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Publication Number:  FHWA-HRT-16-007    Date:  January 2016
Publication Number: FHWA-HRT-16-007
Date: January 2016

 

Long-Term Bridge Performance (LTBP) Program Protocols, Version 1

Spatial Context Protocols (SC)

FLD-OP-SC-001, Data Collection Grid and Coordinate System for Bridge Decks

FLD-OP-SC-002, Structure Segmentation and Element Identification System

FLD-OP-SC-003, Determination of Local Origins for Elements

Long-Term Bridge Performance Program Logo

Data Collection Grid and Coordinate System for Bridge Decks
LTBP Protocol #: FLD-OP-SC-001

1.

Data Collected

  
1.1 Physical layout of a grid for data collection on a bridge deck.  
1.2 Location and description of the origin for a rectangular coordinate system.  

2.

Onsite Equipment and Personnel Requirements

  
2.1 Equipment:  
2.1.1 PRE-PL-LO-004, Personal Health and Safety Plan.  
2.1.2 Temporary (water-soluble) paint.  
2.1.3 Measuring wheel.  
2.1.3 Tape measure.  
2.1.4 6-ft folding rule.  
2.1.5 Hand compass or other device for measuring angles.  
2.1.6 Jig or similar tool for marking the grid nodes.  
2.1.7 Temporary marker.  
2.1.8 Digital camera.  
2.1.9 Pencil, sketch pad, and clipboard.  
2.2 Personnel: PRE-PL-LO-005, Personnel Qualifications.  

3.

Methodology

  
3.1 Measure and record the bridge skew angle.  
3.2 Establish the origin of the rectangular coordinate system at the end of the bridge with the lowest mileage point on the linear referencing system of the route that is carried on the bridge. For bridges on highways that to do not have a linear referencing system, the origin will be located at the most southerly point on the northbound side of a north-south local road or the most westerly point on the eastbound side of an east-west local road.  
3.2.1 Mark the origin for the coordinate system for bridge decks with water-soluble paint.  
3.2.2 The x-axis runs parallel to the centerline of the bridge. The positive direction is determined by the route’s linear referencing system. The y-axis runs across the width of the deck. The convention used is shown in figures 1 through 5, which shows the general location of the origin for different combinations of bridge and traffic patterns. In the case of skewed bridges, the rectangular coordinate system is retained, and the skew angle measured and noted with respect to the y-axis.  

This illustration shows a plan view of an example bridge. The purpose of this illustration is to aid in determination of a grid layout for data collection. The bridge is not skewed, and carries traffic in both directions, divided by a double line. The direction of increasing linear reference is from left to right, indicated by an arrow at the bottom of the figure. The origin for the grid is located in the bottom left corner of the plan. The x-axis is defined left to right, along the longitudinal axis of the bridge. The y-axis is defined as perpendicular to the x-axis, transverse to the longitudinal axis of the bridge.
Figure 1. Illustration. Local Coordinate Origin for Non-Skewed Bridge with Two-Way Traffic

This illustration shows a plan view of an example bridge. The purpose of this illustration is to aid in determination of a grid layout for data collection. The bridge is skewed, and carries traffic in both directions, divided by a double line. The direction of increasing linear reference is from left to right, indicated by an arrow at the bottom of the figure. The origin for the grid is located in the bottom left corner of the plan. The x-axis is defined left to right, along the longitudinal axis of the bridge. The y-axis is defined as perpendicular to the x-axis, transverse to the longitudinal axis of the bridge. The skew is a right-hand skew, meaning that the angle is measured clockwise from the y-axis.
Figure 2. Illustration. Local Coordinate Origin for Skewed Bridge with Two-Way Traffic – Right Hand Skew Angle.

This illustration shows a plan view of an example bridge. The purpose of this illustration is to aid in determination of a grid layout for data collection. The bridge is skewed, and carries traffic in both directions, divided by a double line. The direction of increasing linear reference is from left to right, indicated by an arrow at the bottom of the figure. The origin for the grid is located in the bottom left corner of the plan. The x-axis is defined left to right, along the longitudinal axis of the bridge. The y-axis is defined as perpendicular to the x-axis, transverse to the longitudinal axis of the bridge. The skew is a left-hand skew, meaning that the angle is measured counterclockwise from the y-axis.
Figure 3. Illustration. Local Coordinate Origin for Skewed Bridge with Two-Way Traffic – Left Hand Skew Angle.

This illustration shows a plan view of a pair of example twin bridges. The purpose of this illustration is to aid in determination of a grid layout for data collection. The bridges are not skewed, and each carries traffic in one direction, with two lanes. The direction of increasing linear reference is from left to right, indicated by an arrow at the bottom of the figure. The origin for the grid is located in the bottom left corner of the plan for each bridge. The x-axis is defined left to right, along the longitudinal axis of the bridge. The y-axis is defined as perpendicular to the x-axis, transverse to the longitudinal axis of the bridge. One origin is marked for each of the twin bridges.
Figure 4. Illustration. Local Coordinate Origin for Non-Skewed Twin Bridges with One-Way Traffic.

