1. CE SCHEDULING
Review: Three fundamental steps in developing a Schedule are:
Identify the Activities
Determine the Durations
Establish the Logical Inter-relationships
Activities, Durations, Logic

2. CE 405 - SCHEDULING Activities, Durations, Logic
None of these three is really a single, stand-alone operation
Experienced Schedulers often think of these three processes as a single process – especially the relation of durations to logic

3. CE SCHEDULING
What is Logic in the context of a Construction Schedule?

4. CE SCHEDULING
Logic is the relationship(s) that any given Activity has with all the other Activities in the Schedule.
What interaction does this Activity have with the other Activities?
If you change when or how this Activity is done – what happens to the other Activities? – ripple effect

5. CE SCHEDULING
When you are developing the Logic of your Schedule –
What is the primary consideration that you will be addressing if you want to get the work done as expeditiously as possible regarding each and every Activity?

6. CE 405 - SCHEDULING Expedited Logic?
What Activities must be completed before I can Start work on this Activity
What Activities can be worked on at the same time that I am working on this Activity.

7. CE SCHEDULING
The three terms that pertain to the Logic of your Schedule are:
Dependencies

8. CE SCHEDULING
The three terms that pertain to the Logic of your Schedule are:
Dependencies
Sequential work

9. CE SCHEDULING
The three terms that pertain to the Logic of your Schedule are:
Dependencies
Sequential work
Concurrent work

10. CE SCHEDULING
What is your definition of Dependencies in a Schedule?

11. CE 405 - SCHEDULING Definition of Dependencies?
What work (Activities) must be completed before I can start work on this Activity [Predecessors]
What work (Activities) can not start until work on this Activity is completed [Successors]

12. Predecessor - controls the start or finish of another activity
Successor - depends on the start or finish of another activity
Predecessor to Act. B
Successor to Act. B
10-3

13. CE SCHEDULING
What is your definition of Sequence?

14. CE 405 - SCHEDULING Definition of Sequence?
A group (string or chain) of Activities that proceed in a logical order – the preceding Activity has to be Substantially Complete before the follow-on Activity can start

15. Sequence – A group of Activities that logically follow one after the other
10-3

16. CE 405 - SCHEDULING Review:
The term Substantially Complete was used on the preceding slide – what does it mean in relation to a Construction Activity (not the job as a whole)?

17. CE SCHEDULING
Substantially Complete is when work on a given Activity has proceeded to the point that work on following Activities can Start.
Work on a CMU block wall can start even if the forms have not been stripped off the footings

18. CE SCHEDULING
What would be the Activity Sequence for a CMU foundation wall?

19. CE 405 - SCHEDULING Activity Sequence for foundation wall?
Survey/Layout
Excavate
Form/Place Footing
Lay CMU block
Each Successor Activity logically follows the Predecessor Activity

20. CE SCHEDULING
The third term associated with logic is concurrent – what does this mean?

21. CE 405 - SCHEDULING Definition of concurrent?
What other Activities can be worked on at the same time that work is proceeding on this Activity?

22. Concurrent Activities
Concurrent Activities – Activities that can be worked on at the same time
Concurrent Activities
10-3

23. CE 405 - SCHEDULING Definition of concurrent?
After a building is dried-in and the interior is painted – what would be some of the concurrent Activities that could be worked on?
First of all – what does dried-in mean?

24. CE 405 - SCHEDULING Dried-in definition?
All work necessary to “waterproof” the interior is complete
Shingles are on, doors and windows are in, siding/fascia/soffits are done, etc.

25. CE SCHEDULING
What concurrent Activities can be accomplished after the building is dried-in and the sheetrock/painting are done?

