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 fairfaced concrete

Vinay GuptaTandon Consultants Pvt Ltd, New Delhi, India

ABSTRACT: To celebrate 500 years of history of Sikhs and 300 years of establishment of the Khalsa, themega project ‘Khalsa Heritage Complex’ was launched by the Punjab Government. The project comprises a150m long pedestrian bridge to connect Complex ‘A’ and Complex ‘C’. While the Complex ‘A’ houses libraryblocks and a theatre, the Complex ‘C’ mainly houses high-tech exhibits of various types. The special highlightsof the project include (i) 26 m span prestressed concrete ramps in Heritage Museum building (ii) 20 m span RCCroof beams acting as partial catenary in Permanent Exhibit building (iii) 35 m span arch bridges incorporatingprestressed tie beams (iv) Precast canopy over the pedestrian bridge, (v) Specialized Mechanical Connectionbetween in-fill brick walls and the adjoining beam-column frame structure for sustainability during high seismicforces (vi) Inception of large volume of architectural fair faced concrete (vii) Preparation of mock ups of allspecialized elements, prior to their actual construction.

1 INTRODUCTION

World famous Museum, Specialist Architect MosheSafdie & Associates, Bostan, USA were engaged toprepare architectural concept of the project. In turn,Indian local architects Ashok Dhawan, New Delhiwere appointed and Tandon Consultants Pvt. Ltd, NewDelhi were retained as sole Structural Consultants forthe project. The project basically comprises high techexhibits to depict the history of Sikhs and Khalsa, in theform of Multi-Media Exhibits, Libraries and Theatres.

2 CONCEPT FORMS

The 60 acre site, situated in front of the main Anand-pur Sahib Gurudwara was a barren land comprisinga combination of sand hillocks and plains. The archi-tect’s concept inherited a monument emanating fromthe hillocks. For this purpose, photographs of the pre-construction site were taken from all angles, so thatthe hillocks, that would have to be flattened during theconstruction could be rebuilt to, as far as possible, thesame shapes and forms as they existed before construc-tion. Roofs of the main exhibit buildings have beenread as princess’ crown. Stainless steel roof claddingstrengthens the concepts, dictated by the architecturaldemands. An artificial water body, engaging the openareas of the complex adds to nature of Punjab, the landof five rivers. Two sub-complexes are connected by a

Figure 1. A model view of Khalsa Heritage Complex.

pedestrian bridge, having the water body, beneath, seefigure 2. Extensive use of architectonical fair facedconcrete has been made in the project.

3 PROJECT DESCRIPTION

The complex has been divided into

(i) Complex ‘A’, housing a multistoried library com-plex and a 20 m high, 400 seating capacityAuditorium (Theatre).

(ii) Complex ‘B’, incorporating Pedestrian Bridge,having 4 arch spans of 35 m each and a two levelcafeteria below the bridge and

715

Figure 2. Pedestrian bridge.

(iii) Complex ‘C’, comprising various multi-storiedbuildings to house exhibits.

3.1 Complex ‘A’

Apart from multi-storied library structure and 400seat capacity theatre, the complex has 35 m span archbridge (entry walk way) along with handicapped rampstructure. Within the library complex, there is 27 mspan arch bridge that support two upper floors withclosely spaced columns and beams and allows waterto flow underneath the arch, as demanded by architec-tural needs. The auditorium has an air-conditioningsystem where return air is picked up by the pipes,located below the seats. The roof the auditorium hasseveral interesting features like 25 m span roof beams,wherein the beam just above the stage has been pro-vided with 3 m deep RCC suspender to suspend theroof at a lower level.

3.2 Complex ‘B’

The architectural conception demanded the 4 archspans (35 m each) to be separated from each other bya distance of 6 m. Hence, the longitudinal thrust ofone arch could not be balanced by the adjoining archspans. Therefore, each arch span was made indepen-dent, using prestressed tie beam, (4 nos. for each archrib of 7 m width) provided below the ground level, seefigure 3 for details.

The arch rib was constructed in single phase, usingdouble shuttering (top shutter) for part length ofsteeper portions. Since, tie rods (for supporting topshutter) were not permitted for architectural reasons,a specially designed arrangement of 7 m span trussesat 1.2 spacing to support the 1.2 m long pieces of topshutter were used and mobilized in a sequential man-ner, as the concreting and compaction proceeded, seefigure 4.

Figure 3. General arrangement of Pedestrian Arch Bridge.

Figure 4. Arch Rib under construction using double shut-tering.

Figure 5. Precast canopy under construction.

The pedestrian bridge has been provided with a pre-cast canopy, which was precasted and erected from topof the bridge itself. See Top Shutters figures 5 and 6for the arrangement of precasting and erection.

3.3 Complex ‘C’

The Complex ’C’, being large in size, has been sub-divided into two parts, called North Wing and SouthWing, see figures 7 and 8. The North Wing comprisesa boat shaped building called Heritage Museum, a

716

Figure 6. Gantry for erection of precast canopy.

Figure 7. Complex ‘C’ – South Wing.

Figure 8. Complex ‘C’ – North Wing.

flower shaped building called Media Exhibit Build-ing and a triangular Entrance Lobby. The SouthWing comprises Grand Stair Block, Permanent Exhibitand Ramp Block that houses circular ramps for thehandicapped.

3.3.1 Heritage museum buildingUnique feature of this 25 m spans, 20 m high buildingis that it is surrounded by water body, its floor alsohas water ponded there and its roof also has 200 mmdeep water. The boat shaped building has 3 levels ofU-shaped ramps in the middle (see figure 9) for the

Figure 9. Complex ‘C’ – Prestressed concrete ramps ofHeritage Museum.

