1.1 New Construction Techniques for Modern Housing Schemes New Construction Techniques for Modern Housing Schemes Asoka Perera Professor of Civil Engineering Department of Civil Engineering University of Moratuwa 1.2 New Construction Techniques for Modern Housing Schemes • Background – Sri Lanka’s construction industry is yet to be benefited from technologies developed for housing – Small scale applications are visible but largely the construction technology is reinforced concrete, bricks, blocks and other traditional methods. – However many other countries have implemented new housing technologies and getting the benefits. For example Government of Thailand have decided to use pre-cast concrete methods to construct more than 500,000 housing units to solve the housing problem. – Similarly in India the use of new methods have increased. – Generally new methods are cost effective, fast, better appearance, better planned settlements and durable. OVERVIEW 1.3 New Construction Techniques for Modern Housing Schemes OVERVIEW 1.4 New Construction Techniques for Modern Housing Schemes OVERVIEW
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New Construction Techniques for M odern Housing Schemes
New Construction
Techniques for ModernHousing Schemes
Asoka Perera
Professor of Civil Engineering
Department of Civil Engineering
University of Moratuwa
1.2
New Construction Techniques for Modern Housing Schemes
• Background
– Sri Lanka’s construction industry is yet to bebenefited from technologies developed for housing
– Small scale applications are visible but largely theconstruction technology is reinforced concrete,bricks, blocks and other traditional methods.
– However many other countries have implementednew housing technologies and getting the benefits.For example Government of Thailand have decidedto use pre-cast concrete methods to constructmore than 500,000 housing units to solve thehousing problem.
– Similarly in India the use of new methods haveincreased.
– Generally new methods are cost effective, fast,better appearance, better planned settlements anddurable.
OVERVIEW
1.3
New Construction Techniques for M odern Housing Schemes
OVERVIEW
1.4
New Construction Techniques for Modern Housing Schemes
New Construction Techniques for M odern Housing Schemes
• The main pitfall – Many believe alternative materials or methods is
the way to reduce cost or to increase speedcompletely forgetting the design aspects.
– The design aspects are very poorly addressed orcompletely ignored due to the fact thatArchitects, Structural Engineers and ServiceEngineers need to work as a team. Howevermain cost savings are in the area of design.
– It is no doubt that new materials and methodscan be cost effective on top of the designaspects. Further alternative materials andmethods can address some pressing problemssuch shortage of river, shortage of skilled labour(or high cost) etc.
HOUSING TECHNOLOGIES :OVERVIEW
1.10
New Construction Techniques for Modern Housing Schemes
• Three methods
–Design methods, optimization programs etc.Structural Design optimization is a goodexample.
– Alternative construction materials. Materials
such compressed earth blocks, fly ash blocksare good examples.
– New construction methods. New slabconstruction methods, Pre-cast concrete
methods, Ferrocement methods
HOUSING TECHNOLOGIES :OVERVIEW
1.11
New Construction Techniques for M odern Housing Schemes
HOUSING TECHNOLOGIES :OVERVIEW
Tec hnology P ossible Cost
savings
Implementation Challenges
1. D esign
methods
Structural Design
Services design
such as
electrical,
plumbing
Architectural
Design
Up to 30% savings
Up to 20% savings
Up to 20% savings
1. More design work
2. No additional fee, in fact the fee could get
reduced
3. Lack of confidence
4. Lack of familiarity with design methods such as
masonry design.
5. Naturally would like to be extra safe
6. Bill is paid by the client
7. No mechanism to check or to challenge the
efficiency of the design. Very common system
character
8. May require the use of advance methods such as
value analysis – A technique use USA military.
9. Getting and compiling technical information is
difficult.
10. Most popular may not the best.
11. Similar reasons of structural design.
12. Most difficult area for cost applications.
13. People buy Maruti cars as well as Benz cars
1.12
New Construction Techniques for Modern Housing Schemes
HOUSING TECHNOLOGIES :OVERVIEW
Technology Possible Cost
savings
Implementation Challenges
1.Alternative Construction
Materials
Compressed Earth Blocks(CEB)
Waste related products such
as fly ash blocks
UPVC
Cement tiles
Up to maximum of
20% cost savings.
Generally claimedas cost effective or
appear to be cost
effective but not
necessarily.
1.Compliance with existing standards.
Fore example CEB to comply with
BS5628.
2.Lack or non-existence of standardsparticularly for manufacture.
New Construction Techniques for M odern Housing Schemes
• Three methods
– Most cost effective design method. For
example a masonry design could be 30% costeffective than reinforced concrete framearrangement. On the other hand for a buildingof 8 storeys reinforced concrete frame buildingcould be more cost effective than a masonrydesign.
– Cost optimization within a design. Costoptimization can be done to find out the mosteconomical steel and section arrangementconsidering the prices of concrete, steel andformwork.
– Use of value analysis for design of servicessuch as electrical work, plumbing etc.
HOUSING TECHNOLOGIES :DESIGN METHODS
1.14
New Construction Techniques for Modern Housing Schemes
• Most Cost effective Design method
– This could explain best with anexample. For example any house of twostorey and above can be taken. Theexample was taken form Tsunamihousing project in Ratmalana. Eachblock is consist of 8housing units andfour storeys
HOUSING TECHNOLOGIES :DESIGN METHODS
1.15
New Construction Techniques for M odern Housing Schemes
HOUSING TECHNOLOGIES :DESIGN METHODS
1.16
New Construction Techniques for Modern Housing Schemes
New Construction Techniques for M odern Housing Schemes
• Most Cost effective Design method
– The initial arrangement was typicalreinforced concrete frame buildingswith independent footings with plinthbeams, columns, beams and slabs.Table below shows the arrangementcost comparisons with masonry loadbearing wall structure.
HOUSING TECHNOLOGIES :DESIGN METHODS
1.18
New Construction Techniques for Modern Housing Schemes
HOUSING TECHNOLOGIES :DESIGN METHODS
Element
Normal RC Design Masonry Design
Total Cost Total Cost
Footings in foundations 346,546.0 217,338.0
Plinth Beams 104,591.0 71,884.0
Rubble masonry infoundation 79,650.0 223,680.0
Columns 467,265.0 84,460.0
Beams 759,133.0 0.0
Walls 1,040,480.0 1,075,480.0
TOTAL 2,797,665.0 1,672,842.0
Net Saving 1,124,823.0
Saving % 40.2%
Net saving of the project 53,991,504.0
Total Estimate 429,600,000.0
Saving of the project % 12.6%
1.19
New Construction Techniques for M odern Housing Schemes
• Elemental optimum Design :Example froma RC slab
–
Slab also an expensive element in buildings.The optimum slab thickness is the one justsatisfies the deflection requirement and bestreinforcement arrangement is the one justsatisfies the bar spacing requirement (crackcontrol). However when spans becomes larger
the strength requirements supersedes theabove requirements.
HOUSING TECHNOLOGIES :DESIGN METHODS
1.20
New Construction Techniques for Modern Housing Schemes
• Elemental optimum Design :Examplefrom a RC slab
HOUSING TECHNOLOGIES :DESIGN METHODS
Normal RC Design Optimum DesignTotal Cost Total Cost