2. Overview of presentation
Introduction
Constraints during construction
Planning for project
Materials
Techniques for Urban Transportation Structure
Superstructure
Substructure
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3. 1. Introduction
Urban transportation infrastructure involves large
scale construction
There are various constraints.
Need of innovative techniques for timely completion.
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4. 2. Constraints during construction
Space constraint
Time constraint
Utilities
Environment
Aesthetics
Safety
Economy
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5. 2.1 Space constraint
Historical Places
Existing structures
Minimum disturbance
to traffic
Photo.1. Space constraint
Photo: http://www.civil.skanska.com/skanska/templates/page.asp?id=3359
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6. 2.2 Time constraint
Construction of new infrastructure is normally taken up when
existing infrastructure is not sufficient to fulfill the demand.
Urgent need to start and complete the construction
During the construction, the existing infrastructure is strained
further.
So, timely completion of the project is important.
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7. 2.3 Utilities
Infrastructure normally passes through densely populated
area.
So, there are some utilities as
Water mains (Underground)
Sewer lines (Underground)
Telephone lines (underground or overhead)
Power supply lines. (overhead)
These utilities should be diverted, which is time consuming
and costly affair.
Many times, the utilities are not known till the starting of
work.
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8. 2.4 Environment
Air and noise pollution
Due to slow moving vehicular traffic
Due to construction activity
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9. 2.5 Aesthetics
Photo 2. Aesthetics of urban transportation infrastructure
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10. 2.6 Safety
Accidents causes loss of
Life
Property
Environment
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17. 3.6 Composite
Use of metal +
Concrete
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18. 4. Techniques for Construction
Elevated structures are divided it to-
Superstructure
Substructure
Fig. 3. Components of elevated structures
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19. 4.1 Techniques for Superstructure
Techniques-
Span-by-span construction with precast girder.
Precast post-tensioned segmental technique
Continuous units on ground supported staging
Central span by Cantilevering technique
Balanced cantilevering technique
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20. 4.1.1 Span-by-span construction
with precast girders
Most economical
Prestressed girders are lifted
from casting yard and
transported to site on
trailers
At site they are lifted and
placed on pier cap by
cranes.
Deck slab is then casted
over these girders.
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21. 4.1.2 Precast post tensioned
segmental technique
Simply supported post-tensioned units of 2~3 m with
epoxy bonded joints.
For standardization of segments, cable profile is made
horizontal in the middle span.
Fig.5. Construction by Precast post-tensioned segmental technique
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22. 4.1.3 Continuous units on ground
supported staging
At crossing, central span is more.
So prestressed continuous units becomes obligatory.
In such case, central unit can be casted by staging by
diverting traffic
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23. a) End spans are casted on staging
b) Traffic diverted and central span is casted on staging
c) Open to traffic.
Fig 7. Construction of continuous unit on ground supported staging
24. 4.1.4 Central span by cantilevering
technique
End spans are casted on staging
Central span is casted by cantilevering.
When two cantilever meet, the stitch segment is
casted.
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25. a) End spans are casted on staging
b) Cantilevering construction started from ends
c) Cantilevering construction completed from both ends.
Fig 8. Construction of central span by cantilevering
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26. d) Stitch segment is casted
e) Construction completed
Fig 9. Construction of central span by cantilevering
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27. 4.1.5 Balanced cantilevering
technique
Only end portion of end span is casted on staging
Remaining end span and central span is casted by
balanced cantilevering.
When two cantilever meet, the stitch segment is
casted.
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28. a) End portion of end spans are casted on staging
b) Cantilevering construction started from ends in both directions
c) Cantilevering construction completed from both ends.
Fig 10. Construction by balanced cantilevering
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29. d) Ground supported staging at end spans
e) Stitch segment is casted
f) Construction completed
Fig 11. Construction by balanced cantilevering
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30. Fig. 12. Construction by balanced cantilevering
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31. 4.2 Techniques for Substructure
Techniques-
Self supporting cutting.
Sheet piles
Diaphragm wall
Single cast-in-situ bored pile.
Driven casted pile
Group of piles.
Well foundation
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32. 4.2.1 Self supporting cutting
For shallow
depth and hard
soil, soil cutting
is possible at self
supporting
slopes.
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33. 5.2.2 Using sheet pile
For higher depth
&/or soft soil
sheet pile are
preferred.
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34. 4.2.3 Using diaphragm wall
For deep
cutting, diaphra
gm wall is most
useful
These are
installed prior to
taking up the
excavation work.
Generally, it is
part of final
structure
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35. 4.2.4 Cast-in-situ bored pile
150 - 600mm dia to 20m
deep
As a rotary auger causes
minimal vibration it is
ideal for use next to
buildings or underground
services without
destabilization.
Dewatering techniques
can be used if water is
present. Fig 13. Cast-in-situ bored pile
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36. 4.2.5 Driven casted pile
150mm - 600mm to 20m
deep
Used on soft soils overlay.
Permanently steel cased
piles are driven with an
internal drop hammer.
Suitable reinforcement is
then added and the casing
filled with concrete. Fig 14. Driven casted pile
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37. 4.2.6 Group of piles
Most of pile foundations
consists not of a single
pile, but of a group of
piles, which act in the
double role of reinforcing
the soil, and also of carrying
the applied load down to
deeper, stronger soil strata.
Fig 15. Group of piles
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38. 4.2.7 Well foundation.
Used under very heavy
loads to be carried by soft
soil.
Fig 16. Well foundation
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