The Phenomenon of Prefabrication

PRE-CASTING IN CONTEMPORARY CONSTRUCTIONS

BACKGROUND
The concept of precast (also known as “prefabricated”) construction includes those buildings where the majority of structural components are standardized and produced in plants in a location away from the building, and then transported to the site for assembly. These components are manufactured by industrial methods based on mass production in order to build a large number of buildings in a short time at low cost. The main features of this construction process are as follows:

• The division and specialization of the human workforce
• The use of tools, machinery, and other equipment, usually automated, in the production of standard, interchangeable parts and products
This type of construction requires a restructuring of the entire conventional construction  process to enable interaction between the design phase and production planning in order to improve and speed up the construction. One of the key premises for achieving that objective is to design buildings with a regular configuration in plan and elevation.
 Many countries used various precast building systems during the second half of the 20th century to provide low-income housing for the growing urban population.
In general, precast building systems are more economical when compared to conventional multifamily residential construction (apartment buildings) in many countries.  

 CATEGORIES OF PRECAST BUILDING SYSTEMS 


Depending on the load-bearing structure, precast systems can be divided into the following categories:
 • Large-panel systems
 • Frame systems
 • Slab-column systems with walls
 • Mixed systems
 Large-Panel Systems 
                                         The designation “large-panel system” refers to multistory structures composed of large wall and floor concrete panels connected in the vertical and horizontal directions so that the wall panels enclose appropriate spaces for the rooms within a building. These panels form a box-like structure . Both vertical and horizontal panels resist gravity load. Wall panels are usually one story high. Horizontal floor and roof panels span either as one-way or two-way slabs. When properly joined together, these horizontal elements act as diaphragms that transfer the lateral loads to the walls.

Depending on the wall layout, there are three basic configurations of large-panel buildings:

• Cross-wall system.-  The main walls that resist gravity and lateral loads are placed in the short direction of the building.

 • Longitudinal-wall system.-The walls resisting gravity and lateral loads are placed in the longitudinal direction; usually, there is only one longitudinal wall

 • Two-way system. The walls are placed in both directions .

 Thickness of wall panels ranges from 120 mm for interior walls  to 300 mm for exterior walls . Floor panel thickness is 60 mm . Wall panel length is equal to the room length, typically on the order of 2.7 m to 3.6 m.  In some cases, there are no exterior wall panels and the façade walls are made of lightweight concrete  A typical interior wall panel is shown in Figure.

Panel connections represent the key structural components in these systems. Based on their location within a building, these connections can be classified into vertical and horizontal joints. Vertical joints connect the vertical faces of adjoining wall panels and primarily resist vertical seismic shear forces. Horizontal joints connect the horizontal faces of the adjoining wall and floor panels and resist both gravity and seismic loads. 

Depending on the construction method, these joints can be classified as wet and dry. Wet joints are constructed with cast-in-place concrete poured between the precast panels. To ensure structural continuity, protruding reinforcing bars from the panels (dowels) are welded, looped, or otherwise connected in the joint region before the concrete is placed. Dry joints are constructed by bolting or welding together steel plates or other steel inserts cast into the ends of the precast panels for this purpose. Wet joints more closely approximate cast-in-place construction, whereas the force transfer in structures with dry joints is accomplished at discrete points.

Lateral stability of a large-panel building system is provided by the columns tied to the wall panels . Boundary elements are used instead of the columns as “stiffening” elements at the exterior. The unity of wall panels is achieved by means of splice bars welded to the transverse reinforcement of adjacent panels in the vertical joints. Longitudinal dowel bars placed in vertical and horizontal joints provide an increase in bearing area for the transfer of tension across the connections. 

Frame Systems

Precast frames can be constructed using either linear elements or spatial beam-column subassemblages. Precast beam-column subassemblages have the advantage that the connecting faces between the subassemblages can be placed away from the critical frame regions; however, linear elements are generally preferred because of the difficulties associated with forming, handling, and erecting spatial elements. The use of linear elements generally means placing the connecting faces at the beam-column junctions. The beams can be seated on corbels at the columns, for ease of construction and to aid the shear transfer from the beam to the column. The beam-column joints accomplished in this way are hinged. However, rigid beam-column connections are used in some cases, when the continuity of longitudinal reinforcement through the beam-column joint needs to be ensured.. 

Precast reinforced concrete frame with cruciform and linear beam elements is an example of a frame system with precast beam-column subassemblages. The load-bearing structure consists of a precast reinforced concrete space frame and precast floor slabs. The space frame is constructed using two main modular elements: a cruciform element and a linear beam element. The cruciform element consists of the transverse frame joint with half of the adjacent beam and column lengths. The longitudinal frames are constructed by installing the precast beam elements in between the transverse frame joints. The precast elements are joined by welding the projected reinforcement bars (dowels) and casting the concrete in place. 

Joints between the cruciform elements are located at the mid-span of beams and columns, whereas the longitudinal precast beam-column connections are located close to the columns. . Slab-Column Systems with Shear Walls These systems rely on shear walls to sustain lateral load effects, whereas the slab-column structure resists mainly gravity loads.




