1© Awad S. Hanna, PhD, P.E.1 Estimating and Scheduling CEE 492 Lecture 10 Basic Principles and Practices of Project Scheduling

2 What Will You Learn How to plan projects How to make a time schedule How to allocate resources How to monitor progress How to manage and control the project © Awad S. Hanna, PhD, P.E.

3 Four Project Goals Projects should be completed: On Schedule Within Budget Of Acceptable Quality With Zero Accident © Awad S. Hanna, PhD, P.E.

4 Why Do We Need A Schedule? To establish time frame and organize construction activities To provide a communication tool between all parties involved (contractors, subcontractors, A/E, owner) Contractual requirement Can refer to for modifications To show the impact of productivity- related problems on project completion © Awad S. Hanna, PhD, P.E.

5 1. Bar Charts A Graphical representation of a project in which activities types and duration represented by bars whose length is proportional to their duration. The Hierarchy of Schedules © Awad S. Hanna, PhD, P.E.

Bar Chart Example © Awad S. Hanna, PhD, P.E.

7 2. Networks   Definition A network consists of two basic elements, nodes and links between these nodes.   Arrow Diagram Activities are represented by two nodes and one link (ADM)   Precedence Diagram Activities represented by nodes and links represent the relationship (PDM) © Awad S. Hanna, PhD, P.E.

Shingle Roof Paint Hang Door Place Siding Erect Frame Cast Floor Slab Layout Cast Floor Slab Erect Frame Place Siding Hang Door Paint Shingle Roof Arrow Diagram for a Small Garage Layout Precedence Diagram for a Small Garage © Awad S. Hanna, PhD, P.E.

9 PDM - Precedence Diagram   PDM Network rules:   Activities are represented by boxes or nodes that are assigned properties of the activity they represent.   Precedences are shown by arrows that have both Direction and Time properties.   Precedences consist of two parts: A Relationship and a Lag Value or Constraint   Finish - to - StartFS   Finish - to - FinishFF   Start - to - StartSS   Start - to - FinishSF   Lag = X Days (or other time units) Copyright AACE International © Awad S. Hanna, PhD, P.E.

10 Schedule Development Process Typical Steps Step 1 : Study project information and contract documents. Step 2 : Develop work breakdown structure. Step 3 : Develop activity list. Step 4 : Create dependency list. Step 5 : Estimate activity duration. Step 6 : Draw the CPM diagram and calculate ESD, EFD,LSD, LFD, TF, FF. Step 7 : Review & Revise. Step 8 : Update © Awad S. Hanna, PhD, P.E.

11 Step 1: Study Project Information and Contract Documents   Total project duration   Total duration for each subcontractor   Job complexity and coordination with other trades   Major milestones   Long-term procurement items   Labor market and attitude © Awad S. Hanna, PhD, P.E.

12 Step 2: Develop Work Breakdown Structure   WBS is a hierarchical system that sub- divides larger elements of the project into smaller elements. © Awad S. Hanna, PhD, P.E.

13 Project Breakdown   Construction stages can be broken down into many operations that define the major elements to be performed.   The Single Relationship Finish to Start relationship Each activity must be selected so that all the previously required activities must be completed before the chosen one can begin and all the following activities cannot be started until the chosen one is completed. © Awad S. Hanna, PhD, P.E.

Activity Relationships A B L = 0 or FS a) Finish-to-start relationship (Start of B immediately follows the finish of A) A B L = 3 or SS =3 b) Start-to-start relationship (Start of B must lag 3 days after the start of A) A B L = 3 or FF =3 c) Finish-to-finish relationship (Finish of B must lag 3 days after the finish of A) A B L = 45 or d) Start-to-finish relationship (Finish of B must lag 45 days after the start of A) © Awad S. Hanna, PhD, P.E.

Work Breakdown Structure: Example Super structure Test Electrical Foundation Site Development External work & Site Improvement Interior work and finishes Office Area Warehouse Addition New Parking Project MechanicalPartitions Doors/ Windows Interior Finishes Electrical Pull wire Electrical conduit Secondary power cable & support Electrical panel & boxes Install light fixtures © Awad S. Hanna, PhD, P.E. General Contractors Level Sub Contractors Level (Ex. Mechanical)

Cost Code 0902N Project Number Area Code Work Type Code Distribution Code  Cost code for labor for installing Aluminum Conduit ½ inch diameter (Negotiated Contract) © Awad S. Hanna, PhD, P.E.

