Advance Prestress Bridge

Advantages of Advantages of PrestressedPrestressedConcrete BridgesConcrete Bridges

FORWARD

Owners and designers Owners and designers

have long recognized the have long recognized the

low initial cost, low low initial cost, low

maintenance needs and maintenance needs and

long life expectancy of long life expectancy of

prestressed concrete prestressed concrete

bridges. This is reflected bridges. This is reflected

in the increasing market in the increasing market

share of prestressed share of prestressed

concrete, which has concrete, which has

grown from zero in 1950 grown from zero in 1950

to more than 55 percent to 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

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This growth continues This growth continues

very rapidly, not only very rapidly, not only

for bridges in the short for bridges in the short

span range, but also span range, but also

for spans in excess of for spans in excess of

150 feet which, 150 feet which,

heretofore, has been heretofore, has been

nearly the exclusive nearly the exclusive

domain of structural domain of structural

steel.steel.


FORWARDBACK

The following examples The following examples

illustrate some of illustrate some of

these key advantages these key advantages

of precast, prestressed of precast, prestressed

concrete bridges: concrete bridges:

Cost Efficiencies

Structural/Engineering

Design Aesthetics

PCI Certified Quality


FORWARDBACK

Many bridge designers Many bridge designers

are surprised to learn are surprised to learn

that precast, that precast,


bridges are usually bridges are usually

lower in first cost than lower in first cost than

all other types of all other types of

bridges. bridges.

Coupled with savings Coupled with savings

in maintenance, in maintenance,

precast bridges offer precast bridges offer

maximum economy.maximum economy.

Cost Efficiencies


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Design Aesthetics


Fast and Easy ConstructionFast and Easy Construction

An old bridge located on a An old bridge located on a main logging road in main logging road in Idaho was replaced with a Idaho was replaced with a prestressed concrete prestressed concrete bridge. The bridge bridge. The bridge consists of integral deck consists of integral deck beams on precast beams on precast concrete abutments and concrete abutments and wing walls. The heavy wing walls. The heavy spring runoff dictated the spring runoff dictated the need for a shallow need for a shallow superstructure, and the superstructure, and the load capacity of the load capacity of the bridge had to be bridge had to be sufficient to carry off-sufficient to carry off-highway logging trucks highway logging trucks that weigh as much as that weigh as much as 110 tons each.110 tons each.

Cost Efficiencies andSpeed of Construction


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The precast prestressed The precast prestressed

bridge system offered two bridge system offered two

principal advantages: principal advantages:

it was it was economicaleconomical and it and it

provided provided minimum minimum

downtimedowntime for construction. for construction.

Project duration was Project duration was

three weeks.three weeks.



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The state of Minnesota The state of Minnesota

saved more than 16% - saved more than 16% -

a half a million dollars – a half a million dollars –

by planning for a by planning for a

prestressed alternate to prestressed alternate to

a steel bridge. a steel bridge.

The 700-foot-long bridge The 700-foot-long bridge

is jointless up to the is jointless up to the

abutments and is the abutments and is the

longest continuous longest continuous

bridge in the state. It bridge in the state. It

also contains the longest also contains the longest

single concrete span.single concrete span.



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A Minnesota A Minnesota

transportation official transportation official

stated, “Originally, we stated, “Originally, we

didn’t think concrete didn’t think concrete

was suited to this… was suited to this…

bridge. However, the bridge. However, the

fabricator showed us it fabricator showed us it

was a viable alternative. was a viable alternative.

Everything went Everything went

smoothly… we’re well smoothly… we’re well

satisfied…” satisfied…”



FORWARDBACK

Precast, prestressed Precast, prestressed

concrete bridge concrete bridge

components are components are easy to easy to

erecterect, particularly when , particularly when

the tops of the units the tops of the units

comprise the entirecomprise the entire

deck slab to form an deck slab to form an

“integral deck” or “integral deck” or

“full-deck” beam. “full-deck” beam.

Easy to ErectEasy to Erect



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In a full-deck bridge, the In a full-deck bridge, the

formwork of the superformwork of the super

structure is eliminated. structure is eliminated.

