- 1 3.1 Introduction to Case Study
- 2 3.2 Assembling Method
- 3 3.3 Evaluation and Comparison
- 4 3.3.1 Cost
- 5 3.3.2 Speed
- 6 3.3.3 Labour Requirement
- 7 3.3.4 Quality
- 8 3.3.5 Productiveness
- 9 Aims
- 10 Description of Datas
- 11 Rationale for Combining Data Points
- 12 Result and Discussion
- 13 Comparison of Labour Productivity between Structural Building Systems
- 14 Cycle Time Comparison between Structural Building Systems
- 15 Summmary
- 16 3.3.6 Wastage
- 17 3.4 Decision
3.1 Introduction to Case Study
Pekeliling Flats is situated on the Lebuhraya Mahameru-bound Jalan Tun Razak, Kuala Lumpur. The flats are besides known as Tunku Abdul Rahman public flats. Pekeliling flats are one of Kuala Lumpurs earliest public lodging undertakings and were built in 1967. There were 11 residential blocks consisting 2,969 units.
For the building of the first pilot undertaking, the Government held a dialogue with a joint venture company Citra/Boon & A ; Cheah which intended to utilize the Gallic Tracoba System of building. But the dialogue was unsuccessful and the undertaking was later opened to public stamp. The stamp was finally awarded to Gammon/Larsen Nielsen utilizing the Danish System of big panel industrialised prefabricated system.Order now
The building was so launched in 1968. The strategy at Jalan Pekeliling comprises 4 blocks of 4-storey flats and stores, 7 blocks of 17-storey flats, numbering 3009 units and was completed within 27 month, including the clip taken in the building of the RM 2.5 million projecting pace for the prefabricated elements at 10? stat mis Jalan Damansara.
The whole building of the level is constructed utilizing the prefabrication of concrete box method which is similar to the “ British Truscon System ” whereby a standard through-shaped concrete boxes, which incorporate frontage walls made from lightweight stuffs, ceilings dwelling of plaster embarkation stapled and every bit good as internal adjustments.
3.2 Assembling Method
- The boxes are made by precasting the walls panels with ribs downwards and smoothing down the concrete as it has semi-set. Once the walls have hardened, they are so removed from the molds by agencies of an overhead gauntry and placed into a gigue.
- Foundations tablets are cast and on top of these precast concrete beams, inverted “ T ” cross subdivision are so laid.
- The boxes are now unloaded straight from the lorry and are placed in place upon these inverted ‘T ‘ beams.
- Once the boxes, which form one class from frontage to fa & amp ; ccedil ; ade have been bolted together along the wall.
- After the boxes are connected together at the structural floor degree of two connection home bases, which are bolted with bolts to weave inserts on either side of the joint.
- Once the boxes, which form one class from frontage to fa & amp ; ccedil ; ade have been bolted together along the wall, where once more the cast-in sockets which joined by steel home bases and bolts, there merely thin perpendicular articulations seeable.
- The perpendicular channels between the bordering ribs of the end-to-end boxes make stiff cross-walls of singular sound insularity.
- Horizontal support rods are lowered and concrete is cast-in, ensuing in the formation of a party wall.
3.3 Evaluation and Comparison
Industrialised prefabricated building of the Pekeliling undertaking was more expensive than the conventional system. Its cost was 8.1 % higher than a conventional lodging undertaking completed around that clip.
There are many advantages you can acquire if you are utilizing precast building method alternatively of utilizing unmoved building method. One of the advantages is the cost deduction. Using precast building method can salvage money or cut down the cost of building because:
- Waste Minimization
- Fewer trucks and less clip are required for building because concrete is made offsite ; peculiarly beneficial in urban countries where minimum traffic break is critical. When fewer trucks are required agencies lesser the cost needed to lease vehicles.
- The decrease in site labour – which partially offsets a deficit of skilled site workers.
Mass production every bit good as off-site production shortens project timeline, gives earlier return on investing, leting earlier tenancy and maintain in agenda. It is estimated that a precast construction takes up to 20 % less clip to build than a similar dramatis personae in situ construction. For illustration, the walls of a edifice can be manufactured while on-site foundations are being built. If the clip is over the agenda or due day of the month, the company needs to pay the amendss.
Provides long service for high usage applications and does non necessitate regular care ; salvage cost in long term.
