Scheduling Flashcards
Why understand CPM schedules?
> To be confident in the associated terminology when dealing with contractors who work w/ them
Primary tool available to the construction project planner
What are the required items for the construction planning phase?
- Identifying activities required and the precedence relationships between activities
- The proper sequencing for the activities required for them to be completed in an optimum amount of time
- The time for materials and installed equipment delivery
- The types, quantities and duration of use of construction equipment
- The classification and number of workers required and for how long
- The amount and timing of financial assistance required
How can you create a schedule?
- Perform WBS (Work Breakdown Structure): identify activities required at the level of complexity desired
- Identify precedence relationships between activities and the proper sequencing for the activities required for them to be completed in optimum time and budget
What are the two types of construction schedules?
- Non-network schedules (eg. Gantt Chart)
2. Network schedules (eg. CPM diagrams, PERT)
What do CPM and PERT stand for?
CPM: Critical Path Method
PERT: Program Evaluation Review Technique
What are some adv. and disadv. of using Gantt charts?
Adv.
> most common
> easy to create and read
> can show logical interrelationships between activities
> can be updated to show status of project
Disadv.
> difficult to show effects of delays, changes, etc.
> does not provide as much useful info as a network schedule
What are the two types of CPM diagrams?
- AOA (activity-on-arrow or arrow) diagram
2. AON (activity-on-node or node) diagram
What is the difference between CPM and PERT?
CPM uses fixed durations for activities, while PERT uses a probability distribution to identify expected durations for activities.
How is the critical path determined?
Critical activities determine project duration and critical path
In AOA diagrams, what do arrows and nodes represent?
Arrows: activities
Nodes: points in time
In AON diagrams, what do boxes and arrows represent?
Boxes: activities
Arrows/Lines: link showing interrelationships of activities
What is Total Float?
It is the max. number of days an activity may be delayed without affecting the project completion time
What is Free Float?
It is the max. time an activity can be delayed without affecting the earliest start of any of the next immediate activities.
What is Independent Float?
It is the max. time an activity may be delayed if the immediate predecessor finishes at its latest finish, and the the immediate successor starts at its earliest start.
What is Critical Path?
It is the longest interconnected path through the network, the length of which equals the project duration activities.
What is Project Crashing?
a technique used to reduce the duration of a project for the least amount of extra cost.
Define Direct Cost:
any cost that can be associated with a discrete physical part of a construction project.
Define Indirect Cost:
any cost that can not be associated with a discrete physical part of a construction project.
What is Resource Leveling
Playing around with the project schedule to potentially reduce the resource requirements
When resource leveling, which activities have priority?
activities with the earliest LS
Say we have good labourers on standby, what can be done to not let them go?
find activities that have float, delay them and move labourers to a later time i.e. bring the peaks down and the valleys up
What are the steps of resource leveling on Ms Project?
1) Assign available resources/resource limit
2) Try leveling resources within available slack
3) If “2)” does not work then level resource w/ out restrictions (outside available slack)
What are the manual resource leveling steps?
1) Assume there is no labour limitation and calculate the project duration
2) Determine the maximum resource requirement in order to complete the project in time
3) Calculate the LS for each activity (LF - DUR)
4) Identify the resource limitation and develop a resource leveling table with time slices
What are the two types of planning?
1) Beginning- to-end planning
2) Top-down planning
Briefly explain beginning-to-end planning.
Begin with activities to be completed and proceed step by step through the project to completion
Briefly explain top-down planning
We start with an overall view of the project and then break it into its major components. Then break down each of the major components into more detail. Continue the process until a sufficient level of detail is attained. The result of this procedure is a Work Breakdown Structure
Why is top-down planning preferred more than beginning-to-end planning in the industry?
When beginning-to -end planning, some projects are so complex that it is difficult to visualize the best way to sequence the
construction operations. Team members may not agree on the level of detail required. There is
also a tendency to use greater detail in the earlier stages of the job and to generalize in the latter
stages. The planning team may leave out entire groups of vital operations and hence drastically
underestimate the time required for completion of the project
What is an advantage of beginning-to-end planning
Taking into account sequence of activities