26. CE 405 - SCHEDULING Concurrent Activities after dried-in?
Interior finishes – baseboard, trim
Finish electrical work/fixtures
Finish mechanical/HVAC
Finish plumbing
Cabinetry
Flooring

27. CE SCHEDULING
What three Scheduling Network Systems are most commonly used for Construction Projects?

28. CE 405 - SCHEDULING 3 Scheduling Network Systems?
Activity-on-Node (AON) [Chptr 6]
Activity-on-Arrow (AOA) [Chptr 7]
Precedence Diagramming Method (PDM – leads, lags) [Chapter 17]
All three use the Critical Path Method (CPM)

29. CE 405 – SCHEDULING CRITICAL PATH
Critical Path Method (CPM) handout
Logic Boxes – numerous layouts
Combination Convention
BOTD + EOTD [Primavera]

30. CE 405 – SCHEDULING CRITICAL PATH
Primavera Combination Logic:
BOTD and EOTD combined
Forward Pass: EF = ES + Dur – 1
Backward Pass: LS = LF – Dur + 1
Total Float: TF = LS – ES
or TF = LF – EF
Critical Path: Sequence where TF = 0

31. CE 405 - SCHEDULING Network Model Characteristics:
1. Discrete Activities
2. Deterministic (vs Probabilistic) Durations
3. Deterministic Logic
4. Activities “Flow” from Start to Finish

32. CE SCHEDULING
What is the definition of “deterministic”?

33. CE 405 - SCHEDULING Definition of “deterministic”?
You have “pre-supposed” (i.e. made your mind up) that things will proceed in a preconceived manner to an all ready decided end result (i.e. a foregone conclusion)
Contrasted with “probabilistic”?

34. CE 405 - SCHEDULING Definition of “probabilistic”?
The likelihood (statistical) that a given alternative or option will happen
Construction Schedules require fixed Start and Finish dates to enable all the participants to Plan the progression of their work
Deterministic = Reasonable Certainty

35. CE 405 - SCHEDULING Network Elements: Activities Milestones
Activity Relationships (Logic)

36. CE SCHEDULING
Review:
What is a Milestone?

37. CE 405 - SCHEDULING Review: What is a Milestone?
A Milestone marks a “point-in-time” – but unlike an Activity, it does not consume any time within a Construction Schedule

38. CE SCHEDULING
What are some examples of Milestones that you might build into your Schedule?

39. CE 405 - SCHEDULING Examples of Milestones? Notice to Proceed (NTP)
Usually considered to be the first day of your Schedule (Day 1)

40. CE 405 - SCHEDULING Examples of Milestones? Notice to Proceed (NTP)
Building “Dried-in”

41. CE 405 - SCHEDULING Examples of Milestones? Notice to Proceed (NTP)
Building “Dried-in”
Contract Substantial Completion
Work on all Activities has progressed to the point that the Project could be used for its intended purpose
Liquidated Damages not assessed

42. CE 405 - SCHEDULING Examples of Milestones? Notice to Proceed (NTP)
Building “Dried-in”
Contract Substantial Completion
Project Complete
The Owner has accepted the work and will make Final Payment

43. CE 405 - SCHEDULING Activity-On-Node (AON) Networks:
AON Networks are normally displayed as “boxes” connected with “lines”. The “lines” indicate some form of relationship between the “boxes” at each end.

44. Red logic boxes
= Critical Path
“X-ed” boxes means Activity is complete.

45. CE SCHEDULING
Primavera software is based on the generic Precedence Diagramming Method (PDM).

46. CE 405 - SCHEDULING Activity-On-Node (AON) Networks:
By definition – preceding [Predecessor] Activities in an AON network must Finish before the following [Successor] Activity can Start. This is described as a “Finish-to-Start” relationship.

47. CE 405 - SCHEDULING REVIEW:
What were the four types of Activity Relationships that we covered during the Bar Chart discussion?

48. CE 405 - SCHEDULING Four types of Activity Relationships: Physical
Safety
Resource
Preferential

49. CE SCHEDULING
What is a Constraint in a Scheduling context?

50. CE 405 - SCHEDULING What is a Constraint in a Scheduling context?
Something that controls the accomplishment of an Activity

51. CE SCHEDULING
Were the four Activity “relationships” that were just discussed potential constraints (physical, resource, safety, preferential)?