Connections between Connections between

adjacent units often consist adjacent units often consist

of welding matching plates of welding matching plates

and grouting continuous and grouting continuous

keyways. Carefully planned keyways. Carefully planned

details speed the details speed the

construction process and construction process and

result in overall economy. result in overall economy.



FORWARDBACK

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



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……but it may be easier but it may be easier and more economical to and more economical to build new ones, or to build new ones, or to utilize precast utilize precast abutments and wing abutments and wing walls supported on cast-walls supported on cast-in-place footings. in-place footings. Because precast Because precast concrete integral deck concrete integral deck bridges with precast bridges with precast abutments can be abutments can be erected without delay erected without delay in cold weather, they in cold weather, they can be opened to can be opened to traffic sooner. traffic sooner.



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Bridge departments are Bridge departments are

challenged to maintain challenged to maintain

traffic flow, minimize traffic flow, minimize

traffic interruptions, and traffic interruptions, and

reduce or eliminate reduce or eliminate

detours during detours during

construction projects.construction projects.

This Florida bridge, This Florida bridge,

damaged in a tanker damaged in a tanker

fire, was completely fire, was completely

rebuilt and opened to rebuilt and opened to

traffic in 18 days.traffic in 18 days.


Fast ConstructionFast Construction


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The The fast constructionfast construction of of

precast concrete integral precast concrete integral

deck bridges is a key deck bridges is a key

advantage. Precast advantage. Precast

concrete bridges can be concrete bridges can be

installed during all seasonsinstalled during all seasons

and opened to traffic more and opened to traffic more

rapidly than any other rapidly than any other

permanent type of bridge, permanent type of bridge,

because of the availability because of the availability

of plant-produced sections of plant-produced sections

and the speed of erecting and the speed of erecting

and finishing construction. and finishing construction.


Fast ConstructionFast ConstructionAll SeasonsAll Seasons


FORWARDBACK

Replacing this bridge onReplacing this bridge on

US Route 95 in Idaho US Route 95 in Idaho

illustrates another example illustrates another example

of the advantages of very of the advantages of very

fast construction:fast construction:

New Year’s Day: Rains and New Year’s Day: Rains and

melting snow washed out melting snow washed out

this bridge over the Little this bridge over the Little

Salmon River linking the Salmon River linking the

northern and southern northern and southern

parts of the state.parts of the state.


FastFastConstructionConstruction


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January 4: The Idaho January 4: The Idaho Department of Transportation Department of Transportation contacted the precaster to contacted the precaster to investigate solutions. They investigate solutions. They determined that the fastest determined that the fastest way to replace the three way to replace the three spans was to use a singlespans was to use a single80-foot span comprised of 80-foot span comprised of bulb-tees with an integral bulb-tees with an integral deck. The top flange would deck. The top flange would be 8-inches thick and be 8-inches thick and 8'-6" wide. The end 8'-6" wide. The end diaphragms would also be diaphragms would also be precast onto the girder ends.precast onto the girder ends.

January 8: Engineers in the January 8: Engineers in the Bridge Section approved shop Bridge Section approved shop drawings and tensioning drawings and tensioning calculations.calculations.




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January 18: Bulb-tees were January 18: Bulb-tees were shipped 240 miles and set shipped 240 miles and set in place…just 17 days after in place…just 17 days after the flood! Included in the the flood! Included in the shipment was intermediate shipment was intermediate steel diaphragms, guard rail steel diaphragms, guard rail posts and guard rail…all the posts and guard rail…all the components to complete components to complete the structure.the structure.

January 25: The project January 25: The project was completed. The bridge was completed. The bridge was in service just 24 days was 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 a this single lane bridge on a major forest road was major forest road was washed out, cutting access washed out, cutting access to a U.S. highway for a half to a U.S. highway for a half dozen residents…including dozen residents…including one with a senior needing one with a senior needing continuing medical care.continuing medical care.

