Planning & Scheduling
Planning: Process of choosing the method and order of work
Scheduling: Process of determining the interrelationship of associated timings of operations.
Steps in Construction Scheduling
- Splitting of the project into work activities
- Determining logic relationships/interrelationships between activities.
- Construction of Network Diagrams.
- Assigning durations to work activities.
- CPM Calculations resulting in start times, finish times and float calculations of activities.
- Marking of critical Path
- Construction of Bar Charts / Time phased diagrams.
- An element of work performed during the course of a project. Or
- An amount of work that can be identified so that we know what it involves and can recognize, when it starts and finishes.
- An activity normally has an expected duration, an expected cost, and expected resource requirements
- Any schematic display of the logical relationship of project activities.
- Always drawn from left to right to reflect project chronology.
- Usually a combination of arrows and nodes.
Mainly of two types:
- Arrow Diagram
- Node Diagram / Precedence Diagram
- Activities shown by Arrows. Relationship between activities shown by nodes / events.
- Length of arrows does not obey any scale.
- Start-to-finish relationships.
- Numbering of nodes / events.
- Activity duration is forecasted by any of the several means, including:
- Check Past Records.
- Check Standards and / or cost guides, if available.
- Ask the workers, who will do it
- make an educated guess
- Any time units may be allotted to activity durations like days, hours, weeks, months, shifts, etc.
- In CPM, a single duration is forecasted for an activity.
- In PERT (Program Evaluation & Review Techniques), 3 durations are forecasted for an activity and mean taken by weighted average method. Then, Project’s Duration or any Event Completion Time is calculated by probability distribution.
- Calculates the following for each activity
EST = Earliest Starting Time
EFT = Earliest Finishing Time
LST = Latest Starting Time
LFT = Latest Finishing Time
TF = Total Float
FF = Free Float
- Total Float is Maximum time for which an activity can be delayed without delaying the project.
- Free Float is maximum time for which an activity cane be delayed without delaying the start of proceeding activity.
- Total Float = Free Float + Interfering Float
- The path (or paths) in the network diagram, from start to finish, on which all the activities have zero total and free floats, is called Critical Path.
- It is the longest path (or paths) from start to finish in a net work diagram.
- It gives minimum normal time to complete a project.
- It is usually marked by double lined arrows in a network diagram.
SINGLE SPAN BRIDGE PROJECT
- Activities shown by Nodes, relationship between Activities shown by arrows or links.
- Easier to construct.
- Generally no need of dummies. Instead dummies used only to give single start or finish.
- CPM Calculations similar to Arrow diagrams.
- Gives Pictorial Representation of Activities.
- Activities begin at EST and show their EFT, FF, TF, Durations, etc.
- Arrows at the relative ends to show dependency.
- Status Line Concept
- Unable to show complete interdependency between Activities.
- Time-scaled Network Diagrams show complete interdependency between Activities.
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