Tiêu chuẩn quốc tế

• Số hiệu / Standard Number: AASHTO GBMS:1993
• Năm ban hành / Publication date: 1993
• Tình trạng / Status: W - Hết hiệu lực
• Tên tiếng Anh / Title in English: Guidelines for Bridge Management Systems
• Số trang / Page: 42

Phạm vi áp dụng / Scope of standard

Scope of the Problem

There are approximately 577,000 bridges throughout the United
States. Most of these bridges were constructed during two great
building booms, the Depression years and the Interstate
construction era.' A large percentage of the roughly 90,000 bridges
built in the 1930s are reaching the end of their useful life and
must be replaced or rehabilitated. The 223,000 bridges built
between 1956 and 1975 are beginning to pass through their midlife
and most will require deck replacement or major repairs.

The vagaries of political support and funding for bridges have
left many states and localities with insufficient funds to address
these important needs. Even agencies that have kept up with most of
their needs occasionally encounter funding shortfalls. Limited
funds must be managed as wisely as possible.

Over the next two decades bridge managers will be attempting to
balance limited, inadequate resources against increasing bridge
needs. Structural failure cannot be tolerated, yet funds often must
be thinly spread because they are limited. The best action for each
bridge, considered alone, is not necessarily the best action when
faced with funding constraints. InsufFrcient funds often mean
delaying or downscoping the ideal type of project. Also, some
agencies try to keep all bridges for which they are responsible
open and without load restrictions, but others find that limited
funds necessitate posting and closing of deteriorated bridges.

Besides ensuring the best use of limited funds, other concerns
in the management of the nation's bridges are safety, preservation
of investment, and serving commerce and the motoring public.
Highway and transportation agencies must carefully monitor
potentially severe safety problems such as bridges subject to
collapse due to scouring or lack of structural support. They must
identify premature deterioration and damage of bridges and use
these funds to avoid further deterioration and correct damage
through proper maintenance and repair. These agencies also must
strive to reduce inconvenience and disruptions to commerce and
passenger travel due to load and clearance restrictions or closing
of bridges.

The complexity of the bridge management problem is magnified by
the wide variety of bridge designs and materials ranging from
simple concrete slabs to steel trusses to cable-stayed bridges.
Bridges of different designs and materials deteriorate at different
rates. and so do their components. Bridges are made up of major
components: deck, superstructure and substructure, and numerous
subcomponents such as the roadway wearing surface, railings,
joints, bearings, girders, bracing, abutments, and piers. Decisions
as to the timing and the nature of maintenance and repairs to
components depend not just on their deterioration rate but also
interconnections among them. For example, a deteriorated steel
girder may result from chloride contaminated water leaking through
poor deck expansion joints. Repair of the joints should precede or
accompany the repair or replacement of the girder.

Public officials, administrators, and bridge engineers have
increasingly acknowledged the need for new analytical methods and
procedures to assess the current and future conditions of bridges
and determine the best possible allocation of funds among various
types of bridge maintenance, repair, rehabilitation, replacement,
and improvement work. The advent of BMS is a response to this
need.

A BMS facilitates budget and program formulation by providing a
structured process based upon sound economic and engineering
analysis. This process also helps to mediate among all the players
that interact in bridge funding and spending decisions:
professional staff, administrators, elected officials, and the
general public.

Each state has responsibility for managing from roughly five
hundred to more than twenty thousand bridges. The scope and
complexity of the bridge management problem is such that guidelines
are needed for state agencies regarding the development,
implementation, and enhancement of a BMS. These guidelines are
intended to inform state agencies of the essential fundamental
characteristics of a BMS, implementation options, and reasonable
expectations, and to promote areas of uniformity in state practices
and data collection. These guidelines will also be useful to
regional and local agencies and to bridge and turnpike
authorities.