Within only 15 of receiving Within only 15 of receiving plans, the precaster had plans, the precaster had fabricated the 135-foot-long fabricated the 135-foot-long spans with 7’-6”-wide spans with 7’-6”-wide integral decks, and the integral decks, and the bridge was opened to traffic bridge 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 on In Ketchikan, Alaska a bridge on the only highway to the north the only highway to the north was washed out when an old was washed out when an old dam gave way on October 26. dam gave way on October 26. Integral deck girders were Integral deck girders were selected for the 85-ft span. The selected for the 85-ft span. The 12 girders were designed and 12 girders were designed and precast in the state of precast in the state of Washington, then shipped by Washington, then shipped by rail and barge to Alaska. The rail and barge to Alaska. The girders were installed and the girders were installed and the bridge was completed and bridge was completed and opened to traffic on December opened to traffic on December 19 - only 54 days after the 19 - only 54 days after the washout - despite the problems washout - despite the problems of design, remote location, of design, remote location, great distances, and adverse great distances, and adverse weather conditions during the weather conditions during the onset of an Alaskan winter!onset of an Alaskan winter!


AdverseAdverseWeatherWeatherConditionsConditions


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To accurately compare To accurately compare

costs, consider a bridge’s costs, consider a bridge’s

life-cycle: The initial life-cycle: The initial

cost of the structure cost of the structure

must be added to the must be added to the

total operating cost.total operating cost.

For stationary bridges, For stationary bridges,

the operating cost is the the operating cost is the

maintenance cost.maintenance cost.


Life Cycle Cost =

Initial Structure +

Total Operating Costs(Maintenance)


FORWARDBACK

The durability of precast The durability of precast


bridges designed and built bridges designed and built

in accordance with AASHTO in accordance with AASHTO

or AREMA specifications or AREMA specifications

means there should be means there should be

little, if any need for little, if any need for

maintenance. One of the maintenance. One of the

reasons designers select reasons designers select

integral deck prestressed integral deck prestressed

concrete is the durability of concrete is the durability of

the precast, prestressed the precast, prestressed

concrete and the resulting concrete and the resulting

low maintenance low maintenance

requirements.requirements.


DurableDurable


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Fatigue problems are Fatigue problems are

nonexistent because only nonexistent because only

minor net stresses are minor net stresses are

induced by traffic loads. induced by traffic loads.


DurableDurable


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And of course, no painting is And of course, no painting is

needed. Some bridge needed. Some bridge

engineers estimate the life-engineers estimate the life-

cycle cost of re-painting cycle cost of re-painting

steel bridges to be 15 to 25% steel bridges to be 15 to 25%

of the initial cost. Painting of the initial cost. Painting

bridges is environmentally bridges is environmentally

unfriendly and can be unfriendly and can be

especially dangerous or especially dangerous or

expensive when done over expensive when done over

busy highways, streams, busy highways, streams,

railroad rights-of-way or in railroad 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 224 the superstructures of 224 bridges are precast bridges are precast prestressed concrete beams. prestressed concrete beams. These bridges, built during These bridges, built during 1957 and 1958, have 1957 and 1958, have withstood heavy traffic and withstood heavy traffic and severe weathering and yet severe weathering and yet require very little require very little maintenance. Other projects maintenance. Other projects in all parts of North America in all parts of North America have exhibited similar have exhibited similar experience little or no ‑experience little or no ‑maintenance has been maintenance has been required on precast required on precast prestressed concrete prestressed concrete bridges.bridges.


Minimal MaintenanceMinimal Maintenance


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In addition to its cost In addition to its cost

efficiencies and speed efficiencies and speed

of construction, of construction,

precast concrete precast concrete

provides important provides important

structural and structural and

engineering engineering

advantagesadvantages as well. as well.

Cost Efficiencies



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Design Aesthetics


A common requirement of A common requirement of

many bridges is that the many bridges is that the

superstructure be as superstructure be as

shallow as possible in order shallow as possible in order

to provide maximum to provide maximum

clearance with minimum clearance with minimum

approach grades.approach grades.