52. CE SCHEDULING
Were the four Activity “relationships” that were just discussed potential constraints (physical, resource, safety, preferential)?
Absolutely.
What are some other common constraints you will encounter?

53. CE 405 - SCHEDULING Other common constraints? 1. Financial
Does the Owner have sufficient funding to pay for the work
Do you (Contractor) have enough $ to buy materials and pay labor?
Are your subs financially solvent?

54. CE 405 - SCHEDULING Other common constraints? Financial
Environmental –
Spawning/Nesting periods
Monsoon/Runoff periods
Daily Noise Restriction timeframes

55. CE 405 - SCHEDULING Other common constraints? Financial Environmental
Contractual –
Required completion of one phase before starting on another

56. CE 405 - SCHEDULING Other common constraints? Financial Environmental
Contractual
Regulatory –
Compliance with local, county, state, or federal requirements

57. CE 405 - SCHEDULING What are the impacts of these common constraints?
Reduce Scheduling Flexibility
Lengthen Project Duration
Increase Project Cost
Complicate/Confuse your basic Scheduling Logic

58. CE SCHEDULING
Every Baseline Schedule overlooks some of these fundamental, basic common constraints.
One of the reasons that Schedules have to be continuously updated.

59. CE SCHEDULING
What will be the Predecessor for most of your initial Procurement Activities (i.e. Prepare Shop Drawings for Windows)?

60. CE SCHEDULING
Predecessor for most of your initial Procurement Activities?
Notice to Proceed
The only initial constraint for most Procurement Activities is having the Owner tell you to start work
Oftentimes you will start on your Submittals before receiving NTP

61. ACTIVITY RELATIONSHIPS
Other Relationship Terminology
Multiple Successors – “Merge”
Multiple Predecessors – “Burst”
Combinational Logic

62. MERGE

63. ACTIVITY RELATIONSHIPS
Think of a “Merge” as a “funnel” where the whole Project “necks-down” (i.e. a bottleneck) and has to flow through a single Activity.
A “Merge” is also referred to as “Multiple Predecessor Logic”

64. BURST

65. ACTIVITY RELATIONSHIPS
A “Burst” is just the opposite of a “Merge” – once the Predecessor Activity is substantially complete, numerous other Successor Activities can start.
A “Burst” is also referred to as “Multiple Successor Logic”

66. ACTIVITY RELATIONSHIPS
Logic Busts
Incorrect
Open-Ends
Redundant
Loops

67. ACTIVITY RELATIONSHIPS
Logic Busts
Incorrect – When your Schedule shows that you will be painting a wall before you hang and tape the drywall – the Predecessor is not a realistic constraint on the Successor activity

68. ACTIVITY RELATIONSHIPS
Logic Busts
2. Open-Ends – Your Schedule should always Start with one single Activity (normally NTP); and should always Finish with one single Activity (normally Project Complete).

69. ACTIVITY RELATIONSHIPS
Logic Busts
2. Open-Ends – When an Activity does not have a Predecessor, the Scheduling software default assumption is that the Activity starts on Day 1. This creates unrealistic durations and does not link Predecessor Activities.

70. ACTIVITY RELATIONSHIPS
2. Open-Ends – When an Activity does not have a Successor, the Scheduling software assumes that the required Finish date is the last day of your Schedule. This creates an unrealistic duration and does not constrain Successors that are dependent on this Activity’s completion.

71. Open Ends continued:
FINISH 10 70
START 20 30 50 60 80 90 40
NOTE: Recommend that each project have only two open ends, the NTP activity and the Project Complete activity.
11-10

72. Open Ends continued:
Oops! Open ends!
FINISH 10 70
START 20 30 50 60 80 90 40
Notice the relationship between activity 30 and 50 is missing, creating two additional open ends. What will happen when this network is scheduled?
11-10

73. Open Ends:
No predecessor - activity uses Project start date as its early start
No successor - activity uses project finish as its late finish
Open ended activities can portray an unrealistic amount of total float.
11-10