17 Format Change   MasterFormat 1995 Edition   16 Construction Divisions   MasterFormat 2004 Edition   2 Groups   5 Subgroups   49 Construction Divisions © Awad S. Hanna, PhD, P.E.

18 Types of Activities   Mobilization   Engineering   Procurement/Approval   Construction   Subcontract   Completion © Awad S. Hanna, PhD, P.E.

19 Principles and Practices of Project Scheduling Example Work break down structure Alliant has decided to self perform the electrical work for their new warehouse expansion of 100,000sq.ft, of which 12,500sq.ft is office space. The warehouse space allows 42.65ft and 53.31ft of clearance to the bottom of the exposed roof structure above. The project is located 20miles from Alliant office in Madison Wisconsin. The site is large with adequate access and plenty of surrounding space for lay down area. Develop what your team can agree is an appropriate Work Breakdown Structure (WBS) of approximately activities for the entire project. Expand the electrical work node to show more details of electrical construction activities. Be prepared to share your WBS with the class. © Awad S. Hanna, PhD, P.E.

20 © Awad S. Hanna, PhD, P.E.

21 © Awad S. Hanna, PhD, P.E.

Work Breakdown Structure Site Development Foundation Superstructure Shell Interior work and finishes (office) Interior work and finishes (warehouse / Manufacturing) Alternation to existing structure External work and Site improvement Manufacturing / Warehouse Expansion Install site drains Install Sprinkler fire loop Install water main City Connection to sanitary sewer Construct manholes Pull wire Test electrical system Electrical Panel & fixture Install light fixture Secondary power cable Electrical conduit © Awad S. Hanna, PhD, P.E.

Bar Chart for Category of WBS Section Materials and Subcontractors (Procurement) Site Preparation and Utilities Foundation and Superstructure Exterior Building Skin Roof Level Work Interior Work and Finishes Alteration Work External Works / Site Improvements Networks No Scale Site Items Foundations To Subsequent Construction Networks Essential Intl. Utilities Complete Site Prep and Utilities FoundationsSuperstructure External Walls Roof Construction Roof Level Works Interior Finishes Alterations External Works Last stage External Works 1 st Stage Completion © Awad S. Hanna, PhD, P.E. General Contractors Scope

24 Step 3: Develop Activity List   Mobilize   Under slab work   Install switch gear and substations   Secondary power cable and supports   Branch conduit for office   Primary conduit   Pull wires for office   Branch conduit   Wall sockets and light fixtures for office   Panels and boxes for office   Pull wire   Road lighting   Wall sockets and light fixtures   Panels and boxes   Test electric for office   Test electrical   Install and test vending equipment for office   Test and activate power   Install and test vending equipment   Punch list © Awad S. Hanna, PhD, P.E.  Subcontractors Scope (Electrical)

Step 4: Create Dependency List and Eliminate Redundancy © Awad S. Hanna, PhD, P.E.

26 Establish the Sequence of Work Establish the Sequence of Work 1.Physical Exists between two or more activities when one cannot start until another is partially or totally complete (i.e. cannot pull wire until conduits have been installed) 2.Safety Exists when simultaneous performance of two activities can result in a safety hazard 3.Resource Due to limited resources availability, two activities may not be able to use resource at the same time (i.e. a crane cannot be used for both pouring walls and erecting steel) 4.Preferential How the scheduler wishes certain activities to be sequenced (where to start, winter work) © Awad S. Hanna, PhD, P.E.

Precedence Diagram - Sequence Stepped and Numbered © Awad S. Hanna, PhD, P.E.

28 Step 5: Estimate Activity Duration From company's record From standard estimating guide Interviewing field personnel © Awad S. Hanna, PhD, P.E.

29 © © Awad S. Hanna, PhD, P.E.

Examples of Sources other than R.S. Means © Awad S. Hanna, PhD, P.E.30

31 © Awad S. Hanna, PhD, P.E. The NECA Manual of Labor Units

32 Calculation of Activity Durations   Labor-hour Productivity Method Total Labor-hours required for an activity = (Labor-hours /Unit )* (QTY) Total Days = © Awad S. Hanna, PhD, P.E.