Fewer stuffs are required because precise mixture proportions and tighter tolerances are accomplishable. Less concrete waste is created due to tight control of measures of constitutional stuffs. Waste stuffs are more readily recycled because concrete production is in one location. Sand and acids for completing surfaces are reused. Steel signifiers and other stuffs are reused. Decreased demands for formwork, entree staging and less trust on moisture trades. The decreased demand for site supervising by the chief contractor besides saves money. Compared to project unmoved concrete, the undermentioned per centums of nest eggs can be expected: 75 per cent in footings of formwork and staging and 90 % for wet concrete. Reclaimable – precast concrete constructions in urban countries can be recycled into fill and route base stuff at the terminal of their utile life.
Priced in the $ 55 – $ 65 scope per additive pes of wall, precast systems are competitory with other foundation walls, peculiarly when costs are examined as an assembly that includes termss and sub-slab drainage. Precast walls can be installed rapidly in any conditions. Because the concrete is cured in the mill, precast foundations can be backfilled every bit shortly as the slab is placed and first floor brace is in topographic point, heightening jobsite safety and site handiness. Door and window gaps, steel beam pockets, and brick shelfs must be cast into the panels, so orders must be customized. The wall sub-base must be compacted and leveled, similar to preciseness required of termss.
In doing cost comparings between alternate systems, it is imperative that entire like for like costs are considered. There are significant nest eggs to be made utilizing precast building which are non apparent when a direct elemental cost comparing is made with alternate building methods. To acquire an accurate like for like cost, whole edifice costs must be estimated. To accurately assess whole edifice cost, each of the advantages of precast must be accurately costed.
Savingss through factors such as earlier completion day of the months, built-in fireproofing, reduced formwork, staging, reduced wet trades and increased budget control can be important. Besides, fast-track procurance and building may understate capital costs by cut downing funding costs and procuring earlier rental income. The precast frame bundle typically includes columns, beams, floors, wall panels, stepss, landings, balconies etc. , all of which have an built-in minimal one-hour fire protection.
Specialist precast frame manufacturers will help design squads in measuring the range for standardised precast constituents for a peculiar undertaking. Budget costings and hard-on programmes can be prepared by the precaster on reception of outline drawings and a list of public presentation standards.
For contractors and specifiers, there is a large difference between monetary value and cost. While monetary value is but one component of cost, it is the initial, most seeable and the easier of the two to understand. Concentrating on monetary value is non a preferable scheme in any concern, particularly where high-quality, dependable manufactured goods are concerned. Alternatively, for precast concrete merchandises, the focal point should be on the Entire Cost of Ownership ( TCO ) .
How is TCO calculated? The Entire Cost of Ownership is equal to the amount of the four cost constituents: quality, service, bringing and monetary value.
In footings of cost elements, a distinguishable advantage of precast concrete over cast-in-place ( CIP ) is speed of bringing and easiness of installing, or service. Both contribute straight to take down Total Cost of Ownership. Precast concrete, particularly when produced in certified workss, boasts the extra benefit of higher quality. Controlled batch proportions placed under unvarying conditions systematically creates a better merchandise than can be cast in topographic point. For illustration intents, we will utilize an ordinary precast belowground construction.
On the building site, programming is an of import, unpredictable and expensive hazard. Nature stacks the cost odds against CIP concrete. It is a much quicker and less hazardous pick to hold the precast delivered and installed the same twenty-four hours instead than unearth, signifier, pour and deprive the CIP concrete, remedy, moist cogent evidence and backfill. Given the cost matrix in Example 1, it could salvage six yearss in building programming.
For illustration intents, see a typical below-grade construction. For the inside dimensions of a 4-by-8-by-4-foot construction of either precast ( 6 inches thick ) or CIP ( 8 inches thick ) , assume these facts:
- CIP requires three separate yearss to pour the base, walls and top. Bring arounding and depriving adds one twenty-four hours to each measure, necessitating six yearss to project on site.
- Damp proofing adds one twenty-four hours to the CIP procedure, numbering seven working yearss of open-hole clip.
- Leting an mean $ 350 per three-dimensional pace for little occupations ( ready mix, rebar, mastic, labour and equipment ) , the 4 three-dimensional paces of CIP required monetary values out at $ 1,400.
