Tailor Made Concrete Structures – Walraven & Stoelhorst (eds)
© 2008 Taylor & Francis Group, London, ISBN 978-0-415-47535-8
Challenging concrete structure with a blend of architectural fair
faced concrete
Vinay Gupta
Tandon Consultants Pvt Ltd, New Delhi, India
ABSTRACT: To celebrate 500 years of history of Sikhs and 300 years of establishment of the Khalsa, the
mega project ‘Khalsa Heritage Complex’ was launched by the Punjab Government. The project comprises a
150m long pedestrian bridge to connect Complex ‘A’ and Complex ‘C’. While the Complex ‘A’ houses library
blocks and a theatre, the Complex ‘C’ mainly houses high-tech exhibits of various types. The special highlights
of the project include (i) 26 m span prestressed concrete ramps in Heritage Museum building (ii) 20 m span RCC
roof beams acting as partial catenary in Permanent Exhibit building (iii) 35 m span arch bridges incorporating
prestressed tie beams (iv) Precast canopy over the pedestrian bridge, (v) Specialized Mechanical Connection
between in-fill brick walls and the adjoining beam-column frame structure for sustainability during high seismic
forces (vi) Inception of large volume of architectural fair faced concrete (vii) Preparation of mock ups of all
specialized elements, prior to their actual construction.
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INTRODUCTION
World famous Museum, Specialist Architect Moshe
Safdie & Associates, Bostan, USA were engaged to
prepare architectural concept of the project. In turn,
Indian local architects Ashok Dhawan, New Delhi
were appointed and Tandon Consultants Pvt. Ltd, New
Delhi were retained as sole Structural Consultants for
the project. The project basically comprises high tech
exhibits to depict the history of Sikhs and Khalsa, in the
form of Multi-Media Exhibits, Libraries and Theatres.
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CONCEPT FORMS
Figure 1. A model view of Khalsa Heritage Complex.
The 60 acre site, situated in front of the main Anandpur Sahib Gurudwara was a barren land comprising
a combination of sand hillocks and plains. The architect’s concept inherited a monument emanating from
the hillocks. For this purpose, photographs of the preconstruction site were taken from all angles, so that
the hillocks, that would have to be flattened during the
construction could be rebuilt to, as far as possible, the
same shapes and forms as they existed before construction. Roofs of the main exhibit buildings have been
read as princess’ crown. Stainless steel roof cladding
strengthens the concepts, dictated by the architectural
demands. An artificial water body, engaging the open
areas of the complex adds to nature of Punjab, the land
of five rivers. Two sub-complexes are connected by a
pedestrian bridge, having the water body, beneath, see
figure 2. Extensive use of architectonical fair faced
concrete has been made in the project.
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PROJECT DESCRIPTION
The complex has been divided into
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(i) Complex ‘A’, housing a multistoried library complex and a 20 m high, 400 seating capacity
Auditorium (Theatre).
(ii) Complex ‘B’, incorporating Pedestrian Bridge,
having 4 arch spans of 35 m each and a two level
cafeteria below the bridge and
Figure 3. General arrangement of Pedestrian Arch Bridge.
Figure 2. Pedestrian bridge.
(iii) Complex ‘C’, comprising various multi-storied
buildings to house exhibits.
3.1
Complex ‘A’
Apart from multi-storied library structure and 400
seat capacity theatre, the complex has 35 m span arch
bridge (entry walk way) along with handicapped ramp
structure. Within the library complex, there is 27 m
span arch bridge that support two upper floors with
closely spaced columns and beams and allows water
to flow underneath the arch, as demanded by architectural needs. The auditorium has an air-conditioning
system where return air is picked up by the pipes,
located below the seats. The roof the auditorium has
several interesting features like 25 m span roof beams,
wherein the beam just above the stage has been provided with 3 m deep RCC suspender to suspend the
roof at a lower level.
3.2
Figure 4. Arch Rib under construction using double shuttering.
Complex ‘B’
The architectural conception demanded the 4 arch
spans (35 m each) to be separated from each other by
a distance of 6 m. Hence, the longitudinal thrust of
one arch could not be balanced by the adjoining arch
spans. Therefore, each arch span was made independent, using prestressed tie beam, (4 nos. for each arch
rib of 7 m width) provided below the ground level, see
figure 3 for details.
The arch rib was constructed in single phase, using
double shuttering (top shutter) for part length of
steeper portions. Since, tie rods (for supporting top
shutter) were not permitted for architectural reasons,
a specially designed arrangement of 7 m span trusses
at 1.2 spacing to support the 1.2 m long pieces of top
shutter were used and mobilized in a sequential manner, as the concreting and compaction proceeded, see
figure 4.
Figure 5. Precast canopy under construction.
The pedestrian bridge has been provided with a precast canopy, which was precasted and erected from top
of the bridge itself. See Top Shutters figures 5 and 6
for the arrangement of precasting and erection.
3.3 Complex ‘C’
The Complex ’C’, being large in size, has been subdivided into two parts, called North Wing and South
Wing, see figures 7 and 8. The North Wing comprises
a boat shaped building called Heritage Museum, a
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Figure 6. Gantry for erection of precast canopy.
Figure 9. Complex ‘C’ – Prestressed concrete ramps of
Heritage Museum.
Figure 7. Complex ‘C’ – South Wing.
Figure 10. Circular cutout to receive fiber optics feature.
visitors movement, who would watch the exhibits displayed on the side walls. The ramps comprise 26 m
span Prestressed Concrete Slabs, post-tensioned using
4S-13 cables provided using flat metallic sheathing.
