Project Planning and Control Part 7

Một điều chủ yếu của một công trình dân dụng và bản chất xây dựng và các dạng khác là có liên quan với xây dựng cơ khí - cả hai đềuthiết thực và có thể được áp dụng cho các tình huống thực tế.
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Project Planning and Control Part 7 28 Worked examples The previous chapters describe the various meth- ods and techniques developed to produce mean- ingful and practical network programmes. In this chapter most of these techniques are combined in two fully worked examples. One is mainly of a civil engineering and building nature and the other is concerned with mechanical erection – both are practical and could be applied to real situations. The first example covers the planning, man- hour control and cost control of a construction project of a bungalow. Before any planning work is started, it is advantageous to write down the salient parameters of the design and construction, or what is grandly called the ‘design and construction philosophy’. This ensures that everyone who participates in the project knows not only what has to be done but why it is being done in a particular way. Indeed, if the design and construction philosophy is circulated before the programme, time- and cost-saving suggestions may well be volunteered by some recipients which, if acceptable, can be incorporated into the final plan. Worked examples Example 1 Small bungalow Design and construction philosophy 1 The bungalow is constructed on strip footings. 2 External walls are in two skins of brick with a cavity. Internal partitions are in plasterboard on timber studding. 3 The floor is suspended on brick piers over an oversite concrete slab. Floorboards are T & G pine. 4 The roof is tiled on timber-trussed rafters with external gutters. 5 Internal finish is plaster on brick finished with emulsion paint. 6 Construction is by direct labour specially hired for the purpose. This includes specialist trades such as electrics and plumbing. 7 The work is financed by a bank loan, which is paid four-weekly on the basis of a regular site measure. 8 Labour is paid weekly. Suppliers and plant hire are paid 4 weeks after delivery. Materials and plant must be ordered 2 weeks before site requirement. 9 The average labour rate is £5 per hour or £250 per week for a 50-hour working week. This covers labourers and tradesmen. Figure 28.1 Bungalow (six rooms) 257 Project Planning and Control 10 The cross-section of the bungalow is shown in Figure 28.1 and the sequence of activities is set out in Table 28.1, which shows the dependencies of each activity. All durations are in weeks. The activity letters refer to the activities shown on the cross-section diagram of Figure 28.1, and on subsequent tables only these activity letters will be used. The total float column can, of course, only be completed when the network shown in Figure 28.2 has been analysed (see Table 28.1). Table 28.1 Activity Activity – description Duration Dependency Total letter (weeks) float A Clear ground 2 Start 0 B Lay foundations 3 A 0 C Build dwarf walls 2 B 0 D Oversite concrete 1 B 1 E Floor joists 2 C and D 0 F Main walls 5 E 0 G Door and window frames 3 E 2 H Ceiling joists 2 F and G 4 J Roof timbers 6 F and G 0 K Tiles 2 H and J 1 L Floorboards 3 H and J 0 M Ceiling boards 2 K and L 0 N Skirtings 1 K and L 1 P Glazing 2 M and N 0 Q Plastering 2 P 2 R Electrics 3 P 1 S Plumbing and heating 4 P 0 T Painting 3 Q, R and S 0 0 = Critical Table 28.2 shows the complete analysis of the network including TLe (latest time end event), TEe (earliest time and event), TEb (earliest time beginning event), total float and free float. It will be noted that none of the activities have free float. As mentioned in Chapter ??, free float is often confined to the dummy activities, which have been omitted from the table. 258 0 2 5 7 9 14 A B C E F 1 2 3 5 7 9 2 3 2 2 5 0 2 5 7 9 14 5 6 9 12 14 D G 4 6 8 10 1 3 6 7 11 14 14 16 22 25 2 ...