A case study pertains contractors who bids on projects from County of San Francisco, the Public Utilities Commission as well as the Water Department.
Most of these jobs include concrete of a well-defining and widely-used kind through quantities usually small in comparison to what is needed for residential or office building projects. Concrete is a very common construction material. Projects ranging from a single family home to a high-rise building all may need concrete for their foundation, slabs, columns, beams, walls, etc. to be constructed. In urban settings, the task of delivering concrete moreoften than not has been delegated to ready-mix batch plants and contractors has to rely on the timing and reliability of their service.
Although this set-up puts the contractor‟s project somewhat at the mercy of the batch plant, most batch plants perform at their very best to meet their customers‟ schedules.
On-time delivery is part of the product they sell. The interplay between contractors and batch plants is interesting. On one hand, the contractor must order a large enough quantity, sufficiently long ahead of time to ensure available batch plant capacity and timely delivery service in order to maximize productivity of their placing crew.
On the other hand, the batch plant tries to time its deliveries so that all projects are served according to the contractors‟ needs and the plant as well
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as the trucks and drivers have little idle time. This balancing act between the two parties is not always achieved due to the nature of concrete and the nature of the production systems being used.
In addition to contractors and batch plants, this balancing act also involves the suppliers of raw materials to the batch plant, crews on site that erect formwork and tie reinforcing basin preparation for concrete placement, as well as others.
Although the interdependence of all these parties typically results in uncertainties rippling through the supply chain, the focus of this paper is limited to the downstream-, namely the contractor vs. batch plant relationship.
The batch plant could, in order to level its load, vary its unit price of ready-mix concrete based on the time and day of the week at which concrete is to be delivered. This would illustrate a market mechanism at work, however, we are not aware of such differential pricing being advertised in the industry today.
As one can imagine the city imposes limits on working hours in order to avoid congestion during peak traffic times, excessively long closure of a road for vehicular or of a sidewalk for pedestrian traffic, undue inconvenience of road users and complaints about noise from citizens or area residents. In addition, contractors must obtain a work permit from the city in order to work at a specific location.
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This contractor s main concern has been tardiness of deliveries made by batch plants. Because most of these jobs have restricted working hours, punctual delivery is of paramount importance.
However because each order is small ( a few cubic yard at a time),this Contractor cannot get any plants attention. Went plant truck arrive late to his jobs, he loses that time for the concrete to set and may therefore not be able to open the site to traffic when needed.
To achieve on-time performance this contractor has acquired a fleet of small revolving-drum trucks as well as dump trucks (used to fill „potholes with concrete) to meet his projects concrete transportation needs, The latter trucks are not so good as the former for transporting concrete as the mix may segregate.
This contractor has its trucks pull into any batch- plant during operating hours and order concrete. The contractor-owned trucks simply join the line of plant trucks waiting to be loaded. The driver then goes to the operator‟s walk-up window and orders the needed mix design and quantity. The batch plant fills these trucks in the same way as it fills its own in a first-in-first-out manner. The contractor then gets billed on a regular basis for exact amount loaded. At the site, the driver works with the crew in placing concrete.
Providing one‟s own ready-mix trucks does not mean that the unit price of concrete is any cheaper but it overcomes many scheduling hassles. No advance order needs to be placed to reserve plant capacity as only a few cubic yards of commodity mix are needed each time.
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By taking control over the transportations process and the contractors crew can work at their own pace and not have to fret over when concrete would arrive.
This kanban system work well especially on these projects where timing of need is not dictated exclusively be the contractor, but as is the case here also to a significant extent by the owne.This contractors has its trucks pull into any batch-plant during operating hours and order concrete. The contractor-owned truck simply join the line of plant trucks waiting to be loaded. The driver then goes to the operators walk-up window and orders the needed mix design and quantity.
The batch plant fills these trucks in the same way as it fills its own, in a firstin- first –out manner. The contractor then gets billed on a regular basis for exact amount loaded. At the site the driver works with the crew in placing concrete.
Providing ones own ready mix trucks does not mean that the unit price of concrete is any cheaper but it overcomes many scheduling hassle. No advance order needs to be placed to reserve plant capacity as only a few cubic yards of commodity mix are needed each time.
By taking control over the transportation process and using trucks as kanban each time concrete is needed, the contractor‟s crew can work at their own pace and not have to fret over when concrete would arrive. This kanban system works well especially on these projects where timing of need is not dictated exclusively by the contractor, but as is the case here, also to a significant extent by the owner.
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This contractor thus controls what is otherwise a system variable controlled by an upstream supplier, namely the batch plant‟s delivery of concrete. As a result, the contractor can better schedule his work and be more reliable in making project due dates. Should one batch plant not be able to serve his needs, he can easily go elsewhere. The contractors pays for this ability. He now needs to have capital tied up in trucks and is responsible for hiring and training drivers. Because he has a fairly steady need for concrete from one project to the next(contrary to many other who need concrete only for one phase of their work.)he can keep them gainfully employed.
