25 RECENT TRENDS IN BUILDING DESIGNS, PREFABRICATION – METHODS AND TECHNIQUES; GREEN AND SUSTAINABLE TECHNOLOGY

Rymala Mathen

RECENT TRENDS IN BUILDING DESIGNS, PREFABRICATION – METHODS AND TECHNIQUES; GREEN AND SUSTAINABLE TECHNOLOGY

• Prefabrication – Definition, Meaning
• Classification-column and beam system, panel system, Box system, Closed or open system, site oriented or factory oriented system.
• Advantages of Prefabrication-(speed, disciplined use of scarce material, cost reduction, superior quality control and high productivity) and
• Disadvantages
• Areas where prefabrication techniques can be introduced.

Prefabrication means the use of manufactured units or assembling the components of a structure or a building in a factory or a manufacturing site, and transporting them to the building location or the construction site. When several components or units are assembled together on-site to complete the structure of a building, it is called a Prefabricated building Prefabrication- History

• Prefabricated housing became popular during the Second World War as mass accommodation for military personnel was needed and also it was used as a means ofproviding quick and cheap quality housing as a replacement for the housing destroyed during war
• The world’s first prefabricated, pre-cast paneled apartment blocks were pioneered by city engineer John Alexander Brodie, in Liverpool in 1906 after World War 2 which was demolished in the 1960s amid much controversy.
• Prefabricated homes kits were produced in the United States in 1908, which enabled Californian prospectors to quickly construct accommodation.
• Steel, aluminium, timber or asbestos, were the construction materials used depending on the type of dwelling.

But in India, house construction has been in the conventional manner in the organized sector, where burnt bricks, cement mortar, RCC, glass, aluminium, Ceramic tiles, etc were used which are all labour intensive, time consuming and expensive.

Present designs of houses in India are not at all eco friendly. An independent house of say, 900 sq.ft carpet area takes at least one year to complete and costs as high as Rupees fifty lakhs. On the other hand, a dwelling unit of similar size in a multi storied apartment building in urban India takes more than three years to complete and costs anything in the range of rupees thirty lakhs to 100 lakhs.

India being the second most populous country in the world, more than half of its population of people live without a proper house. These populace is classified as the below poverty line (BPL) people whose average family income is less than Rs 5000 per month. It is not possible for them to afford a housing unit even if it costs only one tenth of the cost of a small house.

Besides, in the construction field, India has a serious shortage of skilled labour like masons, carpenters, electricians, plumbers, construction supervisors, planners, experienced engineers and architects. India has many governmental organizations like the Central Building Research Institute (CBRI) doing research work in this field and popularize useful technologies and many state government sponsored housing boards and other such governmental organizations. However, none of them have deviated much from the conventional methods of construction and could not popularize any practical and aesthetic housing designs which are affordable and also good to live comfortably.

Due to rapid growth of concrete constructions especially Kerala, there is a serious depletion of river sand in many regions in India and now river sand has become a scarce commodity that it is being imported from far away countries like Combodia. Even Rock sand (crushed rock), known as factory made sand is also an alternative. The cost of river sand which was only a few hundred rupees twenty years ago is now costing over Rs. 10,000/- a cubic metre and is a punishable offence under environment protection Act (Protection of water bodies). Cost of standard burnt brick has also increased many fold.

Due to its thermal characteristics, concrete buildings are not at all comfortable to live. RCC roofs absorb all the heat of the sun during the day and radiate it inwards in the night which cause discomfort for the dwellers. People who can afford, will use air conditioners which consume so much electricity making India a power hungry nation already, even with half of its population sleeping in the open skies!

All these reasons call for urgent actions to popularize alternative design and construction technologies with regard to the future houses in India both for the urban and the rural people. This is an area where dynamic and visionary entrepreneurs can think differently and evolve a business model that is useful to them, the users and the society.

Prefabrication–methods and techniques

Let us think about designing, manufacturing and marketing completely dismantled houses which also will be aesthetically better, comfortable, affordable and easy to maintain with a long life which could be assembled with the help of trained personnel at site in a few days which is not very difficult today as technologies and know how already exist in the world elsewhere.

