31

CONSTRUCTION PLANNING AND SCHEDULING

31.1 INTRODUCTION

Planning is the process of devising of a scheme for doing, making or arranging a project or programme before the commencement of a work. Thus, construction planning is a process requiring the use of intellectual faculties, imagination, foresight and sound judgement to decide in advance as to what is to be done, how and where it is to be done, who will do it and how the results are to be evaluated.

In any project the sequence through which the project is to develop should be decided. The requirement is met in a systematic manner by scheduling or programming. Scheduling considers the main construction activity and also supporting elements such as labour, material, equipment and expenditure. All the activities consume resources of three kinds, viz., time, labour and material.

Here, the construction project may be housing-complex project, multi-storeyed building projects, factory-building projects, which involves in land acquisition, planning of the project, method of construction, material procurement, construction stages, etc.

31.2 OBJECTIVES OF PLANNING

The main objective of any planning, particularly construction planning, is to execute the project most economically both in terms of money and time. Effective planning includes the following factors:

1. Design of each element of the project.
2. Selection of equipment and machinery depending on the magnitude of the project.
3. Arrangement of repair of equipment and machinery near the site of project to keep them ready to work at all times.
4. Procurement of material well in advance.
5. Employment of trained and experienced staff on the project.
6. Arrangement of welfare schemes for the staff members and workers such as medical and recreational facilities.
7. Arranging constant flow of funds for the completion of the project.
8. Providing safety measures such as ventilation, arrangement of light, water and first aid.
9. Arrangements or means of communication and feedback, etc.

31.3 STAGES OF PLANNNING

During the planning of a construction project, the entire project is phased out identifying the sequence of construction. Secondly each phase is divided for operation into a number of jobs or units of construction. Different stages of planning are as follows:

1. Job planning
2. Technical planning
3. Contract planning

31.3.1 Job Planning

Each job or unit of construction has to be further planned with respect to the following:

1. Manner of Execution of the Job

The jobs may be executed departmentally or through contractor. In case the work is done through the contractor, type of contract is to be finalised.

2. Duration of the Job

The factors which contribute for the duration of job or the proposed period of its completion are:

1. Urgency of the work
2. Availability of resources
3. Position of the construction with reference to network

3. Planning of Resources

Resources of a construction project comprises of the following:

1. Plant, equipment and machinery
2. Construction stores
3. Both technical and non-technical staff and skilled and unskilled labour
4. Construction Material

31.3.2 Technical Planning

Technical planning is done by engineer or concerned authority for economical execution of the construction project. It starts after the administrative approval of the work is obtained for technical sanction. Technical planning is carried out in order to satisfy the following objects:

1. Finalisation of design, provide detailed drawing and specification to be adopted.
2. Preparation of a detailed estimate and modification of estimate if necessary.
3. Deciding the executive authority, like departmentally or though contract.
4. Planning resources and initiating procurement action.
5. Foresee the obstacles in the completion of the project and take necessary steps for fruitful completion.

31.3.3 Contract Planning

Contract planning is divided into the following two categories:

1. Pre-tender planning
2. Post-tender planning

1. Pre-tender Planning

Planning required for the time of inviting of tenders up to the receipt of the same is termed as pre-tender planning. It consists of the following works:

(i) Finalisation and Acquisition of Site

Before issue of order to contractors the acquisition of the project site has to be finalised and legal issues if any should be finalised.

(ii) Planning of Resources

Resource planning includes the following: (a) availability of site, (b) availability of stores, (c) availability of labour and (d) availability of equipment and plants.

(iii) Planning Time Limit

The requirement of resources and time limit are inter-related and both these aspects are to be taken together. In some cases the time needed for completion is decided based on the available resources. Such is the case when the work has to be completed departmentally. Even when the work has to be executed by the contractor, circumstances of the project has to be decided and modified before inviting tenders. As a matter of fact the contractor submits tender considering the following aspects: (a) site survey, (b) availability of materials, (c) equipment and plants to be hired and purchased, (d) fuel, (e) labour, (f) facilities for camp and (g) study of drawing/design/specifications.

2. Post-tender Planning

In post-tender planning the following aspects are considered irrespective of the work done by contractor or departmentally: (a) setting camp site office, (b) welfare of staff/labour amenities, (c) materials required, (d) labour required, (e) equipment, (f) safety measures to avoid accidents and theft, (g) follow-up of drawing/specifications and (h) billing, to record progress, to calculate materials, labour, etc.

