Advance Prestress Bridge

Advantages ofAdvantages of
PrestressedPrestressed
Concrete BridgesConcrete Bridges
FORWARD

Owners and designersOwners and designers
have long recognized thehave long recognized the
low initial cost, lowlow initial cost, low
maintenance needs andmaintenance needs and
long life expectancy oflong life expectancy of
prestressed concreteprestressed concrete
bridges. This is reflectedbridges. This is reflected
in the increasing marketin the increasing market
share of prestressedshare of prestressed
concrete, which hasconcrete, which has
grown from zero in 1950grown from zero in 1950
to more than 55 percentto more than 55 percent
today.today.
ADVANTAGES OF PRESTRESSED BRIDGES -- CASE STUDIES
Bridges BuiltBridges Built
Source: National Bridge Inventory Data
0
10
20
30
40
50
60
50 55 60 65 70 75 80 85 90 95 00
Year Built
% Built
S/S
R/C
P/C
T
FORWARDBACK

This growth continuesThis growth continues
very rapidly, not onlyvery rapidly, not only
for bridges in the shortfor bridges in the short
span range, but alsospan range, but also
for spans in excess offor spans in excess of
150 feet which,150 feet which,
heretofore, has beenheretofore, has been
nearly the exclusivenearly the exclusive
domain of structuraldomain of structural
steel.steel.
FORWARDBACK

The following examplesThe following examples
illustrate some ofillustrate some of
these key advantagesthese key advantages
of precast, prestressedof precast, prestressed
concrete bridges:concrete bridges:
Cost Efficiencies
Structural/Engineering
Design Aesthetics
PCI Certified Quality
FORWARDBACK

Many bridge designersMany bridge designers
are surprised to learnare surprised to learn
that precast,that precast,
bridges are usuallybridges are usually
lower in first cost thanlower in first cost than
all other types ofall other types of
bridges.bridges.
Coupled with savingsCoupled with savings
in maintenance,in maintenance,
precast bridges offerprecast bridges offer
maximum economy.maximum economy.
Cost Efficiencies
FORWARDBACK
Design Aesthetics

Fast and Easy ConstructionFast and Easy Construction
An old bridge located on aAn old bridge located on a
main logging road inmain logging road in
Idaho was replaced with aIdaho was replaced with a
bridge. The bridgebridge. The bridge
consists of integral deckconsists of integral deck
beams on precastbeams on precast
concrete abutments andconcrete abutments and
wing walls. The heavywing walls. The heavy
spring runoff dictated thespring runoff dictated the
need for a shallowneed for a shallow
superstructure, and thesuperstructure, and the
load capacity of theload capacity of the
bridge had to bebridge had to be
sufficient to carry off-sufficient to carry off-
highway logging truckshighway logging trucks
that weigh as much asthat weigh as much as
110 tons each.110 tons each.
Cost Efficiencies and
Speed of Construction
FORWARDBACK

The precast prestressedThe precast prestressed
bridge system offered twobridge system offered two
principal advantages:principal advantages:
it wasit was economicaleconomical and itand it
providedprovided minimumminimum
downtimedowntime for construction.for construction.
Project duration wasProject duration was
three weeks.three weeks.
FORWARDBACK

The state of MinnesotaThe state of Minnesota
saved more than 16% -saved more than 16% -
a half a million dollars –a half a million dollars –
by planning for aby planning for a
prestressed alternate toprestressed alternate to
a steel bridge.a steel bridge.
The 700-foot-long bridgeThe 700-foot-long bridge
is jointless up to theis jointless up to the
abutments and is theabutments and is the
longest continuouslongest continuous
bridge in the state. Itbridge in the state. It
also contains the longestalso contains the longest
single concrete span.single concrete span.
FORWARDBACK

A MinnesotaA Minnesota
transportation officialtransportation official
stated, “Originally, westated, “Originally, we
didn’t think concretedidn’t think concrete
was suited to this…was suited to this…
bridge. However, thebridge. However, the
fabricator showed us itfabricator showed us it
was a viable alternative.was a viable alternative.
Everything wentEverything went
smoothly… we’re wellsmoothly… we’re well
satisfied…”satisfied…”
FORWARDBACK