•  What is Prefabrication?.
•  Let us take an example from house-building to illustrate the process of prefabrication. Building a house involve transportation of bricks, timber, cement, sand, steel and aggregate, etc. to the construction site and construct the house on site from these materials.

In prefabricated construction, conventional method of construction will be only for the foundations, while sections of walls, floors and roof are prefabricated (assembled) in a factory (possibly with window and door frames included), transported to the site, lifted into place by a crane and bolted together.

• “Precast units” means prefabricated concrete structural components can be also called as Precast members” or precast elements”, which means that before being taken to the actual construction site for erection, they are cast in advance and given sufficient time to harden and acquire strength. “Prefabricated construction” refers to the construction methods which make use of prefabricated components .

Example- concrete panels, slabs, beams or girders manufactured in a plant or constructed in a place other than their final intended location.

Generally prefabricated systems can be classified on the basis of structural action as follows

1. Column and beam system
2. Panel systems
3. Box systems
4. closed’ or ‘open’
5. site oriented or factory oriented

Now let us see one by one

1.    Column and beam system

• In these, precast concrete columns and beams with in filled units for floors and roofs as well as for walls are used for the construction .

• Walls can be of precast units or  in-situ-brick or light weight block masonry construction

•  These types of systems have been developed by research institutions, public and private sector units and individuals for residential and institutional buildings

2.   Panel systems (small panel and large panel systems)

•  For load bearing walls and floor slabs of the structure, normal weight panels, light weight concrete panels or brick panels are used.
• Examples: The UCOPAN system belong to the small panel system and the large panel residential construction of 144 flats in Besant Nagar, Madras27 storied Petit Hall construction by Shah construction company Bombay and Large number of flats built by Hindustan Prefabs Ltd. New Delhi belongs to large panel type.

    3.  Box systems

• The three dimensional or volumetric approaches are based on boxlike modules of room sized scale.
• They can be made of a variety of materials like wood, steel or concrete.
• Box units are designed to permit stacking, the loads being carried by the side wall or by columns along the periphery.
• In India, service core units have been tried in three dimensional box unit shapes.

   4.   Closed’ or ‘open’ & site oriented or factory oriented Prefabrication .

• A closed system may be defined as an industrialized building system which is internally compatible but which cannot be combined with other systems to permit the assembly of hybrid or mixed system
• An open system offers more flexibility and freedom in that it is made up of components or sub systems which can be combined with in- situ construction resulting in partial pre fabrication.
• Prefabrication system are also sometimes categorized as site oriented or factory oriented depending upon whether the components are produced at the site or the factory.

From the view of degree of precast construction it can be also classified as

1.Smal/medium/large prefabrication

2.   Cast-in-site prefabrication

3.   Factory prefabrication

4.   Open/closed system of prefabrication

5.   Partial/Total prefabrication

Advantages of prefabrication as given by G. Madhava Rao & D.S. Ramachandra Murthy(1996) are:

•       Speed

•       Disciplined use of scarce material

•       Cost reduction

•       Superior quality control and

•       High productivity

Speed: construction time can be reduced by as much as 40% for single storied houses and by 25% to 40% for multistoried flats.

 Speed helps not only in wiping out the accumulated backlog of housing and other buildings but also to keep promise made to the people and also for ensuring quicker turn of capital.

Disciplined use of scarce material: Prefabrication helps to reduce the consumption of scarce materials to minimum by employing standardized components so that its design can be optimized by employing sophisticated methods.

Cost reduction: In the beginning, because of the higher capital investment, industrialized building techniques and prefabrication may tend to be marginally more expensive than traditional construction.

  But with an assured demand, due to the savings in materials, labour and economies resulting from bulk purchase and the scale of operation, cost reduction is possible to the extent of 10% to 15 per cent.

 Since formwork and scaffolding are largely eliminated, the quantities of materials required are less,

Favourable weight – Total weight of the building is reduced by the use of structural sections where less concrete and steel is needed.

