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REPORT
This report is an archived publication and may contain dated technical, contact, and link information
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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

Long-Term Bridge Performance Program Logo

Structure Segmentation and Element Identification System
LTBP Protocol #: FLD-OP-SC-002

1.

Data Collected

  
1.1 None. This protocol provides a system for creating a unique identifier for each bridge element other than the deck.  

2.

Onsite Equipment and Personnel Requirements

  
2.1 Equipment: PRE-PL-LO-004, Personal Health and Safety Plan.  
2.2 Personnel: PRE-PL-LO-005, Personnel Qualifications.  

3.

Methodology

  
3.1 Assign a unique identifier to each element of the bridge superstructure and the substructure using the system described below. The unique identifier is a combination of alphanumeric characters, with the number and sequence of characters depending on the type of element being identified. Figure 1 shows an example of the unique identifiers for a two-span continuous bridge with five lines of girders in each span and diaphragms between the girders at the one-quarter points and over the pier.  

This illustration shows a plan view of an example bridge. The purpose of this illustration is to aid in identifying bridge elements for data collection through segmental inspection. The bridge is not skewed, and the deck has been removed from the illustration so a line drawing of the superstructure is visible. The bridge is a two-span continuous bridge, with five girders, and three rows of diaphragms for each span, plus a row of end diaphragms at each abutment and the central pier. Each span is identified by dimensions on the bottom of the figure. The direction of increasing linear reference is from left to right, indicated by an arrow at the bottom of the figure. Three major transverse axes are indicated by dotted lines. At the left side, the line is identified as “Abutment A, Bearing Line, Diaphragm Line.” In the middle of the span, the line is identified as “Pier 1, Single Bearing Line, Diaphragm Line.” At the right-hand side, the line is identified as “Abutment B, Bearing Line, Diaphragm Line.” The origin is located in the bottom left corner of Span 1. Directly to the right of the origin, Girder “1B” is identified by an arrow, indicating Girder B on Span 1. On the left-hand side of the figure, each girder is identified by a letter, for example “Girder A.” The letters increase moving from bottom to top. At the top left corner of the figure, “Bearing AE” is identified at the left end of Girder E, over Abutment A. Girder Bay “1CD” is identified by an arrow, located between Girder C and D, on Span 1. In the middle of Span 1, towards the bottom, Diaphragm “1Di3AB” is identified by an arrow, located on Span 1, the third diaphragm in from the abutment, inclusive of the end diaphragm, between Girder A and B. A typical girder bay is called out with an arrow on Span 1 as well. “Bearing P1D” is identified with an arrow, located along Girder D at the intersection of the line indicating Pier 1. Overhang “2EZ” is identified by an arrow, indicating the area of the deck that would exist outside of Girder E on Span 2. Girder Bay “2AB” is identified by an arrow, located between Girder A and B, on Span 2. Diaphragm “2Di1DE” is identified by an arrow, located on Span 2, the first diaphragm to the right of the pier, exclusive of the end diaphragm at the pier which is considered part of Span 1, between Girder D and E. A typical overhang is called out with an arrow on Span 2. The edge of the deck is also called out with an arrow on Span 2 as well.

