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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
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|Publication Number: FHWA-HRT-07-002 Date: Jan/Feb 2007|
Publication Number: FHWA-HRT-07-002
Issue No: Vol. 70 No. 4
Date: Jan/Feb 2007
Today's transportation asset manager faces many competing priorities and must rely on well-defined, high-quality, reliable data based on standards created for infrastructure such as bridges.
|(Above) Lights such as these on a bridge over the Potomac River near Shepherdstown, WV, are not included among CoRe elements, but States are devising their own lists for inspection and maintenance purposes and are including such features. Photo: bd Systems, Inc.|
For the past decade, most States have employed the model of Commonly Recognized [CoRe] Elements for Bridge Inspection, developed in the mid-1990s by the Federal Highway Administration (FHWA) and American Association of State Highway and Transportation Officials (AASHTO) to define bridge elements. The CoRe elements standards provide a basis for data collection, performance measurement, resource allocation, and management decisions.
The CoRe standards cover most bridge elements in the States. However, some bridge elements that States want to address cannot be covered using descriptions provided through the CoRe elements. New elements have been defined by States as non-CoRe elements to supplement the CoRe elements defined by AASHTO. Since publication of the AASHTO Guide for Commonly Recognized Structural Elements in December 1997, no modifications have been made to accommodate new bridge elements or clarify the description of existing CoRe bridge elements, or to add new materials in the definition of CoRe bridge elements.
"The 108 CoRe elements, developed some time ago, were a basic start for collecting bridge system information," says Bruce Thill, bridge asset manager at the Washington State Department of Transportation (WSDOT). "Over the years, WSDOT and many other States have found more accurate element data necessary to manage bridge materials, products, and portions of the bridge structure. It would seem reasonable to update the CoRe elements and improve the quality of data based on common management practices or need."
A recent inquiry by FHWA may support that view. In 2003, FHWA's Bridge Management Information Systems Laboratory (BMIS) gathered data about element-level bridge inspections from the States. The goal of the study was to determine how States use the CoRe standards and what non-CoRe elements the States created to meet their needs.
"FHWA is interested in further exploration of potential national uses of element-based bridge inspection data," says Thomas Everett, principal bridge engineer and bridge programs team leader in FHWA's Office of Bridge Technology. "Definition of the CoRe elements was in part intended to establish sufficient uniformity to facilitate data sharing and use across State and local borders. The variability in elements introduced through customization and deviation from the defined CoRe elements raises many questions regarding the usefulness of the data at the national level."
The data from the States arrived in different formats and structures. Some States provided the information following the data structure used by the Pontis® Bridge Management System, the preferred computer-based program for bridge data management developed in 1990-1991 by FHWA and the California Department of Transportation. Pontis includes tables for element definitions, types, categories, and materials.
FHWA's inquiry into how the CoRe model was serving States found shortcomings in various areas. For instance, States felt the need to describe non-CoRe elements not defined among the CoRe elements, describe elements made of different material not described by the CoRe standards, define elements with more details, specify parts of the CoRe elements, and describe the protection systems of elements. One State even described features merely associated with bridges and defined maintenance and equipment related to them.
Using the data gathered from the States, the FHWA BMIS lab further studied a sample of States that provided data using the Pontis data structure. The sample of States included Arkansas, Illinois, Oklahoma, Virginia, and the District of Columbia. Washington State, which did not use the Pontis data structure, also was included because it defined a large number (232) of non-CoRe elements.
Examples of non-CoRe elements defined in the States include sidewalks and retaining walls; girders constructed with rolled, riveted, and welded steel; cantilever span abutments; steel sliding plate joints; and steel finger joints.
Before the CoRe model came online, bridge managers used data based on the National Bridge Inspection Standards (NBIS) to help make decisions. The NBIS approach provided a consistent standard for collecting bridge data, but it was not comprehensive enough to fully support sound management decisions, especially when considering economic factors.
Among the shortcomings was the fact that each bridge was divided into only four major parts for condition assessment: superstructure, substructure, deck, and culverts. With this lack of detail, NBIS was insufficient to identify proper repair strategies or estimate costs. Similarly, each of the four major parts was rated on a 0-9 scale by severity of deterioration, without identifying the deterioration process or its extent.