Superior quality control: Superior quality control can be ensured due to the use of machines, better Working environment provided by the factory, specialized labour and skilled supervision from factory production or site production and also minimizes heavy recurring maintenance expenditure.

 High productivity: Productivity can be improved as a result of better organisation and supervision and labour specialization.

  Inclement weather does not hold up operations as the components are factory produced.

Problems in Prefabricated Construction

Problems according to M S Palanichamy, G Jeyakumar,& K L Muthuramu(2002), are as follows

 Transporting the prefabricated components from the factory to the site is more difficult than the transport of materials and of erecting and interconnecting them to form the final structure in the site.

    These operations associated with prefabrication entail additional costs and technical problems. To justify the choice of prefabricated construction in any particular case, the advantages must of course outweigh the disadvantages.

Areas where prefabrication techniques can be introduced

1. Foundation:

2. Walls:

3.  Floors and Roofs:

4.  Doors and windows:

5. Precast sanitary core units-

6.  Ferro cement products:

7. Design of joints

Foundation:

• Because of the varying soil condition prevailing in different sites and complexity, it is generally found easier and more practicable to make foundation by conventional methods using in-situ techniques rather than prefabrication.
• However for column pedestals ,precast concrete pile foundations can be used.

Walls:

•  In India, small, medium, and large panel techniques which are proved to be economical for medium and high rise buildings have been developed and executed for walling
• Large panel construction and similar heavy prefabrication may be used in walls only in cases where it proves economical.
• Partial prefabrication is an important technology breakthrough from conventional to industrialised building methods.

The common precast roofing/ flooring components used in India are;

i) Precast funicular shells, channel units

ii)   Precast ribbed units

iii)   Light weight concrete slabs

iv)  Pre stressed hollow cored slabs

v)  Precast battens and hollow block construction

vi)  Plate floor systems

vii)   Shirke’s 3S system

viii)   Precast RC planks and joists system

ix)  Light weight aerated concrete units

Precast roofing/ flooring components

(i) For use as flooring and roofing units, SERC (Structural and Engineering Research Centre), Madras has developed Precast funicular shells, channel units, hollow cored units and cellular units . These shells through form concepts of nature, utilising the strength, utilise minimum of materials to maximum structural advantage.

(ii) Precast ribbed units: They are essentially one way spanning system. These may be reinforced or pre stressed concrete depending upon their loading and span. And are in the form of a single or double Tee or a channel section and Light weight concrete slabs. These are structurally efficient and in addition provide a flat ceiling. Hollow cores can be used as service ducts.

Depending upon their loading and span, it can be reinforced or pre stressed.

(iv) Pre stressed hollow cored slabs: Spiral system has facility for producing pre stressed hollow cored slabs to any desired length and of 1200mm wide and 150mm thickness.

(v) Precast battens and hollow block construction can be used in pre tensioned floor strips. This precast flooring system is suitable for residential, school or office buildings.

 (vi) Plate floor systems: system developed by SERC Madras consists of this precast reinforced concrete plates elements of 4 cm to 5cm thickness used in conjunction with in-situ screeding concrete to act as a composite slab. The main advantage of this system are; elimination of centring, speedier construction, plastering of ceiling can be avoided and cost saving. Shirke’s 3S system -precast concrete squares

 (vii)  Shirke’s 3S system: In this, squares or rectangular columns of precast concrete are hollow at the centre, with 45mm  shell thickness. Beam used for 3S system are of standard cross-section and of various length and size as per the loading and span  requirements. For flooring and roofing,  light weight concrete siporex slabs (Light

(viii)  Precast RC planks and joists system- This roofing system consists of RCC planks placed over partially Precast RCC joists and over the planks and beams cast-in-situ concrete is laid.

(ix)   Light weight aerated concrete units: are manufactured in the form of blocks, slabs and reinforced slab strips. They are used in composite floors spanning in one or two direction. In many housing projects in India, these types of flooring have been adopted.

4.  Doors and windows

•    Various types and size of doors and windows are used in buildings. Normally timber and steel frames are used for windows and doors.

