Typical staged construction methods
supported
- Staged placement of beams and
slab for continuous structures (PCC beams or steel beams)
- Cast insitu span-by-span
construction of continuous beams
- Precast segmental
span-by-span erection
- Cast insitu balanced
cantilever construction
- Precast segmental balanced
cantilever construction
- Progressive erection of
precast segmental decks
- Incremental launching
- Balanced placement for
cable-stayed bridges
Stationary / travelling
formwork

Span-by-span
The erection of all segments
for a span in a set, which is then aligned, jointed, and
ultimately, usually, longitudinally post-tensioned together to
make a complete span.
In LUSAS, this can be modelled
as a line beam model with optional fleshing of the deck
cross-section to show results contours.
The
animation below shows the construction sequence for the twin rib
span-by-span example shown (substructure not included).
The
analysis can incorporate post-tensioning
between stages, and creep effects as construction
continues, as required.

Progressive placement
A one-directional placement
process where bridge segments are placed in sequence,
extending out over supports as an ever increasing cantilever,
until the next support is reached.

Progressive placement with
jacking-up of supports
A one-directional placement
process where bridge segments are placed in sequence,
extending out over supports as an ever increasing cantilever,
until the next support is reached and then jacked-up into
position.

Balanced cantilever
The building of a bridge
superstructure from both sides of a pier in a scales-like
fashion.

Using LUSAS, creep
/ shrinkage analysis can incorporate an age attribute (for precast elements)
and checks on robustness
can also be made as, for example, where a segment may be
inadvertantly dropped by crane and where dynamic effects (impulse)
are important. 2nd order (P-delta) effects could also be included.

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Incremental launching
Incremental launching
involves the casting of a continous
chain of bridge segments on-site adjacent to the actual
location of the bridge and then pushing the growing
superstructure out over temporary and permanent supports at
the bridge's location. A good example of a bridge built
using this method of construction is the Blackwater
Viaduct in the Republic of Ireland.
Using LUSAS, incremental
launching can be carried out for both in-line deck launching,
or for a curved deck launch. Modelling of incremental
launching can be done in two ways, either by pushing the model
over a series of fixed supports or by activating and moving a
series of supports backwards under a model that is
incrementally being added to. Examples of both methods are
shown below.
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Photo:
Benaim |
Click to play each movie (in new window)


Staged
Construction Analysis : Example of use
The
Original I95
Mississippi
River Bridge was designed to be a record-breaking, cable-stayed structure
linking the States of Illinois and Missouri in the USA, helping to
relieve traffic on existing bridges across the river.
Designed
by Modjeski & Masters for its clients Missouri and Illinois
Departments of Transportation, staged construction facilities in
LUSAS Bridge were used to model an 800 day construction
period, followed by a 10000 day period to allow for creep
over that length of time.

This
Post-tensioning
Certain types of
staged construction analysis may also require post-tensioning.
See the post-tensioning
product information page for more details.
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