Precast, prestressedPrecast, prestressed
concrete bridgeconcrete bridge
components arecomponents are easy toeasy to
erecterect, particularly when, particularly when
the tops of the unitsthe tops of the units
comprise the entirecomprise the entire
deck slab to form andeck slab to form an
“integral deck” or“integral deck” or
“full-deck” beam.“full-deck” beam.
Easy to ErectEasy to Erect
FORWARDBACK

In a full-deck bridge, theIn a full-deck bridge, the
formwork of the superformwork of the super
structure is eliminated.structure is eliminated.
Connections betweenConnections between
adjacent units often consistadjacent units often consist
of welding matching platesof welding matching plates
and grouting continuousand grouting continuous
keyways. Carefully plannedkeyways. Carefully planned
details speed thedetails speed the
construction process andconstruction process and
result in overall economy.result in overall economy.
FORWARDBACK

Substandard bridges areSubstandard bridges are
easily replaced witheasily replaced with
precast prestressedprecast prestressed
sections. In some cases,sections. In some cases,
existing abutments canexisting abutments can
be used…be used…
FORWARDBACK

……but it may be easierbut it may be easier
and more economical toand more economical to
build new ones, or tobuild new ones, or to
utilize precastutilize precast
abutments and wingabutments and wing
walls supported on cast-walls supported on cast-
in-place footings.in-place footings.
Because precastBecause precast
concrete integral deckconcrete integral deck
bridges with precastbridges with precast
abutments can beabutments can be
erected without delayerected without delay
in cold weather, theyin cold weather, they
can be opened tocan be opened to
traffic sooner.traffic sooner.
FORWARDBACK

Bridge departments areBridge departments are
challenged to maintainchallenged to maintain
traffic flow, minimizetraffic flow, minimize
traffic interruptions, andtraffic interruptions, and
reduce or eliminatereduce or eliminate
detours duringdetours during
construction projects.construction projects.
This Florida bridge,This Florida bridge,
damaged in a tankerdamaged in a tanker
fire, was completelyfire, was completely
rebuilt and opened torebuilt and opened to
traffic in 18 days.traffic in 18 days.
Fast ConstructionFast Construction
FORWARDBACK

TheThe fast constructionfast construction ofof
precast concrete integralprecast concrete integral
deck bridges is a keydeck bridges is a key
advantage. Precastadvantage. Precast
concrete bridges can beconcrete bridges can be
installed during all seasonsinstalled during all seasons
and opened to traffic moreand opened to traffic more
rapidly than any otherrapidly than any other
permanent type of bridge,permanent type of bridge,
because of the availabilitybecause of the availability
of plant-produced sectionsof plant-produced sections
and the speed of erectingand the speed of erecting
and finishing construction.and finishing construction.
All SeasonsAll Seasons
FORWARDBACK

Replacing this bridge onReplacing this bridge on
US Route 95 in IdahoUS Route 95 in Idaho
illustrates another exampleillustrates another example
of the advantages of veryof the advantages of very
fast construction:fast construction:
New Year’s Day: Rains andNew Year’s Day: Rains and
melting snow washed outmelting snow washed out
this bridge over the Littlethis bridge over the Little
Salmon River linking theSalmon River linking the
northern and southernnorthern and southern
parts of the state.parts of the state.
FastFast
ConstructionConstruction
FORWARDBACK

January 4: The IdahoJanuary 4: The Idaho
Department of TransportationDepartment of Transportation
contacted the precaster tocontacted the precaster to
investigate solutions. Theyinvestigate solutions. They
determined that the fastestdetermined that the fastest
way to replace the threeway to replace the three
spans was to use a singlespans was to use a single
80-foot span comprised of80-foot span comprised of
bulb-tees with an integralbulb-tees with an integral
deck. The top flange woulddeck. The top flange would
be 8-inches thick andbe 8-inches thick and
8'-6" wide. The end8'-6" wide. The end
diaphragms would also bediaphragms would also be
precast onto the girder ends.precast onto the girder ends.
January 8: Engineers in theJanuary 8: Engineers in the
Bridge Section approved shopBridge Section approved shop
drawings and tensioningdrawings and tensioning
calculations.calculations.
FORWARDBACK

