The Future - PowerPoint PPT Presentation

1 / 25
About This Presentation
Title:

The Future

Description:

... as well as reduced long-term costs due to fewer replacements and fewer repairs. ... higher strengths are becoming more common as higher strength concretes are used ... – PowerPoint PPT presentation

Number of Views:21
Avg rating:3.0/5.0
Slides: 26
Provided by: nancyc89
Category:
Tags: future

less

Transcript and Presenter's Notes

Title: The Future


1

The Future
FORWARD
2

THE FUTURE
  • Material properties, such as corrosion
    resistance, fire resistance and durability are
    being continuously improved and exploited.
  • These inherent qualities of precast prestressed
    concrete and its considerable design flexibility
    also make it ideal for a wide variety of other
    applications poles, piles, culverts, storage
    tanks, retaining walls, sound barriers and even
    railroad ties.

FORWARD
BACK
3

THE FUTURE
  • The benefits of High Performance Concrete are
    already beginning to be applied. These include
    reduced initial construction costs that result
    from wider girder spacing and longer spans as
    well as reduced long-term costs due to fewer
    replacements and fewer repairs. High Performance
    Concrete is being increasingly specified for the
    nations bridges and structures.

FORWARD
BACK
4

THE FUTURE
  • One form of HPC is high strength concrete. A
    strength of 14,000 psi was specified here for the
    beams of the Louetta Road Bridge, a demonstration
    project, located in Houston, Texas. High strength
    concrete was also used in this bridge for the
    stay-in-place deck panels, the cast-in-place
    concrete deck and precast segmental piers.

FORWARD
BACK
5

THE FUTURE
  • The Giles Road Bridge in Sarpy County, Nebraska
    also was constructed using High Strength
    Concrete. Completed in 1996, it is another
    example of a bridge with 12,000 to 14,000 psi
    concrete girders and a 5,000 to 8,000 psi
    concrete deck. The Federal Highway
    Administration, together with PCI and several
    states, continues to promote the use of High
    Performance Concrete in bridge applications. For
    the precast industry, High Performance Concrete
    often involves higher than average compressive
    strength.

FORWARD
BACK
6

THE FUTURE
  • However, other factors, such as low permeability
    and resistance to freeze-thaw not just strength
    may be features of High Performance Concrete
    depending on the geographic location of the
    bridge and the component for which it is used.
    Lightweight aggregate concrete with strengths in
    the 7,000 to 10,000 psi range is also being used
    on some newer bridges. Lightweight concrete
    provides reduced dead-loads and seismic forces.

FORWARD
BACK
7

THE FUTURE
  • Strands of larger diameters and higher strengths
    are becoming more common as higher strength
    concretes are used and the demand for higher
    tensile force increases. When 0.6 inch diameter
    strands are used in conjunction with high
    strength concrete, in the 10,000 to 12,000 psi
    range, standard I-beams and other products are
    able to reach significantly longer spans never
    thought possible before. Even larger and stronger
    strand are on the horizon. Corrosion-resistant
    steels and coatings promise unlimited durability.

Corrosion-resistant coatings Stainless-clad Corros
ion-resistant steel
0.7"?
FORWARD
BACK
8

THE FUTURE
  • Nonmetallic reinforcement such as glass, carbon
    and aramid fiber composites will be increasingly
    used for special applications. A recent
    demonstration project has shown the compatibility
    of carbon fiber strands for prestressing a bridge
    girder. Both, internally bonded prestressing and
    external unbonded prestressing systems are used.

FORWARD
BACK
9

THE FUTURE
  • Synthetic, organic and steel fibers have been
    shown to improve toughness and shrinkage
    cracking. Recent developments in high
    performance fiber-reinforced concrete hold
    promise in terms of performance and
    cost-effectiveness.

FORWARD
BACK
10
THE FUTURE
  • Reinforcing steel corrosion

Migration of chlorides, H20 and O2 into the
concrete, no corrosion and no damage to concrete
Corrosion of the steel reinforcement and cracking
and/or spalling of concrete
Initiation
Propagation (corrosion)
Degree of Corrosion
Critical chloride threshold
I
Time
FORWARD
BACK
11

THE FUTURE
Corrosion mechanism of steel
Corrosion Mechanisms Can be Minimized By Avoiding
Microgalvanic Cell Formation Present in
Conventional and Micro-Alloyed Steels
FORWARD
BACK
12

THE FUTURE
MMFX is not a stainless steel but Step 1 of its
production adds chromium and reduces the carbon
content. Benefits of adding chromium to reduce
the steels corrosion rate.
FORWARD
BACK
13
THE FUTURE
The Second Step to Achieving Microstructure Steel
MMFX approach to altering the micro-structure of
the steel Produce a Microcomposite Steel that
Eliminates Formation of Microstructural Galvanic
Cells
FORWARD
BACK
14
THE FUTURE
FORWARD
BACK
15
THE FUTURE
FORWARD
BACK
16

THE FUTURE
  • Self Consolidating concrete is an extremely
    cohesive and flowable material capable of being
    placed without vibration. It can be placed very
    fast at a very dramatic reduction in noise.

FORWARD
BACK
17

THE FUTURE
  • The cohesion of the fresh concrete and no
    negative effects from vibration will result in a
    more homogeneous surface layer. This reduces
    permeability, increases resistance to chloride
    ingress, carbonation and other chemical attack

FORWARD
BACK
18

THE FUTURE
  • Another development has been the use of precast
    deck panels. Used as stay-in-place forms, the
    panels reduce labor for field placement of
    reinforcing steel and concrete for bridge decks,
    resulting in considerable savings. The panels
    become composite with the field-placed concrete
    for live loads. Theyre made of high-quality,
    plant-produced concrete and contain the primary
    tensile reinforcement between beams. They remain
    crack-free, protecting this important reinforcing
    steel.

FORWARD
BACK
19

THE FUTURE
  • Full-depth precast deck panels promise to provide
    the solution for extended closings due to deck
    replacement. The technique applies to new
    construction as well. Precast highway paving
    panels are being demonstrated in Texas to speed
    lane widenings and reduce traffic closures and
    detours. Refined materials and methods are making
    these solution an exciting new part of the
    designers tool box.

FORWARD
BACK
20

THE FUTURE
  • Another innovation is the development of
    horizontally curved precast concrete bridges
    which is creating exciting new options in
    contemporary bridge designs. This technique
    involves post-tensioning precast elements
    together in the plants before shipment or in the
    field after erection.

FORWARD
BACK
21
THE FUTURE
Spliced girders give Prestressed concrete girders
the ability to reach further and longer
FORWARD
BACK
22

THE FUTURE
  • And yet another solution for curved structures is
    segmental construction. Working together with the
    American Segmental Bridge Institute (ASBI) and
    the AASHTO Bridge Subcommittee, PCI has endorsed
    a family of standard shapes for segmental bridges
    that is intended to reduce the cost of segmental
    bridges for smaller structures such as urban
    grade separations.

FORWARD
BACK
23

THE FUTURE
  • Prestressed concrete got its start as the
    original composite material and further
    developments by the industry and its suppliers
    have continued to refine the performance of the
    product for the bridge market.

FORWARD
BACK
24

THE FUTURE
  • Today, it still gives the public extremely good
    value for its money. The reputation of the
    precast prestressed concrete industry has been
    built on the strength, imagination, consistency
    and integrity of its people and products alike.
    In the future, it will continue to be the
    solution of choice.

FORWARD
BACK
25
Thank You for Your Attention
BACK
Write a Comment
User Comments (0)
About PowerShow.com