Work Scheduling
In
Work Scheduling
• Work scheduling is a tool of planning of project, which decide in advance about what to do and when to do considering how to do and who is to do .
• It is a time phased plan for performing the work necessary to complete the project
• It is a graphical representation of plan which shows the starting and completion dates of each activity and the sequential relationship among the various activities • It
– Predicts project completion time and activity completion time – Controls financing and payment
– Serves as a record
– Helps to plan resources required for construction – Supports to cash management
Scheduling Tools
• Bar Chart /Gantt Chart
• Critical Path Method (CPM)
• Program Evaluation and Review Techniques (PERT)
Bar charts are mostly used in work scheduling
of simple small and medium span bridges and
CPM is mostly used in complex medium and
large span bridges in Nepal
Bar Chart
Graphical representation of various activities/works with their starting and completion time and duration.
In bar chart, activities/works are represented by horizontal bars and the length of bar indicates the time/duration required for accomplishment of that particular activity/work
Bar chart may be linked bar chart or milestones chart
Linked bar chart
Modified bar chart in which links between succeeding and preceding activities are shown. Links helps to show the effects of delay if any in the activities and helps to calculate float or extra time available for the activities.
Milestone chart
Steps for preparing Bar Chart
1. Break down the whole project in to various activities or sub activities
Identify different works within the activities
2. Estimate the time/duration required for each work.
For each work, estimate how long it will take to do that work.
The time required for execution of a work depends on the method of execution, volume of the work , nature of the work and the time available for completion of the project.
3. Develop a logical and practical sequence of the works
One by one, put everything in order. Make a note of any dependencies, the situations where you can’t do one thing until another is started or finished.
For example Until the laying out of reinforcing bars is completed concreting can not be performed in a structural member.
4. Chunk up the works/activities
After having the sequential order of works/activities with their time duration, reduce the list without losing any specificity.
Division of time depends on the total period available for project. If it is only one year long, you might list items by month. If your project is three years long, then you might list items by quarter. If you are planning over five years, you might break it down to six-month periods.
5. Draw bar chart
Draw bar chart by hand or by word-processing/spreadsheet or any software. Mark the milestones and link lines if any in bar chart
Best scheduling can only be achieved when there are
• Clearly defined activities • Realistic duration
• Knowledge of construction techniques • Knowledge of resources available
Example on Bar Chart Method of Scheduling
Prepare a schedule for the activities involved in detail engineering survey and design of a bridge using Bar Chart
S.N. Activities/Works Time required
(Days) 1 Document preparation for tendering of
Detail survey and design works 3
2 Call for tender 10
3 Evaluation of tender and selection of consultant 4
4 Mobilization of study team 5
5 Detail Engineering Survey 8
6 Gological/Goetechnical Investigation 14
7 Hydrological Study 5
8 Design and detailing 35
9 Submission and approval of report 9
Total no of days -93 Example 1
Prepare a schedule for the activities involved in detail engineering survey and design of a bridge using Bar Chart
S.N
. Activities/Works
Duration / Time
Mangsir 2069 Paush 2069 Falgun 2069
1 2 3 4 1 2 3 4 1 2 3 4
1 Document preparation for tender Detail survey and design works 2 Call for tender
3 Evaluation of tender and selection of consultant
4 Mobilization of study team 5 Detail Engineering Survey 6 Gological/Goetechnical
Investigation 7 Hydrological Study 8 Design and detailing
9 Submission and approval of report
Draft report submission Completion of
study for design
Bar Chart for Detail Engineering Survey and Design of Bridge
Approval of report 3 days 10 days 4 days 3 days 8 days 14 days 5 days 35 days 9 days