 There are two main systems in this category:
 • Lift-slab system with walls
• Prestressed slab-column system

 Reinforced concrete slabs are poured on the ground in forms, one on top of the other. Precast concrete floor slabs are lifted from the ground up to the final height by lifting cranes. The slab panels are lifted to the top of the column and then moved downwards to the final position. Temporary supports are used to keep the slabs in the position until the connection with the columns has been achieved.

In the connections, the steel bars (dowels) that project from the edges of the slabs are welded to the dowels of the adjacent components and transverse reinforcement bars are installed in place. The connections are then filled with concrete that is poured at the site.

Most buildings of this type have some kind of lateral load-resisting elements, mainly consisting of cast-in-place or precast shear walls, etc. In case lateral load-resisting elements (shear walls, etc.) are not present, the lateral load path depends on the ability of the slab-column connections to transfer bending moments. When the connections have been poorly constructed, this is not possible, and the lateral load path may be incomplete.

Another type of precast system is a slab-column system that uses horizontal prestressing in two orthogonal directions to achieve continuity. The precast concrete column elements are 1 to 3 stories high. The reinforced concrete floor slabs fit the clear span between columns. After erecting the slabs and columns of a story, the columns and floor slabs are prestressed by means of prestressing tendons that pass through ducts in the columns at the floor level and along the gaps left between adjacent slabs. After prestressing, the gaps between the slabs are filled with in situ concrete and the tendons then become bonded with the spans. Seismic loads are resisted mainly by the shear walls (precast or cast-in-place) positioned between the columns at appropriate locations. 

EARTHQUAKE PERFORMANCE

There is a general concern among the earthquake engineering community regarding the seismic performance of precast construction.  When it comes to earthquake performance, the fact is that “bad news” is more widely publicized than “good news.” However, few engineers are aware of the good seismic performance (no damage) of several large-panel buildings under construction at the same site.

The precast prestressed slab-column system has undergone extensive laboratory testing that predicted excellent resistance under simulated seismic loading. These building have been subjected to several moderate earthquakes without experiencing significant damage.

Due to their large wall density and box-like structure, large-panel buildings are very stiff and are characterized with a rather small fundamental period. For example, a 9-story building in 

India has a fundamental period of 0.35 to 0.4 sec.

 In general, large-panel buildings performed very well in the past earthquakes. It should be noted, however, that large-panel buildings in the area affected by the Bhuj earthquakes were not designed with seismic provisions. Most such buildings performed well in the first earthquake (M 7.0), but more damage was observed in the second earthquake that occurred the same year (M 7.3), as some buildings had been already weakened by the first earthquake .

Destruction of a Framed structure by Bhuj Earthquake

SEISMIC-STRENGTHENING TECHNOLOGIES

According to recent reports, no major efforts have been reported regarding seismic strengthening of precast concrete buildings. However, seismic strengthening of precast frame buildings was done in New Delhi. The techniques used include the installation of steel straps at the column locations  and reinforcing the joints with steel plates to provide additional lateral confinement of the columns.

 Seismic strengthening of precast columns with steel straps 

ENDNOTES

Definition of “Mass Production” in “Industrial Engineering and Production Management” R.k sahni, , 15th Edition, Vol. 21, p. 204, 1989. 

2 UNIDO, 1983. Design and Construction of Prefabricated Reinforced Concrete Frame and Shear-Wall Buildings. Building Construction Under Seismic Conditions in the Gujarat Region. Volume 2. 

Revealed: Sustainability required in Pre-Fabricated Constructions

First-of-its-kind in India, this 10 storey building in Mohali by Synergy Thrislington was constructed in just 48 hours.

Synergy Thrislington, a Mohali-based infrastructure company has definitely changed the shifted the time dials in fast forward mode. The company entered the Limca Book of Records for constructing a 10-storey commercial building in just 48 hours. The iconic structure - titled Instacon - was completed on December 1, 2012, The first building of its kind in India, the structure was built with the assistance of three cranes and more than 200 highly skilled technicians and workers. With a size of 2,553.60 sq m and a dead load of 1,200-1,500 kg sq m along with a live load of 320-350 kg sq m, the 48-hour masterwork stands tall in the city.

But is this a Marvel or a mere Showpiece!

The ingredients used

The external structure of the building comprises double-skinned PUF panel (PVDF galvalume coated sheet) that ensures thermal insulation. The core material used for Instacon is mild steel, which is lightweight, strong, and flexible. The steel is also coated with rust retardants and anti-corrosive paints to avoid rusting.

However; Brick, sand or gravel is not utilized in the constructing process; however, concrete is used only in the foundation and in a three-inch deck flooring.

The intelligence involved

A smart technique was utilized to create Instacon in a short timeframe. The company made arrangements to ensure that around 80-90 per cent of the work was completed in the factory under a controlled environment. In this system, different units of the building such as wall panels, columns, etc, were produced within the factory and then transported to the actual site where 10-20 per cent of the work was carried out by simply installing them. Also, utility arrangements such as HVAC, plumbing, electrical, fire-fighting, etc, were fitted in the floor frames of steel.