Figure 1. Illustration. Element Identification System—Girder Example.
3.2 Spans: The span number is the first character of the identifiers for the elements that comprise the superstructure. Spans are numbered sequentially, proceeding from the coordinate system origin along the x-axis in the positive direction. The span nearest to the deck origin is span 1; the next span proceeding along the x-axis is span 2; and so on until span N, where N is the total number of spans in the bridge.  
3.3 Girders: The identifier for girders takes the form of “1A,” where:  
3.3.1 The first character is the span number.  
3.3.2 The second character is a letter, identifying the girder line. “A” is the girder line closest to the deck origin; “B” is the next closest, etc.  
3.4 Diaphragms: Diaphragms are labeled along each diaphragm line, starting with the diaphragm line closest to deck origin. The identifier for diaphragms takes the form of “1Di1AB,” where:  
3.4.1 The first character is the span number.  
3.4.2 The next component of the identifier is “Di” plus an integer, identifying the diaphragm line number. Di1 is the diaphragm line closest to the deck origin; DiN is the diaphragm line in the span farthest from the deck origin.  
3.4.3 When the superstructure is continuous over a pier and there is only one diaphragm line at the pier, that diaphragm is identified as the Nth diaphragm in the span with the lower number.  
3.4.4 The last two characters are letters, identifying the two girders to which the diaphragm is connected.  
3.5 Secondary members: Secondary members are identified and labeled on a case‑by‑case basis. For example, if there is wind bracing between girder A and B along the length of the span, it is identified using a four‑component label in the form of “1AB-WB,” where:  
3.5.1 The first character is the span number.  
3.5.2 The second and third characters are letters, identifying the two girders to which the secondary member is connected.  
3.5.3 The last component of the identifier, preceded by a dash, signifies the type of secondary member. For example, a wind brace (WB) between girders A and B in span 1 is identified as 1AB-WB.  
3.6 Girder bays: The identifier for locating defects or instrumentation on the underside of the deck between girders takes the form of “1AB,” where:  
3.6.1 The first character is the span number.  
3.6.2 The second and third characters are letters, identifying the two girders that are the sides of the bays.  
3.7 Overhangs: The identifier for locating defects or instrumentation occurring on deck overhangs outside of the exterior girders takes the form of “1AZ,” where:  
3.7.1 The first character is an integer and identifies the span number.  
3.7.2 The second character is a letter, identifying the exterior girder closest to the overhang.  
3.7.3 The third character is always the letter “Z,” indicating the defect or instrumentation is on an overhang. The letter Z has been chosen to denote overhangs because most girder bridges will not have more than 25 girder lines.  
3.8 Abutments: The abutment nearest to the deck origin is abutment A; the other abutment is abutment B. The deck origin is used to set the orientation of the wingwalls. For abutments, the right wingwall is closest to the deck origin, while the left wingwall is farthest from the deck origin.  
3.9 Piers/pier caps: Piers are numbered sequentially, proceeding from the deck origin along the x‑axis in the positive direction. The pier nearest to the deck origin is pier 1; the next pier proceeding along the x-axis is pier 2; and so on until pier N, where N is the total number of piers in the bridge.  
3.10 Pier columns/piles: The identifier for pier columns/piles takes the form of “P1C1,” where:  
3.10.1 The first two characters are the identifier for the pier.  
3.10.2 The last two characters are the letter “C” and the column number.  
3.10.3 The pier column nearest the deck origin is pier column 1. The first pier column located closest to the deck origin is identified as “P1C1.” In the case where piles are visible or there are multiple rows of pier columns/piles, identification starts at the column/pier nearest the deck origin and proceeds along the y-axis until the end of the row. Identification continues to be numbered in this manner for each row of columns/piles.  
3.11 Joints: Joints are identified by their respective abutment or pier.  
3.11.1 The joint at abutment A is joint A, and the joint at abutment B is joint B.  
3.11.2 The joint at pier 1 is joint P1; the joint at the next pier proceeding along the x-axis is joint P2, and so on until joint PN, where N is the number of piers in the bridge.  
3.12 Bearings: Bearings are identified by a letter, identifying their location on an abutment or pier along the y-axis.  
3.12.1 The identifier for bearings at abutments takes the form of “bearing AA,” where:  
3.12.1.1 The first character is a letter, identifying the abutment.  
3.12.1.2 The second character is a letter, identifying its location along the y-axis. The bearing at abutment A nearest to the deck origin is bearing AA; the next bearing proceeding along the y‑axis is bearing AB, and so on. The bearing at abutment B nearest to the x-axis is bearing BA; the next bearing proceeding along the y-axis is bearing BB, and so on.  