33 Step 6 Draw CPM Schedule © Awad S. Hanna, PhD, P.E.

34 Network Schedule: An Overview   Critical Path Method (CPM)   Network of interconnected activities   Overcome the disadvantages of bar charts © Awad S. Hanna, PhD, P.E.

Precedence Representation Activity Number Activity Name Duration or ESDNO.EFD Description LSDDurationLFD © Awad S. Hanna, PhD, P.E.

36 PDM – Precedence Diagram  PDM Activities comprised of  Activity description  None representing the activity  Arrow representing relationship / dependency  Point indicating direction of relationship / dependency Pull WireInstall Conduit Activity “A”Activity “B” © Awad S. Hanna, PhD, P.E.

37 Rules for Developing Precedence Diagrams Rule #1: Eliminate redundant linkage 20 A 30 B 30 C 20 A 30 B 40 C (a) Incorrect Representation (b) Correct Representation © Awad S. Hanna, PhD, P.E.

Closing The Network to Give Single Beginning and Ending Nodes Rule #2: Every project should have single beginning and ending node AD CE B (a) Incorrect Representation AD CE (b) Correct Representation Starting DummyFinish Dummy B © Awad S. Hanna, PhD, P.E.

39 Rule #3: Before an activity may begin, all activities preceding it must be completed (Finish to Start relationships) Finish to Start Relationship A C B © Awad S. Hanna, PhD, P.E.

40 Rule #4: Activity number must not be duplicated in the network Rule #5: Any two activities may be directly connected by no more than one link AC (Incorrect representation) © Awad S. Hanna, PhD, P.E. Finish to Start Relationship

Retaining Wall Precedence Diagram Wall 1 Wall 2 Footing 1 Footing 2 10 Footing 1 40 Wall 2 20 Footing 2 30 Wall 1 © Awad S. Hanna, PhD, P.E.

42 Scheduling Computations for Precedence Networks © Awad S. Hanna, PhD, P.E.

43 The Four Activity Times   ESD - Early Start Date   EFD - Early Finish Date   LSD - Late Start Date   LFD - Late Finish Date © Awad S. Hanna, PhD, P.E.

44 PDM Activity Notation ES LS EF LF Duration Activity Identifier © Awad S. Hanna, PhD, P.E.

45  Early Start Date ESD, for an activity is the earliest point in time that the activity can begin.  Late Finish Date LFD, for an activity is the latest point in time that activity must be completed without delaying the project. © Awad S. Hanna, PhD, P.E. Start and Finish Dates

46 Forward & Backward Pass Copyright AACE International   Assume all activities:   Begin on the morning of the scheduled start date   End the evening of the scheduled finish date   Milestones occur on the evening of the day its last predecessor finished   Understand how various CPM software programs calculate forward / backward passes   Not all are created equal! © Awad S. Hanna, PhD, P.E.

Critical Path Method ( Free Float and Critical Path) © 10 B C E D F A G Sequence Step TF=0 FF=0 TF=0 FF=0 TF=5 FF=0 TF=6 FF=1 TF=0 FF=0 TF=7 FF=7 TF=0 FF= Free Float for an activity is equal to the value of minimum Link Lag values for all links exit from the activity. © Awad S. Hanna, PhD, P.E.

48 Forward Pass Rules Rule 1: The initial project event is assumed to occur at time zero. Rule 2: All activities are assumed to start as soon as possible, that is, as soon as all the predecessor activities are completed. Rule 3: The early finish time of an activity is merely the sum of its early start date and the estimated activity duration. © Awad S. Hanna, PhD, P.E.

49 Forward Pass Rules (cont.) Rule 4: The late Start Date LSD I is found by subtracting the activity duration T I from the Late Finish Date LFD I LSD I = LFD I - T I © Awad S. Hanna, PhD, P.E.

50 Forward Pass Rules (cont.) Rule 5: At merge point, the early start is the largest value of the preceding early finish time EFD = 6 EFD = 9 ESD = 9 Forward © Awad S. Hanna, PhD, P.E.

Forward Pass Example © Awad S. Hanna, PhD, P.E.