So can the actual time can be framed as a Record?

The costs

The cost of Instacon is about $1.5 million. In this project, the work done at the job site was minimum, which enabled bringing down the project costs associated with subcontractors, scheduling, weather, staging, delivery and inspection. The foundation cost of the project was also reduced with the use of steel framing, which is lighter than the conventional RCC structure. An interesting fact: the depth of the foundation for the project is less compared to conventional buildings.

But being an Engineer for the same company and one of the few inmates to have access to Instacon, I came across squeaking Sounds from the building floors,

This is because steel and PUF panel both have expansion & contraction coefficient respectively which allows building to contract and expand at times releasing sounds like an old wood house. This expansion can lead to cracking in window panels and glasses all the times as cracks can be seen in many panes and need to be changes on a routine basis.

For the last two years the building is inhospitable, The only purpose it serves is to attract contracts from bidders who are fooled by vibrancies of construction in short space of time and sometimes as modern monuments for dignitaries arriving in the city.

In fact, if I talk about the cost involved and the return or the business given by the marvel including maintenance is meager or nil.

The building is claimed to be Earthquake resistant, Soundproof, Heatproof and low on Carbon Credit but these claims are false as when PUF panel put under test it resist in give results claimed by company.

Indeed, there is an urgent requirement to upgrade the buildings with substitute materials that are environment-friendly, time-saving and cost-effective. Hopefully, Instacon inspires many more speedy and green projects in India keeping in mind the urgency the project deserves.

Project details

Size of the project: 2,553.60 sq m
Developer: Synergy Thrislington. www.synergythrislington.com

https://www.youtube.com/watch?v=HFqJG0nDu1E

                                 Section of PUF panel used

                                   Section & Elevation

Minimal Time Consumption Constructing High-Rise Buildings

Optimal Time Utilization whilst Constructing Tall Buildings

Abstract:

The triangle of project objectives - cost, quality and time is well known. The relative priorities among them are established by the client/owner. Over the last three decades, special needs pertaining to construction of tall buildings have been established. Particular emphasis have been given to reducing construction schedules. Real estate costs, housing demands, and growth of major cities in developing countries have changes the core concept of traditional construction management and methods.

Being a contemporary civil engineer, I analyze the main factors influencing construction schedules of tall buildings and describing methods and measures that have been successfully used in achieving time reduction in overall construction schedule.

Background:

Time over-runs in construction projects have often been one of the more remarkable 'failure modes' drawing criticism on construction industry. Resulting in overheads incurred by all participants,as well as potential claims for progress disruptions by contractors, and/or liquidated damages by clients are the most common consequences.

 There is a global competitiveness going on to improve such failures of time lag.

Management Method

Project Planning and Management:

                                                            The major activities in the construction of tall buildings generally are classified into the following packages:-

1. Site set-up.Activities necessary to establish temporary facilities at the work place and prepare the site for subsequent activities, including site layout.
2. Pilling.Activities  necessary to complete the groundwork up to but excluding ground floor slab, as well as foundations, under slab drainage, basement etc.
3. Pile caps/raft.Activities necessary to construct pile caps in the case of pile foundation, or the raft foundation, including the ground floor slab.
4. Superstructure.Activities necessary to erect the load bearing frame starting from the ground floor column/wall element, upto and including the main roof and upper roof, as well as pre-cast facade installation.
5. Electrical & Mechanical (E&M)services.Activities necessary to install the E&M works including electrical, fire services, elevators, water pump and water supply system, waste water system, telephone system, storm water drainage, lighting protection etc.
6. Finishes.Activities necessary to complete the building including any brickwork for internal partitions, plastering and tiling, carpentry and joinery, ironmongery, steel and metal works, glazing , painting, window installation, wall finishes etc.
7. External works. Other works adjacent to the building including underground cable ducts and drainage, covered walkways, planters, access roads, paving ,play areas, pavillion etc.

The duration of construction is the time span from beginning of foundation to completion and handover of building to client.The total schedule can be determined based upon the duration of the above phases

As common duration for tasks will be established. Contractors and managers knows how long it will take to drill and pour piles, what equipment to use, and so forth. they also know how to reduce this time through the controls of some variables in present.As once a better time ti perform an activity is achieved, there is both the challenge and competence to do it better next time.

Based on this knowledge, if the construction durations of every phase can be estimated reliably and objectively in the design stage, time uncertainty will be minimized in the construction stage.

In few newer studies the researchers found the 7 most important variables affecting the time schedule of tall structures are:

• Area of external cladding.
• Height of the building.
• Ratio of total gross area  to the number of stories.
• Type of foundation.
• Information flow between architect/engineer and contractors.
• Presence / absence of precast facade.
• Type of scheme(purchased/rental)

Managers are or to be alerted to the relevance of these factors whenever they have time constraints. The more accurate the information about these areas, the more reliable are the schedules.