January 18: Bulb-tees wereJanuary 18: Bulb-tees were
shipped 240 miles and setshipped 240 miles and set
in place…just 17 days afterin place…just 17 days after
the flood! Included in thethe flood! Included in the
shipment was intermediateshipment was intermediate
steel diaphragms, guard railsteel diaphragms, guard rail
posts and guard rail…all theposts and guard rail…all the
components to completecomponents to complete
the structure.the structure.
January 25: The projectJanuary 25: The project
was completed. The bridgewas completed. The bridge
was in service just 24 dayswas in service just 24 days
after the flood!after the flood!
FORWARDBACK

As a result of a Winter flood,As a result of a Winter flood,
this single lane bridge on athis single lane bridge on a
major forest road wasmajor forest road was
washed out, cutting accesswashed out, cutting access
to a U.S. highway for a halfto a U.S. highway for a half
dozen residents…includingdozen residents…including
one with a senior needingone with a senior needing
continuing medical care.continuing medical care.
Within only 15 of receivingWithin only 15 of receiving
plans, the precaster hadplans, the precaster had
fabricated the 135-foot-longfabricated the 135-foot-long
spans with 7’-6”-widespans with 7’-6”-wide
integral decks, and theintegral decks, and the
bridge was opened to trafficbridge was opened to traffic
3 days later – 18 days in all.3 days later – 18 days in all.
Simple SolutionSimple Solution
FORWARDBACK

In Ketchikan, Alaska a bridge onIn Ketchikan, Alaska a bridge on
the only highway to the norththe only highway to the north
was washed out when an oldwas washed out when an old
dam gave way on October 26.dam gave way on October 26.
Integral deck girders wereIntegral deck girders were
selected for the 85-ft span. Theselected for the 85-ft span. The
12 girders were designed and12 girders were designed and
precast in the state ofprecast in the state of
Washington, then shipped byWashington, then shipped by
rail and barge to Alaska. Therail and barge to Alaska. The
girders were installed and thegirders were installed and the
bridge was completed andbridge was completed and
opened to traffic on Decemberopened to traffic on December
19 - only 54 days after the19 - only 54 days after the
washout - despite the problemswashout - despite the problems
of design, remote location,of design, remote location,
great distances, and adversegreat distances, and adverse
weather conditions during theweather conditions during the
onset of an Alaskan winter!onset of an Alaskan winter!
AdverseAdverse
WeatherWeather
ConditionsConditions
FORWARDBACK

To accurately compareTo accurately compare
costs, consider a bridge’scosts, consider a bridge’s
life-cycle: The initiallife-cycle: The initial
cost of the structurecost of the structure
must be added to themust be added to the
total operating cost.total operating cost.
For stationary bridges,For stationary bridges,
the operating cost is thethe operating cost is the
maintenance cost.maintenance cost.
Life Cycle Cost =
Initial Structure +
Total Operating Costs
(Maintenance)
FORWARDBACK

The durability of precastThe durability of precast
bridges designed and builtbridges designed and built
in accordance with AASHTOin accordance with AASHTO
or AREMA specificationsor AREMA specifications
means there should bemeans there should be
little, if any need forlittle, if any need for
maintenance. One of themaintenance. One of the
reasons designers selectreasons designers select
integral deck prestressedintegral deck prestressed
concrete is the durability ofconcrete is the durability of
the precast, prestressedthe precast, prestressed
concrete and the resultingconcrete and the resulting
low maintenancelow maintenance
requirements.requirements.
DurableDurable
FORWARDBACK

Fatigue problems areFatigue problems are
nonexistent because onlynonexistent because only
minor net stresses areminor net stresses are
induced by traffic loads.induced by traffic loads.
DurableDurable
FORWARDBACK

