Structural Analysis of Historic Construction – D’Ayala & Fodde (eds)© 2008 Taylor & Francis Group, London, ISBN 978-0-415-46872-5

Significance of a Mughal Mall and its role in achieving safety

Saptarshi SanyalSchool of Planning and Architecture, New Delhi, India

ABSTRACT: The fascinating and unique covered market, Chatta Chowk Bazaar, was designed for the fortress-palace, Redfort, the magnum opus of 17th century Mughal Emperor Shahjahan’s new capital in Shahjahanabad,Delhi. This building was the subject of documentation and comprehensive qualitative studies, undertaken byarchitectural conservation students of School of Planning and Architecture in 2006–07. The direction andapproach given by the conservation studio’s faculty, one of knowledge systems, was significant in guidingthe studies selected and the way the structure was analysed, resulting in an appreciation of the many dimensionsof the historic building. These revealed architect Shahjahan’s immense knowledge of architecture, qualifiedthrough primary studies of Mughal architecture in Delhi including the palace-complex and secondary studiesof his other projects. This paper attempts to illustrate, through this case, how superior structural know-howand stability, are integral to a significant historic building, which is a knowledge system, and how an essentialconsequence of such significance, is safety.

1 INTRODUCTION

In Aug-Dec 2006, the Conservation Studio team ofSchool of Planning and Architecture in an exer-cise “The Past, Present and Future of the Mall thatShahjahan built”, documented and analysed the ChattaChowk Bazaar, an imperial marketplace at Redfort inShahjahanabad, the erstwhile Mughal capital at Delhi.This building was built by the fifth Mughal Emperor,Shahjahan, remembered globally because of his con-ception and architectural accomplishment of the worldfamous Taj Mahal at Agra.

The objective of this project was to formulate aconservation proposal for the building addressing theaspects of reuse and historic fabric. Guided by Prof.Nalini Thakur and Ar. Sanjay Bharadwaj, the Mughalarchitectural context in Delhi was studied, includingthe role of Shahjahan as an architect-planner in hisworks, which revealed that while his contribution toarchitecture was quite significant, this Bazaar is typo-logically unique in this part of the world. As a part ofproperty inscribed in the recent inclusion of Redfortin World Heritage, the Bazaar is also the significant“living” heritage in the Redfort.

In this exercise, the architectural Knowledge Sys-tems approach applied to this case helped the appraisalof its embedded values as being very relevant in con-servation for future use. While present usage is inconflict with these values, causing degradation of itstechnological and structural memory, the building inquestion still survives “safely”.

This paper firstly addresses the structural sig-nificance of the building, as revealed through theprimary and secondary studies of the building andits context. Secondly, it suggests how the aspectof structural significance compliments and informsthe knowledge required to achieve safety in his-toric constructions, as revealed in this case, in thecontext of the observed situation and its currentissues.

2 THE KNOWLEDGE SYSTEMS APPROACHAPPLIED

2.1 Contextual studies: Mughal Delhi, Shahjahan,Shahjahanabad and Redfort

The generation of knowledge started by looking at thehistoric city itself, here Mughal Delhi and its archi-tecture, as it existed on the ground. The secondarystudies on the cultural upbringing and achievementsof the architect of the Bazaar, Shahjahan, corrob-orated inferences about his contribution to Mughalarchitecture, and the significance of his buildings,most of which could be appreciated as outstand-ing knowledge systems. Moreover, it was found thatShahjahan’s knowledge was not restricted to individualbuildings but encompassed palace and city planning,as demonstrated by the Redfort and his capital ofShahjahanabad, with the Chatta Chowk Bazaar as anintegral part of both (Figure 1).

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Figure 1. The Chatta Chowk Bazaar in Shahjahanabad, itsarticulation of the processional imperial axis from the city tothe palace.

Figure 2. Original plan and section of the Bazaar.

2.2 Primary studies of the building

The documentation of the Bazaar was through archi-tectural drawings of the existing state. With theadvantage of having a modular system, the ‘original’designed structure was deciphered by removing theaccretions and alterations from the measured drawings(Figure 2).

These preliminary exercises helped in identifyingthe structural form of the building holistically. Theterm “Mall” thus addressed the fundamental charac-teristics of the building, functionally, architecturallyand formally. This building can be described as a two-storied linear arcaded structure with an octagonal courthalfway through its length, with eight arcade bays oneither side, contiguous with the western entry of theRedfort, the Lahore Gate (Figure 3).

