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In this Chapter 2, it is the literature review of pre-fabrication construction method in construction industry. First, it will be reviews on the pros and cons for pre-fabrication and cast in-situ as applied in Malaysia's construction industry. Next, will be review on the comparison of construction cost of prefabrication and cast in-situ technology in typical wall element. Last, the review on the construction speed between pre-fabrication and cast in-situ method in typical wall element.
IBS is a technique of construction, which introduced by CIDB was succeed and applied the prefabricated technology into the construction industry in Malaysia. IBS is define as a construction system in which components are manufactured in a factory, on or off site, positioned and assembled into structure with minimal additional site work (CIDB, 2003). Dietz, A.G.H (1971) earlier defined IBS as total integration of all subsystem and components into overall process fully utilising industrialised production, transportation and assembly techniques.
The benefits of IBS systems are to reduce the construction time, convenience for site management, better productivity, better quality control, reduced wastages of materials, etc. In order to having an industrialised construction industry and achieving Open Building by the year 2010, CIDB has introduced IBS Roadmap 2003-2010 in order to achieve the aim. There have 5-M strategy in IBS Roadmap 2003-2010, there are manpower, materials-components-machines, management-processes-methods, monetary and marketing.
In the late 60s, IBS has been used in Malaysia. The first IBS project was a construct 7 blocks of 17 storeys flats, which involved 3000 units of low-cost flat and 40 units of shop lot along Jalan Pekeliling, Kuala Lumpur in the year 1964. This project was using the Danish System of large panels in a pre-fabricated system in which undertaken by Gammon/ Larsen Nielsen. After this, the government had launched a second project in the year 1965. The project was using French Estoit System that undertaken by Hochtief/ Chee Seng. The project was a construct 6 blocks of 17 storeys flats and 3 blocks of 18 storeys flats at Jalan Rifle Range.
There are many factors (pros and cons) need to be consider as to whether or not the pre-fabrication will be more economical or efficiency than the conventional construction method, which is cast in-situ. According to Nicolas S.Y. Yeung, Albert P.C. Chan and Daniel W.M. Chan, pre-fabrication will contribute to improved build ability and associated efficiency gains in terms of time, cost, quality, safety and environmental targets. Table 1 below are the summary of the advantages and disadvantages for pre-fabrication and cast in-situ method.
In order to make the installation procedures successful, meeting is the most important issue needs to be carrying out with all the parties involved like Employer, Consultant, Contractor, employees, labours, etc before installations. The discussion during meeting should included the site access for deliver the pre-fabricated components to site, components' size and weight, installation procedures, storage issues, etc. It is important that the Employer and other parties to understand the installation procedures and function for the final output.
The delivery trucks should have a clear access to the site and can lift those components to the site safely without cause any damage of the works around the site. In addition, the site area mush be accommodate for the components handling and storages. Upon the components delivered to site, the site must be able for crane to move around the product to the selected location without coming in close with other works.
The schedule for the installation procedures should included detailed information such as when the pre-fabricated components need to join. Before process the works accordance with the schedule, the schedule first should be reviewed and agree by the Contractor or Construction Manager. Normally, the crane for located those components around the site are very expensive, which it can be a heavy-duty crane. Therefore, it is important for the schedule properly prepared in order to make the installation run smoothly and reduce the construction cost.
2.3.4 Lifting System
If the pre-fabricated components are small and light, it can install and lift by using light-duty crane. On the other hand, if the components are very large and heavy, it can found difficulties in lifting in which required heavy-duty crane to lift the components to selected location. Besides, if the components no need to be turned vertically like pre-fabricated floor slab, it can be lifted straight away from the truck to the selected location. If the components need to be turned vertically like pre-fabricated brick wall, it is more difficulties to hook up the components. According to the DOSH, all the lifting hardware must have a certification verify the capacity and safe working load.
Most of the components usually lifted on top of the structures to the selected location. However, if the components need to be place and there have existing structures on top of it, it can found complexity because of the nature of final locations and the surrounding elements already fixed in place. Besides, for the components need to fix vertically in existing structures like wall elements, it can also found difficulties in which the components cannot damage surrounding structures.
2.3.5 Bracing and Stabilizing
Certain pre-fabricated components required a temporary bracing and stabilizing to against loads like incomplete works, wind, movement, etc in order to join those components successfully. Therefore, on site should stored some bracing and readily available when it is needed. Bracing should not take out until the pre-fabricated components are within the tolerable placement and the proper connections have made. This is because when the pre-fabricated component has erected and the crane still carrying the load, the bracing may attacked.
Some of the pre-fabricated components required welding and only certified welders could carry out the welding process. Normally, the pre-fabricated components need to weld immediately after the component placed. At the same time, it required adequate workspace for welders to the welding process. After the components have welded, the site inspection is required in order to prevent the connections exposed to weather. If found that the connections have exposed to weather, the weld need to be cover with the protective coating.
Grouting either is carrying out before or after the pre-fabricated components has placed. Some of the components after placed in proper location may require grouting. The purpose of grouting is to remove of air voids.