And of course, no painting isAnd of course, no painting is
needed. Some bridgeneeded. Some bridge
engineers estimate the life-engineers estimate the life-
cycle cost of re-paintingcycle cost of re-painting
steel bridges to be 15 to 25%steel bridges to be 15 to 25%
of the initial cost. Paintingof the initial cost. Painting
bridges is environmentallybridges is environmentally
unfriendly and can beunfriendly and can be
especially dangerous orespecially dangerous or
expensive when done overexpensive when done over
busy highways, streams,busy highways, streams,
railroad rights-of-way or inrailroad rights-of-way or in
rugged terrain.rugged terrain.
Painting Steel BridgePainting Steel Bridge
FORWARDBACK

On the Illinois Toll Highway,On the Illinois Toll Highway,
the superstructures of 224the superstructures of 224
bridges are precastbridges are precast
prestressed concrete beams.prestressed concrete beams.
These bridges, built duringThese bridges, built during
1957 and 1958, have1957 and 1958, have
withstood heavy traffic andwithstood heavy traffic and
severe weathering and yetsevere weathering and yet
require very littlerequire very little
maintenance. Other projectsmaintenance. Other projects
in all parts of North Americain all parts of North America
have exhibited similarhave exhibited similar
experience little or no‑experience little or no‑
maintenance has beenmaintenance has been
required on precastrequired on precast
bridges.bridges.
Minimal MaintenanceMinimal Maintenance
FORWARDBACK

In addition to its costIn addition to its cost
efficiencies and speedefficiencies and speed
of construction,of construction,
precast concreteprecast concrete
provides importantprovides important
structural andstructural and
engineeringengineering
advantagesadvantages as well.as well.
Cost Efficiencies
FORWARDBACK
Design Aesthetics

A common requirement ofA common requirement of
many bridges is that themany bridges is that the
superstructure be assuperstructure be as
shallow as possible in ordershallow as possible in order
to provide maximumto provide maximum
clearance with minimumclearance with minimum
approach grades.approach grades.
Through the technique ofThrough the technique of
prestressing, the designerprestressing, the designer
can utilize the maximumcan utilize the maximum
possible span-to-depthpossible span-to-depth
ratio. This superstructureratio. This superstructure
occupies just 13 inchesoccupies just 13 inches
of profile.of profile.
Advantages
Shallow SuperstructureShallow Superstructure
FORWARDBACK

Span-to-depth ratios as highSpan-to-depth ratios as high
as 30:1 can be achieved withas 30:1 can be achieved with
solid slabs, voided slabs, boxsolid slabs, voided slabs, box
beams, multi-stemmed units,beams, multi-stemmed units,
or bulb-tee sections. Evenor bulb-tee sections. Even
though deeper sections willthough deeper sections will
require less prestressingrequire less prestressing
steel, the overall economysteel, the overall economy
of a project may dictate theof a project may dictate the
highest possible span-to-highest possible span-to-
depth ratio.depth ratio.
These HPC girders areThese HPC girders are
4'-6" deep and span 157 ft.4'-6" deep and span 157 ft.
A span/depth ratio ofA span/depth ratio of
nearly 35!nearly 35!
Shallow SuperstructureShallow Superstructure
Advantages
FORWARDBACK

Precast prestressedPrecast prestressed
concrete integral deckconcrete integral deck
girders were selected togirders were selected to
provide a shallowprovide a shallow
superstructure for asuperstructure for a
bridge over a busy urbanbridge over a busy urban
highway in Denver. Evenhighway in Denver. Even
though the bridge mustthough the bridge must
carry frequent heavycarry frequent heavy
truck traffic, the totaltruck traffic, the total
depth of the girders isdepth of the girders is
only 3 feet, including theonly 3 feet, including the
3-inch wearing surface,3-inch wearing surface,
for a span of 80 feet.for a span of 80 feet.
Adaptable to Many SituationsAdaptable to Many Situations
Advantages
FORWARDBACK