52 Backward Pass Rules Rule 6: In the backward pass, the latest finish date of an activity is the smallest late start value of the following activities. (i.e. activities bursting from activity in question) LFD = 37 LSD = 42 LSD = 37 Backward 12 © Awad S. Hanna, PhD, P.E.

Backward Pass Example © Awad S. Hanna, PhD, P.E.

54 Float Concept   Total Float: The time span in which the completion of an activity may occur and not delay the termination of the project.   Free Float: The time span in which the completion of an activity may occur and not delay the termination of the project nor delay the start of the following activity. © Awad S. Hanna, PhD, P.E.

55 Link Lag   A link lag is the difference between the early start date of an activity and the early finish date of the preceding activity. LAG IJ = ESD J - EFD I I Activity EFD J ESD J EFD I ESD I J Activity © Awad S. Hanna, PhD, P.E.

56 Critical Path   The Critical Path is the sequential combination of activities and relationships from project start to finish that requires the longest time to complete.   The Critical Path is the path with the least path float. © Awad S. Hanna, PhD, P.E.

57 Workshop 1. Data for a small project is tabulated below. Construct a precedence network for this project and compute early start and finish dates, total floats, and free floats for each activity. Show these values on the network and indicate the critical path. Ⓒ © Awad S. Hanna, PhD, P.E.

#11 Pull Wires 8 #8 Branch Conduit 9 #4 Secondary power cable & Supports 5 #6 Primary Conduit 10 #16 Test electrical 3 #20 Punch List 1 #18 Test and Activate power 4 #14 Panels and Boxes 6 #19 Install and Test Vending Equipment #2 Under slab work ESDEFD LSDLFD Lag Act.# Activity Duration #12 Road Lighting #9 Wall sockets & light fixtures for office 6 #5 Branch Conduit for office 5 #7 Pull Wires for office 4 #10 Panels and Boxes for office 3 #15 Test electric for office 3 #17 Install and Test Vending Equipment for office 7 #13 Wall sockets & light fixtures Office Warehouse 1 #3 Install Sw. Gear and Substations 6 #1 Mobilize 5 Precedence Diagram (Electrical Project)

59 Step 7   Compare duration to industry standard and the Hanna Charts.   Review coordination with other trades and make sure that density level is 250 sq.ft / worker or more.   Review activities that can lead to delay. © Awad S. Hanna, PhD, P.E.

60 Step 8. Updating the Schedule Purpose: To correct the target plan to meet the project objective Source of changes in the original plan: Unforeseen events (delay) Error in the original plan (duration and logic) Change orders (added and deleted scope) Procurement delay Labor difficulties (strike, jurisdictional disputes, availability) Accidents © Awad S. Hanna, PhD, P.E.

61 Project Control   Small projects - low cost - short duration   Detailed network   Reporting mechanism   Middle-sized projects (300 activities)   Detailed network   Summary network   Area and craft network   Large Projects   Same as middle-size project + summary bar chart © Awad S. Hanna, PhD, P.E.

62 Setting the Target Schedule   Early Start Schedule As Target for Control   Problem: Requires high effort to keep the plan working   Late Start Schedule As Target for Control   Problem: Because every activity is timed to start as late as possible, project overruns are sure to follow © Awad S. Hanna, PhD, P.E.

63 Target Schedule   Activities may be positioned for early or late start or somewhere in between.   Non-critical activities allow intermediate start. © Awad S. Hanna, PhD, P.E.

64 Anticipated Target S-Curve © Awad S. Hanna, PhD, P.E.

65 The S-Curve Fields © Awad S. Hanna, PhD, P.E.

66 Sample Project Cost Data © Awad S. Hanna, PhD, P.E.

67 Early Start Tree © Awad S. Hanna, PhD, P.E.

68 Late Start Tree © Awad S. Hanna, PhD, P.E.

69 Target Network © Awad S. Hanna, PhD, P.E.

70 Project S-Curve © Awad S. Hanna, PhD, P.E.

71 Resource Leveling Advantages/Applications of Resource Leveling 1. Maintains the lowest uniform number of employees to perform the work 2. Allows for planning of material delivery 3. Reduces the daily demand for dollars © Awad S. Hanna, PhD, P.E.

