Modeling and Simulation of Public Housing Construction in Hong Kong
Erection of all-
Fixing-bar for slab
Fixing-bar for wall
Lifting bar for slab
Lifting bar for wall
3.1 Modeling the Construction Process of a Floor Cycle
There are four wings on each floor. Wings A and C are identical, so are wings B and D. After certain differences, all wings involve the same construction process. After investigating site operations and contractors’ plans, the major construction activities are abstracted as listed in Table 2 for a floor cycle.
Table 2: Major construction
precast semi-slab Installation of façade wall Lifting bracing frame
Required resources CarpG*
ConcG Crane, ConcG InsG
See Table 1 for Resource Symbols
for slab Placing concrete for wall Striking off wall- form
Erecting timber form for corridor
The 13 activities repeat in each of the four wings, which means a total of 52 activities for the entire floor construction. In the AweSim model, activities are labeled by:
i = wing A, B, C, or D
Activity can be any of above 13 activities. For example, P C W B i n d i c a t e s p l a c i n g c o n c r e t e f o r w a l l a t w i n g B .
The major modeling elements are ACTIVITY, AWAIT, and FREE nodes (Pritsker 1997). AWAIT, and FREE nodes are used to allocate required resources before an activity starts and to free them after use.
performance. The logical sequence among these activities is based on contractors’ site plans, which also determine the priorities for competing shared resources.
3.2 Simulation results of the 6-day cycle
If the resource capacities are given as identical sizes as the existing 6-day cycle plan as in Table 3, run the simulation
model. The time to complete one floor cycle is 61 hours. Contractors use twelve working hours per day for planning 6-day cycle, which means that the 6-day cycle can actually be completed in five days without additional resources. Because there are four wings at each floor, it takes 1.5 days to complete one wing for the 6-day cycle. In other words, a crew simply repeats its work every 1.5 days. If the floor cycle time is reduced to five days, there is no a simple repetitive working pattern for a crew. Instead, the five-day cycle would require a different working plan every day for each gang. That is why contractors like 4-day cycle. They do one wing in one day, and each gang just repeats its work everyday.
Average utilization is defined as average unit of the resource in use during the entire simulation time. Its value is obtained from simulation and is listed in the last column of Table 3.
Table 3: Resource Information
Symbol Crane InsG
S 1 8
No. 1 2
Name Crane Installation gang Bar-fixing gang Concreting gang Carpenter gang
Avg. util. 0.97 2.47
Results in Table 3 show that the crane is highly utilized (97%). Approximately six (5.56) of the eight bar- fixing men are utilized. The utilization of other resources is very low.
The average utilization gives a general overview how a crew is utilized. We can also investigate the utilization process of each resource in order to get a detailed picture how a crew is utilized. Figure 2 plots the utilization of the five crews along the entire simulation time.
The durations of these activities vary in a small range for different wings and are collected from contractors’