3.12.2 The identifier for bearings at piers takes the form of “bearing P1A[1],” where the first two characters identify the pier number, and the last one or two characters identify its location along the y-axis.  
3.12.2.1 When two adjacent spans are continuous for dead load, the pier has one bearing line, as shown in the example in figure 1. The bearing nearest the x-axis at pier 1 is bearing P1A; the next bearing proceeding along the y-axis is bearing P1B; and so on until bearing P1N, where N is the total number of bearings on the pier.  
3.12.2.2 When two adjacent spans are simply supported, the pier has two bearing lines. When a pier has two bearing lines, the bearing numbers at pier 1 have an additional labeling component consisting of the integer 1 or 2 at the end of the bearing number. The bearings in the first bearing line (the one closest to the deck origin) are bearings P1A1 through P1N1; the bearings in the second bearing line at pier 1 are bearings P1A2 through P1N2.  
3.13 The following describes the segmentation of the two-span continuous bridge shown in figure 1 using the system described above. Items marked with an asterisk (*) are not assigned a unique element identifier.  
  • Span 1
    • Deck
      • Railings*
      • Curb*
      • Overlay*
      • Top of deck*
      • Bottom of deck*
      • Bays  1AB  1BC  1CD  1DE
      • Overhangs
        • Overhang 1AZ
        • Overhang 1EZ
    • Superstructure
      • Girder 1A
      • Girder 1B
      • Girder 1C
      • Girder 1D
      • Girder 1E
      • Diaphragms
        • ■ End diaphragms 1Di1AB, 1Di1BC, 1Di1CD, 1Di1DE  
          ■ Intermediate diaphragms 1Di2AB, 1Di2BC, 1Di2CD, 1Di2DE  
          ■ Intermediate diaphragms 1Di3AB, 1Di3BC, 1Di3CD, 1Di3DE  
          ■ Intermediate diaphragms 1Di4AB, 1Di4BC, 1Di4CD, 1Di4DE  
          ■ End diaphragms 1Di5AB, 1Di5BC, 1Di5CD, 1Di5DE  
      • Secondary Members – None
    • Abutment A
      • Left wingwall
      • Right wingwall
      • Joint A
      • Bearings
        • Bearing AA
        • Bearing AB
        • Bearing AC
        • Bearing AD
        • Bearing AE
      • Bridge pedestal/seat*
      • Backwall*
      • Stem*
      • Footings*
      • Piles
    • Pier 1 (repeat for total number of piers)
      • Joint P1
      • Pier cap
      • Bearings
        • Bearing P1A
        • Bearing P1B
        • Bearing P1C
        • Bearing P1D
        • Bearing P1E
      • Pier columns
        • Pier Column P1C1
        • Pier Column P1C2
        • Pier Column P1C3
        • Pier Column P1C4
      • Footings*
      • Piles
  • Span 2
    • Deck
      • Railings*
      • Curb*
      • Overlay*
      • Top of deck*
      • Bottom of deck*
      • Bays   2AB  2BC  2CD  2DE
      • Overhangs
        • Overhang 2AZ
        • Overhang 2EZ
    • Superstructure
      • Girder 2A
      • Girder 2B
      • Girder 2C
      • Girder 2D
      • Girder 2E
      • Diaphragms
        • ■ Intermediate diaphragms 2Di1AB, 2Di1BC, 2Di1CD, 2Di1DE  
          ■ Intermediate diaphragms 2Di2AB, 2Di2BC, 2Di2CD, 2Di2DE  
          ■ Intermediate diaphragms 2Di3AB, 2Di3BC, 2Di3CD, 2Di3DE  
          ■ End diaphragms 2Di4AB, 2Di4BC, 2Di4CD, 2Di4DE  
      • Secondary Members – None
    • Abutment B
      • Left wingwall
      • Right wingwall
      • Joint B
      • Bearings
        • Bearing BA
        • Bearing BB
        • Bearing BC
        • Bearing BD
        • Bearing BE
      • Bridge pedestal/seat*
      • Backwall*
      • Stem*
      • Footings*
      • Piles

4.

Data Collection Table

  
4.1 None.  

5.

Criteria for Data Validation

  
5.1 None.  

6.

Commentary/Background

  
6.1 It is not practical to use the rectangular coordinate system on the top of the deck (FLD‑OP‑SC‑001, Data Collection Grid and Coordinate System for Bridge Decks) as a basis for locating, measuring, and documenting defects or placing instrumentation on other elements of the bridge, including abutments, wingwalls, pier columns, pier caps, joints, bearings, girders, diaphragms, secondary superstructure elements, girder bays, and deck overhangs. For these elements, it is more practical to have an identification system that creates a unique identifier for each individual element. The identification system assigns each individual element a unique identifier consisting of a specific combination of whole numbers and letters.  
6.2 The origin of the rectangular coordinate system for the top of the deck is the starting point for numbering and lettering of elements. Refer to FLD-OP-SC-001, Data Collection Grid and Coordinate System for Bridge Decks, for a description of the coordinate system and for the location of the coordinate system origin.  
6.3 Web stiffeners, both vertical and longitudinal, are not assigned a unique element identifier; they are considered part of the steel girder element.  

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 FLD-OP-SC-001, Data Collection Grid and Coordinate System for Bridge Decks.  
7.2 External: None.  

 

 

 

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