This illustration shows a plan view of an example bridge. The purpose of this illustration is to aid in determination of a grid layout for data collection. The bridge is not skewed, and carries traffic in two lanes in both directions, divided by a median barrier. The direction of increasing linear reference is from left to right, indicated by an arrow at the bottom of the figure. The origin for the grid is located in the bottom left corner of the plan. The x-axis is defined left to right, along the longitudinal axis of the bridge. The y-axis is defined as perpendicular to the x-axis, transverse to the longitudinal axis of the bridge. A single origin is used.
Figure 5. Illustration. Local Coordinate Origin for Non-Skewed Single Bridge with Two-Way Traffic and a Median Barrier.

3.3 In accordance with the right-hand rule, the positive z-axis protrudes from the bridge deck towards the sky.  
3.4 The rectangular coordinate system for the bridge deck is established with an origin (x = 0, y = 0, z= 0) matching the intersection of either of the following (figure 6):  
3.4.1 The innermost face of a solid bridge parapet or raised curb and the transverse edge of the top of the deck.  
3.4.2 The outer edge of the bridge deck (beyond an open metal railing) and the transverse edge of the top of the deck.  

This illustration shows a partial cross section view of two example bridges. The purpose of this illustration is to aid in determination of a grid layout for data collection. The figure contains two partial cross section views. The top view shows a schematic of a bridge deck with a concrete barrier wall. The origin is identified at the inside edge of the barrier, where it meets the deck. The y-axis is identified right to left, which is transverse to the longitudinal axis of the bridge. The z-axis is defined as perpendicular to the y-axis, which is orthogonal to the plane of the bridge deck. The bottom view shows a schematic of a bridge deck with a metal barrier. The origin is identified at the outside edge of the deck, outside of the barrier. The y-axis is identified right to left, which is transverse to the longitudinal axis of the bridge. The z-axis is defined as perpendicular to the y-axis, which is orthogonal to the plane of the bridge deck.
Figure 6. Illustration. Location of the deck local Origin on Bridge with different types of safety Barriers.
3.5 The coordinates of the grid nodes and other points on a deck surface are numeric, corresponding to the distance (measured in feet) from the origin. That is, a point described as (2.25, 6.5, 0.0) is a location on the top surface of the deck 2.25 ft longitudinally and 6.5 ft transversely from the origin.

NOTE—For the sake of simplicity, all points on the top surface of the deck are considered as having a z coordinate of 0.0. 		 
3.6 Create a 2- by 2-ft data collection grid.  
3.6.1 For all bridges, skewed or not skewed, set the first grid point using a 2-ft offset along the y-axis from the coordinate system origin.  
3.6.2 Mark the 2- by 2-ft grid on the rest of the top surface of the bridge deck using temporary, water- soluble paint (figure 7).  
3.6.3 A jig, or similar apparatus, can be used to standardize the process and quickly mark the grid (figure 7).  
3.6.3.1 Use the rolling wheel to mark nodes spaced 10 ft apart across the deck in both the longitudinal and transverse directions. These markings help properly line up the jig and prevent the propagation and accumulation of error as the jig is moved across the bridge.  
3.6.3.2 Align the jig with the coordinate system origin, and mark the 2- by 2-ft nodes with temporary paint.  
3.6.3.3 Move the jig forward, realign it with the end of the marked grid, and mark the nodes.  
3.6.3.4 Repeat the process to extend the grid across the bridge and to the end of the approach slab.  

The photograph shows two workers on the shoulder of a bridge overpassing a highway in the foreground, and a utility truck on the bridge’s shoulder along with three additional workers in the rear of the photograph. The focus is on the activities of the two workers in the foreground. The workers are creating a data collection grid in order to accurately notate testing areas of the bridge. The workers are using six pieces of PVC to create a data collection grid – this is the jig. The jig has been placed with one end against the retaining wall and the other end touching the shoulder lane marker and the jigs are placed 2-feet apart, encompassing a 12-foot span of the bridge’s shoulder. Each jig has been marked with paint at 12-inch intervals, in alternating colors to assist the workers in the layout of the collection grid. The workers are using hand-held cans of water-soluble spray paint on an extension handle (so that bending is not required), to spray dots in a 2-foot by 2-foot grid pattern, using the black jig marking as a measurement guide.
Figure 7. Photo. Layout of the Data Collection Grid with Jig.

