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Shi, Zeng and Tam

2.1 Floor Cycle Time

2.3 Construction Resources

Standardization is one of the many interesting features of public housing in Hong Kong. Currently public housing stocks are designed with 39 or 44 stories high to maximize land usage. Each floor has the same layout of four wings: A, B, C, and D as illustrated in Fig. 1.

D

Tower canes are extensively used in public housing construction in Hong Kong. Because of high-rising (e.g. 39 stories), tower canes are needed for many construction activities such as installing pre-fabricated panels and pouring concrete. Therefore, tower cranes are usually one of the controlling resources. One tower crane is used for 8- day and 6-day floor cycle plans. Two tower cranes or the combination of one tower crane and one concrete pump are used for 4-day floor cycle plan.

Housing construction is labor intensive. Many special

A

C

gangs gang gang

or crews are needed, mainly including: installation (InsG), bar-fixing gang (BarG), concrete-placing

(ConcG),

and

carpenter

gang

(CarpG).

The

five

major types of resources summarized in Table 1:

and their functions

are

B

Table 1: Major Resources and Their Functions

Pre-fabricated walls

Name Crane

Symbol Crane

Required by activities

Lifting,

installation

of

Figure 1: Floor Plan of Public Housing

As many other housing projects, the duration of a public housing project is controlled by the construction of the framework structures of the building. Starting from level 2, the construction process is repetitive from one floor to next floor. The time required to construct one floor is called the floor cycle time. Although the floor cycle time varies from low floors to higher floors, site data show that the variations are minimal. It can be treated as an important indicator with

respect to contractors

the plan

project duration. their site operations

As a matter of based on the cycle

fact, time.

With the introduction of pre-fabrication and construction methods, Hong Kong contractors have able to reduce the floor cycle time from 8 days to 6

new been days.

Recently,

some

contractors

can

complete

one

floor

cycle

in

4

3

Installation gang

Bar-fixing gang Concreting gang Carpenter gang

InsG

BarG

ConcG

CarpG

façade walls and precast semi-slabs, erection of wall-forms, and placing concrete. Striking off wall-form, erection of wall-form, and installation of façade walls and precast semi-slabs. Fixing bar for walls and slabs. Placing concrete for walls and slabs Erecting timer forms

SIMULATION STUDY

days.

With the increased annual production target,

contractors

are

required

to

study

the

possibility

of

2

days

the per

floor cycle.

2.2 Pre-fabricated Concrete Panels

Pre-fabricated concrete panels are

extensively

used

including external facade walls and semi-slabs. Eight pieces of these panels are used to form the entire non-bearing walls for each wing (four pieces on each side, see Fig. 1). These concrete panels are precasted off-site, and installed on site. In addition to time reduction, pre-fabrication also improves the quality by minimizing works in the air.

As discussed in the previous section, the construction of each floor is a typical repetitive process. The six-day floor cycle is currently used in public housing projects by most contractors, and will be used as the basis in this study. A simulation model is studied to represent the construction process. A general simulation language named AweSim (Pritsker 1997) is employed to facilitate modeling and

simulation. The cycle time and utilization of

then analyzed.

Afterwards, cycle

time

resources

are

reduction

is

explored by changing crew sizes.

1306

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