Any civil engineering work has to be set out before starting of construction. Primarily excavation has to be started for which marking has to be done. Marking for excavation of a typical building area is explained below.
In order to carry out construction exactly according to plan, the outline of excavation and centre line of walls are marked on the ground (Fig. 31.6).
Figure 31.6 Setting out for a building
The following procedure is followed:
- Based on the plan the centre lines of the walls are calculated. The centre lines of the room are set out by setting perpendiculars in the ratio 3:4:5. The corner points are identified as A, B, C, D, E, F and G. These points are marked by driving pegs.
- The setting of corner points are checked based on the diagonal distances AC, BD, DG and EF.
- At the time of excavation the pegs at A, B, C, … may be removed. The centre lines are extended and the centre points are marked 2 m away from the outer edge of excavation. Accordingly the points A1, A2, B1, B2 … are marked with stout pegs.
- Then the width of excavation is set around the centre line and marked by thread with pegs at appropriate positions.
- Further the excavation line is then marked by lime or by making a ferrow with a spade.
- Based on field conditions more pegs are driven.
Example 31.1
The following project is to be represented by a bar chart. The duration of each activity is in working days. Draw the bar chart with working days in the horizontal scale.
Activities 1 and 2 can occur concurrently.
Activity 3 can start 5 days after the commencement of activity 2.
Activities 4 and 6 can start concurrently after activity 3 is completed.
Activity 5 should follow activity 4.
Activity 7 should begin concurrently with activity 8 after 5.
Solution:
Activities are taken in y-axis and working days in x-axis and the bar chart is drawn as shown in Fig. 31.7.
Figure 31.7 Bar chart
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