Ready-mix concrete is a prototypical of a JIT production system in construction. Two practices regarding ready-mix batching and delivery were described in this paper and depicted using value stream mapping symbols.
Each case highlighted the presence of buffers of information, materials, and time as well as production order and withdrawal mechanisms positioned at strategic locations to meet specific system requirements, as defined by the nature of the contractor‟s work. One alternative is favored over the other depending on the amount of control the contractor wants in terms of on-time delivery of concrete and the variability in the contractor‟s demand for concrete project after project. While these practices clearly exemplify JIT production, the paper was limited in scope. No data was included to characterize the actual performance in terms of timeliness, buffer sizes, error rates, etc. Moreover, the paper focused on batching and delivery, which are only parts of the entire concrete production system.
Current practices for managing the concrete supply chain upstream in terms
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of raw materials acquisition or prerequisite work on site are not geared oward JIT production. Further investigation is therefore warranted and significant process improvements may be achieved by those working towards fully implementing a lean construction system.
Case Study 2 :
Fakuda Production System (FPS)
The construction companies that adopted the Toyota Production System and Just in Time on a large scale in Japan are Fakuda Corporation in the field of building construction and couple of companies in the field of housing construction. Fakuda Corp. is a Niigita-based construction company having annual sales of $ 946 million (in 2003).With the objective of making construction work more efficient and reducing construction costs, the company introduced the system in construction work in 2002.
In order to introduce the system the company received guidance from consultants CULMAN CO.LTD who were former employees of Toyota otor Corp. This building production system is called the Fakuda Production System ( FPS)
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The material distribution facilities were established so that materials can be delivered to the site JIT. In addition, the JIT material distribution network was set up to link the field office,branch offices, and material distribution facilities, Necessary materials are delivered to the predetermined location(
Room C on Floor B at Site A,for example)in time. To visualize the JIT delivery process, the JIT delivery system board is posted to boost awareness.
Time is Money among
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workers. The JIT ideal is elimination of physical buffers (materials or time)between production processes, and the achievement of one piece flow within processes, i.e. batch sizes of one.JIT was able to virtually eliminate such in-process inventories because production scheduling provided sufficiently stable coordination of flows. Construction scheduling does not provide such stabilization. Consequently, it is not appropriate to simply eliminate physical buffers without first attacking the causes of variation and uncertainty. Even though manufacturing and construction share the same ultimate objective of reducing variation and waste, their strategies for achieving that objective must be different. Materials constitute a huge proportion of the cost of construction. Materials are sometimes ordered weeks or even months ahead of requirement leading to uneconomical inventory on construction sites or contractors' warehouses. Building material inventory represents cost to procure, cost to store and insure, cost to guard against theft and cost incurred when inventory becomes obsolete. This paper presents an overview of the Just-in-Time (JIT) production system and discusses application and implementation issues for the control of material inventory in building construction.
JIT ensures that suppliers deliver directly to the production floor to achieve either a reduction in inventory or zero inventory and consequently a reduction in production costs. Implementation of JIT building material management in construction has the potential to realize the same far reaching benefits experienced in manufacturing. Relevant factors to consider in JIT implementation for material inventory management in construction are implications for construction output and quantities, production planning,
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design planning, construction contractor and suppliers' relationships, material sourcing, and education and training.
Case Study 3
The Byggelogistik project
Up till now Byggelogistik has been tested on six housing schemes, the first being Sophiehaven approximately 20 miles north of Copenhagen. The project is a typical Danish social housing project comprising 100 flats in two stories blocks, erected in two phases - not a big project on an international scale (Bertelsen 1993, 1994-1, 1994-2). Contractually the project was undertaken by a general contractor and approximately 10 trade contractors.
The general contractor's staff participated in the whole planning of the project. It was also from the staff of the general contactor that the provider was recruited and his job developed, as the project progressed, into being the production manager of the construction site. He planned the day-to-day operations, he provided the materials required, he coordinated the individual trade contractors' works and he followed up on the co-operation with the wholesale dealers. In order not to overreach the experiment in the first phase it was decided to restrict the logistics to a minor number of the trades. This decision caused a great deal of trouble. Those not participating were repeatedly in the way of those who were. In the second phase all trades participated and this problem was solved. Even though the methods were developed with EDP in mind the first tests were restricted to management by
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paper and pencil only. EDP was used in the usual manner in the participants' own operations but no attempt was made to use IT in the logistics.
