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EXTENDED ABSTRACT
APPLICATION OF LEAN CONSTRUCTION CONCEPT WITH PULL SYSTEM SIMULATION IN PRECAST CONCRETE PRODUCTION AND ERECTION
PROCESS
( Case Study : Rusunawa Jatinangor ITB Construction Project )
Pandu Prabowo Indrajaya Student ID : 15008039
(Civil Engineering Study Program, Faculty of Civil and Environmental Engineering) The amount of waste in the construction process is a problem that needs to be considered by constractors. Waste in construction process affects construction completion time , available space during the construction process, and also relates to project cost. The lean production was introduced by the manufacturing industry in an effort to reduce waste during the production process. This principle was later adopted in the construction environment as lean construction (Koskela 1993). Lean construction principles give attention to efforts to reduce waste and increase the value . Problems are often encountered in the implementation of the use of precast concrete construction, among others, the uncertainty on variation of demands from construction site and the imbalance between the production of precast concrete in the casting yard to the installation process in the field which resulted in a substantial product inventory in the stock yards which is a waste.
Production process control system plays an important role in this regard. Currently there are two process control system, the push system and pull system. A lean supply system adopts a pull system in the control of the production process. The study was preceded by the creation of CSM ( Current State Mapping ) and FSM ( Future State Mapping ). Then push and pull model system is made based on these mappings. The CSM and FSM models introduced in this research are modified versions of a previous study conducted by Purnama (2005) based on the model of Tommelein and Weissenberger (1999). This final project work simulates the precast concrete production and erection process in a rusunawa building construction by introducing lean process principles. Web cyclone is used as process simulation tool. Figures 1 and 2 show the simulation scheme for the push and pull system. Table 1 shows the simulation result.
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2
Fixed Tower Crane Available Clean,instal & Set
Forms 3
Forms Ready
4
Pour Concrete Steel Bar Available
Concrete Ready-mix Available
Concrete Placed
Spread, vibrate, finish 2
5 6
7
8
Concrete Finish Curing
Concrete Cured Strip & Lift Out
Concrete Concrete Available
Lift Into Stock Yard Concrete wait in
Stock Yard Erect Into
Construction Site
9 10
11 12 14
13 15
16 17
Spreading Tool Available
Curing Bag Available 20 19
Concrete Form Available
18 1
Figure 1. Push System Model Simulation
Fixed Tower Crane Available Clean,instal & Set
Forms 3
Forms Ready 4
Pour Concrete Steel Bar Available
Concrete Ready-mix Available
Concrete Placed
Spread, vibrate, finish 2
5 6
7
8
Concrete Finish Curing
Concrete Cured Strip & Lift Out
Concrete Concrete Available
Lift Into Stock Yard Concrete wait in
Stock Yard Erect Into
Construction Site
9 10
11 12 14
13 15
16 17
Spreading Tool Available
Curing Bag Available 20 19
Feed Back (Kanban Withdrawal and
Production 21
18 Concrete Form
Available 1
Figure 2. Pull System Model Simulation
3 Table 1. Simulation Result
Based From Simulation
Real Condition No Parameter Push System Pull System
1 Simulation Time 64 days 77 days
2 Produktivity 0,034 unit/min 0,028 unit/min
3 Avg Inventory 5 component 3 component
4 Max Inventory 65 component 53 component
5 Waiting Time 137 min 79,5 min 3-7 days
6 % idle Pracetak 48, 2% 34%
7 % idle Tower Crane 33,2 44,2%
Based From Calculation
Real Condition No Parameter Push System Pull System
1 Production Time 53 days 103 days 63 days
2 Erection Time 103 days 103 days 120 days
3 (Produc+Erect) Time 117 days 107 days
4 Column Avg Inventory 283 component 22 component 5 Beam Avg Inventory 393 component 32 component 6 Slab Avg Inventory 452 component 34 component
7 Column Max Inventory 481 component 38 component 120 component 8 Beam Max Inventory 743 component 58 component 75 component 9 Slab Max Inventory 773 component 54 component 150 component
Based on the simulation results it is known that the application of pull systems can reduce the amount of inventory and the waiting time component. This is because the pull system simulation model is based on the average number of components to be erected while the push system model is based on the average number of components to be manufactured.
Push system cycle time is smaller than the pull system’s because of the push system continuously produces a greater amount than the pull system.
The application of lean construction, the pull system has showed improvement compared to a push system, by reducing waste in the form of a reduction in construction time, the amount of inventory, and the waiting time of precast concrete components in stock yard.
With less inventory, the land required for storage space precast concrete components can be reduced and facilitate the movement of precast concrete components in stock yard in the storage, and retrieval for erection in the field where all this will reduce expenditures.
Keywords : waste, lean construction, push system, pull system, inventory, waiting time