Figure 10. Circular cutout to receive fiber optics feature.

visitors movement, who would watch the exhibits dis-played on the side walls. The ramps comprise 26 mspan Prestressed Concrete Slabs, post-tensioned using4S-13 cables provided using flat metallic sheathing.

3.3.2 Media exhibit buildingThis building has circular coffer structure at interme-diate level. The roof is made out of radial concretebeams and slabs. Outer periphery is made out of RCCwalls stiffened with buttresses. Invariably, stainlesssteel roof cladding along with sandwiched P.U insu-lation has been provided over the RCC roof slab. Thestructure also incorporates a circular cut out at inter-mediate level to house special feature incorporatingfiber optics, see figure 10.

3.3.3 Permanent exhibit buildingThis 5 storied structure has been provided with 600deep coffer slab in the lower floors for spans of 20 m,in order to have smaller structural depth and allowspace for services. The roof has interesting features of

717

Figure 11. Radial RCC roof beams.

Figure 12. Complex ‘C’ – Entrance lobby.

20 m span concrete beams, radically arranged, whichpartly act as catenary structure. Thereby 20 m spancould be managed in a small structural depth of700 mm, see figure 11.The roof profile follows the sur-face of a sphere, thereby making the maximum heightof the roof little over 20 m from the previous level andtotal maximum height of the building approximately45 m. It may be noticed that triangle shaped roof hasbecome near vertical (over 600 to horizontal) at theends, wherein top shutter became mandatory to be ableto pour and compact the concrete properly.

3.3.4 Entrance lobbyThe triangular entrance lobby of 25 m span has beenprovided with triangular coffers wherein the reinforce-ment has been placed at three different levels, so thatthey are not required to be joggled at the junctions toavoid clashing, see figure 12.

4 SEISMIC ANALYSIS AND DESIGN

Owing to the highly irregular shape of the build-ings, expansion joints have been provided at almost

Figure 13. Structural model for analysis of permanentexhibit building.

Figure 14. Connection of brick wall with RCC members.

all such locations to maintain, as far as possible, regu-lar structure between the successive expansion joints.Space frame has been analyses for seismic forces usingResponse Spectrum Method with the help of the soft-ware STAAD, see figure 13. RCC walls and floorslabs have also been suitably idealized in the gril-lage model. The project site lies in the highest seismiczone of India i.e. Zone –V. Up to date ductility provi-sions as per IS: 13920 have been followed. The brickwalls have been fastened to the adjoining RCC beamsand columns using a specialized anchoring system,detailed incorporating expansion fasteners and MSplates, see figure 14.

5 ARCHITECTURE FAIR FACED CONCRETE

Camouflaging of fair faced concrete with fancy archi-tectural finishes creates and excellent blend of struc-ture and traditional architecture. An extensive studywas carried out to find ways and means to obtain aconcrete colour and surface finish, that would meet

718

Figure 15. Mockup of precast canopy.

the architect’s expectations.A round the world trip wasmade by the author, along with other concerned, inorder to study various methods of concreting includ-ing associated quality control measures exercised atvarious project sites. In conclusion, simple things liketype of cement used, shuttering material used, tampingof shuttering, form release agent used, time of decen-tering, edge protection, temperature etc, all affect theaesthetics and quality of concrete.

For the project in question, trials were made withdifferent compositions of grey and white cement toobtain a particular colour. When the concept failedto meet the architect’s demand, it was found, throughtrials, that Blast Furnance Slag cement (PSC) gave aparticular type of light grey colour of concrete, whichwas acceptably used. PSC als has a distinct advantageof possessing lower heat of hydration, thereby reducingearly thermal cracks. After trying steel, marine ply-wood etc, it was found that Resin Coated Ply importedfrom Finland produced the most satisfactory surfacefinish. Even the shuttering joints were planned by thearchitects, as per the architectural acceptability. Min-eral oil based form release agents were found to leave abrownish tinch on concrete surface. So it was decidednot to use any form release agent and do a very gradualdeshuttering, in order to prevent spalling of concrete.Time of deshuttering was laso found to have effecton concrete colour. Therefore, it was ensured that theentire shuttering of an area was deshuttered at the sametime to maintain harmony of colour. Reinforcementhas high specific heat, due to which it gets heatedmuch more than the ambient temperatures. This hotreinforcement causes stains on the concrete surface.

Figure 16. Mockup of curved roof and stainless steelcladding.

I order to avoid this problem, the reinforcement waskept under shade during high temperature.

6 MOCK-UPS

Apart from following strict quality control checks, thatincorporate material tests and check of site activities,large number of full scale mock ups of specializeditems have been prepared and studied in detail, beforeactual construction of the respective structure. Theseitems include fair faced concrete arch rib, precast con-crete canopy of pedestrian bridge, stainless steel roofcladding, dry fixing of curved stone cladding, stainlesssteel railing etc. refer figures 15 and 16 for some ofsuch mock ups. Purpose of these mock ups is to studythe quality of concrete including its colour, efficacyof shuttering system, achievement of proper curvedalignment of cladding etc.After a careful study of thesemock ups, suggestive improvements, to be incorpo-rated in the final structure, were recorded for suitableaction in due course.

7 CONCLUSIONS

A careful planning and dovetailing of architectural andstructural concepts led to an elegant building. Struc-ture had been able to find its rightful place by providinga large quantum of architectural fair faced concrete andnot merely hiding it inside false ceiling everywhere.

719