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Utilization

Utilization

Utilization

Utilization

Utilization

Fig.2a Utilization of crane

1

0.5

0

0

10

20

30 Time

40

50

Fig.2b Utilization of installation gang

8 7 6 5 4 3 2 1 0

0

10

20

30 Time

40

50

Fig.2c Utilization of bar-fixing gang

8 7 6 5 4 3 2 1 0

0

10

20

30 Time

40

50

Fig.2d Utilization of concreting gang

5

4

3

2

1

0

0

10

20

30 Time

40

50

Fig.2e Utilization of carpenter gang

3

2

1

0

0

10

20

30 Time

40

50

Figure 2 Utilization Process of Resources

60

60

60

60

60

Shi, Zeng and Tam

Fig.2a indicates that the crane is mostly engaged except two short breaks. This confirms that the crane is the bottleneck of the construction process. In order to reduce the cycle time, crane’s capacity should be increased or some duties should be assigned to other equipment, such as concrete pump for placing concrete.

Fig.2b shows that the installation gang, carpenter gang and concrete gang are seldom fully utilized, but bar-fixing is highly utilized most of the time.

3.3 Sensitivity analysis

As concluded previously that the crane is the controlling resource and the bar-fixing gang is also highly utilized, the capacity of crane is doubled to two and bar-fixing gang is increased from 8 to 10.

Changing the capacities of the two resource blocks in

the

simulation

model,

run

the

model

again.

The

new

results can be obtained. hours (i.e. 4 days). The listed in Table 4.

The cycle time is reduced to 48.5 average utilization of the gangs is

Table 4: Modified Resource Information

No

Name

Symbol

Size

Avg. util.

1

Crane

Crane

2

1.23

2

Installation gang

InsG

8

3.13

3

Bar-fixing gang

BarG

10

7.11

4

Concreting gang

ConcG

5

2.31

5

Carpenter gang

CarpG

3

0.90

The average utilization figures in Table 4 show that the utilization of cranes is reduced, but the utilization of other gangs has been improved.

The utilization processes of the five gangs are also plotted from Fig.3a through Fig.3e. These figures show that mostly one or two cranes are busy; the bar-fixing gang is still highly utilized most of the time; the other gangs are low utilized.

CONCLUSION

This paper studied simulation technique for modeling and simulating public housing construction in Hong Kong. The obtained results can not only show the floor cycle construction time but also highlight the utilization of resources. By increasing the capacities of the crane and the

bar-fixing gang to 2 can be reduced to resources is low.

and 10 4 days.

respectively, the floor The utilization of

cycle other

1308

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