defines a bridge as - any structure spanning 20 feet or more
that carries motor vehicle traffic.
Wisconsin has about 13,600 bridges spanning state and local
Of these, about 4,900 are along the state highway system
(numbered state and federal highways) and are the responsibility of
the Wisconsin Department of Transportation (WisDOT).
highway system carries some 60 percent of the state’s overall
Approximately 8,700 bridges are located along the
local roadway system (county and town roads and municipal streets)
and are the responsibility of local governments.
The overall number of bridges fluctuates from year to year as
new bridges are added to the system as part of construction
projects, while some older bridges may be permanently removed.
All bridges in Wisconsin are designed and constructed with one
primary thought in mind – public safety. Additional considerations
are longevity and contributions to economic growth. State and local
bridges are inspected at least once every two years. WisDOT is
responsible for inspections of all bridges along the state highway
system. Municipalities handle inspections for bridges along the
local roadway system. WisDOT and local governments closely follow
federal guidelines in their bridge inspection and maintenance
Along with inspecting and maintaining its own bridges, WisDOT
works closely with cities, villages and towns to rehabilitate and
replace aging bridges. For example, WisDOT oversees the Local
Bridge Improvement Assistance program that helps rehabilitate
and replace, on a cost-shared basis, the most seriously deficient
bridges along the local highway system. A Lift Bridge Aids program
reimburses several Wisconsin cities for costs associated with the
operation of lift bridges. And each year, WisDOT returns a portion of all state-collected transportation revenues to local
governments in the form of General Transportation Aids
help municipalities build and maintain local roads and bridges. In
2012, GTA payments to local governments will total about $404
All of Wisconsin’s 13,600 bridges are inspected at least once
every two years and sometimes more frequently depending on a bridge’s
age, traffic load and any known deficiencies or load restrictions.
Inspection dates and reports for all Wisconsin bridges can be found
on the Highway Structures
Information System portion of the WisDOT web site.
There are different types of bridge inspections from routine to
in-depth depending on a bridge’s individual characteristics and
needs. WisDOT’s trained bridge inspectors follow Federal Highway
Administration (FHWA) standards and guidelines. Some smaller bridges
can be inspected on foot, while others require use of a special
"reach-all" vehicle with a jointed arm and bucket that
provides inspectors an up-close look at the underside of a bridge.
Depending on the size of a bridge, weather conditions and other
factors, a bridge inspection can take from one hour to more than a
week. During bridge inspections, certified inspectors survey:
the superstructure or beams that support the deck looking for
cracks, rust, or any problems with bolts or rivets.
the substructure units (which support the superstructure).
bridge approaches and the deck or surface of the bridge.
on bridges over large bodies of water, inspections require
divers to check supporting piers.
Following a thorough review of the deck, superstructure and
substructure, bridges are assigned a "sufficiency rating"
number between one and 100. The rating takes into account some 75
factors reviewed during an inspection and also considers a bridge’s
age, length and width, and the average amount of traffic the bridge
handles. WisDOT uses the sufficiency ratings to help prioritize
bridge improvements. Under WisDOT's
Local Bridge Improvement Assistance program, municipalities are
eligible for rehabilitation funding on bridges with sufficiency
ratings less than 80, and replacement funding on bridges with
sufficiency ratings less than 50. Each year, all states including
Wisconsin are required to submit a report to the FHWA that reviews
the condition of its bridges.
Generally defined by WisDOT as any structure spanning 20
feet or more that carries motor vehicle traffic.
The pavement surface of a bridge on which vehicles travel.
Deck truss bridge
On a deck truss bridge, the superstructure
typically consists of two or more parallel trusses that are the main
load-carrying members of the bridge and the roadway is placed on top
of the main members. WisDOT no longer builds deck truss bridges on
the state system as they have been replaced with more modern
designs. There are currently 14 deck truss bridges along the
Wisconsin highway system similar in design to the I-35 bridge that
collapsed in Minnesota. WisDOT took immediate steps to inspect these
bridges following the Minnesota tragedy. The inspections found no
significant problems and reaffirmed the bridges are safe for public
A fracture-critical bridge typically has a
steel superstructure with load (tension) carrying members arranged
in a manner in which if one fails, the bridge could partially or
totally collapse. Examples of fracture critical bridges are two
girder bridges or most truss bridges. A fracture critical
designation does not mean a bridge is unsafe. Today, virtually all
new bridges built along Wisconsin’s state highway system are
redundant or constructed in such a fashion that should one bridge
component fail, other elements will pick up the load to avoid a
Engineering term frequently used to
describe older bridges that no longer meet modern geometric
standards. For example, it could refer to a bridge with narrow lanes
or shoulders. A bridge classified as functionally obsolete does not
mean the bridge is unsafe for public travel.
Metal plates used to connect bridge components and
transfer weight between the components. Gusset plates are typically
bolted or riveted together.
Constructing a bridge in such a way that if one
element should fail, other components will pick up the load to avoid
a collapse. Today, virtually all new bridges WisDOT builds along the
state highway system are redundant.
Engineering term referring to a bridge
with one or more elements that will require attention. The
classification does not mean the bridge is unsafe for travel. For
example, it could refer to a combination of elements on a bridge
such as potholes on a bridge deck or rust on metal trusses. These
have little to no impact on a bridge’s overall safe function.
Depending on the extent of the structural deficiency, the bridge may
be load-posted until improvements are completed.
A computed numerical value between zero and 100
used to help determine a bridge’s priority for rehabilitation or
replacement and eligibility for state or federal funding. The rating
considers structural factors noted during a bridge inspection, a
bridge’s geometry and the amount of traffic the bridge handles. A
bridge with a sufficiency rating of 80 or less is eligible for
bridge rehabilitation funding. A bridge with a sufficiency rating of
50 or less is eligible for replacement funding.
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Last modified: December 2, 2011