A. Table Form
Table form is a large pre-assembled formwork and falsework unit, often forming a complete bay of suspended floor slab. It offers mobility and quick installation, fewer joints and better surface finishes. The table form method uses separate vertical forms for walls and horizontal table forms for floor slabs. The work is done in two stages. First, the walls are cast, and forms are stripped, the tables are then positioned, and the horizontal slabs are cast. Once the concrete has achieved sufficient strength, the formwork units are lowered, rolled out from underneath of the newly formed slab and moved by crane to the next position. (Appendix B : photo 2)
B. Tunnel Form
Tunnel form is one of the most frequently used methods of cellular construction as it is cost effectiveness, productivity and quality benefits are being realised on a variety of developments. Tunnel form usually can be reused for 500 to 1,000 times, and is an effective way to construct buildings that have repetitive elements or layouts, such as hotels, apartment blocks and student accommodation. During the construction process, Tunnel Form allows the contractor to cast walls and slabs in a single operation on a daily cycle. Every 24 hours, the formwork is moved so that another tunnel can be formed. This cut down the construction time significantly. (Appendix B : photo 3)
- Prefabricated Construction Method
Prefabricated construction method can be classified into on-site and off-site prefabricated. On-site prefabricated method involves casting structural building elements within site before erecting to actual location. On-site pre-casting provides several advantages over cast in-situ construction. These include mass production of units, cost and time reduction and improved quality of work (CIBD, 1992)[7]. Off-site prefabricated method involves transferring building operations from site to factory. All elements that can be standardised are pre-fabricated in the factory. Prefabrication allows a component to be built whenever convenient, so long as it is delivered to site on time. Normally, this method would involve the assembly of precast elements such as floor slabs, in-filled walls, staircases, etc. into place for incorporation into the main units, columns and beams. This method of construction has reduced the amount of site labour involved in site operations and increased the productivity of the industry.
A. Panel Building Systems
Panel Building Systems comprise of walls, floors and roofs in the form of flat pre-engineered panels that are assembled at site to form the box like elements of the structure. This system having a variety of structural bearing panels/frames shaped and designed for direct interconnection with one another panel. Each panel has an upper stud and a lower stud joined by at least one vertical stud. Generally, Panelised building systems come in two versions, ‘open wall’ and ‘closed wall’. ‘Open-wall’ panels are wall sections containing exterior sheathing only. Plumbing, wiring, insulation, and interior sheathing are installed at the building site. ‘Closed wall’ are shipped from the factory as complete wall systems with exterior sheathing utilities and interior finish materials. The advantages of the panel system are the panels can be produced using computer controlled equipment that transfers panel-cutting instructions directly from digital CAD drawings. The resulting components are precisely engineered and easy to inspect for quality control. Once the panels are shipped to the jobsite, they can be quickly assembled, speeding the onsite construction schedule. (Appendix B : photo 4)
B. Block System
Block Work Systems comprise of Interlocking concrete masonry units, lightweight concrete blocks, etc. (CIDB, 2003)[1]. The system is an alternative to the traditional bonded masonry system where the blocks in the wall are bound through mortar layers. For interlocking concrete masonry unit, the blocks are stacked on one another and three-dimensional interlocking protrusions are provided in the blocks to integrate the blocks into walls. Lightweight concrete block are structurally feasible, lighter weight compared to standard concrete block. Where block should be used to reduce strains on the masons' backs and resultant injury. Masons are able to lay more blocks in less time using lightweight block compared to standard weight block. The use of structural masonry blocks in building construction speeds up the construction process as a result of the elimination of mortar layers. Further, due to the self-aligning features of the blocks, the walls can be assembled at much faster speed compared to mortared masonry construction. (Appendix A : photo 5)
C. Frame System
Frame systems generally constitute parts of the structure, such as beams and columns, fabricated off -site but assembled on-site. Into these are fitted infill units, such as walls, partitions, floors, ceilings, and roofs. These latter elements are also usually fabricated off–site and assembled to the structural elements on-site. Generally, frame system consists of steel, precast concrete components and prefabricated timber frames. (Appendix B – photo 6)
- Composite System
The composite construction method involves casting some elements in the factory while others are cast on site. Types of precast elements usually produced are floor slabs, infilled wall, bathrooms, and staircase. These elements are placed for incorporation into main units, column and beams, which are usually, cast in-situ.