Secondary studies indicated that, though inher-ited typologically from central-Asian counterpartsof the “souk” or Bazaar, integral to Persian andArab cities, the Chatta Chowk Bazaar responded tothe specificities of climate, cultural context as wellas to Shahjahan’s own design of the Redfort andShahjahanabad, all of which is a complex designsynthesis.

Figure 3. Chatta Chowk Bazaar, 1911–12, octagon andarcade; photo: Archaeological Survey of India (ASI) AnnualReport.

2.3 Structural analyses and technical studies

From the structural form of the building thatemerged, critical areas were zoned and their behaviouranalysed. Unfortunately, owing to logistical lim-itations, the foundation could not be examinedand the formal analyses are restricted to thesuperstructure alone.

Technical studies were carried out from the readingof exposed areas of the building fabric, and sampleswere qualitatively studied to understand the construc-tion system in terms of the constituents using sec-ondary references from similar constructions. More-over, a similar building by Shahjahan, a hunting-lodgeat Jaunti village near Delhi, was studied insitu to under-stand construction. This building’s collapse due tounknown reasons exposed a lot of the brick masonrythat is similar to the Chatta Chowk Bazaar and thishelped in building the knowledge base.

2.4 Chatta Chowk Bazaar as a knowledge system

Through studies of the context and the buildingitself, information related to the Chatta Chowk Bazaarrevealed many facets of this structure. Primary andsecondary studies of the architecture and its history,as well as its technology presented disaggregatedinformation. Amalgamating this information with thespecific purpose of conservation, helped to appreciatethis building as a knowledge system, from contex-tual to component levels. This knowledge system hassubsystems of architectural design, structure, con-struction etc. defining its values. For the purpose ofthis paper, although the formal structural knowledgeis highlighted qualitatively, the values revealed by theanalyses shall be critical in guiding still more detailed,quantitative structural analyses.

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3 STRUCTURAL VALUES IN THE BUILDING

3.1 Components of the structure

Before proceeding to the formal aspects of the struc-ture and their analyses, it is necessary to briefly look atthe types of constituent structural components or struc-tural elements in this building, along with their basicmaterials. These components and their behaviour inthe whole structural system allow us to divide theminto three logical groups.

The first of these, vertical elements, have eitherresultant or primary load lines or both which are ver-tical. These elements are subject to buckling understress. They are morphologically in the vertical planeand include walls and piers. In Chatta Chowk Bazaar,these are built in brick with mortar.

Secondly, horizontal elements carry uniformly dis-tributed loads or point loads and are morphologicallyhorizontal or in the horizontal plane. They are sub-ject to bending when loaded. As spanning in ChattaChowk Bazaar uses predominantly arcuate systems,the presence of these is rare. These elements are lin-tels in most small openings and mezzanine floors inthe western gate. They are built in red sandstone.

The most important and commonly used, compos-ite elements dissipate horizontal, vertical and lateralloads in one or more planes. These elements are mor-phologically more complex and the loads in them areindeterminate due to three-dimensional geometries.However, it was possible to qualitatively map the loadtransfer lines in them. These are also built in brick andmortar and include large arch-ribs, domes, segmen-tal domes and pendentives that support domes or flatceilings.

3.2 Formal structural systems and zones

In discussing the findings of qualitative structuralanalyses, the major aspects covered include the spatialzones, structural systems and sub-systems and theirinterfaces and how they contribute to safety.

Spatially speaking, the entire building can bedivided into three distinct zones, each of which incor-porates a particular structural system. These systemsincorporate combinations of the aforementioned ele-ments and structural subsystems, both intrinsicallyand in their physical interfacing. These critical zones,namely the arcade, the octagonal court and gatewaysare explained below with their interfacing.

3.3 Arcade modules

These fundamental units, 16 in number, are repeated oneither side of the octagonal court to give this buildingits most identifiable architectural form: they articulatethe mall character (Figure 4).

Figure 4. The roof of the Mall; the walls have filled up thebalconies over the parapets today as seen in this image.

Figure 5. Diagram of structural system of the arcade.

The central space of a typical module is a cov-ered street, roofed by a segmental dome at a height of10.5 m. Along the length of the street of width 8.3 m,each arcade segment is bound by a combination of twoarch-ribs of depth 1275 mm. and four piers of section900 × 1200 mm. (Figure 5).