Another deficiency was that NBIS condition ratings included subjective interpretations of bridge inspection staff. Because the ratings included multiple distress symptoms and were expected to describe the "general" condition of a bridge, inspectors had to decide which distress was the most representative. A general condition might have been difficult to decide when a bridge had mainly localized problems. Finally, an overall sufficiency rating based on NBIS data helped determine Federal funding allocations, but the rating emphasized large-scale functional and geometric characteristics, making it irrelevant for maintenance decisionmaking.
During development of Pontis in the early 1990s, the shortcomings of NBIS were addressed through a standardized description of bridge elements at a greater level of detail, with a roster of up to 160 elements. Each bridge would be characterized by an average of about 10. "This would provide a common nucleus for implementing the system in a large number of States, allow for sharing of bridge management data, and generally would be a significant step forward in the state of the practice of bridge inspection," says Richard Shepard, director of the El Dorado County [CA] Transportation Department and a frequent speaker on bridge management.
As soon as Pontis was completed, several States began applying its standardized elements to their bridge inspections. They wrote their own inspection manuals and provided their own inspector training.
In 1993 under FHWA guidance, a task force was created to revise the standards based on that early experience. The new standard, the Commonly Recognized Elements for Bridge Inspection, would be somewhat more generic than the first version, less tied to Pontis, and with a smaller set (108) of standardized elements. The new approach specified the definition of each element, the unit of measurement, and definitions of a set of three to five standardized condition states, and listed typical feasible actions for each condition state. During AASHTO's Bridge Subcommittee meeting in May 1995, the CoRe Element Manual was accepted as an official AASHTO manual.
Around the same time, discussion took place about making the CoRe Element Manual a national standard as part of the NBIS, but this never made it to fruition. Instead, FHWA in 1997 developed a translator algorithm to convert the new, more detailed CoRe element condition data into NBIS condition ratings consistent with the old standard. This conversion enabled States to perform inspections under the new standard while still reporting results to FHWA under the old standard.
Even though the CoRe Element Manual has not been revised since 1995, most of the States using it have written their own field guides with specific variations, that is, non-CoRe elements. Currently, more than 40 States have made the transition to an element-level inspection standard based on the CoRe elements.
Drawing on the available data for a small sample of States that defined non-CoRe elements, the BMIS researchers found the following commonalities in the reasons behind States' definition of non-CoRe elements in their bridge inspection work and recordkeeping:
To describe elements not included among the CoRe elements. In many cases, States described various elements on their bridges simply because they were not addressed by the CoRe element descriptions. These elements include, for example, sidewalks, curbs, medians, retaining walls, wing walls (attached to abutments), head walls (in culverts), web walls, spandrel walls, and crash walls.
Distribution of Non-CoRe Elements in the Superstructure Category by Type and Material
|Reinforced Concrete||Prestressed Concrete||Painted Steel||Unpainted Steel||Unspecified Steel||Other|
|Pins and Hangers||1||1|
Distribution of Non-CoRe Elements in the Substructure Category by Type and Material
|Reinforced Concrete||Painted Steel||Unpainted Steel||Unspecified Steel||Timber||Other|
|Footings and Pilings||1||1||1||1|
To identify material not specified in the CoRe elements. Materials covered by the CoRe language include steel (painted and unpainted), concrete (reinforced and prestressed), timber, and "other." This was done largely to lessen the ambiguity around some of the materials. For example, painted and unpainted steel were used instead of "other" material for defining non-CoRe pier wall and abutment elements. Examples of non-CoRe elements using materials not specified for CoRe elements include aluminum girders and concrete trusses.
To specify fracture-critical elements. Fracture-critical elements are tension members or tension components of members whose failure would be expected to result in the collapse of a bridge. CoRe elements do not include indications as to whether they are fracture-critical. States added this quality to account for fracture-critical elements. Examples of these elements include fracture-critical painted steel welded girders, fracture-critical painted steel bottom chords through trusses, and fracture-critical painted steel through trusses—with "fracture-critical" as the new qualifier of existing CoRe elements.
To add more details to CoRe elements. A CoRe element's definition may not be precise enough from a State's perspective. States added details to define some elements more fully. Examples include specifying a column, pier wall, or abutment as having a stone fascia cover; specifying a concrete slab as hollow, a concrete deck as precast, and a concrete girder as post-tensioned; specifying a cable as being in a floating bridge or cable-stayed bridge; and specifying a steel girder as rolled, riveted, welded, or concrete-encased.
|This photo of the Rt. 9 bypass over U.S. 340 in Charlestown, WV, depicts two non-CoRe bridge elements: prestressed concrete girders and diaphragms used to tie adjoining girders together to improve their strength and rigidity and to distribute forces laterally.|
To describe smart flags not included in CoRe elements definitions. A "smart flag" is used to indicate a critical defect in a bridge. CoRe elements include eight smart flags that describe steel fatigue, pack rust, deck cracking, deck or slab soffit, settlement, scour, traffic impact, and section loss. States added to this roster smart flags for erosion control, signing, utility lines, lighting, drains or stream channels, safety inspections, and seismic restrainers.
