CE 405 - SCHEDULING Review: Three fundamental steps in developing a Schedule are: Identify the Activities Determine the Durations Establish the Logical Inter-relationships Activities, Durations, Logic

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

CE 405 - SCHEDULING What is Logic in the context of a Construction Schedule?

CE 405 - 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

CE 405 - 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?

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.

CE 405 - SCHEDULING The three terms that pertain to the Logic of your Schedule are: Dependencies

CE 405 - SCHEDULING The three terms that pertain to the Logic of your Schedule are: Dependencies Sequential work

CE 405 - SCHEDULING The three terms that pertain to the Logic of your Schedule are: Dependencies Sequential work Concurrent work

CE 405 - SCHEDULING What is your definition of Dependencies in a Schedule?

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]

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

CE 405 - SCHEDULING What is your definition of Sequence?

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

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

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)?

CE 405 - 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

CE 405 - SCHEDULING What would be the Activity Sequence for a CMU foundation wall?

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

CE 405 - SCHEDULING The third term associated with logic is concurrent – what does this mean?

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

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

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?

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.

CE 405 - SCHEDULING What concurrent Activities can be accomplished after the building is dried-in and the sheetrock/painting are done?

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

CE 405 - SCHEDULING What three Scheduling Network Systems are most commonly used for Construction Projects?

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)

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

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

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

CE 405 - SCHEDULING What is the definition of “deterministic”?

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”?

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

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

CE 405 - SCHEDULING Review: What is a Milestone?

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

CE 405 - SCHEDULING What are some examples of Milestones that you might build into your Schedule?

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

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

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

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

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.

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

CE 405 - SCHEDULING Primavera software is based on the generic Precedence Diagramming Method (PDM).

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.

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

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

CE 405 - SCHEDULING What is a Constraint in a Scheduling context?

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

CE 405 - SCHEDULING Were the four Activity “relationships” that were just discussed potential constraints (physical, resource, safety, preferential)?

CE 405 - 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?

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?

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

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

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

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

CE 405 - SCHEDULING Every Baseline Schedule overlooks some of these fundamental, basic common constraints. One of the reasons that Schedules have to be continuously updated.

CE 405 - SCHEDULING What will be the Predecessor for most of your initial Procurement Activities (i.e. Prepare Shop Drawings for Windows)?

CE 405 - 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

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

MERGE

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”

BURST

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”

ACTIVITY RELATIONSHIPS Logic Busts Incorrect Open-Ends Redundant Loops

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

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).

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.

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.

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

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

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

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

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

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”

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

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

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

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

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

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

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”.

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.

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

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.

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.

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.

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

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

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

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

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.