72 Resource Histogram © Awad S. Hanna, PhD, P.E.

73 Leveling Example – Traditional Approach © Awad S. Hanna, PhD, P.E.

74 How to Develop Manpower Loading Curve 1. 1.Divide the project into tasks 2. 2.For every task, find out how long it takes and how many workers are required to perform every task 3. 3.Prepare a bar chart or activity network 4. 4.For everyday, find out the number of activities in progress and the total number of workers/day 5. 5.Manpower loading is the relationship between Time or Percent complete (X-axis) and man-hours per week (Y-axis) 6. 6.S-curve is the relationship between Time or Percent complete (X-axis) and Cumulative man- hours per week (Y-axis) © Awad S. Hanna, PhD, P.E.

2 12 x Cumulative man-hour © Awad S. Hanna, PhD, P.E. How to Develop Manpower Loading Curve

76 Trapezoidal Method © Awad S. Hanna, PhD, P.E.

Mechanical All Others All Electrical Mechanical Industrial © Awad S. Hanna, PhD, P.E. Normal Project Duration for Mechanical and Electrical Projects

78 Electrical Estimating Data Note : Industry average data was used for this example. It is recommended that actual company data be used for such calculations. Structure DescriptionSF/MHStructure DescriptionSF/MH Commercial Stores23.82Parking Lots, 2.5 FC149 Commercial Stores, Quality Retail14.88Garages, 5 FC98.4 Market Buildings22.93Assembly Buildings, Lt. Industrial22.53 Recreational Buildings20.42Laboratory Buildings, Wet Science7.7 Schools, Elementary & High8.7City Hall9.71 College Buildings13.8Hotel, Low Rise25.95 College Dormitory21.73Hotel, Mid Rise21.33 Clinic-MOB8.42Hotel, High Rise, First Class19.32 Hospitals, Full Service5.96Hotel, High Rise, Deluxe17.39 Office Buildings, Low Rise13.95Hotel, High Rise, Luxury14.86 Office Buildings, High Rise17.27Housing, Low Rise42.58 Warehouses44.01Housing, High Rise29.8 © Awad S. Hanna, PhD, P.E.

79 Problem statement: Badger Electric has contracted to perform the electrical work for a new warehouse of 100,000 sq. ft., of which 12,500 sq. ft. is office space. The project is located 20 miles from Badger’s office in Madison, WI. The site is large with adequate access and plenty of space for lay down area. Determine: 1) Approximate workhours to complete the electrical work, 2) Normal electrical project duration, and 3) Peak number of workers. Example Problem © Awad S. Hanna, PhD, P.E.

80 TT method for Workforce Loading 0.5x to 0.6x0.25x0.15x to 0.25x Peak Workforce Project Duration Figure 1: Trapezoidal Technique © Awad S. Hanna, PhD, P.E.

81 Effect of Schedule Compression & Acceleration 1. Overtime 2. Overmanning 3. Shift © Awad S. Hanna, PhD, P.E.

1. Effect of overtime Cumulative Effect of Overtime on Productivity 50- and 60-Hour Work-Weeks Productivity Weeks 60 Hour Week 50 Hour Week Figure is based on information from Scheduled Overtime Effect on Construction Projects, The Business Roundtable(1980) © Awad S. Hanna, PhD, P.E.

1. Effect of Overtime (Cont.) Scheduled Overtime: Productivity RateActual Hour Hours Gained Number of Output Over 40 Hours Overtime 40 Hour 50 Hour60 Hour50 Hour60 Hour 50 Hour 60 Hour Work Weeks WeekWeekWeekWeekWeekWeekWeek & up  Scheduled Overtime Productivity decreases in terms of Hours per Week for 50 and 60-Hour Weeks (The Business Roundtable 1980) ©

84 Productivity Loss = *Act. Peak/Avg * Log (Act. Peak) Applicable Range Peak/Avg. Ratio: 1.7~3.8 Actual Peak: 4 ~ 50 Project Size: 700 ~208,000 Manhrs 2. Quantifying Impact of Overmanning © Awad S. Hanna, PhD, P.E.

85 Quantifying Impact Productivity Loss = Ln (%Shift Work) Applicable Range % Shift Work: 2%~53% Project Size: 3,000 ~ 550,000 Manhrs © Awad S. Hanna, PhD, P.E.