These variable also inturn have influence on other factors such  as:-

1. The duration of piling works is related to piling cost, type of foundation and depth of foundation excavations.
2. The time required for superstructure construction is affected by the height of the building, labor availability and the presence / absence of pre-cast facade
3. Durations for E&M services and finishes are dependent upon the 'critical' superstructure duration.
4. Both planned and actual overall construction durations are related to construction cost, presence/absence of pre-cast facade, type of scheme (rental/purchase) and height or number of stories of the building.

Effective communication between several groups and hierarchical levels involved in a project emphasizes the need for efficient method of information processing in the building industry. Speed of decision-making involving all project teams; both formal and informal communication between client and consultant & between consultant and contractor affects the duration of primary work packages for building projects. Therefore, to accelerate communication and decision making among all parties, appropriate overall organisational structures and information communication network system linking all project teams should be developed through out the whole life of the project. The roles and responsibilities of those involved should be defined clearly, and designated decision makers should be clearly identified.

In my research other studies conducted over the years around the globe indicate that while procurement and non-procurement related factors contribute to cost over-runs are mainly influenced by non-procurement variables such as project characteristics (e.g complexity level of design and construction requirements) and client representative characteristics.

Many studies of delays in various construction industries have elicited diverse sets of causative factors. Table below provide a comparative overview of a cross-section of such factors as identified by different researchers. It shows that 'material shortage or late material delivery' is the most frequently cited cause of delays followed by others variably.

A cross-section of  findings on the major factors causing delays in construction projects

Construction Process and Materials:

Jump Form System to Construct Concrete Core Walls:-
                                                                                             The use of a climbing formwork system( sometimes referred to as self-climbing or self-lifting) to construct core walls of high rise buildings is successful in contemporary times in reducing construction times, primarily because the process become repetitive through the whole height of the building.

explaining the working

Basically it consist of a frame constructed from structural steel members over the score wall. Steel panels are hung from this frame, some supported on rollers. After the concrete walls are poured, the framework is released and rolled back from the concrete face. Jacks then lift or climb the whole frame up one level. All the framework panels are attached to the frame. The whole process take one and a half hours. The mould are cleaned after lifted out of the finished units and then re-assembled.

The cycle continues normally four days. Faster times have been achieved

Climbing Formwork on a concrete Pier

• Pre-Fabrication of Elements:

Prefabrication of elements is another method that has been successfully used to save time in construction of tall buildings. The repetitiveness of many elements makes this process suitable and very effective. Walls, Staircases, External facades and Door sets are the common examples of prefabricated elements.

Components are manufactured units, made to pre-determined sizes, to be used in buildings.Dimensional coordination governs their design and use and governs  their design and use. For example a prefabricated standard staircase components with a rise of 266 cm will govern the floor to floor height of the building in which it is to be fixed.

Prefabricated wall panels will closely govern the story height and the length of the building.

The advantages of Prefabrication are many a few are as:

1. Mass production of Units

•            Automation of the manufacturing process can save labor and reduce price.
•            Designers can become familiar with the standard units and have ready access to details.

     2.  Reduction of cost and Construction time on site

•            Less work to be done on site.
•            Saving in the use of formwork on site.
•            Precast units can be erected in bad weather.

     3.  Construction over and under water

•            No or little formwork is required.
•            False work is not required.
•            Minimal disruption to traffic.

     4.  Solution to the problem of local resources and labor

•            Units can be produced thousand of miles away from site.

The advantages of Prefabrication are as:

1. A small number of units required may prove to be uneconomical.
2. Special connections such as special bearings to transmit the vertical and horizontal loads, can add cost to the system.
3. Water proofing at joints.
4. Transportation difficulties.
5. Need for cranes.

Construction Equipments:  

Facilitating horizontal and vertical movements is one of the main tasks in tall buildings construction that must be accomplished in order to develop a schedule that is effective and tight.

• Hoists
• Gondolas/Swinging stage
• Work platform
• Elevators
• Cranes
• Modern use of Robotics in construction ;where application was impossible and troublesome to great success

Conclusion and Recommendation:

The pace of  living has changed along with the evolution of cities of the world; economic factors increasingly are shaping the needs for the new millenium and the construction industry is responding by aiming to speed up building processes. High rise buildings are particularly important . Government, researchers and firms of different countries around the world are targeting their effort towards reducing time in construction of such structures.

Management method, construction process and materials, and construction equipments have been successfully used in reducing time in overall schedule of tall buildings.

Significant factors that have emerged with regard to applying management methods to reduce construction schedules of tall buildings are
(a) Project scope factors (actual cost, present/absence of precast facade, height and number of stories)
(b)Non scope factors such as speed of decision making involving all project teams, information flow         between consultant and contractor and informal communication between architect/engineer and            contractor.
other factors such as Jump form system, Prefabrication elements have taken over the past repetitiveness and used to good optimum use these times of construction along with the new equipments.
It is my belief that this trend will be intensified in the near future. It is hoped this paper will help initiate and contribute to continual improvement of schedule performance of construction industry.