This bridge illustrates theThis bridge illustrates the
high span-to-depth ratioshigh span-to-depth ratios
possible with integralpossible with integral
deck prestresseddeck prestressed
concrete.concrete.
Advantages
High Span-to-Depth RatioHigh Span-to-Depth Ratio
FORWARDBACK

Bridges are subjected to anBridges are subjected to an
assortment of hostileassortment of hostile
environments as well asenvironments as well as
repeated impact loadings.repeated impact loadings.
Some must endure intenseSome must endure intense
sun, extreme temperaturessun, extreme temperatures
and brackish waters. Othersand brackish waters. Others
must withstand not only themust withstand not only the
freezing and thawingfreezing and thawing
provided by nature but alsoprovided by nature but also
the potential for damagethe potential for damage
through the use of de-icerthrough the use of de-icer
chemicals. Dense, highchemicals. Dense, high
strength prestressedstrength prestressed
concrete has excellentconcrete has excellent
freeze-thaw and chemicalfreeze-thaw and chemical
resistance.resistance.
Advantages
FORWARDBACK

GreaterGreater fire resistancefire resistance isis
another advantage. Thisanother advantage. This
timber bridgetimber bridge
experienced a dramaticexperienced a dramatic
fire…fire…
Fire ResistanceFire Resistance
Advantages
FORWARDBACK

……it was replaced by a lowit was replaced by a low
maintenance prestressedmaintenance prestressed
concrete bridge erectedconcrete bridge erected
without falsework over anwithout falsework over an
environmentally-sensitiveenvironmentally-sensitive
area…area…
Advantages
FORWARDBACK

Prestressed concrete bridgesPrestressed concrete bridges
havehave excellent ridingexcellent riding
characteristicscharacteristics thatthat
minimize traffic vibrations.minimize traffic vibrations.
The public will not onlyThe public will not only bebe
safe but alsosafe but also feelfeel secure andsecure and
comfortable on a prestressedcomfortable on a prestressed
concrete bridge. Trafficconcrete bridge. Traffic
vibrations are held to anvibrations are held to an
absolute minimum. Theabsolute minimum. The
owner will have a structureowner will have a structure
on which the deck is lesson which the deck is less
likely to crack prematurely.likely to crack prematurely.
Continuous spans even holdContinuous spans even hold
deck joints to a smoothdeck joints to a smooth
minimum.minimum.
Excellent Riding CharacteristicsExcellent Riding Characteristics
Advantages
FORWARDBACK

Steel girder bridges frequentlySteel girder bridges frequently
exhibit noticeable vibrations.exhibit noticeable vibrations.
The natural frequency ofThe natural frequency of
vibration of these bridges oftenvibration of these bridges often
coincides with the frequencies ofcoincides with the frequencies of
traffic and then resonancetraffic and then resonance
occurs. Because of their massoccurs. Because of their mass
and stiffness, the naturaland stiffness, the natural
frequency of vibration offrequency of vibration of
prestressed girder bridges rarelyprestressed girder bridges rarely
coincides with the vehiclecoincides with the vehicle
frequencies. Documented casesfrequencies. Documented cases
show that light bulbs in fixturesshow that light bulbs in fixtures
installed on steel bridges burninstalled on steel bridges burn
out more rapidly as a result ofout more rapidly as a result of
such vibrations. Reports aresuch vibrations. Reports are
surfacing that indicate decks onsurfacing that indicate decks on
steel bridges are more prone tosteel bridges are more prone to
cracking and deterioration.cracking and deterioration.
Advantages
Excellent Riding CharacteristicsExcellent Riding Characteristics
FORWARDBACK

The clean, attractiveThe clean, attractive
lines of concrete beamslines of concrete beams
also help bridgealso help bridge
designers meet thedesigners meet the
most demandingmost demanding
aesthetic requirements.aesthetic requirements.
Cost Efficiencies
Design Aesthetics
FORWARDBACK

