Presentation on theme: "CE 405 - SCHEDULING Review: Three fundamental steps in developing a Schedule are: 1.Identify the Activities 2.Determine the Durations 3.Establish the Logical."— Presentation transcript:
CE 405 - SCHEDULING Review: Three fundamental steps in developing a Schedule are: 1.Identify the Activities 2.Determine the Durations 3.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. 1.What interaction does this Activity have with the other Activities? 2.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? 1.What Activities must be completed before I can Start work on this Activity 2.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: 1.Dependencies
CE 405 - SCHEDULING The three terms that pertain to the Logic of your Schedule are: 1.Dependencies 2.Sequential work
CE 405 - SCHEDULING The three terms that pertain to the Logic of your Schedule are: 1.Dependencies 2.Sequential work 3.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? 1.Survey/Layout 2.Excavate 3.Form/Place Footing 4.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 – 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? 1.Interior finishes – baseboard, trim 2.Finish electrical work/fixtures 3.Finish mechanical/HVAC 4.Finish plumbing 5.Cabinetry 6.Flooring
CE 405 - SCHEDULING What three Scheduling Network Systems are most commonly used for Construction Projects?
CE 405 - SCHEDULING 3 Scheduling Network Systems? 1.Activity-on-Node (AON) [Chptr 6] 2.Activity-on-Arrow (AOA) [Chptr 7] 3.Precedence Diagramming Method (PDM – leads, lags) [Chapter 17] All three use the Critical Path Method (CPM)
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 orTF = 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 ofdeterministic?
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 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? 1.Notice to Proceed (NTP) Usually considered to be the first day of your Schedule (Day 1)
CE 405 - SCHEDULING Examples of Milestones? 1.Notice to Proceed (NTP) 2.Building Dried-in
CE 405 - SCHEDULING Examples of Milestones? 1.Notice to Proceed (NTP) 2.Building Dried-in 3.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? 1.Notice to Proceed (NTP) 2.Building Dried-in 3.Contract Substantial Completion 4.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 aFinish-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: 1.Physical 2.Safety 3.Resource 4.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? 1.Financial 2.Environmental – Spawning/Nesting periods Monsoon/Runoff periods Daily Noise Restriction timeframes
CE 405 - SCHEDULING Other common constraints? 1.Financial 2.Environmental 3.Contractual – Required completion of one phase before starting on another
CE 405 - SCHEDULING Other common constraints? 1.Financial 2.Environmental 3.Contractual 4.Regulatory – Compliance with local, county, state, or federal requirements
CE 405 - SCHEDULING What are the impacts of these common constraints? 1.Reduce Scheduling Flexibility 2.Lengthen Project Duration 3.Increase Project Cost 4.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 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 asMultiple Predecessor Logic
ACTIVITY RELATIONSHIPS A Burst is just the opposite of aMerge – once the Predecessor Activity is substantially complete, numerous other Successor Activities can start. A Burst is also referred to asMultiple Successor Logic
ACTIVITY RELATIONSHIPS Logic Busts 1.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 Activitys completion.
11-10 1070 809030506020 40 Open Ends continued: START FINISH NOTE: Recommend that each project have only two open ends, the NTP activity and the Project Complete activity.
11-10 1070 809030506020 40 Open Ends continued: START FINISH Notice the relationship between activity 30 and 50 is missing, creating two additional open ends. What will happen when this network is scheduled? Oops! 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. Open Ends: 11-10
1070 809030506020 40 Open Ends continued: START FINISH 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. Oops! Open ends!
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 4.Loops – The infamous Do Loop As in Hes stuck in a Do Loop.
ACTIVITY RELATIONSHIPS 4.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
Loops indicate circular logic between two activities. Scheduling Software will not calculate a schedule until the loop is eliminated. Circular Relationships (Loops): SA1000SA1020SA1010 11-9
ACTIVITY RELATIONSHIPS 4.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 4.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 Dont 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: 1.Responsibility 2.Area/Phase 3.Trade 4.Department
CE 405 - SCHEDULING Activity Coding Systems Each Activity Code can be broken down further (SureTrak Values) Department could include: 1.Construction 2.Planning and Design 3.Purchasing
CE 405 - SCHEDULING Responsibility could include: 1.Project Manager 2.Superintendent 3.Carpentry Foreman 4.Mechanical Subcontractor 5.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.