Incremental-Push-Launching-Method.ppt ppt

incremental push launch method

1. INCREMENTAL PUSH
LAUNCHING
METHOD
Advanced Construction Methods
Prepared by
Mr. P .A. Nadgouda
Assistant Professor
D.Y.Patil College of Engineering & Technology
Kolhapur
Unit : 02

2. Concept
The basic concept of INCREIMENTAL
PUSH LAUNCHING METHOD (ILM) is to
prefabricate approximately 10m to 30m long units
of the bridge under factory conditions behind an
abutment and launch the units by sliding them on
Teflon bearings into final position without the aid
of scaffolding.

3. The total deck slab of the bridge is
subdivided longitudinally into section of 10m to
30m length, depending upon the length of the
span and time available for construction.
Each section is concreted immediately
behind the abutment of the bridge in steel framed
forms.
These steel frames which remain in same
place for concreting all sections.

5. •The forms are designed in such a way that it can
be moved transversely or rotated on hinges to
facilitate easy stripping after sufficient hardening
of the concrete.
•The forms are hydraulically or mechanically
activated to ensure rapid stripping.

6. •This is the launching
equipment, which consists
of a combination of
hydraulic jacks acting
vertically and horizontally
on sliding bearings.
• The sliding bearing consists
of concrete blocks covered
with stainless steel and
Teflon-coated reinforced
elastometic pads.

7. •A section is manufactured in formwork in lengths
corresponding to one-third to one-half of the normal
span length. After the stripping of the forms, tendons
are inserted and stressed.
•The section is then jacked forward, sliding on the
Teflon, which, in turn, is affixed to stainless steel
plates on top of the piers.
•A new section is then constructed immediately
adjoining the rear end of the first. Pre-stressing
tendons are spliced so that the two segments are
joined as one longer pre-stressed unit and then jacked
forward another length.

8. •At the head of the first section, a steel nose
consisting of a light truss is attached to
facilitate reaching of the first and subsequent
piers without including a too large cantilever
moment during construction.
•The second and following sections are
concreted directly on the face of the hardened
portion and the longitudinal reinforcement can
continue across the construction joint.
•The pushing is achieved by hydraulic jack
which acts against the abutment.

9. Launching Process

11. How hydraulic Jack works?

12. •Low capacity hydraulic jack would be
enough to move the bridge decks.
•Intermediate pier supports or towers
may be used to give temporary support
across longer spans since the practical
limit of a span length for this type of
construction is about 60 meters.

13. •When launching from both ends of the bridge,
different curvatures may be used, but this must be
constant for each launching point. Similarly, the super-
elevation must be constant.
•After the launched bridge is in place, the bearing seats
may be jacked up to remove the Teflon, and the
permanent bearings are installed. Jacking points should
have the required supplemental reinforcing to permit
this application of force at a location offset from the
permanent bearings.

14. Features of the incremental launching
method
•Construction is carried out completely without falsework, so
that there is no problem in passing over obstacles below, such
as roads, railways, rivers, buildings areas.
•The superstructure is made up of units of 15 to 25 m length,
each completed in one week; there are no joints, since each
unit is concreted directly against the preceding one.
•It is a economic construction technique.
•To achieve quality work with reduced amount of labour.
•It is a speedy construction technique.

15. THANK YOU