Bridge chapter 6

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INFOLINK UNIVERSITY COLLEGEINFOLINK UNIVERSITY COLLEGE
HAWASSA CAMPUSHAWASSA CAMPUS
Fundamentals ofFundamentals of
Bridge DesignBridge Design
December, 2018
By:- Daniel Alemayehu
December 7, 2018 1Daniel A.
CHAPTER 6CHAPTER 6
SUBSUB--STRUCTURESTRUCTURE
December 7, 2018 Daniel A. 2

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1. Piers
Piers provide vertical supports for spans at
intermediate points and perform two main
functions:
transferring superstructure vertical loads
to the foundations
resisting horizontal forces acting on the
bridge
(Cont’d)
Generally piers are subjected to:
• Dead loads • Live loads and impact from the
superstructure
• Wind loads on the structure and the live loads
• Centrifugal force from the superstructure
• Longitudinal force from live loads (vehicular
braking force)
• Drag forces due to the friction at bearings

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(Cont’d)
• Earth pressure • Stream flow pressure
• Ice pressure • Earthquake forces
• Thermal and shrinkage forces
• Ship impact forces
• Force due to prestressing of the superstructure
• Forces due to settlement of foundations
Types of PiersTypes of Piers
Solid Wall Pier: A solid wall pier (also
known as a continuous wall pier) as its name
would imply, consists of a solid wall which
extends up from a foundation consisting of a
footing or piles.

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Cont’d
Hammerhead Pier: utilizes one or more
columns with a pier cap in the shape of a
hammer. Mainly found in urban settings
because they are both attractive and occupy a
minimum of space, thereby providing room
for underpass traffic.
Cont’d
Column Bent Pier: consists of a cap beam
and supporting columns in a frame-type
structure. In dense urban interchanges, use of
column bent piers can lead to a cluttered
image producing a “concrete jungle” effect.

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Cont’d
Pile Bent Pier: is a variation on the column
bent pier with the supporting columns and
footing replaced with individual supporting
piles. The end piles are generally equipped
with a batter in the transverse direction.
Cont’dCont’d
Generally, the selection of pier type is made
based on the following considerations.
Aesthetics
Economy
Superstructure type
Flow of water and
Traffic under the bridge

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Design CriteriaDesign Criteria
In general, the design of a highway
bridge pier should address:
Safety against overturning
Safety against sliding
Safety against bearing failure of the soil
Safety against excessive or differential
settlement
Backwall and WingwallBackwall and Wingwall
 Wing wall: is a side wall to the abutment
back wall designed to assist in confining
earth behind the abutment backwall.
 Back wall: (stem), is the primary component
of the abutment acting as a retaining
structure at each approach.

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AbutmentAbutment
Abutment is component of a bridge and;
provides the vertical support to the bridge
superstructure at the bridge ends
connects the bridge with the approach
roadway
retains the roadway base materials
Types of AbutmentTypes of Abutment
 From the view of the relation between the
bridge abutment and roadway or water flow
that the bridge overpasses, bridge abutments
can be divided into two categories:
Open-end abutment and
Closed-end abutment.

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OpenOpen--endAbutmentendAbutment
there are slopes b/n the bridge abutment face
and the edge of the roadway or river canal that
the bridge overpasses.
It imposes much less impact on the
environment and the traffic flows under the
bridge than a closed-end abutment.
Also, future widening of the roadway or
water flow canal under the bridge by adjusting
the slope ratios is easier. However, the
existence of slopes usually requires longer
bridge spans and some extra earthwork.December 7, 2018 15Daniel A.
Cont’dCont’d

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ClosedClosed--end Abutmentend Abutment
 Is constructed close to the edge of the
roadways or water canals.
 Because of the vertical clearance
requirements, high abutment walls
must be constructed.
 The high abutment walls and larger
backfill volume often result in higher
abutment construction costs and more
settlement of road approaches than for
the open-end abutment.
Cont’dCont’d

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Cont’d
 Generally, the open-end abutments are more
economical, adaptable, and attractive than
the closed-end abutments.
 However, bridges with closed-end
abutments have been widely constructed in
urban areas and for rail transportation
systems because of the right-of-way
restriction and the large scale of the live
load for trains, which usually results in
shorter bridge spans.
Cont’dCont’d
Based on the connections between the
abutment stem and the bridge
superstructure, the abutments also can be
grouped in two categories:
the monolithic abutment and
the seat type abutment.

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Cont’dCont’d
Abutments can be classified based on the
load resisting mechanism as:
 Gravity abutments: resist the load acting
with its dead weight and dead weight of
retained soil or backfill on its inclined back
face. They can be constructed using stone
masonry or concrete masonry.
 Cantilever abutments: load resistance
derived from cantilever action and usually
constructed from reinforced concrete.
Cont’dCont’d
 Counterfort abutments: ties (counterforts)
are provided to tie the stem to the footing.
 Reinforced earth abutments: use of
multiple-layer strips or fibers to reinforce the
fill material in the lateral direction so that the
integrated fill material will act as a gravity
retaining structure. Overturning and sliding
are needed to be checked under the
assumption that the reinforced soil body acts
as a gravity retaining wall.

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Cont’dCont’d
THE END!

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