A seminar report on
SEGMENTAL CONSTRUCTION OF BRIDGES
• CONSTRUCTION TECHNIQUES
• DESIGN CONSIDERATIONS
• CASE STUDY
• What is Segmental Bridge Construction ?
In contrast to classical monolithic structures a
segmental bridge consists of “small” Pieces
stressed together by external tendons.
Segmental construction is gaining popularity as a
method of construction where the local terrain and/or
traffic prohibit the erection of conventional false work.
Why go for Segmental Construction?
• Segmental construction technique, facilitates
construction of longer span bridges, reduces
intermediate piers and thus obstruction to flow
and avoid system of erection of staging from
river bed level, and has been a very effective and
economical technique in such situations.
• This method of const. first developed in
western Europe particularly in France &
Germany during 1950’s.
• Over 70 bridges of this type under const.
during 1971-75 in France.
• In India during 1960-61,@ 250m long
Barak bridge was constructed.
• Delicate process & needs fine balance
• Any Imbalance leads to damages, so needs careful &
systematic approach in casting of segments.
• For that proper flow chart of the activities & sequence
there for to drawn.
• Launching & const. sequence differ according to con. tech,
& its depends on the con. site, geological studies etc.
• The techniques can broadly be classified as under:
• Cantilever Method for Cast-in-situ Construction
• Incremental Launching Method.
• Construction with Precast Segments.
Cantilever Method for Cast-in-situ
Pier head is casted with detailed
A steel gantry then designed &
Thereafter, soffit shuttering,
shuttering for web & deck
shuttering is fixed to the
overhanging portion of the gantry
on both sides.
Reinforcement is then tied as per
Then concreting is done on both
sides of the gantry.
Photo1: Construction of initial unit
Cantilever Method for Cast-in-situ
Construction of one unit each
on both sides of pier head 7 days.
Erection of gantry - 10 days.
Casting of each subsequent
cantilever units (including
prestressing of cables to be
anchored at that units) - 7
with pier cap during
Precast Segmental Bridge Construction
using Launching Truss
• It is economical for large project, due to
investment req. for casting, handling &
erection of precast segments.
• The construction of a flyover in an urban
environment is not always welcomed by
the society because of traffic disturbance
& construction delays, nuisance caused
during concreting & erecting the formwork
at site and noise & visual pollution.
• Segments are casted
in the casting yard.
• launching girder is
used for erection of
• The launching girder
has two parallel
provided with hangers
to hold the segments
Finalization of the dimension of box girder depending
upon the width of the carriageway/ footpath. Depth at
root section however mainly depends upon the span
length and is normally equal to 1/8 of span.
Based on the length of the arm, it is then divided into
likely construction units. Length of each unit is generally
kept in the range of 3.0 m to 4.0 m based on the
construction convenience and gantry parameters.
• Ganga bridge at Buxar•
This balanced cantilever bridge is situated in Bihar on an important
highway link on Ganga river.
No. of span- 12.
10 intermediate spans of 101.22m & two end spans of 55.03m.
Out of 12 T-arms, central 10 T-arms, were constructed using Precast segments &
one each on either bank was insitu.
The weight of Precast segments was varying between 2.13m near pier to 3m for the
• With the introduction of in-situ segmental construction
the problem of constructing longer span over rivers,
creeks as well as gorges was successfully overcome.
• Precast prestressed segmental construction is a
versatile technique for construction of present day fast
track jobs. Segments can be cast away from actual site,
their by minimizing hindrance to traffic & public in urban
• In casting yard better control on quality & dimensional
tolerances can be achieved. Segment casting can start
independently as work on foundations progresses, their
by reducing overall completion time.
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