Multi-Span Large Bridges – Pacheco & Magalhães (Eds.
)
© 2015 Taylor & Francis Group, London, ISBN 978-1-138-02757-2
Construction of Panipat Elevated Expressway on NH-1 on BOT basis
P.N.S.S. Sastry
Larsen and Toubro Infrastructure Engineering Limited, Chennai, India
ABSTRACT: Time is the essence of “Build Operate and Transfer (BOT)” type of contracts.
Construction of long elevated corridors in urban busy traffic environment is challenging one in
BOT projects especially in meeting the construction time schedule. Panipat Elevated Corridor on
National Highways (NH)-1, India is one such project. The total time frame for completion of
elevated corridor and complete service and main carriage At-Grade was 36 months. The elevated
corridor falls in the road project having a six-lane facility, covering a length of about 10 km from km
86.00 to km 96.00 through Panipat city on NH 1, India. The elevated corridor is 3.4 km long with
dual carriage way. The over-all deck width of each carriage way is 11.75 m. From the economics
and construction point of view Pre-Tensioned I Girder with cast-In-place deck slab was adopted.
Typical five span continuous modules of 29.5 m + 31.0 m × 3 + 29.5 m are adopted for the project.
All continuous spans are supported with two POT-PTFE bearings beneath each diaphragm. Hammer
head piers with Pile foundations is adopted for substructure and foundations respectively. Among
various structural component cast-in-place deck slab takes long duration with minimal staging
arrangement. In this situation, generally contractors will opt for permanent shuttering, which is an
additional cost and increases dead weight and quantities in substructure and foundation. To achieve
minimum cost solution and increase in speed of construction, for the first time in India, partial
precast deck slab is used for such long corridor. The paper presents “Design and Construction
Methodology” adopted
1 INTRODUCTION
National Highways Authority of India (NHAI) awarded Construction of Six Lane access controlled
highway from Km 86.00 to Km 95.700 and 2 lane side roads of NH-1 including elevated structure
covering Gohana road junction to Skylark tourist complex at Panipat in the State of Haryana on
Built Operate and Transfer Basis to Concessionaire M/s Larsen and Toubro Limited (L&T).
The challenge before L&T was to meet the scheduled time of construction, while maintaining the
dense traffic movement at grade during construction, where traffic snarls, congestion bottlenecks
and crowded market places is order of the day. Once the project is thrown open, expressway will
provide comfortable, hindrance free smooth sail-through at Panipat city.
1.1 Salient feature of the project
Major portion of the scope of work of Concessionaire are
– Access controlled 6-lane highway in the reach km 86.000 to km 96.000
– Separate 2 lane peripheral road with paved shoulder on either side of access controlled 6-lane
highway for the local traffic.
– Three underpasses to accommodate 4-lane divided carriageway.
– Construction of 2 new minor bridges and road furniture including toll plaza.
701
Figure 1. Deck cross section.
2 ELEVATED PORTION
2.1 Choice of basic spans
Overall cost of superstructure, substructure and foundation including construction methodology per
meter run governs the span configuration. Since deep pile foundations are required, after studying
several alternatives a typical module of five span continuous unit of 29.5 m + 3 × 32 + 29.5 m
appeared to be the best choice. This configuration also meets obligatory span requirements at
important road crossings and also provides maximum repetitions.
2.2 Deck cross section
The elevated two lane carriage way for each direction shall be provided on separate substructure
and foundations as per concession agreement. Deck cross section is shown in below Figure 1.
2.3 Choice of basic structural forms for superstructure
In BOT projects, early completion of project drives all the engineering decisions. Therefore, precast
superstructure is the most preferred option. Two options were studied namely Precast I girder cum
cast in-place deck slab and Segmental Precast Box Girder. From Transportation and Erection point
of view Pre-cast I girder was preferred over Precast Segmental Box Girder. For speedy production
of girder, Pre-tensioned I girder was preferred over Post-Tension girders, moreover it is economical
as 1200 girders were to be cast in short time.
2.4 Feature of the typical span configuration
The deck cross section is divided into two independent carriageways. Each carriageway consists of
six girder of 2.0 m overall depth. The girders get connected at the top by deck slab and at the ends
by diaphragms. The deck slab and diaphragms are cast-in-place simultaneously with the permanent
bearing is position.
