPTH_POINT table contains rut-depth information collected manually in the field using a 1.2-m (4-ft) straightedge. These measurements were primarily limited to SPS-3 test sections; however, these measurements were also made on other test sections. The coverage of these data varies between LTPP regions.

9.3 LONGITUDINAL PROFILE

The vast majority of longitudinal profile measurements are taken on LTPP test sections using inertial profilers. To date, three models of inertial profilers have been used. The first profiler was the K.J. Law Engineering model DNC690. This profiler was used from June 1989 through April 1997. The second inertial profiler used on LTPP test sections was the K.J. Law Engineering model T6600. The transition to the model T6600 began in July 1996. Implementation dates for the new equipment varied by region. In July 2002, the transition began to implement the International Cybernetics Corporation model MDR4086L3 profiler. Each of these profilers used different types of instrumentation technology. Descriptions of these profilers can be found in the references listed in appendix A. From a data availability perspective, only 0.305-m (1-ft) moving average profile data are available for measurement with the DNC690. The raw 25-mm (1-inch) interval profile measurements are available offline for measurements taken with T6600 and MDR4086L3 devices. The raw data can be requested through ltppinfo@fhwa.dot.gov.

For a small number of test sections, primarily those located in Alaska, Hawaii, and Puerto Rico, where it is not practical to obtain measurements using an LTPP inertial profiler, longitudinal profile measurements are taken using a device manufactured by FACE®, called Dipstick®, which is operated manually. This device measures the surface elevation at 0.305-m (1-ft) intervals.

9.3.1 MON_PROFILE Tables

MON_PROFILE_MASTER: This table contains information on the measurement device, measurement date, other measurement conditions, and computed profile and ride parameters. Some of the computed parameters include the International Roughness Index (IRI), the Mays Index, the Root Mean Square Vertical Acceleration (RMSVA), and an approximation of the American Association of State Highway Officials (AASHO) Road Test slope variance parameter. These data are collected for each measurement pass on a section. For inertial profilers, data are collected for at least five repeat measurement passes on the same day.

MON_PROFILE_DATA: For inertial profilers, this table contains the 0.305- or 0.300-m (1- or 0.98-ft) moving average of the profile measurements, stored at 0.153- or 0.150-m (0.5- or 0.49-ft) intervals, depending on the measurement device. For the FACE Dipstick, the raw 0.305-m (1-ft) interval measurements are collected. This is currently the largest online table in the database. This table is typically subdivided by STATE_CODE to reduce it to a convenient size for distribution.

9.4 DEFLECTION MEASUREMENTS

LTPP regional contractors take deflection measurements using FWDs . FWD data, pavement temperature gradient data , and computed parameters based on FWD measurements are stored in tables whose names begin with MON_DEFL.

Because of the large volume of deflection testing conducted by the LTPP program, data recorded in a single FWD output file is spread across multiple tables to reduce redundancy and improve data storage efficiency. The overall structural relationship between the tables used to store FWD data is shown in figure 8. While this can be daunting to users accustomed to flat formats, with an understanding of the relationships between these tables, the data can be reassembled into any desired format. Example SQL scripts for building a data set for backcalculation are included in appendix C.

Because of the size of the deflection time-history data , they are not stored in the database. Time-history files in their native format can be requested through ltppinfo@fhwa.dot.gov.

9.4.1 MON_DEFL Tables

MON_DEFL_MASTER: This table contains summary information on measurements taken during a measurement day. Data stored in this table include test date, number of deflection measurement passes, FWD serial number, operator, data collection software, and the format of the time-history files generated. This is the parent table for all other tables stored in the MON_DEFL submodule.

MON_DEFL_LOC_INFO: This table contains information specific to each point at which testing was conducted. Its contents include the time at which testing was initiated, the longitudinal and transverse location of the test point, and the air and pavement surface temperatures measured by instruments on the FWD. The LANE_NO field indicates the type of deflection test (basin or load transfer), the general location of the test (lane edge, wheel path, lane center, corner, or joint), and the type of surface material being tested. These codes are shown under LANE_SPEC in the CODES table. The CONFIGURATION_NO field is used to link to the MON_DEFL_DEV_CONFIG and MON_DEFL_DEV_SENSOR tables that contain data on sensor spacing and calibration.

Figure 8. Structural relationship between tables used to store FWD data. Flowchart.

