Launch Slideshow

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New hope for old bridges

New hope for old bridges

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

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    Table 1. Defect definitions for concrete deck/slab

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    Source: AASHTO Bridge Element Inspection Manual

    Table 2. Condition state definitions

By Kenneth Hooker

Chronic underfunding has forced transportation departments to defer much-needed bridge maintenance and repair for years. Inspecting decks and other components is standard operating procedure for flagging incipient problems and initiating timely repairs.

To guide asset-management 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) Bridge Element Inspection Manual is designed to help agencies achieve that goal. Although it replaces the AASHTO Guide for Commonly Recognized Structural Elements, the new manual builds on the element-level condition assessment methods its predecessor espoused.

It helps inspectors identify every piece or element of the structure, 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 to perform comprehensive inspections, and for managers to understand and compare the reported information.

It also provides specific guidance for assessing two sets of structural elements.

National Elements are 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 intended to provide consistent information across the country.

Management Elements are components like joints, wearing surfaces, and protective coating systems that are often tracked using bridge management systems (see sidebar). Because they're not used to make national policy, agencies can modify the condition-assessment language for these elements to meet their particular needs.

An example: deck inspection

Let's look at how you'd use the manual to inspect a reinforced concrete deck.

As a National Bridge Element, the deck should be considered separately from substructure and superstructure components as well as any joint-filling materials or applied wearing surface.

The following steps go into the deck element inspection.

1. Determine the 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 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 defects represent, then to Table 2 to find the corresponding condition state.

3. The evaluation is meant to be three-dimensional; that is, 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 visible surface to assess the surfaces that aren't visible. If neither the top nor bottom surface is visible, you'll need to use destructive methods, nondestructive testing, or indications provided by the material covering the surface.

4. Report the percentages of surface area you've found to be in each of the standard condition states.

This methodology generates data that allows for a simple comparison between different bridges both within and across jurisdictions. When the data are fed into the Bridge Health Index and from there into FHWA's nationwide condition and performance report, the results provide:

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

    The AASHTO Bridge Element Inspection Manual is available for purchase at www.bookstore.transportation.org.

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

    PONTIS: TOP TOOL FOR BRIDGE MANAGEMENT

    Released in 1992 and repeatedly updated since then, Pontis is the nation's predominant bridge management system, used by 44 state DOTs. It was developed for the Federal Highway Administration but is now owned by the American Association of State and Highway Officials (AASHTO).

    Agencies use the comprehensive Windows-based program to record 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 system is maintained through the association's joint software development program, which pools resources to produce a complex system that's far less expensive than a comparable custom-designed tool would be.

    At the same time, though, it supports a high level of customization. Agencies can define their own elements, deterioration models, and business rules to run in simulations. They design their own screen layouts, reports, and data-entry forms. The system's open architecture allows users 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 this month, will accommodate the element structure outlined in the recently released AASHTO Bridge Element Inspection Manual. Visit www.aashtoware.org for more information.

    WEB EXTRA

    For links to AASHTO's inspection manual and a Pontis software demo, click here.