3.6.4 A grid similar to the one in figure 8 is replicated on the bridge at the start of each data collection cycle. The origin of the grid should always match the origin established at the time of the first data collection cycle.  
3.7 Take photos of the coordinate system origin and the grid laid out on the deck using FLD‑DC‑PH‑002, Photographing for Documentation Purposes, and create a photo log.  
3.8 Storing data, documents, and images:  
3.8.1 FLD-DS-LS-001, Data, Document, and Image Storage—Local, for local storage.  
3.8.2 FLD-DS-RS-001, Data, Document, and Image Storage—Remote, for remote storage.  
3.9 Reporting: Transfer all metadata, data, documents, and images to FHWA, and/or upload all metadata, data, documents, and images into the Long-Term Bridge Performance (LTBP) Bridge Portal.  

4.

Data Collection Table

  
4.1 Table:  
# Field Name Data Type Accuracy Unit Field Description Row Color
1 State
Text
 
 
 State Code; e.g., Virginia = VA
Green
2 NBI structure number
Text
 
 
 Item 8, structure number; from NBI Coding Guide
Green
3 Structure name
Text
 
 
 Descriptive name for the bridge; e.g., Route 15 SB over I–66
Green
4 Protocol name
Text
 
 
 Title of the protocol
Green
5 Protocol version
Text
Month and year
 
 Month and year the protocol version was published; e.g., May 2015
Green
6 Personnel performing data collection activities
Text
 
 
 First name(s) Last name(s)
Green
7 Date grid created
Text
Exact date
Date
 mm/dd/yyyy
Green
8 Description of the location of the grid origin
 
 
 
 Description of the origin of the coordinate system; e.g., on the top surface of the deck at the junction of the top transverse edge of the deck and the interior face of the raised curb or the parapet
Green
9 Bridge skew angle with respect to y-axis
Number
1
Degrees and minutes
 If applicable
Yellow
10 Photo of bridge deck with coordinate system origin marked with temporary marker
BLOB
 
 
  
Yellow
11 Photo of bridge deck with grid painted on it
BLOB
 
 
  
Yellow
12 Comments
Text
 
 
  
Orange
4.2 Table Key:  
Column Descriptions
#
 Sequential number of data item
Field Name
 Data field name
Data Type
 Type of data, such as text, number, predefined list, binary large object (BLOB), or PDF file
Accuracy
 Accuracy to which the data are recorded
Unit
 Unit in which a measurement is taken and recorded
Field Description
 Commentary on the data or list of items in a predefined list
Row Color Key
Green
 Data items only entered once for each protocol for each day the protocol is applied
Pink
 Logical breakdown of data by elements or defect types (not always used)
Blue
 Data identifying the element being evaluated or the type of defect being identified
Yellow
 LTBP data reported individually for each element or defect identified
Orange
 Comments on the data collection or data entered

5.

Criteria for Data Validation

  
5.1 Compare measured skew angle to the value obtained using PRE-ED-BD-001, Plans and Specifications for Bridge Design and Construction.  
5.2 Verify origin is properly located; spot check painted nodes with tape measure to verify 2- by 2‑ft spacing.  
5.3 Tolerances for grid location: actual x and y coordinates of each painted node must be within 1inch (0.083 feet) of the theoretical coordinate system values.  

6.

Commentary/Background

  
6.1 This protocol describes how a rectangular coordinate system is established at each bridge and a 2‑ by 2-ft data collection grid is laid out on the top of the deck before data collection begins. The coordinate system provides a fixed reference for locating the position of defects observed on the top surface of the deck or overlay (if any) and the approach slabs; it also provides a fixed reference for locating sampling or testing points where NDE tests will be conducted, cores will be obtained, etc. A common coordinate system allows data from all testing methods to be easily tied to a location on the bridge and facilitates data fusion and analysis, allowing data from different tests to be layered and directly compared.  
6.2 The linear referencing system is a system that allows location of any point or feature on a highway with respect to a known point. On a highway, the linear referencing system is often shown using mile post numbers, which generally increase from south to north or west to east. The zero mileage point of the route’s linear referencing system is at the southernmost or the westernmost point of the route within the State lines.  
6.3 The locations of defects as well as sampling and testing points on other elements of the bridge, including the underside of the deck, girders, etc., are identified and documented using the element identification system described in FLD-OP-SC-002, Structure Segmentation and Element Identification System, and the local element origins established using FLD-OP-SC-003, Determination of Local Origins for Elements.  

7.

References

  
7.1 LTBP Protocols:  
7.1.1 PRE-PL-LO-004, Personal Health and Safety Plan.  
7.1.2 PRE-PL-LO-005, Personnel Qualifications.  
7.1.3 PRE-ED-BD-001, Plans and Specifications for Bridge Design and Construction.  
7.1.4 FLD-OP-SC-002, Structure Segmentation and Element Identification System.  
7.1.5 FLD-OP-SC-003, Determination of Local Origins for Elements.  
7.1.6 FLD-DC-PH-002, Photographing for Documentation Purposes.  
7.1.7 FLD-DS-LS-001, Data, Document, and Image Storage—Local.  
7.1.8 FLD-DS-RS-001, Data, Document, and Image Storage—Remote.  
7.2 External: None.  

 

 

 

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