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.
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
gangs gang gang
or crews are needed, mainly including: installation (InsG), bar-fixing gang (BarG), concrete-placing
major types of resources summarized in Table 1:
and their functions
Table 1: Major Resources and Their Functions
Required by activities
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
project duration. their site operations
As a matter of based on the cycle
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.
Bar-fixing gang Concreting gang Carpenter gang
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
With the increased annual production target,
2.2 Pre-fabricated Concrete Panels
Pre-fabricated concrete panels are
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
explored by changing crew sizes.