- Precast takes merely one twenty-four hours to present and put in, including backfill of the pre-damp proofed unit.
- The precast option to bring forth and truck to the occupation site monetary values out at $ 2,000.
- Installing the precast requires a four-hour minimal charge of $ 400 for a 20-ton Crane.
- Hardware costs for adjustments, embedded points, etc. , are indistinguishable for precast and CIP.
The TCO of precast is fixed at $ 2,400. However, the TCO of CIP is merely get downing at $ 1,400. That raises the inquiry among skeptics as to why a contractor would pass more for precast. But many savvy contractors and specifiers recognize that their costs are really less with precast.
The six yearss of extra programming are required by the mechanics of pouring and bring arounding concrete on site. The work could be done off site in a quality controlled precast works while other work on site advancements. Even if a contractor has a concrete crew making multiple undertakings on site, the efficiency gained by replacing every bit much precast as possible can non be ignored.
A contractor saves money for every minute he or she is in front of agenda. If a $ 1 million contract outputs a 10 per centum net income border and can be completed in 10 months that equates to $ 10,000 per month, or $ 333 per twenty-four hours in net income. Salvaging six yearss means an extra net income of 6 ten $ 333 or $ 2,000. Furthermore, that nest eggs is compounded by the riddance of general conditions costs of approximately $ 500 per twenty-four hours for the load of supervising, insurance, fixed and variable occupation site costs, etc.
And these are merely existent costs. Add to this the turning away of liquidated amendss, and the cost advantage of precast concrete becomes the overpowering pick. The cost advantages are summarized in Example 2.
The undertaking took 27 months to finish, inclusive of the clip taken in puting up the precasting mills. The building period was comparable to the fastest conventional building. Thus industrialised edifice has the undermentioned advantages in footings of clip economy.
- Salvaging of clip and stuffs involved in the hard-on of stagings
- Shorter building clip as a consequence of well planned and coordinated sequence of building
- Not affected by weather status as edifice constituents are manufactured in the mill, and there is no on-site concreting.
3.3.3 Labour Requirement
Industrialised prefabricated system enable labour economy of 30 % -40 % chiefly of skilled labors such as brick beds, plasterers and carpenters. In Malaysia, skilled labor in the edifice industry is scarce so it is expensive. The debut of industrialized edifice system can evidently better the state of affairs.
As we all know, labour can split into three types. There are unskilled labour, semi-skilled labor and skill labor. Labour productiveness is defined as the manhours required to finish the structural component of one unit house. A sum of 499 informations points were obtained from seven residential undertakings constructed between January 2003 and April 2004. Analysis of Variance ( ANOVA ) indicated that the labour productiveness was significantly different between four structural constructing systems for illustration. The average labor productiveness for conventional edifice system was 4.20 manhours followed by dramatis personae unmoved table signifier manhours, cast unmoved half tunnel signifier 1.88 manhours and precast concrete system 1.33 manhours. Furthermore, the analysis of crew size indicated that the mean crew size for conventional edifice system of 24 workers was significantly different from the IBS of 22 workers. However, the crew size within the IBS was found to be undistinguished. The rhythm clip measured in yearss per house was found to be significantly different between structural constructing systems with the conventional edifice system of 4.9 yearss, cast unmoved table signifier of 3.9 yearss, cast unmoved half tunnel signifier of 2.9 yearss and precast concrete system of 2.3 yearss.
The labour productiveness obtained from this survey could be used as a preliminary guideline for client or adviser to place the most appropriate edifice system for transporting out a building undertaking and finding the labour demand in the building industry. Further, the comparing of crew size indicated that the conventional edifice system of 22 workers was significantly different from the IBS of 18 workers. Similarly, the rhythm clip of 17 yearss per house for conventional edifice system was found to be significantly different from the IBS of four yearss. As a decision, utilizing conventional method necessitate more labors to be done on site comparison to the pre dramatis personae building or Industrialised Buildiing System ( IBS ) . When utilizing precast, the demand of labor will cut down because there is less work to be done site. The figure of labor besides will little compare to the in- situ building method.
The finished visual aspect of the edifice was of a much higher quality than that achieved in conventionally built low cost lodging units. In peculiar, the coating of interior walls was much better to that achieved utilizing cement-sand hollow blocks. There were serious environmental jobs and some emphasiss were caused as a direct consequence of the particularization of the system. These jobs can be overcome by alterations in the particularization.