  

INTER-STELLAR SCIENCE OF DESIGN IN ANCIENT HINDU TEMPLE

Constructing DIVINE

Abstract:

 This paper describes initial research on a project designed to understand the experiences of past generations of constructors and make that knowledge accessible to future generations of engineering students and construction practitioners. Much in the same way as medical students can trace their lineage back to Hippocrates, this project aims to provide architecture, engineering, and construction students, and professionals alike, a sense of their professional history. The project was developed around three time epochs, four geographic regions, and three different project types. I investigated issues such as the flow of money, training of workers, sharing of design knowledge, and nature of contracts and agreements.

The central question posed by this work is how should knowledge of the history and evolution of construction practices be incorporated in the dialog that educators have with students and with the larger professional community? This research has led to multifaceted results. On the one hand, the message to students should be pride in their professional heritage because throughout time constructors and designers have used knowledge, perseverance, and innovation to accomplish remarkable projects.

On the other hand, we have shown that much of what is considered new in the industry alternative project delivery methods , worker safety programs, public private partnerships, and globalization have historical antecedents and are not new at all.

                                   “Who knows only his own generation remains always a child”

It is certainly true that all can benefit from the wisdom and experience of past generations. This paper describes initial research on a project designed to understand the experiences of past generations of constructors and make that knowledge accessible to future generations of engineering students and construction practitioners.

Interstellar Cosmology in the Hindu Temple

According to the Sthapatya Veda (the Indian tradition of architecture), the temple and the  town should mirror the cosmos. The temple architecture and the city plan are, therefore, related in their conception. Volwahsen (2001) has remarked on the continuity in the Indian architectural tradition. The Harappan cities have a grid plan, just as is recommended in the Vedic manuals. The square shape represents the heavens, with the  four directions representing the cardinal directions as well as the two solstices and the equinoxes of the sun’s orbit.

The monument that has been studied most extensively for its cosmological basis is the  Angkor Wat temple. Although it is located in Cambodia, it was built according to the principles of Indian architecture.

This paper presents the basis of the Hindu temple design going back to the earliest period. We trace this design back to the fire altars of the Vedic period which were themselves designed to represent astronomical knowledge. An assumed equivalence between the outer and the inner cosmos is central to the conception of the temple. It is because of this equivalence that numbers such as 108 and 360 are important in the temple design.

The number 108 represents the distance from the earth to the sun and the moon in sun and moon diameters, respectively. The diameter of the sun is also 108 times the diameter of the earth, but that fact is not likely to have been known to the Vedic rishis. This number of dance poses (karanas) given in the Natya Shastra is also 108, as is the number 1o f beads in a rosary (japamala). The “distance” between the body and the inner sun is also taken to be 108, and the number of marmas in Ayurveda is 107. The total number of syllables in the Rigveda is taken to be 432,000, a number related to 108. The number 360, the number of days in the civil year, is also taken to be the number of bones in the developing foetus, a number that fuses later into the 206 bones of the adult. 

The centrality of this number in Vedic ritual is stressed in the Shatapatha Brahmana. The primary Vedic number is three, representing the tripartite division of the physical world into the earth, the atmosphere, and the sky and that of the person into the physical body, the pranas, and the inner sky. The Hindu temple also represents the Meru mountain, the navel of the earth. The Brihat Samhita 56 lists the many design requirements that the temple building must satisfy. For example, it says “the height of the temple should be double its width, and the height of the foundation above the ground with the steps equal to a third of this height. The sanctum sanctorum should be half the width of the temple” and so on. It also lists twenty types of temples that range from one to twelve storeys in height.

(a) An exotic depiction of the temple of Angkor Wat in Garnier's 1873 publication Voyage d'exploration en Indo-Chine; (b) The first photograph of Angkor Wat ever taken, by John Thomson 1866 (Source: (a) Francis Garnier, Voyage d'exploration en Indo-Chine effectué pendant les années 1866, 1867) 

We first summarize some relevant characteristics of the Angkor Wat temple that emphasize the relationship of the design to astronomy. This will be followed by sections on the Vedic antecedents of the temple and the medieval expression of the philosophy behind its design. We will also consider the question of the chaitya hall with its pointed arch as an alternate tradition within India that has been connected to the Lycian arch which may have influenced the design of the cathedral.

The most impressive aspect of the temple representation is that it occurs both at the level of the part as well as the whole in a recursive fashion, mirroring the Vedic idea of the microcosm symbolize the macrocosm at various levels of expressions. This is done not only in the domain of numbers and directions, but also using appropriate mythological themes, and historical incidents. The mythological scenes skillfully use the oppositions and complementarity between the gods, goddesses, asuras, and humans defined over ordinary and sacred time and space

Speaking just of numbers, the various lengths and circumferences of units representing the motion of the moon may equal 27, 28, 29 (nakshatras or days of the month), 354 (days of the lunar year), or 360 (tithis of the lunar year). Other lengths represent the solar year (360, 365, or 366) or larger time cycles. For example, the west-east axis represents  the periods of the yugas. The width of the moat is 439.78 cubit; the distance from the first step of the western entrance gateway to balustrade wall at the end of causeway is 867.03 cubit; the distance from the first step of the  western entrance gateway to the first step of the central tower is 1,296.07 cubit; and the distance from the first step of bridge to the geographic center of the temple is 1,734.41 cubit. These correspond to the periods of 432,000; 864,000; 1,296,000; 1,728,000 years for the Kali, Dvapara, Treta, and Krita yuga, respectively. It has been suggested that the very slight discrepancy in the equations might be due to human error or erosion or sinking of the structure.

