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Standardized deck inspections facilitate planning

Standardized deck inspections facilitate planning

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    Photo: CTLGroup

    The new manual advocates nondestructive evaluation, such as impulse response testing, when more than visual inspection is needed.

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    AASHTO Bridge Element Inspection Manual

    Table 1. Defect definitions for concrete deck/slab

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    AASHTO Bridge Element Inspection Manual

    Table 2. Condition state definitions

AASHTO's new inspection guide may help boost repair funding.

Chronic underfunding has deferred much-needed maintenance and repair of U.S. bridges for years. As a result, deterioration of concrete bridge decks is a major reason that a quarter of the nation's bridges are now considered either structurally deficient or functionally obsolete.

Regular inspection of decks and other bridge elements provides a way to monitor their condition, flag incipient problems, and initiate timely repairs. To guide repair plans most effectively, though, inspections need to be performed as objectively and consistently as possible. The American Association of State Highway and Transportation Officials' (AASHTO) new Bridge Element Inspection Manual is designed to help agencies achieve that goal.

The 172-page manual and CD-ROM, published in February, replaces the AASHTO Guide for Commonly Recognized Structural Elements and builds on the element-level condition assessment methods it espoused. The manual helps inspectors identify every piece or element of a bridge, specifically defines four standard condition states (good, fair, poor, and severe) for each element, and outlines clear reporting methods. It's intended to make it easier for inspectors to perform comprehensive inspections, and for managers to understand and compare the reported information.

It also provides specific guidance for assessing the condition of two element sets. Those identified as National Bridge Elements represent the bridge's primary structural components - they conform to the Federal Highway Administration's (FHWA) Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation's Bridges, and are meant to provide consistent information across the country. Those identified as Bridge Management Elements include components such as joints, wearing surfaces, and protective coating systems that are often tracked using bridge management systems (see sidebar). Agencies can modify the condition-assessment language for these elements to meet their particular needs, because the Bridge Management Elements are not used in policy-making at the national level. The new manual also allows agencies the flexibility to develop additional elements of their own, within the overall element framework.

Pontis: AASHTO's answer to bridge management
Pontis, first developed for FHWA and now owned by AASHTO, is the predominant bridge management system in the United States, currently used by 44 state DOTs. Pontis was released in 1992 and has been updated often since then.

Agencies can use this comprehensive Windows-based system to record bridge inventory and inspection information, project service requirements and deterioration rates, model the effects and costs of various maintenance and repair alternatives, and develop an optimal preservation policy.

The bridge management system is maintained through AASHTO's joint software development program, so member agencies benefit from pooling resources to produce a complex system that's far less expensive than a comparable custom-designed one would be. At the same time, the system is designed to support a high level of customization. Agencies using it can define their own bridge elements, deterioration models, and business rules to run in simulations. They can also design their own screen layouts, reports, and data-entry forms. The system's open architecture allows agencies to add database tables and build their own interfaces between the Pontis database and other agency databases.

A new version of the software, due for release in July, will accommodate the new element structure outlined in the newly releases AASHTO Bridge Element Inspection Manual. View an informative overview of the system at http://www.youtube.com/watch?v=BI5NxFmxthI.

Bridge deck inspection

Consider a concrete bridge deck inspection as an example. The reinforced concrete deck is a National Bridge Element, considered separately from the bridge's substructure and superstructure components and separately from any joint-filling materials or applied wearing surface. The following steps go into the deck element inspection.

1. Determine the deck area in square feet or square meters, measured from edge to edge, including any median areas and accounting for any ramps or flares. Report the prevalence of each defined condition state as a percentage of the overall deck area.

2. Examine the deck for manual-defined defects- cracks; spalls, delaminations, and patched areas; efflorescence; and reduced load capacity. Refer to Table 1 to determine what level of severity the observed defects represent, then to Table 2 to find the corresponding condition state.

3. Note that the deck evaluation is meant to be three-dimensional; that is, the defects observed on the top and bottom surfaces of the slab should be captured using the defined condition states. You can use the condition of the available visible surface to assess the surfaces that aren't visible for inspection. If neither the top nor bottom surface is visible, though, you'll need to assess the condition using destructive methods, nondestructive testing, or indications provided by the material covering the surface.

4. Once you've assessed the deck conditions, report the percentages of the surface area you've found to be in each of the standard condition states.

By using the new AASHTO manual, agencies can provide inspection data that allows for a simple comparison between different bridges both within and across jurisdictions. It offers an enhanced tool to guide local maintenance and repair priorities. And when these data are fed into the Bridge Health Index and from there into FHWA's nationwide condition and performance report, the results should provide:

  • Convincing evidence that more resources must be devoted to bridge repair and rehabilitation
  • Confidence that resources will be deployed to most benefit the nation as a whole.

    AASHTO's Bridge Element Inspection Manual is available for purchase at https://bookstore.transportation.org/Item_details.aspx?id=1748. PW

    - Kenneth Hooker is a freelance writer based in Oak Park, Ill.