74. Open Ends continued:
Oops! Open ends!
FINISH 10 70
START 20 30 50 60 80 90 40
Activity 30 “thinks” it has until the end of the job to get done.
Activity 50 “thinks” it can start at the beginning of the job.
Both have an unrealistic amount of float.
11-10

75. ACTIVITY RELATIONSHIPS
Logic Busts
2. Open-Ends – Fortunately for you, SureTrak provides an Error Report that lists the Activities in your Schedule with Open-Ends

76. ACTIVITY RELATIONSHIPS
Logic Busts
3. Redundant – Usually develops in Sequential Activities where a Predecessor is shown to not only constrain the immediate Successor, but also “Successors-to-the-immediate-Successor”

77. Redundant Logic – When an Activity is a Predecessor more than once for an Activity that occurs later in the Project
10-3

78. ACTIVITY RELATIONSHIPS
Logic Busts
3. Redundant – This becomes a problem when you have to revise your Schedule and you are unaware or overlook the secondary constraint

79. ACTIVITY RELATIONSHIPS
Loops – The infamous “Do Loop”
As in “He’s stuck in a Do Loop.”

80. ACTIVITY RELATIONSHIPS
Loops – The infamous “Do Loop”
It goes back to the Basic and Fortran 4 programming languages and “If-Do” commands.
A common error caused the computer to “run in a circle” that it could not progress out of

81. Circular Relationships (Loops):
Loops indicate circular logic between two activities.
Scheduling Software will not calculate a schedule until the loop is eliminated.
SA1000
SA1010
SA1020
11-9

82. ACTIVITY RELATIONSHIPS
Loops – The infamous “Do Loop”
Eventually the computer would “Time-Out” and reject your program
Then you would go thru your box of computer cards, one-by-one, and try to figure out where your error was

83. ACTIVITY RELATIONSHIPS
Loops – “Logic Loops” (Circular Logic) are the same phenomenon, but SureTrak again gives you an Error Report that tells you which Activities are the problem
The computer is essentially just like a dog “Chasing-its-tail”.

84. CE 405 - SCHEDULING Activity Numbering
SureTrak automatically assigns numbers to your Activities as you load them into your Schedule. The default spacing is an increment of 10.
Other than the fact that each Activity will have a unique number, these numbers are meaningless.

85. CE 405 - SCHEDULING Activity Numbering
Don’t waste your time trying to group your Activities by number – there are much easier ways to do it

86. CE 405 - SCHEDULING Activity Numbering
Work Breakdown Structures (WBS) – many companies have elaborate, extensive numerical coding systems used primarily for accounting or to develop historical estimating info. Each company has its own “twist” on these – we will not use them.

87. CE 405 - SCHEDULING Activity Coding Systems
These are what we will use in SureTrak to group, sort, organize, prioritize – whatever you want to do to select certain groups of Activities for the purpose that you need.

88. CE 405 - SCHEDULING Activity Coding Systems
You can assign Activity Codes at any time to as many Activities that you select – organizing your Schedule this way gives you infinite flexibility.

89. CE 405 - SCHEDULING Activity Coding Systems
SureTrak provides you with numerous Activity Code groups and you can also create your own specialized Activity Codes
At the end of the Semester, we will develop reports sorted and prioritized by Activity Code

90. CE 405 - SCHEDULING Activity Coding Systems
Some common Activity Codes are:
Responsibility
Area/Phase
Trade
Department

92. CE 405 - SCHEDULING Activity Coding Systems
Each Activity Code can be broken down further (SureTrak “Values”)
Department could include:
Construction
Planning and Design
Purchasing

94. CE 405 - SCHEDULING Responsibility could include: Project Manager
Superintendent
Carpentry Foreman
Mechanical Subcontractor
Soil Testing Firm
Whatever you need for the Job

95. CE 405 - SCHEDULING Closing Comment
For your Schedule to be the effective communication tool that it needs to be, the logic has to be complete and appropriately detailed so it “flows” in a coherent manner for everyone who uses it.