Figure 8. Complex ‘C’ – North Wing.
flower shaped building called Media Exhibit Building and a triangular Entrance Lobby. The South
Wing comprises Grand Stair Block, Permanent Exhibit
and Ramp Block that houses circular ramps for the
handicapped.
3.3.1 Heritage museum building
Unique feature of this 25 m spans, 20 m high building
is that it is surrounded by water body, its floor also
has water ponded there and its roof also has 200 mm
deep water. The boat shaped building has 3 levels of
U-shaped ramps in the middle (see figure 9) for the
3.3.2 Media exhibit building
This building has circular coffer structure at intermediate level. The roof is made out of radial concrete
beams and slabs. Outer periphery is made out of RCC
walls stiffened with buttresses. Invariably, stainless
steel roof cladding along with sandwiched P.U insulation has been provided over the RCC roof slab. The
structure also incorporates a circular cut out at intermediate level to house special feature incorporating
fiber optics, see figure 10.
3.3.3 Permanent exhibit building
This 5 storied structure has been provided with 600
deep coffer slab in the lower floors for spans of 20 m,
in order to have smaller structural depth and allow
space for services. The roof has interesting features of
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Figure 11. Radial RCC roof beams.
Figure 13. Structural model for analysis of permanent
exhibit building.
Figure 12. Complex ‘C’ – Entrance lobby.
Figure 14. Connection of brick wall with RCC members.
20 m span concrete beams, radically arranged, which
partly act as catenary structure. Thereby 20 m span
could be managed in a small structural depth of
700 mm, see figure 11.The roof profile follows the surface of a sphere, thereby making the maximum height
of the roof little over 20 m from the previous level and
total maximum height of the building approximately
45 m. It may be noticed that triangle shaped roof has
become near vertical (over 600 to horizontal) at the
ends, wherein top shutter became mandatory to be able
to pour and compact the concrete properly.
3.3.4 Entrance lobby
The triangular entrance lobby of 25 m span has been
provided with triangular coffers wherein the reinforcement has been placed at three different levels, so that
they are not required to be joggled at the junctions to
avoid clashing, see figure 12.
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SEISMIC ANALYSIS AND DESIGN
Owing to the highly irregular shape of the buildings, expansion joints have been provided at almost
all such locations to maintain, as far as possible, regular structure between the successive expansion joints.
Space frame has been analyses for seismic forces using
Response Spectrum Method with the help of the software STAAD, see figure 13. RCC walls and floor
slabs have also been suitably idealized in the grillage model. The project site lies in the highest seismic
zone of India i.e. Zone –V. Up to date ductility provisions as per IS: 13920 have been followed. The brick
walls have been fastened to the adjoining RCC beams
and columns using a specialized anchoring system,
detailed incorporating expansion fasteners and MS
plates, see figure 14.
5 ARCHITECTURE FAIR FACED CONCRETE
Camouflaging of fair faced concrete with fancy architectural finishes creates and excellent blend of structure and traditional architecture. An extensive study
was carried out to find ways and means to obtain a
concrete colour and surface finish, that would meet
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Figure 15. Mockup of precast canopy.
the architect’s expectations. A round the world trip was
made by the author, along with other concerned, in
order to study various methods of concreting including associated quality control measures exercised at
various project sites. In conclusion, simple things like
type of cement used, shuttering material used, tamping
of shuttering, form release agent used, time of decentering, edge protection, temperature etc, all affect the
aesthetics and quality of concrete.
For the project in question, trials were made with
different compositions of grey and white cement to
obtain a particular colour. When the concept failed
to meet the architect’s demand, it was found, through
trials, that Blast Furnance Slag cement (PSC) gave a
particular type of light grey colour of concrete, which
was acceptably used. PSC als has a distinct advantage
of possessing lower heat of hydration, thereby reducing
early thermal cracks. After trying steel, marine plywood etc, it was found that Resin Coated Ply imported
from Finland produced the most satisfactory surface
finish. Even the shuttering joints were planned by the
architects, as per the architectural acceptability. Mineral oil based form release agents were found to leave a
brownish tinch on concrete surface. So it was decided
not to use any form release agent and do a very gradual
deshuttering, in order to prevent spalling of concrete.
Time of deshuttering was laso found to have effect
on concrete colour. Therefore, it was ensured that the
entire shuttering of an area was deshuttered at the same
time to maintain harmony of colour. Reinforcement
has high specific heat, due to which it gets heated
much more than the ambient temperatures. This hot
reinforcement causes stains on the concrete surface.
Figure 16. Mockup of curved roof and stainless steel
cladding.
I order to avoid this problem, the reinforcement was
kept under shade during high temperature.
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MOCK-UPS
Apart from following strict quality control checks, that
incorporate material tests and check of site activities,
large number of full scale mock ups of specialized
items have been prepared and studied in detail, before
actual construction of the respective structure. These
items include fair faced concrete arch rib, precast concrete canopy of pedestrian bridge, stainless steel roof
cladding, dry fixing of curved stone cladding, stainless
steel railing etc. refer figures 15 and 16 for some of
such mock ups. Purpose of these mock ups is to study
the quality of concrete including its colour, efficacy
of shuttering system, achievement of proper curved
alignment of cladding etc.After a careful study of these
mock ups, suggestive improvements, to be incorporated in the final structure, were recorded for suitable
action in due course.
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CONCLUSIONS
A careful planning and dovetailing of architectural and
structural concepts led to an elegant building. Structure had been able to find its rightful place by providing
a large quantum of architectural fair faced concrete and
not merely hiding it inside false ceiling everywhere.
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