In the works executed by contractors, responsibility is fixed for recording the work in diary the day-to-day details of work done. The planned progress in the form of bar charts or progress reports should be known to the contractor as well as to the engineer’s representative. It is normally the practice for all civil engineering projects to make controlled construction stores available to the contractor.

31.3.4 Advantages and Limitations of Planning

Following are the advantages and limitations of planning:

1. Advantages

1. Decision of network or bar chart makes the contractor to know more about the job.
2. With proper planning, the financial burden will be lessened for the contractor.
3. By proper programming, weekly supply of labour can be attended.
4. Programme provides a standard against which actual work can be measured.

2. Limitations

1. Effectiveness depends on correct assumptions.
2. Planning is expensive.
3. Planning delays action.
4. Planning encourages of false sense of activity.

31.4 SCHEDULING PROCEDURES

Various scheduling procedures are discussed below.

31.4.1 Construction Schedule

This schedule consists of duration of construction of various components of the work. Based on the availability of the following data, the construction schedule can be made:

1. Number of activities
2. Quantity of various items of works
3. Labour contribution and number of field workers
4. Machinery required
5. Stages of activities to be executed

31.4.2 Labour Schedule

Under this schedule one can know in advance the type of labour and their numbers required from time to time. This is needed to recruit the persons (both skilled and unskilled labour) needed so as to have a continuous flow of work without any disruption.

31.4.3 Material Schedule

This is an important schedule by which one will be in a position to know the requirement of various construction materials well ahead. This helps to start the work and continue without any dearth for materials at any stage. If adequate fund and storage facility are available, materials which can not be spoiled with time may be stored to some extent.

31.4.4 Equipment Schedule

The success of any project depends to a large extent on the proper use of construction equipment. Properly maintained equipment and application in construction can bring down construction time and cost. Further proper deployment of equipment judiciously yields economical result without heavy financial burden in the project. Thus project management should properly plan the judicious deployment of equipment.

31.4.5 Expenditure Schedule

The project engineer and his team have to primarily judge to give the most economical construction. Thus it is essential to review the financial position of the project at regular intervals so as to ensure the following:

1. The annual expenditure, if any, of the project has to be kept within the allotment.
2. A properly balanced expenditure will result in an early completion of work.

31.5 SCHEDULING TECHNIQUES

In any project the sequence through which the project is to develop should be decided. The requirement is met in a systematic manner by scheduling techniques. The project scheduling techniques are concerned with the resource time. One of the objectives of project management is to optimise the use of resources. Scheduling techniques offer solutions to optimisation of project time.

Technical scheduling can be done by different methods depending on the size of the project. The methods used are as follows:

1. Bar charts
2. Milestone charts
3. Network analysis

31.5.1 Bar Charts

1. Principle of Bar Chart

In dealing with complex projects, a pictorial representation showing the various jobs to be done and the time and money they involve is generally helpful. One such pictorial chart, also known as the bar chart, was developed by Henry Gantt around 1900. Bar chart is also referred to as Gantt chart.

A bar chart consists of two coordinate axes, viz., one representing the time elapsed and the other representing the job or activities to be performed. The jobs are represented in the form of bars as shown in Fig. 31.1.

Figure 31.1 Bar chart

The beginning and end of each bar represent the time of start and time of finish of that activity. The length of the bar represents the time required for the completion of the job or activity.

In any project there may be some activities which are to be taken up simultaneously but may take different lengths of time for their completion (e.g., Activities A and C) and some activities have to be taken up only after the completion of some other activity (e.g., Activities A and B). There may also be some activities which are independent of all other activities (e.g., Activities D and E).

2. Example

Let us consider the steps involved in the construction of a factory shed. Major activities identified in the construction of a factory shed where machines are to be erected are presented in Table 31.1. The activities have been identified and arranged in logical sequence. At the factory site no water is available and is not feasible to get water from surrounding. Hence, a bore well has to be sunk before starting the actual construction. Hence, excavation of foundation and sinking of bore well may be started simultaneously. That is, at the end of one week, water will be available.

Other activities succeed one after the other. These activities are shown in a bar chart in Fig.31.2, with the given data and given precedence/succedence relationships.