The arch-ribs are subject to smaller lateral thrustsfrom the roof (Figure 5, A) and larger arch-actionsresulting in cumulative horizontal and vertical com-ponents at the springing point that exerts an outwardhorizontal thrust at this point. This thrust is containedby the stepped section of the transverse wall (Figure 5,B) of the building on either side and the piers accom-modate the vertical loads. In effect, shoring these pierstoday couldn’t render the extent of safety to the coveredstreet that the original design of these walls deliver.

An important subsystem here is formed by thearches that are along the length of the street on eachfloor.These are designed to span 3 m and rise to heightsof 1.5 m on the lower storey and 1.35 m on the upper.

The first floor arch accommodates the load of theroof in excess of that carried by the arch-rib of the streetwhile the lower arch, along with defining the cell’s

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Figure 6. Arch subsystem along arcade with parapets onfirst floor: 1912 photo from ASI Annual Reports.

opening, acts with the pier in supporting the inter-mediate floor. The lower floor arch, characteristic toShahjahan’s design, is clearly designed for structuralsafety, as suggested by the absence of a wall on theupper floor; the first floor arch overlooks the streetover a low sandstone parapet (Figure 6).

In the arcade module, it is also necessary to referto the structural subsystems that spatially form twocells on the lower storey and one on the upper. Each ofthese measures 9 m. square. Roofs of these completelyenclosed cells are supported by the technically supe-rior elements of pendentives (Figure 7), as opposedto squinches or traebeate devices. On the first floor, asemi-covered projection at the entrance inverts accessof the cells. They are approached from the outer sidesof the building. Here also, a half-dome is formed bypendentives that partially enclose this space. This kindof a design detail, for a small span of 3 m, demon-strates technical knowledge, which today makes theseareas safe.

When symmetrically arranged, these arcade sys-tems in the building cancel any possibility of unbal-anced stresses or lateral thrusts.The following sectionsexamine the design of the critical asymmetrical junc-tions of these with morphologically distinct spatialzones to dissipate extra stresses.

3.4 Octagonal court and arcade module interface

The “Chowk” or court at the centre of the long Bazaar,is both visually and spatially conspicuous by being asource of light for the otherwise covered street. Besidesthis significant environmental function, its role as astructural system contributing to safety by design isfar from negligible. To appreciate this point, refer toFigure 8 below, where the terminating arcade systemmay be viewed in the absence of the built elements

Figure 7. Pendentives used in the cells, photo of corner.

Figure 8. Diagram of octagonal court interface with arcade:vertical loading components shaded in plan and axonometric.

contiguous with this open space. Taking this perspec-tive, it becomes clear that the springing point of thelast arch-rib is thrust outward by the lateral stressescaused due to the arcade’s roof.

The plan (Figure 8, B) shows us how this very lineforms the shorter edge of the octagon that, in the ver-tical plane has a solid wall mass, adding a verticalcomponent. This is in supplement to the wall abovehalf of the arch-rib span, as part of a long edge ofthe octagon. The vertical component thus added, istransferred to the arches in the shorter faces and subse-quently to piers that form the vertices (Figure 8, A–B).The lateral (non-orthogonal) component is then dissi-pated along the staircase block down to the archedopening on the outer edge of the building, beyond theoctagon at the lower level.

The massing of the building around the octago-nal court suggests that risk of failure at all pointsis eliminated by increasing the vertical loads at allnodal points that are prone to asymmetric loading.Thisis a demonstration of the building design achievingsafety through elements in vertical planes. However, itshould be appreciated that the outer built areas of this

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Figure 9. “Safe” structural design of Lahore Gate andarcade interface highlighting the critical components in thediagram.

space, owing to planar design of the elements, are thestructurally the most fallible.

3.5 Gate and arcade module interface

The longer ends of Chatta Chowk Bazaar are definedby two distinct gateways. These are the LahoreGate and the “Darwaza-i-Chatta-Chowk”, the Bazaar’sentrance and exit points respectively as one walks intothe palace-citadel.Though different in scale and mildlydifferent in design, the structural behaviour of thesetwo spatial zones is quite similar. The more elaborateand larger of the two, the Lahore Gate and its junctionwith the arcade system, shall be discussed here.