To explain more details of the joint/seal elements. CoRe joint elements include open or strip seal expansion joints and pourable, compression, or modular joint seals. Other joint or joint-seal elements were defined by States as new non-CoRe elements. Examples of the new joints include steel angle header joints, steel sliding plate joints, steel finger joints, and asphalt plug joints. Examples of the new seal elements include premolded seals, silicon rubber seals, concrete seals, steel reinforcement seals, polymer seals, anchored seals, and welded seals.
|The stone fascia cover added to this bridge pier provides added protection against scour and debris flows. Photo: bd Systems, Inc.|
|Some States have opted to add more detail to the joint/seal elements on the CoRe roster. Here, steel finger joints connect portions of a bridge and allow for movement due to weight loadings, temperature changes, and other factors. Photo: bd Systems, Inc.|
To detail part of a CoRe element. Some States preferred to define part of a CoRe element as a new non-CoRe element. Examples here include abutment back walls, abutment timber bulkheads, girder/stringer/beam ends, and timber deck runners.
To expand protection systems for decks or slabs. Seven types of protection systems related to concrete decks or slabs are included as CoRe elements. Some States used more detailed descriptions for the protection systems and defined them as non-CoRe elements. (Oklahoma defined 19 systems for decks and 22 for slabs.)
To identify protection systems for decks and slabs as separate non-CoRe elements. Protection systems for concrete decks and slabs are included in the definition of deck/slab CoRe elements. A number of States, however, allocated separate non-CoRe elements to define these protection systems. These elements include asphaltic concrete overlays, rigid concrete overlays, polymer overlays, waterproofing membranes, and stay-in-place steel sheet forms.
To detail paint/protection systems for steel CoRe elements. One State used the type of paint or cover for steel elements to redefine CoRe elements into new non-CoRe elements. Examples include lead/non-lead/overcoat-painted steel elements, partially painted weather steel elements, and concrete-encased steel elements.
To identify paint systems for steel as separate non-CoRe elements. Similar to defining the protection systems for concrete decks and slabs as new elements, Washington State defined paint systems for steel as new non-CoRe elements. Examples here include red lead alkyd paint systems, zinc/urethane paint systems, coal tar epoxy paint systems, galvanizing protection systems, epoxy paint for weathering steel, and zinc vinyl paint.
To describe features associated with the bridge. Some features that exist on bridges but are not considered integral parts were defined by States as non-CoRe elements. Examples of these include utilities, fencing, lighting, guardrails, and railroad shielding.
To store maintenance-related information. One explanation for Washington State defining nearly 200 non-CoRe elements is that it used the element definition table to store other maintenance-related information. Washington was the only State to establish this type of non-CoRe elements definition, and the data are used exclusively to support its bridge maintenance business process.
States vary significantly in their use of non-CoRe elements. Generally, the elements are used to clarify, expand, and otherwise augment the information provided through CoRe elements. Although a standard in CoRe element definitions exists, does the transportation community need more flexibility so that States can more fully support their business models and needs?
|Washington and other States have added such non-CoRe elements as metal pedestrian rails, concrete sidewalks, and pedestrian safety barriers to their roster of data used in bridge inspections and maintenance. This photo taken near Harpers Ferry, WV, captures all three elements.|
Adel Al-Wazeer is a senior research engineer with bd Systems, Inc., a subsidiary of SAIC, working at FHWA's BMIS laboratory at the Turner-Fairbank Highway Research Center.
Bobby Harris is senior manager at bd Systems, Inc., and serves as the contractor's project manager at the FHWA BMIS laboratory. He has 19 years of experience in transportation information technology design and implementation, with 9 years supporting bridge management research.
Christopher Nutakor, Ph.D., P.E., P.M.P., works at the Federal Transit Administration, where he is a team leader in the Program Management division.
For more information, contact Adel Al-Wazeer at 202-493-3202 or email@example.com.