Through the technique of Through the technique of

prestressing, the designer prestressing, the designer

can utilize the maximum can utilize the maximum

possible span-to-depth possible span-to-depth

ratio. This superstructure ratio. This superstructure

occupies just 13 inches occupies just 13 inches

of profile.of profile.

Structural/EngineeringAdvantages

Shallow SuperstructureShallow Superstructure


FORWARDBACK

Span-to-depth ratios as high Span-to-depth ratios as high

as 30:1 can be achieved with as 30:1 can be achieved with

solid slabs, voided slabs, box solid slabs, voided slabs, box

beams, multi-stemmed units, beams, multi-stemmed units,

or bulb-tee sections. Even or bulb-tee sections. Even

though deeper sections will though deeper sections will

require less prestressing require less prestressing

steel, the overall economy steel, the overall economy

of a project may dictate the of a project may dictate the

highest possible span-to-highest possible span-to-

depth ratio.depth ratio.

These HPC girders are These HPC girders are

4'-6" deep and span 157 ft. 4'-6" deep and span 157 ft.

A span/depth ratio of A span/depth ratio of

nearly 35!nearly 35!Shallow SuperstructureShallow Superstructure



FORWARDBACK

Precast prestressed Precast prestressed concrete integral deck concrete integral deck girders were selected to girders were selected to provide a shallow provide a shallow superstructure for a superstructure for a bridge over a busy urban bridge over a busy urban highway in Denver. Even highway in Denver. Even though the bridge must though the bridge must carry frequent heavy carry frequent heavy truck traffic, the total truck traffic, the total depth of the girders is depth of the girders is only 3 feet, including the only 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



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This bridge illustrates the This bridge illustrates the

high span-to-depth ratios high span-to-depth ratios

possible with integral possible with integral

deck prestressed deck prestressed

concrete.concrete.


High Span-to-Depth RatioHigh Span-to-Depth Ratio


FORWARDBACK

Bridges are subjected to an Bridges are subjected to an assortment of hostile assortment of hostile environments as well as environments as well as repeated impact loadings. repeated impact loadings. Some must endure intense Some must endure intense sun, extreme temperatures sun, extreme temperatures and brackish waters. Others and brackish waters. Others must withstand not only the must withstand not only the freezing and thawing freezing and thawing provided by nature but also provided by nature but also the potential for damage the potential for damage through the use of de-icer through the use of de-icer chemicals. Dense, high chemicals. Dense, high strength prestressed strength prestressed concrete has excellent concrete has excellent freeze-thaw and chemical freeze-thaw and chemical resistance. resistance.



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Greater Greater fire resistancefire resistance is is

another advantage. This another advantage. This

timber bridge timber bridge

experienced a dramatic experienced a dramatic

fire… fire…

Fire ResistanceFire Resistance



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……it was replaced by a low it was replaced by a low

maintenance prestressed maintenance prestressed

concrete bridge erected concrete bridge erected

without falsework over an without falsework over an

environmentally-sensitive environmentally-sensitive

area…area…



FORWARDBACK

Prestressed concrete bridges Prestressed concrete bridges have have excellent riding excellent riding characteristicscharacteristics that that minimize traffic vibrations. minimize traffic vibrations. The public will not only The public will not only bebe safe but also safe but also feelfeel secure and secure and comfortable on a prestressed comfortable on a prestressed concrete bridge. Traffic concrete bridge. Traffic vibrations are held to an vibrations are held to an absolute minimum. The absolute minimum. The owner will have a structure owner will have a structure on which the deck is less on which the deck is less likely to crack prematurely. likely to crack prematurely. Continuous spans even hold Continuous spans even hold deck joints to a smooth deck joints to a smooth minimum.minimum.