In the central tower, the topmost elevation has external axial dimensions of 189.00 cubit east-west, and 176.37 cubit north-south, with the sum of 365.37. This division of the almost exact length of the solar year into unequal halves remained a mystery for some time until it was found to be connected with the Shatapatha Brahmana numbers for the asymmetric motion of the sun. Over the half-millenia of Khmer rule, the city of Angkor became a great pilgrimage destination because of the notion of Devaraja, that has been explained by Lokesh Chandra as a coronation icon. Jayavarman II (802-850) was the first to use this royal icon. According to Lokesh Chandra (1995), “Devaraja means `King of the Gods' and not `God-King'. He is Indra and refers to the highly efficacious aindra mahabhisheka of the Rigvedic rajasuya tradition as elaborated in the Aitareya-brahmana. It was not a simple but a great coronation, a mahabhisheka. It was of extraordinary significance that Jayavarman II performed a Rigvedic rite, which lent him charismatic authority.”
The increasingly larger temples built by the Khmer kings continued to function as the locus of the devotion to the Devaraja, and were at the same time earthly and symbolic representations of mythical Mt. Meru, the cosmological home of the Hindu gods and the axis of the world-system. The symbol of the king's divine authority was the sign (linga) of Shiva within the temple's inner sanctuary, which represented both the axes of the physical and the psychological worlds. The worship of Shiva and Vishnu separately, and together as Harihara, had been popular for considerable time in southeast Asia; Jayavarman's chief innovation was to use ancient Vedic mahabhisheka to define the symbol of government. 
To quote Lokesh Chandra further, “The icon used by Jayavarman II for his aindra mahabhisheka, his Devaraja = Indra (icon), became the symbol of the Cambodian state, as the sacred and secular sovereignty denoted by Prajapatishvara/Brahma, as the continuity of the vital flow of the universal (jagat) into the stability of the terrestrial kingdom (raja = rajya}). As the founder of the new Kambuja state, he contributed a national palladium under its Cambodian appellation kamraten jagat ta raja/rajya. Whenever the capital was transferred by his successors, it was taken to the new nagara, for it had to be constantly in the capital.” 
Angkor Wat is the supreme masterpiece of Khmer art. The descriptions of the temple fall far short of communicating the great size, the perfect proportions, and the astoundingly beautiful sculpture that everywhere presents itself to the viewer. Its architecture is majestic and its representation of form and movement from Indian mythology has astonishing grace and power. The inner galleries of the temple have depiction of the battle of Kurukshetra, procession of King Suryavarman and his ministers, scenes from heavens and hells, churning of the sea of milk, the battle of Vishnu and the asuras, victory of Krishna over Bana, battle of the devas and asuras, Ravana shaking Kailasa with Shiva and Parvati atop, and the battle of Lanka between Rama and Ravana. These and other scenes are drawn with great artistic beauty. No wonder, the temple ranks amongst the greatest creations of human imagination. 
4Numbers at Angkor Wat 
The temple has 1300-m north-south axis and 1500-m west-east axis. The temple faces toward the west because that situates it to the east with respect to the worshiper, the appropriate direction for Vishnu who is a solar deity. At the heart of the temple are three rising, concentric galleries. Bordering these is further space, and a rectangular moat. 
About 40 m in from the moat is a laterite wall, 4.5 m high, with large single entrances from the east, north, and south, and five entrances on the west. Mannikka has suggested that the Vastupurusha mandala at Angkor Wat forms a grid of 49, rather than the standard of 64 or 81. Various numbers from the Vedic astronomy are encountered at Angkor Wat as simple counts, or measurements in cubits, or phyeam = 4 cubits. Some of these represent just the basic constants of the system, while others provide specific information related to the orientation of the temple related to the nakshatras and the positions of the planets. For an example of the latter, consider that the length of the north-south axis, door to door, in the sanctuary is 13.41 cubits, which according to Mannikka represents the fact that the north celestial pole is 13.43 degrees above the northern horizon at Angkor. This number is also basic to the second gallery, devoted to Brahma who is ``situated'' at the north celestial pole. 
The order in which the planets rose over the eastern horizon at the end of July 1131 is represented in the bas-relief of the northwest corner pavilion: Saturn (Agni), Jupiter (Indra), Venus (Kubera), Mars (Skanda), and Mercury (Varuna). 