•  Cost can be reduced if standard and optimised dimensions and restricted number of doors and window sizes are evolved and thereby cost of construction can be economised.

5. Precast sanitary core units- Ferro cement products:

•   Ferro cement products are highly versatile form of Reinforced Concrete made of cement mortar, and wire mesh reinforcement and provide strength and serviceability.

•  Structures can be thin and light. It can be easily precast and in case of local damage it’s amenable to repairs. Conservation of timber, considerable saving in form work particularly for complex shapes and saving in cost is possible.

•   Service core units; Ferrocement consists of bathroom and toilet units, trusses and rafters and water tanks. E- units consisting of WC and bath units are also available.

6.  Design of joints:

recast building by its very nature of as strong as the connection between the individual elements, Joints are classified with respect to location, direction and function.

   •      Interior horizontal wall: wall to floor joint

•      Exterior horizontal wall: wall to floor joint

•      Horizontal :  floor to floor joint

•      Vertical : wall to wall joint

Provision of transverse, longitudinal vertical and peripheral ties in the precast building establishes the structural integrity and continuity.

RECOMMENDATIONS FOR THE ERECTION

1.   Setting out and marking: Prior to erection, all measurements must be checked and sufficient marks set out to enable fast and accurate erecting.

2.    Anchor bolts and dowel bars :In placing groups of bolts or dowel bars, one bolt (dowel bar) in each group should be getting out to facilitate location of the member, or even better the tops of all bolts (dowel bars) should be so defined that even the shortest bolt is sufficiently long to allow minor adjustments.

3.    Mortar or Cast -in-place Joints: The performance of these joints depends on the strength of the hardened mortar or in-situ concrete. The mix should be aimed at achieving full compaction with the available means, and on the other hand at keeping shrinkage to a minimum which calls for extensive curing.

Since hardening of the mortar (concrete) is influenced by the ambient temperature, heating of the mortar or the concrete and even heating of the adjacent precast concrete might be required during the cold season.

. 4 Dowel holes: For grouting, dowel holes with the following possibilities may be considered;

• Upward dowel holes can be grouted either by injecting or by pouring a sand-cement grout containing a cement grout containing cement not susceptible to bleeding, or by a pure cement grout with an injection agent.

•  Downward dowel holes: which are cast in, can be grouted similarly. If they are drilled, these should be filled either with a grout to which a synthetic resin dispersion agent is added, or with a synthetic resin with a quartz filler. In any case these holes must be filled just prior to placing the dowel bars and must then be clean and air-dry.

  •  Recesses, pockets: Depending on the size, these should be filled with a dry to half plastic sand-cement mortar or in-situ concrete to which a synthetic resin dispersion agent might be added for better bonding.

5.  Welding of reinforcing bars

• Welds between reinforcing bars, pertaining to the same joint, should be identical as possible. To attain this, each pair of bars to be welded in the same joint should be so bent, and if necessary cut, that the distance between the welding faces are equal to that of the other pairs. Furthermore there must be sufficient projection to prevent overheating of the concrete and also sufficient room between the concrete faces for laying the welds, and the bars.

• A minimum distance of five times the bar diameter should be provided between the edge of the weld nearest to the concrete and the concrete face. Moreover, welding operations should confine to the relevant standard specifications, codes of practice etc.

Stability measures during erection

•   The overall stability of the structure as well as the stability of each element should be ensured by temporary supports, struts, braces etc. Until the connections are load transferring.

•  There should not be any obstruction to the erection equipment (cranes etc.) so that the order of erection can be ensured.

7.    Corrosion protection

•   Projecting reinforcing bars should also be corrosion protected over a short distance from both sides of the interface with a coating of epoxy, rust proof paint as they will prevent the corrosion at the interface between the precast element and the in-situ concrete or mortar fill and also set out for steel parts.

Conclusion:

•  Therefore, by opting for prefabricated building solutions like the ‘India Concept House’ over traditionally constructed homes, one can achieve cost savings both in the short term and over the life of the structure.