Excellent Riding CharacteristicsExcellent Riding Characteristics



FORWARDBACK

Steel girder bridges frequently Steel girder bridges frequently exhibit noticeable vibrations. exhibit noticeable vibrations. The natural frequency of The natural frequency of vibration of these bridges often vibration of these bridges often coincides with the frequencies of coincides with the frequencies of traffic and then resonance traffic and then resonance occurs. Because of their mass occurs. Because of their mass and stiffness, the natural and stiffness, the natural frequency of vibration of frequency of vibration of prestressed girder bridges rarely prestressed girder bridges rarely coincides with the vehicle coincides with the vehicle frequencies. Documented cases frequencies. Documented cases show that light bulbs in fixtures show that light bulbs in fixtures installed on steel bridges burn installed on steel bridges burn out more rapidly as a result of out more rapidly as a result of such vibrations. Reports are such vibrations. Reports are surfacing that indicate decks on surfacing that indicate decks on steel bridges are more prone to steel bridges are more prone to cracking and deterioration. cracking and deterioration.


Excellent Riding CharacteristicsExcellent Riding Characteristics


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The clean, attractive The clean, attractive

lines of concrete beams lines of concrete beams

also help bridge also help bridge

designers meet the designers meet the

most demanding most demanding

aesthetic requirements. aesthetic requirements.

Cost Efficiencies

Design Aesthetics


FORWARDBACK



Prestressed concrete Prestressed concrete

bridges can be attractive bridges can be attractive

from above, below, and from above, below, and

from the side because of from the side because of

the simple and clean the simple and clean

shapes of the members shapes of the members

used. The high span-to-used. The high span-to-

depth ratios made depth ratios made

possible through the use possible through the use

of prestressing, result in of prestressing, result in

strong, tough, durable strong, tough, durable

and yet graceful bridges. and yet graceful bridges.

Design Aesthetics


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Prestressed concrete is Prestressed concrete is

efficient because it is a efficient because it is a

composite of high-composite of high-

strength steel and strength steel and

high-performance high-performance

concrete. To ensure concrete. To ensure

this efficiency and to this efficiency and to

comply with exacting comply with exacting

project specifications, project specifications,

precasting plants have precasting plants have

developed developed

sophisticated quality sophisticated quality

assurance programs. assurance programs.

Cost Efficiencies



FORWARDBACK


Design Aesthetics

Precast, prestressed Precast, prestressed

concrete products are concrete products are

inspectedinspected both during and both during and

following production. following production.

In fact, every operation in In fact, every operation in

the manufacturing process the manufacturing process

provides a point of provides a point of

inspection and control. inspection and control.



FORWARDBACK

Today’s bridge designs Today’s bridge designs

use more high-use more high-

performance materials performance materials

and sophisticated and sophisticated

solutions than ever solutions than ever

before. More and more, before. More and more,

engineers are requiring engineers are requiring

only qualified sources only qualified sources

with certified technicians with certified technicians

and inspectors. and inspectors.



FORWARDBACK

A plant that is PCI-certified tells A plant that is PCI-certified tells the engineer five important the engineer five important things:things:


Independent Auditors;Unannounced Audits

Audits Based onNational Standards

1.1. The production facility has The production facility has demonstrated its capability to demonstrated its capability to produce quality products to produce quality products to the satisfaction of a the satisfaction of a nationally recognized, nationally recognized, independent consulting independent consulting engineering and inspection engineering and inspection firm engaged by PCI for firm engaged by PCI for multiple, unannounced multiple, unannounced annual audits.annual audits.

2.2. The rigid audits the plant The rigid audits the plant undergoes are based on undergoes are based on published industry standards – published industry standards – the the PCI Manual for Quality PCI Manual for Quality Control for Plants and Control for Plants and Production of Precast Production of Precast Structural Concrete.Structural Concrete.


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Five important things cont.:Five important things cont.:

3.3. The plant practices a The plant practices a documented and PCI-documented and PCI-approved quality assurance approved quality assurance program open for review.program open for review.

4.4. The plant has PCI-certified The plant has PCI-certified QC personnel.QC personnel.

5.5. The producer has PCI The producer has PCI confirmed capabilitiesconfirmed capabilities. .


Independent Auditors;Unannounced Audits

Audits Based onNational Standards

Documented Quality System

Certified Personnel

Confirmed Capabilities


FORWARDBACK

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



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