There are many indispensable elements in building industry. One of them is building labour productiveness. Its chief applications include building planning, programming, cost estimating, accounting and cost control. As a affair of fact, international labor factors and besides suggested ways in which they could later be applied to find comparative international building cost and labour demand are generated by labour productiveness rates.
The survey on labour productiveness for building industry has been conducted by many research workers. However, the bulk of them put their concentration on labour intensive conventional unmoved building system. Merely a fat batch of attending is devoted to vexing inquiry such as productiveness measuring for industrialized edifice systems ( IBS ) in despite of the proliferation of the systems in Malaysia. The precast building system can be termed as industrialized edifice systems ( IBS ) besides. During the Eighth Malaysia Plan ( 2001-2005 ) whereby 600,000 to 800,000 houses are expected to be built, the demand for immense demand for lodging industry consequences in the development of these IBSs.
The conventional unmoved building system which is presently being used by the building industry is incapable to get by with the demand in a stipulated period. The method is labour intensive. Since this method requires a batch of work force, so it relies to a great extent on foreign workers. Therefore, productiveness research attending shall be swerved toward IBS which utilizes the doctrine of assembly activity. For productiveness betterment in constructing industry from trade activity to assembly activity, there is a enormous potency as depicted in Table 1.
Large figure of surveies focused on labour productiveness for individual operation such reinforcement saloon productiveness, productiveness of concrete and formwork productiveness, whereas, merely little attempt is devoted towards the combined labour productiveness for combination of all the individual operation that form the structural component of one unit house. Therefore, this conducted survey introduces a standardized information aggregation methodological analysis for mensurating and comparing the conventional and industrialized edifice systems in facets of labour productiveness and rhythm clip.
Description of Datas
The information for this survey were acquired from seven ongoing residential undertakings constructed between January 2003 and April 2004. A amount of 499 informations points were observed during that period. The information of undertakings gross floor country per unit house vary in size in interval between 60m? to 84m? . Prison guard contractors were in charged in four undertakings while the staying undertakings were built by a general contractor. In table 2, the undertaking features are presented. ( Refer to the Appendix for informations )
Carpenter, barbender, concretor and Crane operator were in charged in installing and hard-on of these structural elements. Therefore, the labour productiveness of one unit house is calculated as below.
Labour productiveness for structural component of one unit houses
=Crew Size woodworking, barbender, concretor and Crane operator x work timeBuilding gross floor country ( M2 )
=Total manhoursBuilding gross floor country ( M2 )
All informations were collected via a standardized information aggregation signifier as shown in Table 3. Every twenty-four hours, informations aggregators were designated to ongoing building sites and 30 proceedingss were spent per site for observation and record of the crew size, work clip and location of work topographic point. Daily observation is recommended because all workers were paid daily. Since workers absenteeism might happen during the building period and hebdomadal or monthly informations variableness are excessively big to enable dependable analyses, hebdomadal or monthly observation is non favourable. Daily observation can besides demo high grade of variableness due to assorted perturbation undertaking related factors but non every bit much as other observation. Observation on every hr is besides non suggested because it is really expensive and spends a batch of clip. Some confidential information was obtained through direct interview with the undertaking directors. Workers ‘ day-to-day pay is one of the confidential information. Besides that, regular interviews to place and understand any distinctive features hold and break to the undertakings were indispensable to carried out.
Rationale for Combining Data Points
The size of the information points has a great consequence on the rightness, truth and dependability of statistical analysis. When a individual independent variable is used, little sample with 20 informations points is ideal. And yet, a big sample of 1000 information points or more will do the statistical analysis sensitive and undependable. Furthermore, distinctive features in observations or unusual conditions will convey some inexact informations points that cause a deadly consequence on the analysis. The principle for uniting the information points from different undertakings into four structural constructing systems are as follows:
- All undertakings are residential undertakings. They consist of insistent structural designs. No particular formwork system is needed because they do non hold any distinctive features architectural characteristics.
- Workers in charged in all operations are semi-skilled and skilled workers. The manual sleight is about the same.
- The effects of conditions and temperature are minimized since all undertakings are located within 30 km distance.
