Collection of Inventory Information

Bridge inventory information can be collected at office or during inspections, which are commonly carried out after construction or reconstruction of a bridge but can also be done directly before condition assessment. The main idea of the collection of the inventory information is to prepare the background database for the maintenance and rehabilitation planning. Without correct inventory information it is not possible to carry out condition assessment.

The main purpose of is to obtain inventory data required for network level planning and informed decision making. The inventory information will be collected with standardized series of data items that enables geometry, construction, and function of a bridge to be identified and described.

Inventory Information Collection

The main activity to collect the relevant information without on-site visit is locating, finding, and reviewing the bridge structure files and plans. The success of this type of inventory inspection is largely dependent on the effort put in documenting of previous design and building process. The data collection activities include reviewing the bridge structure files, plans and documents to identify the main measurements, possible components, and elements. If the data is collected by personnel without proper preparation, in Annex A of this document the basic components and parameters with terminology is presented to increase the basic knowledge level.

Possible sources of information about the bridge can be:

• The “Design” and “As-built” bridge plans. The bridge plans contain information about the bridge type, the number of spans, the use of simple or continuous spans, and the materials used to construct the bridge. They also contain information about the presence of composite action between the deck and girders, the use of framing action at the substructure members, and the kind of connection details used. The year of construction and the design loading are also usually contained in the bridge plans.
• Previous inspection reports that are done prior to the development of the system. Previous inspection reports provide valuable information about the history of the bridge, documenting its condition in previous years. This information can be used to determine which components and elements of the bridge warrant special attention. It also allows to some extent to compare the current levels of deterioration with those noted during the previous inspections to help determine the rate of deterioration.
• Maintenance and repair records that are done prior to the development of the system. Maintenance and repair records allow the inspector to report all subsequent repairs during the inspection phase, noting the types, extent, and dates of the repairs.
• Rehabilitation/Retrofit plans. Rehabilitation plans show modifications and replacements performed on the structure. Just as with the design plans, “As-Built (or record) drawings are preferable.
• Geotechnical data if available. Geotechnical data provides information about the foundation material below the structure. Sand, silt, or clay is more susceptible to settlement and scour problems than is rock. Therefore, structures founded on these materials should generally be given special attention with respect to foundation and scour issues than those founded on a rock.
• Hydrologic data if available. Hydrologic data provides information about the shape and location of the channel, the presence of protection devices, flood frequencies, and water elevations for various flood intervals. This information is necessary for scour evaluation, expected flood flows, and water velocity.
• Roadway plans. Roadway plans may provide some information if the structure plans are not available.

Although the information collection without inspections is a possibility, it is still suggested to check and enter the information during the inventory inspection. Without on-site visits, it is possible to collect inventory information more than ten structures in a day at an average.

The main activity to collect the relevant information only with inspections defining, counting, measuring, and recording the bridge structure information. The success of this type of inventory inspection is largely dependent on the effort put in the inspections and taking correct photos for post processing in office. During inventory information collection inspection, the main objective is to measure main dimensions (length, width, span length etc.) and define all bridge elements and typologies. Inventory information is most important part of the database, because without the correct information the system is useless. Based on the collected information, it is possible to distinguish the different types of bridges, present the quantifiable values of structures, and do the initial analysis of bridge network. Inventory information is collected only for bridges and bigger culverts (overall length of over 1.8m).

The data collection can be divided into two separate parts: (1) Dates, location, and measurements, (2) features and elements. The sequence for collecting inventory information is as follows:

1. Search for the bridge in the database (if one exists) or name the bridge after the location (village, road etc.)
2. Define the location or save the bridge GPS location.
3. Measure the main dimensions (Figure 3b. Main transverse dimensions of a bridge. Examples of a few cases of different bridge types)
4. Define the elements (Chapter 4.1.1)

Overall Bridge Identification Information

Bridge Location

The location data (Table 4.2. Bridge location details to be collected) is collected in same format for all the bridges.

The road section data available in the database should be considered as primary location reference data to be used during the data collection. The referencing data should be verified.

The chainage data should be collected according to Figure 2. If available, GPS coordinates should be added.

Measurement points of the Chainage (Flow Direction: Upstream to downstream) 

Bridge Geometry

The bridge measurements should be recorded with the resolution of 0.1 m. Preferably on site, but design information can also be a good input. The following Figure 3a and 3b illustrate the main longitudinal and transverse dimensions of a bridge with a few case examples.

Main longitudinal dimensions of a bridge. The overall length is measured from the end of a wingwall to the other side’s wingwall’s end, while the total length is measured without the wingwalls, the distance between the last expansion joints, the expansion joints themselves counted out.