Figure 31.2 Bar chart for factory shed

As seen from the bar chart, the total time required for completion of the factory shed project is about 30 weeks.

3. Limitations of Bar Chart

Following are the limitations of a bar chart:

1. A bar chart can be successfully used only for small projects.
2. Bar charts can not be updated when there are many changes.
3. The progress of the project can not be assessed at different stages scientifically.
4. Bar charts do not equate time with cost. That is time-cost relationship can not be derived.
5. Delay in the work can not be deducted.
6. It does not clearly show the interdependencies between the various activities in the project.
7. It does not reflect the critical activities of the project.
8. Bar charts do not provide methods for optimising allocation of resources.

31.5.2 Milestone Charts

1. Principle of Milestone Chart

The shortcomings or the inadequacies of the bar chart have been modified to some extent in milestone chart. In every activity, there are certain key events which are to be carried out for the completion of the activity. Such key events are called milestones and they are represented by a square or circle. These events are those which can be easily identified over the main bar representing the activity.

It has been observed in a long time activity the details will be lacking. If the activity is broken into a number of sub-activities or key events each one can be recognised during the progress of the project. In such cases controlling can be done easily and some inter-relationships may be established between the activities. In a milestone chart, the events are in chronological, but in a logical sequence. Figures 31.3 and 31.4 show the conventional bar chart and milestone chart.

Figure 31.3 Conventional bar chart

Figure 31.4 Milestone chart

2. Limitations of Milestone Chart

Following are the limitations of a milestone chart:

1. This method has one great deficiency, that is, it does not clearly show the interdependencies between events.
2. Here the events are in chronological order but not in a logical and sequential order.

31.5.3 Network Analysis

1. Principle of Network Analysis

The network analysis techniques, developed between 1950s and 1960s, have now come to be used as an effective management tool for planning, scheduling and controlling of complex projects.

The term project network analysis is a general term covers all the network techniques used for planning, scheduling and controlling of projects. The three techniques commonly used are as follows:

1. Critical Path Method (CPM)
2. Program Evaluation and Review Technique (PERT) and
3. Precedence Diagramming Method (PDM) or Precedence Network Analysis (PNA).

These network techniques produce time-oriented diagrams having activities organised into a logical order.

2. Network Diagram

Network Diagram is a graphical flow plan of the activities that are to be accomplished for completing the project. The precedence and succedence relationships between activities are identified first.

Sequencing activities refers to finding out the logical relationships among the activities of a project and arranging them accordingly. By studying the project features the different activities involved in a project the concerned officer-in-change of the project establishes the precedence-succedence relationships between the activities.

While deciding the logical relationships between the different activities, activities which are mandatory to be operated before some of the activities to be taken up have to be identified. In addition there may be certain activities which may not be mandatory dependencies (such activities are called discretionary dependencies) are to be identified. After finalising all the activities and finding their characteristics the network diagram for the project can be drawn.

Activities of construction of a building are given in Table 31.2 and shown as network diagram in Fig. 31.5.

Figure 31.5 Network diagram for construction activity

3. Definitions of Network Techniques

(i) Critical Path Method (CPM)

In a network the sequence of activities arranged in each path will have different duration. The path that has the longest duration is called critical paths.

(ii) Program Evaluation and Review Technique (PERT)

It uses three times, viz., optimistic time estimate, pessimistic time estimate and most likely time estimate.

(iii) Precedence Network

Here each activity is represented by a rectangular or square box. The time duration of the activity is incorporated inside the modal box.

31.6 SITE CLEARANCE

Clearing of vegetation and trees is usually necessary before undertaking any construction operation. It is very difficult to handle equipment and materials in the presence of trees, bushes, grass and weeds. Presence of these materials along with earth materials may lead to settlement at a later stage. Crawler dozers, equipped with special cleaning blades, are the best equipment needed for site clearance.

Type of vegetation, condition of soil and topography, quantity of clearance needed, and the purpose for which cleaning is done are the factors to be considered in planning the sequence of operation.

The factors are:

1. Removing trees and stumps and roots
2. Removing surface vegetation
3. Disposing of the vegetation by stacking and ultimately burning.
4. Knocking out all vegetation stumps and roots, chopping or crushing them and later burning.
5. Killing or retarding the growth of bush by cutting the roots below the surface of the ground.