S.N. Activities/Works
Days required to complete
the work
Human Resources
Labour Mason Carpenter Bar
bender Welder
1 Diversion of stream 1 4 - - -
-2 Construction of platform of well 1 4 - - -
-3 Fabrication and placement of well curb 2 2 1 - - 1
4 Form works of well up to 3 m height 2 2 - 1 -
-5 Bar cutting and bending 2 1 - - 1
-6 Reinforcement layout in well 2 2 - - 1
-7 Concreting of well steining up to 3m ht. 1 4 2 - -
-8 Dredging and sinking of well 2 2 1 - -
-9 Concreting of lower plug 1 3 1 - -
-10 Filling of granular materials 2 4 1 - -
-11 Concreting of upper plug 1 3 1 - -
-12 Placement of reinforcement for well cap 2 2 - - 1
-13 Form works for well cap 1 1 1 -
-14 Concreting of well cap 1 3 1 - -
-Prepare bar schedule and resource aggregation chart for the activities
involved in the construction of the two well foundations by using Bar Chart Example 2
S.N. Activities/Works Duration (Days)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
1 Diversion of stream
2 Construction of platform of well
3 Fabrication and placement of well curb
4 Form works of well up to 3 m height
5 Bar cutting and bending up to 3 m height
6 Reinforcement layout in well up to 3 m height
7 Concreting of well steining up to 3m height
8 Dredging and sinking of well up to 3m height
9 Concreting of lower plug 10 Filling of granular materials 11 Concreting of upper plug 12 Placement of reinforcement
for well cap
13 Form works for well cap 14 Concreting of well cap
Bar Chart of Well Construction Well at right bank
S.N. Activities/Works Duration (Days)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
1 Diversion of stream
2 Construction of platform of well
3 Fabrication and placement of well curb
4 Form works of well up to 3 m height
5 Bar cutting and bending up to 3 m height
6 Reinforcement layout in well up to 3 m height
7 Concreting of well steining up to 3m height
8 Dredging and sinking of well up to 3m height
Human Resources Aggregation Chart/Table
Labour 4 4 7 3 5 5 4 4 6 2 5 1 1 1 0 0 0 2 2 2 2 2 2 4 4 6 2 4
Mason 1 1 1 1 2 2 2 2
Carpenter 1 1 1 1 1 1 1 1
Bar bender 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
It is a logical representation of different activities and their interrelationships in a diagrammatic form (Network Diagram).
Arrows and nodes are used in a network diagram and they represent activities and events respectively. Activity is a task to be performed, which takes time for completion. Event is an important instance in a project’s life from where an activity starts or where an activity ends.
Critical path is the longest path in a network diagram, which takes maximum time among the alternative paths through which a project will be completed.
Rules for preparing Network Diagram
• Initial event should be one in network diagram and should contain only out going arrow.
• Until and unless all activities leading to an event are completed no
event is occurred.
• Until and unless the preceding events are completed no activity is started.
• Network path shall not be turned back. Event should not be dependent
on the succeeding events.
• Before reaching the objective, every activity should be completed.
• Final event should be only one.
• Network should contain all constraints and interdependencies
• In network, time flows from left to right
• The length of an arrow in a network diagram does not represent time.
• Number given to a preceding event should be smaller than the number
Example on Critical Path Method of Scheduling
A bridge requires six intermediate piers consisting of concrete cap supported by steel piles. All piles will be driven before any caps are started. Sequential information about the activities of this project is given below. Draw network diagram
Activity Proceeded by Followed by Days require for the activity A Drive piles - B 20
B Erect forms for caps 1 and 2 A C,E 4
C Place reinforcement for caps 1 and 2 B D,F 2
D Place concrete for caps 1 and 2 C G 2
E Erect forms for caps 3 and 4 B F,H 4
F Place reinforcement for caps 3 and 4 C,E G,I 2
G Place concrete for caps 3 and 4 D,F J 2
H Erect forms for caps 5 and 6 E I 4
I Place reinforcement for caps 5 and 6 F,H J 2
1 2 3 5 6 4 7 9 8 10 11 A B E H C F I D G J Network diagram
20 days 4 days 4 days 4 days
2 days
2 days
2 days 2 days
2 days 2 days
Path ABCDGJ = 32 days Path ABEFGJ = 34 days