Prestressed concretePrestressed concrete
bridges can be attractivebridges can be attractive
from above, below, andfrom above, below, and
from the side because offrom the side because of
the simple and cleanthe simple and clean
shapes of the membersshapes of the members
used. The high span-to-used. The high span-to-
depth ratios madedepth ratios made
possible through the usepossible through the use
of prestressing, result inof prestressing, result in
strong, tough, durablestrong, tough, durable
and yet graceful bridges.and yet graceful bridges.
Design Aesthetics
FORWARDBACK

Prestressed concrete isPrestressed concrete is
efficient because it is aefficient because it is a
composite of high-composite of high-
strength steel andstrength steel and
high-performancehigh-performance
concrete. To ensureconcrete. To ensure
this efficiency and tothis efficiency and to
comply with exactingcomply with exacting
project specifications,project specifications,
precasting plants haveprecasting plants have
developeddeveloped
sophisticated qualitysophisticated quality
assurance programs.assurance programs.
Cost Efficiencies
FORWARDBACK
Design Aesthetics

Precast, prestressedPrecast, prestressed
concrete products areconcrete products are
inspectedinspected both during andboth during and
following production.following production.
In fact, every operation inIn fact, every operation in
the manufacturing processthe manufacturing process
provides a point ofprovides a point of
inspection and control.inspection and control.
FORWARDBACK

Today’s bridge designsToday’s bridge designs
use more high-use more high-
performance materialsperformance materials
and sophisticatedand sophisticated
solutions than eversolutions than ever
before. More and more,before. More and more,
engineers are requiringengineers are requiring
only qualified sourcesonly qualified sources
with certified technicianswith certified technicians
and inspectors.and inspectors.
FORWARDBACK

A plant that is PCI-certified tellsA plant that is PCI-certified tells
the engineer five importantthe engineer five important
things:things:
 Independent Auditors;
Unannounced Audits
 Audits Based on
National Standards
1.1. The production facility hasThe production facility has
demonstrated its capability todemonstrated its capability to
produce quality products toproduce quality products to
the satisfaction of athe satisfaction of a
nationally recognized,nationally recognized,
independent consultingindependent consulting
engineering and inspectionengineering and inspection
firm engaged by PCI forfirm engaged by PCI for
multiple, unannouncedmultiple, unannounced
annual audits.annual audits.
2.2. The rigid audits the plantThe rigid audits the plant
undergoes are based onundergoes are based on
published industry standards –published industry standards –
thethe PCI Manual for QualityPCI Manual for Quality
Control for Plants andControl for Plants and
Production of PrecastProduction of Precast
Structural Concrete.Structural Concrete.
FORWARDBACK

Five important things cont.:Five important things cont.:
3.3. The plant practices aThe plant practices a
documented and PCI-documented and PCI-
approved quality assuranceapproved quality assurance
program open for review.program open for review.
4.4. The plant has PCI-certifiedThe plant has PCI-certified
QC personnel.QC personnel.
5.5. The producer has PCIThe producer has PCI
confirmed capabilitiesconfirmed capabilities..
 Independent Auditors;
Unannounced Audits
 Audits Based on
National Standards
 Documented Quality System
 Certified Personnel
 Confirmed Capabilities
FORWARDBACK

To maintain PCI Certification,To maintain PCI Certification,
producers are audited andproducers are audited and
graded semi-annually on moregraded semi-annually on more
than 150 items that include anthan 150 items that include an
inspection of all raw materials;inspection of all raw materials;
concrete mixing, placing,concrete mixing, placing,
finishing and curing; tensioningfinishing and curing; tensioning
and de-tensioning of strands;and de-tensioning of strands;
temperature controls; stripping,temperature controls; stripping,
stockpiling and inspection ofstockpiling and inspection of
product. In addition,product. In addition,
engineering, shop drawings,engineering, shop drawings,
record keeping, purchasing,record keeping, purchasing,
personnel training, and manypersonnel training, and many
other practices related toother practices related to
quality production arequality production are
examined. Failure to maintainexamined. Failure to maintain
acceptable standards makes lossacceptable standards makes loss
of certification mandatory.of certification mandatory.
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