3. Roofs
Light weight galvanised steel truss system that provides for high speed on site erection through its simple fastening system. The simple fastening system enables easy on site assembly and significantly reduced burden some transportation costs, coupled with precision engineering, which means that there is no cutting or drilling on site. This truss system can be flat packed and assembled on site or preassembled at the factory. The trusses give the similar properties as conventional timber trusses but with many more advantages. The advantages such as not prone to shrinkage, warping, rot, infestation or moisture absorption, long term protection against insects and trusses are light easily handled and reduce the need for on site cranes. Light weight galvanised steel truss system enable a great deal of design flexibility. The truss is designed and engineered according to architects’ specifications and each truss is manufactured to suit the individual house or building design. (Appendix B – photo 7)
4. Windows and Door
Architecturally it is usual to have large windows on south and west facing facades to maximise solar gain and day lighting. There are many advantages in the use of window wall panels which can be delivered fully glazed and in sizes that provide a full room or dwelling facade in one element. This reduces the number of site joints and leads to more efficient installation. These can be combined with concrete or other panellised systems to advantage.
5. Internal Walls and Partitions
Drywall is a kind of factory made wall panel. It replaces the traditional brick and block dividing wall in buildings. It involves less labour and skill requirement, and provides a shorter construction time, better product quality and higher flexibility for future layout changes. Full height panels are assembled and conduits can be easily installed through its preformed tubular spaces with minimal cutting, jointing and patching up. Its lightweight characteristic, at about half the weight of solid concrete block reduces the dead load imposed on the building structure. The surface of the wall panel can be easily finished with a thin coat of skim plaster in lieu of the thick cement sand plaster in traditional block wall. Much less wet trade work is involved in the assembly process and less construction waste is generated at the end. There are many advantages of drywall over the traditional plaster wall covering methods. Drywall/Gypsum wallboard is applied dry, so no moisture need be introduced to the underlying structure during construction. Therefore save time waiting for the plaster to dry, and construction can take place. Drywall is less labour intensive for installation, finished wall interiors are easier to paint and maintain, weighs significantly less than plaster, putting less stress on structures and fire resistance that plaster.
6. Electrical and Mechanical Services
Electrical and Mechanical (EM) system are also one of the factor for ease maintenance and shorter the construction period. Similar to C&S, there are some of EM systems / equipments can be prefabricated at factories. For instance, by using the withdrawable type of electrical switchboard such as ‘Schneider Blokset’ can reduce the delivery and installation time; by using the ‘busway trunking system’ instead of cabling can also shorter the delivery and installation time. We can also introduce the under-floor trunking cabling system instead of cast-in system for open area like office. Beside, all these systems provide a flexible maintenance / modification advantage as the operator can modify the system as simple as ‘plug and play’. With this kind of advantage, operator can minimise the manpower cost and down time / interruption of a running system.
Various electrical and mechanical equipments can provide high efficiency, energy saving, less maintenance and long lifespan. For instance, High Efficiency (HE) motor, Variable Speed Drive, Soft Starter can be use for air-conditioning, fire fighting, plumbing and lift system. For Electrical system, we can use maintenance free dry type low loss transformer and high efficiency long lifespan lamp such as Metal Halide lamp, Mercury lamp and Compact Fluorescent lamp to reduce energy consumption and lesser replacement. High efficiency lamp with high lumen will reduce the quantities of installation and subsequently shorter the installation period. Programmable Logic Control (PLC) base system is an advance tool with above features. PLC provides flexible of control system modification, speed up design / fabrication / testing & commissioning time, energy consumption optimising.
7. Lift Shafts, Stairs and Balconies
Prefabricated lift shaft elements in concrete and steel that can be installed speedily. A major issue to be considered the differential movement between the shaft liner and adjacent construction, but if this can be dealt are considerable benefits from their use. Precast concrete stairs provide early construction access, but must be carefully protected. Steel staircases can provide with tread pans filled with concrete, tiling or other finishes at a later date. Balconies can be prefabricated but problems of tolerance have been found at installation time at construction site. However, sub-assemblies should be considered in such circumstances.
REFERENCE
1. CIDB (2003), Construction Industry Master Plan 2006-2015, CIDB publication
2. “www.doli.state.mn.us/pdf/bc_rules_mr1361.pdf “
3. Junid, S, (1986), Industrialized Building System. Proceeding of UNESCO/FEISEAP regional workshop.
- Badir, Y.F., Kadir, M.R.A. and Ali, A.A. (1998), “Theory of classification on Badir-Razali building system classification”, Bulletin of Institution of Engineers, Malaysia, October.
5. Ismail, E. (2001), “Industrialised building system for housing in Malaysia”, paper presented at
The Sixth Asia-Pacific Science and Technology Management Seminar, Tokyo, November.
6. Al-Khaiat, H., and N. Qaddumi. 1989. Technical Views on the Use of Pre-fabricated Building Systems in Kuwait Housing Projects. Journal of Housing Science. 13(3): 243-250.
7. Construction Industry Development Board (CIDB) (1992), Raising Singapore’s Construction Productivity, CIDB Construction Productivity Taskforce Report, CIDB, Singapore.