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8. 4KF3 Ch. 8 Scheduling Resources and Costs.docx

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McMaster University
Steve Way

Chapter 8: Scheduling Resources and Costs 4KF3 Lecture Notes Scheduling Problems  There are two generic scheduling problems; 1. Time‐constrained project 2. Resource‐constrained project Resource‐constrained Project  Prioritize and allocate resources to minimize delays and maximize resource utilization  Often achieved through levelling or smoothing Time‐constrained Project  Expend resources to achieve schedule targets  Typically achieved through project crashing Resource Leveling  Resource leveling aims to minimize the period‐by-period variations in resource loading by shifting tasks within their slack allowances  The purpose is to create a smoother distribution of resource usage  Several advantages include: – Less hands‐on management is required – May be able to use a “just‐in‐time” inventory policy Page 1 of 15 Chapter 8: Scheduling Resources and Costs 4KF3 Resource Levelling  When resources are leveled, the associated costs also tend to be leveled  The project manager must be aware of the cash flows associated with the project and of the  means of shifting them in ways that are useful to the parent firm  Resource leveling is a procedure that can be used for almost all projects, whether or not resources are constrained Leveling Steps  Develop a network diagram – Determine the critical path – Find activity slack (or float)  Develop a resource loading table  Determine activity late finish dates  Identify resource over allocation  Level the resource‐loading table Network Diagram  Your network will let you determine; o The critical path o Activity durations o Activity slack Page 2 of 15 Chapter 8: Scheduling Resources and Costs 4KF3 Determine Resource Hours  Note that the hours per day is less than eight – Resources are not always available full‐time Step 1: Resource‐Loading Table Step 2: Determine Late Finish Dates  This tells you which activities have slack and which activities are on the critical path  This in turn lets you identify your options Page 3 of 15 Chapter 8: Scheduling Resources and Costs 4KF3 Step 3: Identify Overallocations  Compare usage to a threshold value – January 12th uses 10 resources – too many  Step 4: Level  Level in order to resolve the overallocations  Leveling is an iterative (repeating) process  Resources loading is reconfigured to eliminate overallocations Step 4 – Phase 1  Identify candidates for reconfiguration – Look at the period of overallocation – Determine which activities utilize the resource(s) during that period Step 4 – Phase 1  Activities C, D, E contribute to the overallocation  Activity C is on the critical path  Activities D&E are candidates for reconfiguration Step 4 – Phase 2  Select the activity to be reconfigured  Heuristic (rules of thumb) for prioritizing resource allocation; 1. Activities with the smallest amount of slack 2. Activities with the smallest duration 3. Activities with the lowest activity identification number Page 4 of 15 Chapter 8: Scheduling Resources and Costs 4KF3 4. Activities with the most successor tasks 5. Activities requiring the most resources Step 4 – Phase 2  Activity E has the smallest amount of slack so Activity D should be changed  But that would mean splitting activity D Step 4 – Phase 3  Make adjustments to the schedule  Here Activity E is delayed by 1 day Repeat as Needed  January 12th no longer has an overallocation  Remember, that leveling is an iterative process  Each change has a ripple effect Page 5 of 15 Chapter 8: Scheduling Resources and Costs 4KF3 Step 3: Identify Overallocations  January 22 now has an overallocation Step 4 – Phase 1  Identify candidates for reconfiguration – Activities E, F, I & J all utilize resources on the 22 Step 4 – Phase 2  Activities E & F have no slack time – they are on the critical path Page 6 of 15 Chapter 8: Scheduling Resources and Costs 4KF3 Step 4 – Phase 2  Activities I & J are candidates for reconfiguration  Activity I has the least slack so it gets the resources first, we will delay activity J Step 4 – Phase 3  Make adjustments to the schedule  Here Activity J is delayed by 1 day Resource‐Loading Charts  Steps; 1. Create the activity network diagram Page 7 of 15 Chapter 8: Scheduling Resources and Costs 4KF3 2. Create a table of listing activities, resource usage by activity, duration, early start, slack and late finish 3. List activities in order of increasing slack 4. Draw an initial resource‐loading chart 5. Rearrange activities within their slack 6. Rearrange activities with extra slack if necessary Resource‐Loading Charts Multi‐Project Environments  Key problems; – Inefficient use of resources – Resource bottlenecks – Ripple effects – Heightened pressure on personnel to multi‐task The challenge is to balance the trade-offs between; – Schedule slippage o Remember, late projects often incur penalties. – Resource utilization o You want to smooth your utilization of resources across your portfolio of projects – In‐process Inventory o In this case, in‐process inventory is project work delayed due to lack of resources Resolving Resource Decisions – First in line o Compare start dates – Greatest resource demand o Allocate resources to projects with the greatest resource needs – Greatest resource utilization o Minimize resource idle time – favour projects which use a variety of resources – Minimum late finish time o Activities with the earliest late finish dates are assigned resources first. Page 8 of 15 Chapter 8: Scheduling Resources and Costs 4KF3 – Mathematical programming – Most possible jobs Time‐Phased Time Budget  Define work (what)  Identify time (how long)  Identify time‐phased budget (cost)  Identify resources (how much)  Identify responsible (who)  Identify monitoring points (how well) Critical Chain Path Management  Delays in many projects caused by: – Parkinson’s Law – Self‐protection – Dropped baton – Excessive Multi‐tasking – Resource Bottlenecks – Student syndrome Critical Chain Project Management  Use true 50/50 estimates  Use buffers instead of slack: – Project buffer – Feeder buffer – Resource buffers  Buffers vs. Slack CPM – No Resources Page 9 of 15 Chapter 8: Scheduling Resources and Costs 4KF3 CPM – Resources Limited CCPM Using Buffers Page 10 of 15 Chapter 8: Scheduling Resources and Costs 4KF3 Reading Notes Overview of the Resourcing Scheduling Problem  Will the assigned labour and/or equipment be adequate and available to deal with my project? Will outside contractors have to be used? Do unforeseen resource dependencies exist? Is there a new critical path? How much flexibility do we have in using resources? Is the original deadline realistic?  Resource smoothing: if resources are adequate but the demand varies widely over the life of the project, it may be desirable to even out resource demand by delaying noncritical activities (using slack) to lower peak deman
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