Figure 8. Structural relationship between tables used to store FWD data.

MON_DEFL_DROP_DATA: This table contains peak deflection and applied load measurements for every drop conducted at each test point on a section. This is currently the second largest table in the database. Each record represents one test drop. The NON_DECREASING_DEFL field is populated with a 1 if a nondecreasing deflection pattern is detected for a basin test.

MON_DEFL_DEV_CONFIG: This table and its child, MON_DEFL_DEV_SENSORS, contain information specific to the configuration of the FWD during testing. These configurations are typically stable over many tests. Its contents include the number of deflection sensors used, load plate radius, and load cell and temperature sensor calibration factors. This table is linked to MON_DEFL_LOC_INFO through the CONFIGURATION_NO field.

MON_DEFL_DEV_SENSORS: This table contains deflection sensor offset , calibration factors, and serial numbers. This table is linked to MON_DEFL_LOC_INFO through the CONFIGURATION_NO field. The CENTER_OFFSET_FLAG field is populated when the location of a sensor is considered suspect based on analysis of the deflection basin.

MON_DEFL_EST_SENSOR_OFFSET: This table contains estimates of deflection sensor offset in those cases where analysis of the deflection basin suggests that the reported location in the MON_DEFL_DEV_SENSOR table is not correct and corroborating evidence of sensor misplacement does not exist. Values in this table are determined based on engineering analysis of the deflection data.

MON_DEFL_TEMP_DEPTHS: This table contains the depths at which temperature gradient data are collected during FWD testing. Generally, temperature measurements are taken at a minimum of three depths in the pavement structure. In some cases, it has been found that the temperature depth holes were drilled completely through the bound surface layer and into the base material. Data users should evaluate the hole depths against the information stored in the TST_L05A and TST_L05B tables to determine their position in the pavement structure.

MON_DEFL_TEMP_VALUES: This table contains temperatures measured at the depths recorded in the MON_DEFL_TEMP_DEPTHS table.

MON_DEFL_BUFFER_SHAPE: This table contains information on the four different styles of buffers used on the LTPP FWDs. Buffer use is aggregated by time period.

MON_DEFL_FWDCHECK_CMNTS: This table contains comments from the results of the analysis of section homogeneity, nonrepresentative test pit and section data, and structural capacity from the FWDCHECK program. Use of the FWDCHECK program was discontinued by the LTPP program. Users interested in these data are cautioned that the table storage structure does not permit a direct association with the deflection measurement data set that the calculations are based on.

9.5 BACKCALCULATION TABLES

In 1997, data were extracted from the deflection data tables for backcalculation of material properties of layers in the pavement structure. The data used in these computations and their results are stored in tables whose names begin with either MON_DEFL_FLX or MON_DEFL_RGD. The MON_DEFL_FLX tables contain the inputs and results of the layered elastic analysis conducted on both flexible and rigid pavement structures. The MON_DEFL_RGD tables contain the inputs and results of slab analysis based on plate theory that was conducted on PCC-surfaced pavement structures. LTPP analysis contractors performed these computations. References to publications documenting these analytical procedures can be found on the LTPP Web site.

These computations were performed external to the database and have not been updated. At this time, available FWD and related pavement structure data greatly exceed the volume of data available at the time of the data extraction for these data. Furthermore, over time, other problems have been found in the data set that could affect the results. Users of these data are cautioned to fully evaluate the terms of the calculation and the current status of the raw data used in the calculations.

MON_DEFL_FLX_BAKCAL_BASIN: This table contains an average of the applied load and the measurements from each deflection sensor for multiple drops, at the same point, from the same drop height.

MON_DEFL_FLX_BAKCAL_LAYER: This table contains information on the layer structure and material properties used in the backcalculation computation. BAKCAL_LAYER_NO conforms to the layer referencing system used by the computer program and the other FLX_BAKCAL tables. Links to the LTPP layer referencing method are stored in the fields whose names are similar to L05B_LAYER_NO_#.

MON_DEFL_FLX_BAKCAL_POINT: This table contains the results of the elastic layer analytical backcalculation computation for each test point on a test section by layer type, drop height, and test time. Inclusion of records in this table in the section statistics is based on the value stored in the ERROR_RMSE field. Values in this field that are greater than 2 are not included in the section statistical summaries.