Result and Discussion
The information analysis and consequences focus on two specific topics as described below:
- Labour productiveness comparing between structural constructing systems utilizing analysis of discrepancy ( ANOVA ) .
- Cycle clip comparing between structural constructing systems utilizing analysis of discrepancy ( ANOVA ) .
Comparison of Labour Productivity between Structural Building Systems
This subdivision evaluates the labour productiveness comparing between structural constructing systems. Table 4 presents the descriptive statistic for labour productiveness comparing between undertakings while Table 5 presents the labour productiveness comparing between constructing systems utilizing the mean information from the seven undertakings. Analysis of Variance ( ANOVA ) consequences of labour productiveness between the four edifice systems was found to be statistically important different as shown in Table 6. The precast concrete system was the most productive edifice system with labour productiveness of 1.33 manhours/m? followed by dramatis personae unmoved half tunnel ( 1.88 manhours/m? ) , cast unmoved table signifier ( 2.70 manhours/m? ) and conventional edifice system ( 4.20 manhours/m? ) . Taking the conventional edifice system as the benchmark of 100 % , the dramatis personae unmoved table signifier system achieved a building velocity of 135 % followed by the dramatis personae unmoved half tunnel signifier system of 155 % and precast concrete system of 168 % .
The consequence was in tandem with the figure of trades for each edifice system. For illustration, the conventional edifice system consisted of four major operations, viz. the hard-on of scaffolding and formwork, installing of support bars, casting of concrete and dismantlement of scaffolding and formwork ; hence, it was extremely labour intensifier. However, merely a few building operations are needed for industrialised edifice system. For case, the precast concrete system was pre-assembly in mill, therefore cut downing on-site labor input. Besides that, no staging is required for cast unmoved tunnel signifier system to back up the slab.
Cycle Time Comparison between Structural Building Systems
This subdivision examines the rhythm clip measured in yearss required to finish the structural component of one unit house. Table 7 shows the rhythm clip for each undertaking while Table 8 shows the mean rhythm clip for four structural constructing systems.
In Table 9, analysis of discrepancy ( ANOVA ) consequences indicated that there was important different between the four edifice systems in term of rhythm clip per house, . The average rhythm times were 4.9 yearss for conventional edifice system, 3.9 yearss for cast unmoved tabular array signifier, 2.9 yearss for cast unmoved half tunnel signifier and 2.3 yearss for precast concrete system. In term of per centum, the conventional edifice system required 26 % more rhythm clip than cast unmoved tabular array signifier system, 41 % of cast unmoved half tunnel signifier system, and 53 % of precast concrete system.
This survey has introduced the standardised informations aggregation methodological analysis for mensurating and comparing the edifice structural component of conventional and industrialized edifice system. Research workers are enabled to unite informations points from assorted undertakings to bring forth a larger database if they adopt this methodological analysis. The rational for uniting the information point is that the bulk of residential undertakings has a simple structural layout program and do non hold any distinctive features architectural characteristics. A sum of 499 labour productiveness informations points were obtained from seven ongoing residential undertakings. The consequences and treatment evolves on comparing between structural constructing systems in footings of labour productiveness and rhythm clip per structural component of one house.
In facet of labour productiveness comparing, the precast concrete system was the most productive edifice system with labour productiveness of 1.33 manhours/m? compare to the conventional edifice system with labour productiveness of 4.20 manhours/m? . Besides that, presuming the conventional edifice system as the benchmark of 100 % , precast concrete system achieved a building velocity of 168 % . For case, when the first house constructed utilizing conventional edifice system is merely done, whereas the first house constructed utilizing precast concrete system was done and the 2nd house is constructed about 68 % completed.
The comparing of rhythm clip per house indicated that the two edifice systems were significantly different. The average rhythm times were 4.9 yearss for conventional edifice system and 2.3 yearss for precast concrete system. In term of per centum, the conventional edifice system required 53 % more rhythm clip than precast concrete system.
Finally, the precast concrete system is preferred comparison with conventional edifice system because the edifice plants can be done faster since it requires less clip to build wholly.