Inspired by the Toyota Production System the aim of Byggelogistik is to reduce cost by eliminating waste of all kinds. Foremost waste of materials, but also waste of labour time and transportation. In this the Byggelogistik concept is an instrument for making the whole building process more effective. The main objective is to look not only at direct transportation costs but at all costs in the building procesrelated to materials delivery. Materials are not considered delivered until the workers lay their hands on them in the exact quantity as the first step in the construction. Packing, temporary storage, on site transportation, on site losses and breakage, and low effectiveness due to badly and impedingly delivered and stored materials are all considered as belonging to the transportation costs. A Swedish study (Hammarlund 1989) has shown that approximately a third of the time used by the worker on the building site is spent procuring his materials in the widest sense, equalling about 10 percent of the total building cost. The hypothesis of Byggelogistik is that a near-optimum form of supply will increase costs only marginally, but will reduce waste of time considerably.
This means that materials delivery in Byggelogistik is looked upon from the point of view of an optimum building process primarily.
Byggelogistik (Bertelsen 1994-1) makes use of a two level logistics with a planning approach for the over all logistics and a JIT consumption approach for the daily deliveries. The logistics are considered already on the
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drawing board. Materials are, where it is possible, specified as belonging to the separate building operation during the detailed design.
In the planning of the operations all supplies are described in detail aiming at JIT supply once a day, comprising only materials needed until the next day, and packed for the various trades and heir individual tasks and work areas.
Such assemblies of materials are named 'units'. Each type of unit is carefully specified to include all materials needed for the particular task, and form of packing as well as equipment for the delivery is detailed. Each type of unit is given a specific number for identification. Several participants in the project consider the unit the most original element in the whole concept. The idea is taken from the Swedish furniture chain Ikea who sells furniture in parts to be assembled by the customer but with all the parts – and often tools and assembly instructions in the same box. In order to manage sorting, packing and delivery a close co-operation with the wholesale dealers must be established. In Denmark 3 kinds of dealers cover all necessary materials, and their warehouses are used as store room for the building site. A few kinds of materials are Delivered directly in units packed by the manufacturer, but most materials are delivered to the warehouse to be sorted and packed in units, ready for transportation as the work progresses. In order to reduce the costs of external transportation joint deliveries are used containing all units from the dealer regardless of contractor, and to minimize internal transportation delivery of units takes place as close to the work area as possible. The dealers' drivers are considered as part of the building team in as much as the aim is to employ the same drivers to load the trucks and deliver the materials every day thereby making them familiar with the ever
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changing lay out of the building site and choose the best sequence for the unloading.
Byggelogistik is characterized by careful planning, daily management executed from the building site - not the head office - and immediate and direct feed back of all mistakes. Careful planning demands that detailed design is fully completed before the building process is started, in order that all materials may be counted and specified in units. In this way delivery schedules on a weekly basis may be worked out right from the start, covering the entire building period, and all materials may be ordered bindingly. Planning must take place in close co-operation between designers and trade contractors, and the wholesale dealer's employees should take part in this. Tests have shown that this kind of co-operation has resulted in a good deal of suggestions for more appropriate solutions and choice of materials. At the same time better terms for delivery are obtained since favorable prices may be offered by the producers due to early notice.
Construction JIT will be advanced by implementing demonstrated techniques and industry research to test theoriesand develop new tools and techniques.
Research topics have beenproposed that constitute a strategy for implementing
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Unit – 9 CASE STUDY IN MALAYSIA (PUTRAJAYA) AN OVERVIEW ON THE CASE STUDY PROJECT
Presint 9 is the selected project to be used as our case study in this task. The selection was made because Presint 9 is one of the examples of constructions using the IBS technique. Located in our Government administration areas, this Presint 9 is one of the projects in the development of Putrajaya areas.
Presint 9 is the residential area construct by Setia Putrajaya Sdn. Bhd. The company had managed to complete the construction of Presint 9 in a minimum time by using the IBS method of construction.
Based on the observation carried out by Putrajaya Holdings, noticed that the contractor only need four (4) month to complete the full structure of the apartment until level six (6) comparing to the used of conventional method that can only construct full structure of the building until level four (4) in the same period. Based on this statement prove that by using the IBS system to the construction of the building may reduced the time for the completion. It also be noted that this IBS system not only give the advantages in term of time to this construction but also give benefit in term of cost for the development. The contractor managed to reduced cost on labor because this method will reduced the used of labor in the construction.
Based on the observation carried out by Putrajaya Holdings, noticed that the contractor only need four (4) month to complete the full structure of the apartment until level six (6) comparing to the used of conventional method that can only construct full structure of the building until level four (4) in the same period. Based on this statement prove that by using the IBS system to the construction of the building may reduced the time for the completion. It also be noted that this IBS system not only give the advantages in term of time to this construction but also give benefit in term of cost for the development. The contractor managed to reduced cost on labor because this method will reduced the used of labor in the construction.