The behavior of the superstructure is simply supported on temporary bearing up to stage of
casting of deck slab and end diaphragms. For all subsequent loads such as superimposed dead
loads and live loads, the behavior is changes to continuous deck of five spans. In simply supported
condition only precast girders are operative and full composite section is effective for subsequent
loads.
In conventional method of construction, in-situ deck slab is cast over either on sacrificial shutters
or removable shutters which will either add additional dead weight on girders or add considerably to
the time taken to cast the deck slab, hence the idea of partial pre-casting of deck slab was adopted.
702
Figure 2. Isometric view of precast slab with truss.
Figure 3. Temporary bearing for deck panel.
For the first time in India for such a long flyover Precast-Deck slab panels have been used as load
bearing members in combination with cast-in-situ slab.
Partial precast against full precast of deck has two advantages namely lesser weight from handling
and erection. Thus longer panels can be used and minimize the number of in-situ stitch especially
over piers.
The in-situ concrete topping fills the gap over beams and shear connectors on the precast girder.
The deck is designed as full composite section between pre-cast panel, in-situ topping and the
supporting beams (longitudinal girders).The in-situ concrete topping provides flexibility to adjust
roadway profile and for differences in beam elevations.
2.5 Design of deck slab
The non-composite panel which is a steel truss with concrete slab of 75mm thick at bottom is
designed for stresses occurring only in the precast units resulting from lifting, transportation, wet
concrete and live load due to construction working personnel. The space truss arrangement with
re-bars as shown below in Figure 2.
Spacing of the trusses is governed by construction loads and permissible tensile stresses in the
concrete. When top in-situ concrete is poured, the truss elements of the precast panel act as shear
connectors to ensure monolithic slab action. To ensure performance one composite panel was tested
for service loads. Truss web members acted as shear transfer reinforcement.
Precast panels are supported on temporary bearing pads to achieve the cross slope. Refer below
Figure 3.
The in-situ portion of deck accommodates reinforcement for negative moment over supports for
both transverse direction as well as longitudinal direction.
703
Figure 4. Erection of Precast Panel is in progress.
Table 1. Construction schedule.
Age (days) Activity
0 day Casting of Girders in Yard
3–5 days Transfer of Pre-stress to Girder
40–45 days Launching of Beams and Casting of deck
60–70 days Shifting of Supports (temporary Supports to Permanent Bearings)
>90 days Laying of SIDL and allow live load
Figure 5. Casting of girders in yard.
2.6 Design of girders
The pre-tensioned girders are designed for stage by stage constructions and continuous five span
unit. The superstructure is analyzed as grillage model for loading coming after composite action.
The portion of the superstructure between the diaphragms is designed as fully pre-stressed a member
with zero tensile stresses during service conditions. The part portion of deck over pier is designed
as reinforced concrete member. The longitudinal reinforcement in the deck slab is designed for
superimposed dead load, live loads and time depended effects such as differential shrinkage and
creep. The superstructure is also checked for differential settlement of 6mm and temperature
gradient as per IRC:6-2000.
The pre-tension girders are monolithic with Reinforced concrete cast-in-situ diaphragms, at this
junction prestress is absent due to transmission length of strands and continuity is achieved through
704
Figure 6. Erection of girders with gantry.
Figure 7. Tying of reinforcement over erected precast panels and girders.
reinforcement. At interface of girder and cast-in-situ diaphragm positive moments develop due to
creep as well as live load effects on remote spans. For positive moments adequate reinforcement is
provided to avoid opening of the joints during service.
3 CONSTRUCTION PROGRAM
For composite construction of the type in which the girders and deck slab/diaphragms are cast at
different time, the construction program has a profound influence in the design of superstructure.
3.1 Casting of girder
All girders are cast at yard by using long line bed. At any given time five girders are produced on a
single bed. To maximize the production and early transfer of prestress stream curing was adopted.
At the time of transfer of prestress minimum 40 Mpa strength was achieved.
Totally 1200 numbers of I girders precast in a nearby casting yard were transported to site through
specifically modified trailers and erected using gantries and heavy lifting cranes.
705
4 CONCLUSIONS
By modifying the construction scheme from conventional method of construction of deck slab
to partial pre-casting there is substantial saving of time and cost of construction. This innovative
method helped L&T to execute the project most efficiently ahead of the construction schedule.
From the date of appointment M/s Larsen & Toubro completed the elevated corridor of 3.6 km
within a time frame of 18 months which includes design, design approval from third party and
construction activities.
706