According to Mannikka, the design of the temple can be seen in three architectural units: 
1. Central sanctuary: Mount Meru, with 45 gods, the north celestial pole, the centre of the mandala, the spring equinox, the axis of the earth, Vishnu, Brahma, and King Suryavarman 
2 Circumferences: the ecliptic, the moon and lunar periodicity, the constellations, the planets, the celestial year, the krita yuga, the grid of the mandala, the history of King Suryavarman 
3 Axes: the building blocks of time (60, 108), the yuga cycles, the solar year, the lunar year, historical dates in Suryavarman's reign, the mandala and its transformation of time, and, finally, the solar year and lunar time cycles from the vantage point of Mount Meru. 
Some basic numbers that we encounter frequently in the architectural plan are given below. For more examples see the book by Mannikka which, however, does not recognize the special place of the altar numbers 78 and 261. Neither does it know the correct significance of the number 108.  21 The earth number shows up as the number of steps to the libraries.
27/28 This count of nakshatras is represented at numerous places; the total inner axes of the sanctuary. 
32/33 This represents the number of devas and it is found as the number of pillars, windows and various lengths. 
44/45 The number of divinities of the Vastupurusha mandala is shown in the total number of steps, main entrance and flanking Central Western entrances. As 450 cubits, various axial entrances and circumference of gallery. 
54 As half of the distance in sun- or moon-diameters to the sun or the moon, 54 cubits or 
54 phyeam are encountered several places on the Western bridge and the outer enclosure. 
78 The atmosphere number is found in the central cruciform, inner axes as 20.08 phyeam, which equals 80.32 cubits. The 20 steps in several of the stairways to the libraries may also represent the same number divided by 4. Further evidence for that comes from the distance of 19.42 phyeam = 77.68 cubits each library, west-east outer axis. Since books represent the `atmosphere' in reaching the `sky' of knowledge, its use in the context of library is very appropriate. 
108 In-and-out circumambulation of four corner towers together; circumambulation of the central Vishnu image from three axial entrances; inner axes of all four corner towers without images; full vertical distance above and below central sanctuary. 
130.5/261 As half of the sky number 261, we find it in the circumambulation path to north end chamber, each end gateway. The number is 32.74 phyeam which equals 130.96 cubits. 
354 The length of the lunar year in days, it is the distance between naga balustrade and first step at end of walkway to upper elevation. 
360 In phyeam, the circumambulation path around the Cruciform Terrace. 
366 Solar axes of gallery from walkway on west to bases on each side. 
371 This is the solar year in tithis, and it is found in an in-and-out circumambulation of all four corner towers. 
Solar and lunar measurements; Temple Antecedents 
The solar and lunar numbers that show up in the design of the Angkor Wat temple are the number of nakshatras, the number of months in the year, the days in the lunar month, the days of the solar month, and so on. Lunar observations appear to have been made from the causeway.
The division of the year into the two halves of 189 and 176.37 was recently explained by the author as being derived from the Shatapatha Brahmana. In layer 5 of the altar described in the Shatapatha, a division of the year into the two halves in the proportion 15:14 is given (Kak, 1998, 2000). This proportion corresponds to the numbers 189 and 176.4 used at Angkor Wat, where in the central tower the topmost elevation has dimensions of 189 east-west and 176.37 north-south. 

 (a) An elevation of the lower eastern section of the central tour of Angkor Wat and (b) a collage of original sculptures, plaster casts and photographs from the real site of Angkor Wat.

The elliptical orbit of the earth together with the fact that the sun is at a slight offset is behind the asymmetry in the sun's orbit. The period from the autumnal equinox to the vernal equinox is smaller than the opposite circuit. The interval between successive perihelia, the anomalistic year, is 365.25964 days which is 0.01845 days longer than the tropical year on which our calendar is based. In 1000 calendar years, the date of the perihelion advances about 18 days. The perihelion was roughly on December 18 during the time of the construction of Angkor Wat; and it was on October 27 during early 2nd millennium BC, the most likely period of the composition of the Shatapatha Brahmana. In all these cases the perihelion occurs during the autumn/winter period, and so byKepler's 2nd law we know that the speed of the sun in its orbit around the earth is greater during the months of  autumn and winter than in spring and summer. 

During the time of the Shatapatha Brahmana, the apogee was about midway through the spring season, which was then somewhat more than 94 days. The extra brick in the spring quadrant may symbolically reflect the discovery that this quarter had more days in it, a discovery made at a time when a satisfactory formula had not yet been developed for the progress of the sun on the ecliptic. 
It is possible that the period from the spring equinox to the fall equinox was taken to be about 189 days by doubling the period of the spring season; 176 days became the period of the reverse circuit. 
Why not assume that there was no more to these numbers than a division into the proportions 15:14 derived from some numerological considerations? First, we have the evidence from the Shatapatha Brahmana that expressly informs us that the count of days from the winter to the summer solstice was different, and shorter, than the count in the reverse order. Second, the altar design is explicitly about the sun's circuit around the earth and so the proportion of 15:14 must be converted into the appropriate count with respect to the length of the year. Furthermore, the many astronomical alignments of the Angkor Wat impress on us the fairly elaborate system of naked-eye observations that were the basis of the temple astronomy. 
But since precisely the same numbers were used in Angkor Wat as were mentioned much earlier in the Shatapatha Brahmana, one would presume that these numbers were used as a part of ancient sacred lore. The count between the solstices has been changing much faster than the count between the equinoxes because the perigee has been, in the past two thousand years somewhere between the autumn and the winter months. Because of its relative constancy, the count between the equinoxes became one of the primary `constants' of Vedic/Puranic astronomy.
The equinoctial half-years are currently about 186 and 179, respectively; and were not much different when Angkor Wat temple was constructed. Given that the length of the year was known to considerable precision there is no reason to assume that these counts were not known. But it appears that a `normative' division according to the ancient proportion was used. 
As it was known that the solar year was about 365.25 days, the old proportion of 15:14 would give the distribution 188.92 and 176.33, and that is very much the Angkor Wat numbers of 189 and 176.37 within human error. In other words, the choice of these `constants' may have been determined by the use of the ancient proportion of 15:14.