•  As the staging area is significantly limited, on-site waste generation is reduced on account of most of the construction taking place at an off-site location. At the same time it helps to reduce the impact of one’s activities on the environment due to reduced impact of construction at building sites for the benefit of future generations.

•  Also, it is more feasible to control waste in a factory, where it can be easily segregated for recycling, when it is created on an assembly line rather than at a building site.

•     Every citizen in general should be aware or made aware of the natural state of environment, its capacity to adjust and to prevent its abuse

•   Architectural design can play a large part in influencing the ways that social groups interact. Unnecessary development should be avoided if sustainable architects take initiatives in retrofitting old structures to serve new needs and also by developing sustainable designs which will help to create a sustainable way of living within a community.

Green and sustainable technology

·         Indoor Air Quality (IAQ) concepts, zero or low VOC paints;

·         Eco friendly materials and finishes used in green technology ;

Introduction:

Now let us see Green and sustainable technology. Our diminishing environmental resources due to the extensive use of the earth which has already exceeded the sustainable limits have resulted in environmental crisis ie. sudden growth of economic activity and human population, depletion of natural resources, ecosystem damage and biodiversity destruction.

Sustainable design: The concept reveals that natural world is an integral part of the human civilization and any design that preserve and perpetuate nature is called a sustainable design.

Sustainable design comply with the principles of economic, social and ecological sustainability which is also referred to as “Green design” “eco design” or design for environment and is the art of designing physical objects, the built environment and services that are eco friendly. Sustainability does not mean low quality of life, but it needs a change in attitude towards non greedy and less consumptive lifestyle.

In short, sustainability is the key to make the natural and cultural system capable of being continued over time and again. Attitudinal changes which embrace global interdependence, environmental stewardship and social responsibility and economic viability is the key for sustainable designs which must use an alternative approach to traditional designs that incorporates changes in the mindset.

.The new term Green buildings generally refers to the concept of using renewable resources and materials for construction as well as the management of the building.

• It ranges from the microcosm of designing small objects for everyday use (including furniture, furnishings, curios and accessories), through to the macrocosm of designing buildings, cities and the earth’s physical surface.

• Now a days, “Go green” is the growing trend in all fields like building architecture, landscape architecture, urban design, urban planning, engineering, Graphic design, interior design, industrial design and Fashion design etc.

• Sustainable landscape architecture is a means of designing outdoor space which can include ecological, social and economic aspects of sustainability.

•  Urban drainage system can improve habitat for fauna and flora, improves the recreation facilities also. The design of a green roof for a roof garden can also be a sustainable feature of a landscape architecture. .

Features of a green building According to P.C. Varghese ( 2007 are;

•      Efficient use of water

•      Energy efficient and eco friendly equipment

•      Use of renewable energy -solar or wind energy

•      Use of recycled or recyclable materials

•      Effective use of landscape

•      Effective control and building management system

•      Indoor air quality for human safety and comfort

Benefits of green buildings

•      Has less impact on environment

•      Enhances occupants’ comfort thus suitable for  health and safety

•      Gives long term economy because of less operating costs

•      Improves the output or productivity of occupants.

•      Many of the urban development projects nowadays try to incorporate these concepts into their designs.

•      Near cities where flyash is in plenty, some of the Govt. agencies such as CPWD insist that the infill material for framed buildings should be flyash bricks instead of clay bricks.

When older buildings are demolished, any good wood, stone is reclaimed, as well as wall panels, partitions etc and many other parts such as doors, windows, mantels hardware can be reused thus , reducing the consumption of new goods. are renewed and reused.

As per A.P. Mishra, Brajendra S. Kusmariya, and Rajendra K. Jain, (2015) Scientists must design safer and cleaner approaches to manufacture the products needed by mankind. the term “green chemistry” is defined as the “invention, design and application of chemical products and processes to reduce or to eliminate the use and generation of hazardous substances.”

Conclusion: Green technology, Eco city concept, Safe indoor air quality, Social sustainability and Sustainable landscape architecture all these contribute to a better living condition amidst urbanization, technological development and population explosion.