Below are the main transverse dimensions of a bridge, with some examples of a few cases of different bridge types.

The carriageway width can be considered as kerb to kerb measure, even though sometimes there may be white edge lines marked on the bridge. Sidewalk width is the width of the foot path unless narrowed further by parapets or barriers. Horizontal clearance is the maximum oversize width that can pass the carriageway, in this case from parapet to parapet. Vertical clearance is unlimited.

In this case the carriageway width is from the kerb until the kerb or clearly elevated and thus separated sidewalk. In this case the horizontal clearance for oversize transport is from parapet to parapet, spanning over the sidewalk.

In this case the carriageway is bordered with concrete barriers. However, in addition to unlimited vertical clearance, also the horizontal clearance is considered unlimited for oversize transport as these barriers stay low and there is nothing to block the clearance at over 1m height. Therefore, the bridge does not pose a width limit for an oversize cargo loaded on a trailer or other special equipment transport.

In this example of a half through H-section truss bridge there is no kerbs or dividing parapets, so the carriageway width is measured from the edge of the deck to the other edge.

In this example of a full box truss bridge the carriageway width is measured from the kerb/barrier to the edge of the deck. Vertical clearance is not anymore unlimited in this type of a bridge, as it’s usually limited by the top chord struts, or even lower because of the diagonal top chord braces as in this example. Note that the clearance is measured at the lowest point over the carriageway. If carriageway is marked then at the lowest point between the edge lines, but if not marked, at the lowest point within the whole carriageway. Horizontal clearance is between the parapets, spanning over the divider, as the concrete barrier is less than 1m high.

Bridge Inventory - General Data

*Skew angle can be determined using the Compass feature on the Tripltek tablet (Outdoors folder): Angle (acute or obtuse) subtended by Route Direction & Normal to the Flow Direction.

Bridge Elements - Surface - Before Bridge

Span Information

(Note that information inserted for Span 1 continues throughout the spans unless it is unique for a span and is changed during the inspection – span length normally on multi-span bridges)

Span 1 - Contains Near Abutment Data

For Multi-span bridges with 'N' spans - Spans 2 to Span (N-1)

As per previous table but with Abutment data removed and the following Pier data added:

End Span 'N'

As per Span 1 table (with far Abutment data) with the Pier Elements from previous table added.

Bridge Elements - Surface - After Bridge

As per Bridge Elements - Surface - Before Bridge table

Bridge Elements - Outer

General Features and Elements

The Bridge Inspector ought to be familiar with the components and elements of the bridge to be inspected ahead of arriving at the site. To provide a reasonable level of confidence in the safety of the bridge, knowledge of the structure and good engineering judgment by the inspector is necessary. The relevant Templates for element information input is presented in Annexes C, D and E. Examples of most common Bridge Construction Types are presented next.

Girder Bridge

Cantilever bridge

Slab bridge

Bailey bridge

Truss bridge

Suspension bridge

Cable stayed bridge

Arch bridge

The Bridge Inspector should be acquainted with the main components of the bridge, if not then Annex A includes the main information. The overall position of elements is presented below.

Typical bridge element locations

Elements

Surface

• Approach way (cover) 10 metres of roadway before and after the structure
• Approach way (side) 10 metres of roadway sides before and after the structure

 

• Overlay/Deck wearing surface –top layer of the bridge, mainly influenced by the traffic.
• Barrier and handrails – safety elements on the sides of a structure

• Signs – related to traffic management, typically sign with a bridge name.
• Parapet

Superstructure

• Deck – load-bearing element that distributes the traffic load from top-layer to girders.
• Edge beam – side of a bridge deck that protects main girders from water and other pollutants.
• Expansion joints – connection points of a road and a bridge or different spans of a bridge. Allows the structure to deform longitudinally without causing additional stresses.
• Main girder – main load-bearing element
• Secondary member – load bearing element for secondary or perpendicular forces

• Other member

Substructure

• Bearings (Select TWO times) – connection between super- and substructure. Allows superstructure to move without causing additional stresses

• Bearing movement indicator
• Drainage – water management elements
• Construction joints/Hinges – special elements of longer structures or structurally designed, keeping the stresses in a safe zone.
• Abutments – load bearing elements of substructure
• Wing walls – keeping the soil of a roadway in place to prevent settlements.
• Piers – load-bearing elements of a substructure located in the middle of a structure.
• Pier Cap – top of the pier, mostly made to transfer the forces from superstructure to substructure.
• Abutment Cap

Other

• Foundation – bottom load-bearing element of a structure. Mainly located in the soil and not visible
• Riverbed protection
• Slope training
• Scour protection