(d) The famous face towers of the Angkorian temples, depicted in (a) Thomson 1875, (b) Fergusson 1876, and Delaporte 1880 (Source: (a) John Thomson, The straits of Malacca, Indo-china and China, London 1875, p.151; (b) James Fergusson, History of Indian and Eastern architecture. Vol. 3 of History of architecture in allcountries, London 1876

 The temple is considered in the image of the Cosmic Purusha, on whose body is displayed all creation in its materiality and movement. Paradoxically, the space of the Purusha (Rigveda 10.90) is in the sanctuary only ten fingers wide, although he pervades the earth. The prototype of the temple is the Agnikshetra, the sacred ground on which the Vedic altars are built. The Agnikshetra is an oblong or trapezoidal area on which the fire altars are built. Tripathi (1990) has argued that the agnichayana sacred ground provides the prototype, because in it is installed a golden disc (rukma) with 21 knobs or hangings representing the sun with a golden image of the purusha on it. Tripathi shows that the detailed ritual includes components that would now be termed Shaivite, Vaishnava, or Shakta. In Nachiketa Agni, 21 bricks of gold are placed one top of the other in a form of shivalinga. The disk of the rukma, which is placed in the navel of the altar on a lotus leaf  is in correspondence to the lotus emanating from Vishnu’s navel which holds the universe.

  Several bricks are named after goddesses, such as the seven krittikas.  

The temple is the representation of the cosmos both at the level of the universe and the individual, making it  possible for the devotee to get inspired to achieve his own spiritual transformation. The purusha placed within the brick structure of the altar represents the consciousness principle within the individual. It is like the relic within the stupa.  

Complementing the tradition of the Vedic ritual was that of the munis and yogis who lived in caves and performed austerities. From this tradition arose the vihara, where the priests lived. The chaitya hall that also housed the stupa may be seen as a development out of the agnichayana tradition where within the brick structure of the altar were buried.

Concluding Remarks  

This paper has shown how the Hindu temple represents the outer and the inner cosmos. The outer cosmos is expressed in terms of various astronomical connections between the temple structure and the motions of the sun, the moon, and the planets. The inner cosmos is represented in terms of the consciousness at the womb of the temple and various levels 

of the superstructure that correspond to the states of consciousness. The position of the gods in the vastupurushamandala within the temple is a symbolic representation of the spatial projections of the cosmic purusha in his own body.  

The temple must be seen as a structure that gives us considerable information about the science and cosmology of its times. Regarding technology behind the constructions, one must look at each structure separately and see how it fits in the evolving techniques of design and artistic representation across the region.

  

References  

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Kak, S., 1993. ``Astronomy of the Vedic Altars," Vistas in Astronomy, 36, 117-140.  

Kak, S., 1995. ``The astronomy of the age of geometric altars," Quarterly Journal of the Royal Astronomical Society, 36, 385-396.  

Kak, S., 1998. ``The sun's orbit in the Brahmanas,'' Indian Journal of History of Science, 33, 175-191.  

Kak, S., 1999. ``The solar equation in Angkor Wat,'' Indian Journal of History of Science, vol. 34, pp. 117-126.  

Kak, S., 2000. The Astronomical Code of the Rgveda. Munshiram Manoharlal, New Delhi.  

Kak, S., 2002. The Gods Within. Munshiram Manoharlal, New Delhi.  

Kamiya, T. 2002. Lycian influence to Indian cave temples. http://www.ne.jp/asahi/arc/ind/lycia/liki_eng.htm  

Kaulacara, R., 1966.  Silpa Prakasa.  Boner, A. and Rath Sarma, S. (eds.). E.J. Brill, Leiden, 1966.  

Kramrisch, S., 1946. The Hindu Temple. The University of Calcutta, Calcutta, 1946; Motilal Banarsidass, Delhi, 1991, page 35-36.  

Lokesh Chandra, 1995. ``Devaraja in Cambodian history'', In Cultural Horizons of India. Aditya Prakashan, New Delhi. 

 Mannikka, Eleanor, 1996. Angkor Wat: Time, Space, and Kingship. Univ of Hawaii Press, Honolulu  

Millar, F.G. and Kak, S., 1999. ``A Brahmanic fire altar explains a solar equation in Angkor Wat,'' Journal of the Royal Astronomical Society of Canada, vol. 93, pp. 216- 220.     Tripathi, V., 1990. Agnicayana. Sampurnanand Sanskrit University, Varanasi.  

Volwahsen, A., 2001. Cosmic Architecture in India. Prestel, New York, and Mapin Publishing,  Ahmedabad.