Being a complex structural system in itself, thisneeds to be described briefly prior to the examina-tion of the intersection with the arcade. Spatially, theinternal clear area of this gate is an irregular octagon(Figure 9, C) that is spanned by a dome (Figure 9,B) touching its longer edges over a distance of 9.3 m.The vertices of the octagon are defined by eight piersthat rise to form, two vaults laterally and two arch-ribslongitudinally, along the longer edges of 4.8 m each.Four pendentives are formed along the shorter edgesof 2.7 m each. These support the large dome overheadwhile along the transverse direction, smaller stonecolumns support a mezzanine spanning the length ofthe vault. The significant transverse depth of the gate,largely of solid masonry, accommodates any lateralthrust.

The presence of the pendentives in this system,illustrates a magnified, finer resolved version of thesub-system described earlier for the cells. Here, allwalls in the cells are replaced by piers, and theircorners, by the shorter edges of the octagon. Thisis a visible sign of structural respect warranted bythe threefold span. Again, structural reliability of

Figure 10. Sunken roof above “Darwazah-i-Chatta-Chowk”.

the pendentives has been employed; this also min-imizes threat to structural safety through equitabledistribution of stresses.

Examination of the intersection with the arcade sys-tem reveals the use of a combination of a segmentaldome, which is a three-dimensional composite ele-ment and dual piers at each end (Figure 9,A) of spansof 4.8 m (gate octagon) and 8.3 m (arcade).The dimen-sions of the pier sections designed in the octagon areroughly 1.1 m square, qualifying the extra load takenby them from the arcade arch. The horizontal thrust ofthe arch-rib of the arcade is directed vertically over thecurved surface of the segmental dome that links the twodifferently sized arches..This intersection thus demon-strates an elimination of unbalanced thrusts, arising intwo very different structural systems.

Apart from the Lahore Gate, it is also noteworthythat the opposite gateway to the east the “Darwaza-i-Chatta-Chowk”, responds to safety in massing. Thisis done by sinking the floor above the dome to makethe roof light (Figure 10), a balance between smallerspan, lower rise of its dome and dead-load of roof.

3.6 Salient aspects in construction

Formal aspects in structural values in Chatta ChowkBazaar are reinforced by certain very significant built-in values in construction. These are the links to thebuilding’s stability, durability and timelessness.

Along with secondary technical sources, the pri-mary information on construction was extracted fromexposed parts of the building’s fabric itself. As men-tioned earlier, the hunting lodge at Jaunti, a technolog-ical contemporary to Chatta Chowk Bazaar, was usedas a resource to understand construction through itsexposed details.

Though the discussion on this aspect is limitedby sources of information, logical conjectures weredrawn to answer questions of longevity and dura-bility of the building’s fabric. As mentioned earlier,the Bazaar is, with rare exceptions, a compressivebrick masonry structure. Two observations described

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Figure 11. Wall construction, Jaunti; and possibly ChattaChowk.

Figure 12. Construction of floor/roof as observed in Jaunti.

below, one about purely compressive elements andthe other about composite elements, indicate the his-toric durability of this building’s fabric vis-à-vis brickconstruction.

In walls and piers of the Chatta Bazaar, brick cours-ing in the core is very different from what it appearsto be on the surface. An interlaced coursing system isfollowed that avoids both vertical as well as horizontaljoints (Figure 11).

Such brick coursing to form walls or piers of thedifferent sizes mentioned earlier, makes these struc-tural elements behave as conceivable monoliths whenloaded vertically, thus making them extremely stable.

With reference to floors, domes and pendentives,a consistently alternating radial pattern is followed inbrickwork. In floors, the smallest faces extend outward(Figure 12), causing contact of the largest faces to formflat arches; in domes, they are radially laid, each courseat a time along the largest face – a method that elim-inates formwork. In pendentives, they are interlaced,similar to that in the walls.

In such coursing also, a high degree of stiffness isachieved in each structural element, intrinsically andpresumably, in their interfaces, or in subsystems.Thesecoursing patterns ensure substantial structural safetydue to a distributed load transfer that takes place fromone structural element to another.

Figure 13. Built interventions and consequences: profile ofcollapsed arch at the octagon; built cubicles on the first floor.

4 VALUES CURRENTLY THREATENED

In spite of the values as explained above, the Bazaaris currently endangered by interventions arising fromlack of information about these. Observations of thealterations that have occurred in this building indicatea lack of knowledge of significance.

While the implications on the structure per se arenot visible, the building lacks severe structural cracksor deflections as yet; they may be anticipated if thesepractices continue. It is essential to see what theseissues are at this juncture, given the significance ofthe building.