31.7 JOB LAYOUT

Overall economy of a project can be achieved by a thorough coordination in planning of services and the construction plant. Such coordinated work will frequently lead to modification in plant facilities and in layout of services.

Thus layout of a construction project camp is governed by the following factors:

1. Type of project.
2. Location where it is situated.
3. Method of execution of the project.
4. Resource availability.
5. Availability of water supply and electrical power.
6. Waste and sewage disposal works.
7. Availability of medical facilities.
8. Availability of welfare facilities such as postal service, market, canteen, etc.
9. Religious facilities.
10. Newspaper and magazines TV and other recreation facilities.

31.8 TEMPORARY SHEDS

As explained in job layout different facilities have to be provided. Since the project has to be completed in a short period facilities can not be made permanently. Thus only temporary sheds made out of sheets are provided with adequate safety.

Facilities like drinking water, sleeping areas, dwelling areas, office, store and all are to be provided in temporary sheds. However, depending on the period of construction the sheds are made big or small with additional strength and durability.

The sheds should withstand all weather conditions and unexpected storm on heavy rain. No water logging should be allowed.

31.9 SETTING OUT WORKS

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:

1. 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.
2. The setting of corner points are checked based on the diagonal distances AC, BD, DG and EF.
3. 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.
4. Then the width of excavation is set around the centre line and marked by thread with pegs at appropriate positions.
5. Further the excavation line is then marked by lime or by making a ferrow with a spade.
6. 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

1. Planning is the process of devising of a scheme for doing, making or arranging a project or programme before the commencement of work.
2. During the planning of a construction project, the entire project is phased out identifying the sequence of construction.
3. Different stages of planning are:

   (i) Job Planning, (ii) Technical Planning and (iii) Contract Planning.

4. Each job or unit of construction has further planned considering:

   (i) Manner of execution of Job

   (ii) Duration of the job

   (iii) Planning of resources

5. Technical planning is done for economical execution of the construction project. It starts after the administrative approval of the work is obtained for technical sanction.
6. Contract planning comprises of (i) pre-tender planning and (ii) post-tender planning.
7. Construction schedule consists of duration of construction of various components of the work.
8. Under labour schedule, one can know in advance the type of labour and their numbers required from time to time.
9. Material schedule is an important schedule by which one will be in a position to know the requirement of various construction materials well ahead.
10. The success of any project depends to a large extent on the proper use of construction equipment.
11. Technical scheduling methods are (i) bar charts, (ii) milestone charts and (iii) network analysis.
12. In dealing with complex projects, a pictorial representation showing the various jobs to be done and the time and money they involve is generally helpful. One such pictorial chart is called bar chart.
13. The shortcomings or the inadequacies of the bar chart have been modified to some extent in milestone chart. In every activity there are certain key events which are to be carried out for the completion of the activity. Such key events are called milestones and they are represented by a square or circle.
14. The term project network analysis is a general term covers all the network techniques used for planning, scheduling and controlling of projects. The three techniques commonly used are:

    (i) Critical Path Method (CPM)

    (ii) Programme Evaluation and Review Technique (PERT), and

    (iii) Precedence Diagramming Method (PDM) or Precedence Network Analysis (PNA).

15. Network diagram is a graphical flow plan of the activities that are to be accomplished for completing the project.
16. In a network the sequence of activities arranged in each path will have different duration. The path that has the longest duration is called critical path.
17. Program Evaluation and Review Technique (PERT) uses three times, viz., optimistic time estimate, pessimistic time estimate and most likely time estimate.
18. In precedence network, each activity is represented by a rectangular or square box. The time duration of the activity is incorporated inside the modal box.

1. Discuss the objectives of construction planning.
2. Explain different stages of planning.
3. What is job planning?
4. Explain what is meant by Technical planning
5. Distinguish between pre-tender planning and post-tender planning.
6. What are the aspects considered by a contractor in submitting a tender?
7. What is a bar chart?
8. How bar chart is different from milestone chart?
9. What is a network diagram?
10. Define critical path.
11. Explain the principle of network analysis.
12. Bring out the importance of site clearance.
13. Explain the factors to be considered in job layout.
14. Explain setting out of works with a suitable example.
15. Bring out the advantages of CPM.
16. What is PERT? In which situation this can be used.