MON_DEFL_FLX_BAKCAL_SECT: This table contains test section summary statistics from the elastic layer analysis. These statistics are based on records in the MON_DEFL_FLX_BAKCAL_POINT table with a value of 1 in the SECTION_STAT_INCLUDE_FLAG field. For database users interested in the evaluation of multiple deflection measurement passes on the same day on SMP test sections, only aggregate statistical summaries for the test day are included in this table.

MON_DEFL_FLX_NMODEL_POINT: This table contains the results of the nonlinear material response models for the pavement layers. Since various types of nonlinear models can be applied to the different pavement layers, this table contains codes that reference the model and the associated coefficients. Data are stored in this table for each deflection test point on a test section.

MON_DEFL_FLX_NMODEL_SECT: This table contains a statistical summary of the results of the nonlinear analysis for the complete test section. These statistics are based on records in the MON_DEFL_FLX_MODEL_POINT table that have a value of 1 in the SECTION_STAT_INCLUDE_FLAG field.

MON_DEFL_RGD_BAKCAL_LAYER: This table contains information on the pavement structure input parameters used in the backcalculation based on plate theory. Information stored in this table includes the thicknesses of the PCC and the base layer, the modulus ratio, the Poisson's ratio, and references to the layers in the TST_L05B table that may have been combined in this analysis.

MON_DEFL_RGD_BAKCAL_BASIN: This table contains the load, deflection basin, and associated parameters used in the analysis, including the average of the applied load and the measurements from each deflection sensor for multiple drops, at the same point, from the same drop height.

MON_DEFL_RGD_BAKCAL_POINT: This table contains the results of the plate theory backcalculation results for each test point on the test section. The table contains the analytical results for four models from the combination of the assumptions of dense liquid/elastic support and full base friction/no base friction. Based on the evaluation of the results by the analysts, the fields for the model results that were not considered appropriate were populated with a 999.9 type of convention.

MON_DEFL_RGD_BAKCAL_SECT: This table contains test section summary statistics from the plate theory backcalculation analysis. These statistics are based on records in the MON_DEFL_RGD_BAKCAL_POINT table with a value of 1 in the SECTION_STAT_INCLUDE_FLAG field. For database users interested in evaluation of multiple deflection measurement passes on the same day on SMP test sections, the MON_DEFL_BAKCAL_RGD-* tables contain a FWD_PASS field that is used to aggregate statistical summaries for each measurement pass on the test day.

9.6 FRICTION

The Friction submodule includes only the MON_FRICTION table. This table contains the results of friction tests on pavement sections where the State/Provincial highway agency was willing to provide the data. Because of the litigious nature of this data, submission is voluntary. The LTPP program has no control over the data collection method, measurement equipment, or calibration of the equipment used for these measurements. The database does not contain surface texture measurements and related information that are traditionally used to link pavement properties to measured friction levels.

9.7 DRAINAGE

Tables in this module contain information on the inspection of drainage features. These tables are currently under construction and are expected to be available in January 2004. Tables in this module will contain information on the condition of the edge drain systems installed at the SPS-1 , -2 , and -6 projects. In the future, tables may be added for other drainage feature evaluations.

MON_DRAIN_MASTER: This table contains information on the permanent features of the edge drain system and the location of the lateral openings. Since the data stored in this table are from inspections on SPS project sites with multiple test sections, the primary keys are related to a project-level identifier. These data are from video inspections of the drainage system that start from an exposed lateral-side drain structure. The key field LATERAL_ID, in combination with PROJECT_STATION and NEAREST_SECTION, provides an indication of the location of the drainage structure being inspected. The SPS_PROJECT_STATIONS table can be used to understand the location of the lateral drain being inspected relative to other sections on SPS projects.

MON_DRAIN_CONDITION: This table contains information regarding the condition of the lateral openings and the area around the lateral openings at the time of inspection.

MON_DRAIN_INSPECT: This table contains information on the results of the video edge drain inspection. Significant events in the inspection are recorded as a function of the distance of insertion of the camera within the drainage pipes.

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The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT).
The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT). Provide leadership and technology for the delivery of long life pavements that meet our customers needs and are safe, cost effective, and can be effectively maintained. Federal Highway Administration's (FHWA) R&T Web site portal, which provides access to or information about the Agency’s R&T program, projects, partnerships, publications, and results.
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