Though the logic for its use has changed over itsthree hundred and fifty odd years of history, it hasfunctionally more or less served as a covered marketstreet in its lower storey. A marked transformation inuse of the building was the housing of soldiers on theupper floors, both in pre-independence (1857–1911)and post-independence times (1947–2003).

The introduction of new masonry viz. walling ofthe balconies facing the street to form rooms, build-ing of bathrooms and toilets on the first-floor terraces(Figure 13, B) were some consequences of this.

Toilets were also introduced in the southern part ofthe building at the octagon on the first floor, mentionedearlier to be a structurally vulnerable area, conse-quently leading to the collapse of the arches on theground floor (Figure 13, A).

A major periodic intervention is the annual renewalof the tar layer covering the arcade’s central street aswell as on the exterior of the building, catering to thenational Independence Day celebration that happensatop the Lahore Gate. Due to this, the shallow plat-form, traditionally used as a seat for the shopkeepers,is almost flushed with the ground today, suggesting noless than 450 mm. of rise in level. In addition to this,the roof of the entire structure was covered with tar-feltin 1911–12. The use of the upper floors as soldiers’quarters caused puncturing of windows through the

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Figure 14. Synthetic and natural threats.

external historic walls (Figure 14, A). Since 1992,foliated arches that form the shop openings were alsogradually walled for signboards.

Electrical interventions have been the most markedwhere ceiling fans and other such fixtures have beenhung from tubular steel rods that puncture the penden-tives in the cells on the first floor. In some cases, thebuttressing wall has also been punctured to link two ormore cells from the inside.

Apart from the synthetic interventions mentionedabove, the southeast corner of the building is alsothreatened by roots of a large tree that has grown intothe wall (Figure 14, B).

5 CONCLUSIONS

The Chatta Chowk Bazaar today is an expression of aunique technological memory. Historically conceivedand built with cognizance of processes, techniques andsystems evolved and perfected over time, it is also sig-nificant in its geographical (here, Indian) context bybeing a lone example of a building type. This typolog-ical significance was achieved through the architect’sknowledge of the structural and construction systems,amongst other things, that could make this architecturenot just possible, but also durable and timeless.

For substantive knowledge generation as explainedabove, the Chatta Chowk Bazaar and its context onthe ground were used as resources to firstly inform itstypological significance and then extend it to includestructural values. It substantiates how the building’svalues are linked to the contemporary need for itssafety and the safety of its users. The issues also indi-cate that the practices that undermine the Bazaar’stypological significance as a historic mall also under-mine its safety because of this significance embodyingnumerous structural values.

The above definition of significance notwithstand-ing, the scope for further enquiry is immense and willcontribute further to the body of knowledge about

Chatta Chowk Bazaar.This building is an irreplaceableand timeless resource in this regard and will have tobe treated with its due respect. The knowledge sys-tems approach has helped acknowledge the value ofthis resource comprehensively and direct an attitudefor best practices in the future.

In the debate between safety and significance, caseslike Chatta Chowk illustrate that they are actually sidesof the same coin. The most effective route to achievesafety in such outstanding knowledge systems, is thusthrough authentic structural conservation, informed bya systematic method to generate knowledge, given thesignificance of these structures.

ACKNOWLEDGEMENTS

The author immensely thanks Prof. Nalini Thakur,School of Planning and Architecture (SPA), for crit-ical guidance, encouragement and contribution in thework on which this paper is based, especially on usingthe Knowledge Systems approach that greatly helpedthe studies. Sessions with co-faculty of studio, Ar.Sanjay Bharadwaj, Morphogenesis, Delhi and on siteresource person, Ar. Rachna Vishwanathan were alsoinstrumental in guiding the documentation and analy-ses. The Archaeological Survey of India (Delhi Circle)and the Chatta Chowk BazaarTraders’WelfareAssoci-ation were very helpful and cooperative during the sitework. Further, the author thanks all his colleagues whoworked on this project, batch of 2006–08, Masters inArchitectural Conservation, SPA: Allahyar Allahyari,Bhavesh Patel, Moinak Bose, Muzakkir Bijli, SidharthRoy & Sonal Chitnis.

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Thakur, Nalini. 2006. Technological Knowledge SystemsApproach - from little insights to a paradigm shift in struc-tural knowledge and application. Structural Analysis ofHistoric Constructions Vol. 1: 25–30

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