In the field of structural concrete building, two basic constructs are by and large applied in pattern which is precast concrete building and conventional dramatis personae unmoved building. Wastage can be defined as goods that are damaged, out of day of the month, reduced, or by and large unsalable, which are destined to be thrown off and which are written off as a loss. Construction waste can be divided into three chief classs viz. material, labour, and machinery waste. However, material wastage is given more concern because most of the natural stuffs used in building industry come from non-renewable resources. The building industry is a major generator of waste stuff. Traditionally, building waste is defined as any stuff, apart from Earth stuffs, which need to be transported elsewhere from the building site or used within the building site itself for the intent of land filling, incineration, recycling, recycling or composting, other than the intended specific intent of the undertaking due to material harm, extra, non-use, or non-compliance with the specifications or being a byproduct of the building procedure.
Material building waste can be classify as natural waste ( ineluctable waste allowed for in the stamp ) , indirect waste ( stuff used for intents other than that for which it was ordered ) , and direct waste ( stuff which is encountered for ) . It is by and large known that there is a comparatively big part of the stuffs being wasted because of hapless stuff control on edifice sites. The job of stuff wastage is non an stray issue on building sites. It is besides an environmental concern. When building waste is viewed from an environmental position a different type of classification must be considered. The environmental standards include the consideration of solid waste. This is divided into four classs: risky waste production, non-hazardous waste production, inert waste production, and radioactive waste production.
The building industry consumes a important sum of edifice stuffs and produces big measures of edifice waste. Construction and destruction ( C & A ; D ) stuff is a mixture of inert and non-inert stuffs originating from building, digging, redevelopment, destruction and roadwork. The composing of building waste is divided into two major classs: inert stuffs ( soft and difficult inert stuffs ) and non-inert waste. The soft inert stuffs ( such as dirt, Earth and slurry ) can be reused as fill stuffs in renewal and Earth make fulling plants. The difficult stuffs ( such as stones and interrupt concrete ) can be reused in renewal plants and/or recycled for building work as farinaceous stuffs, drainage bedclothes beds and concrete application. The non-inert waste ( such as metal, lumber and packaging waste ) can be recycled or disposed of in landfills.
Further, it was shown that there is a noticeable difference in the coevals of material waste between pre-cast and in situ.In general, any decrease in on-site concreting leads to blow decrease. Precasting and prefabrication therefore offers important chances for the decrease of waste. In comparing, the wastage in using precast concrete building method has smaller sum than conventional cast unmoved building method.The chief ground behind this may be due to the negligible wastes arisen during transit and installing at the site.
The pre-cast concrete elements transported to the site were stored unit wise by makers themselves to avoid harm to the elements. Hence the waste originating during transit had been minimized and identified as nothing. Since pre-cast elements were supplied harmonizing to the needed length, waste originating during installing of elements was at a minimal degree and waste happening due to over ordination of stuffs was besides eliminated.
Further, the pre-cast elements were produced at mills under proper supervising utilizing steel molds which can be formed of different sizes. Therefore, the wastage of stuffs during fabrication besides reduced to a considerable sum.
On the other manus, there have larger sum of wastage due to conventional unmoved building than precast concrete building. This big measure of wastage for conventional unmoved building was identified due to the deficiency of supervising, inaccurate commixture methods, inappropriate type of equipment used, hapless storage of stuffs and hapless quality craft and this led to higher waste of stuffs in the undermentioned ways:
- extra cement being used to speed up the hardening procedure
- extra concrete being used due to the breakage of signifier work
- higher waste in theodolite and handling of metal and sand and
- extra concrete being used in uneven surfaces
The aim of an unmoved method is to extinguish and cut down the traditional site-based trades like traditional lumber formwork, brickwork, stick oning and to cut down labour content. Conventional dramatis personae in situ building method utilise lightweight prefabricated formwork made of steel, fibre glass or aluminium in order to replace the bing conventional lumber formwork. The method is suited for big Numberss of lodging units that require insistent use of formwork. The formwork can be reused as many times as possible with minimum wastage.
There is a noticeable difference between the waste of pre-cast building and in situ building. However, because of the important differences in other stuff wastes, it can be said that there is a important decrease of stuff wastages of pre-cast concrete compared to the stuff wastages of conventional unmoved concrete. Therefore it can be concluded that there is a important waste decrease when pre-cast concrete is used.
From the surveies that have been done, it can be concluded that the precast method is better than the conventional Cast-In-Situ method in footings of cost, velocity, labor, quality, wastage and productiveness.