Work Scheduling In

Bridge Construction

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 schedulingof simple small and medium span bridges andCPM is mostly used in complex medium andlarge span bridges in Nepal

Different Scheduling Tools

Bar ChartGraphical representation of various activities/works with theirstarting and completion time and duration.

In bar chart, activities/works are represented by horizontalbars and the length of bar indicates the time/durationrequired for accomplishment of that particular activity/work

Bar chart may be linked bar chart or milestones chart

Linked bar chartModified bar chart in which links between succeeding andpreceding activities are shown. Links helps to show theeffects of delay if any in the activities and helps to calculatefloat or extra time available for the activities.

Milestone chart Improved bar chart in which important events are shown

Steps for preparing Bar Chart

1. Break down the whole project in to various activities or sub activitiesIdentify 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 cant 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.Eliminate interdependencies of work as far as possible in planning

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 yearlong, you might list items by month. If your project is three years long, then you mightlist 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 Knowledge of construction procedures

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/WorksTime required

(Days)

1Document 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

Example 1

S.N.

Activities/Works

Duration / Time

Mangsir 2069 Paush 2069 Falgun 2069

1 2 3 4 1 2 3 4 1 2 3 4

1Document preparation for tenderDetail survey and design works

2 Call for tender

3Evaluation of tender and selection of consultant

4 Mobilization of study team

5 Detail Engineering Survey

6Gological/GoetechnicalInvestigation

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

Project completion period 79 days

S.N. Activities/WorksDays required to complete

the work

Human Resources

Labour Mason CarpenterBar 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/WorksDuration (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

2Construction of platform of well

3Fabrication and placement of well curb

4Form works of well up to 3 m height

5Bar cutting and bending up to 3 m height

6Reinforcement layout in well up to 3 m height

7Concreting of well steining up to 3m height

8Dredging and sinking of well up to 3m height

9 Concreting of lower plug

10 Filling of granular materials

11 Concreting of upper plug

12Placement of reinforcement for well cap

13 Form works for well cap

14 Concreting of well cap

Bar Chart of Well Construction Well at right bankWell at left bank

S.N. Activities/WorksDuration (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

2Construction of platform of well

3Fabrication and placement of well curb

4Form works of well up to 3 m height

5Bar cutting and bending up to 3 m height

6Reinforcement layout in well up to 3 m height

7Concreting of well steining up to 3m height

8Dredging 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

Welder 1 1 1 1

It is a logical representation of different activities and theirinterrelationships in a diagrammatic form (Network Diagram).

Arrows and nodes are used in a network diagram and theyrepresent activities and events respectively. Activity is a task tobe performed, which takes time for completion. Event is animportant instance in a projects life from where an activity startsor where an activity ends.

Critical path is the longest path in a network diagram, whichtakes maximum time among the alternative paths through whicha project will be completed.

Critical Path Method (CPM)

Rules for preparing Network Diagram

Initial event should be one in network diagram and should contain onlyout going arrow.

Until and unless all activities leading to an event are completed noevent is occurred.

Until and unless the preceding events are completed no activity isstarted.

Network path shall not be turned back. Event should not be dependenton 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 numbergiven to the succeeding events.

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

ActivityProceeded

byFollowed

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

J Place concrete for caps 5 and 6 G,I - 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 daysPath ABEFGJ = 34 daysPath ABEHIJ = 36 days

Critical path is 1-2-3-5-6-7-9-10-11