CE 366PROJECT MANAGEMENT AND

ECONOMICS

Robert G. Batson, Ph.D., P.E.Professor of Construction

EngineeringThe University of Alabama

Rbatson@eng.ua.edu

Chapter 4:Project Planning

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Critical Path Method (CPM)• Based on a graphical model of project activities and

their time dependencies, which forms a “directed network”– More detailed than the Gantt Chart representation– Enables utilization of a network algorithm to identify

“critical path” for project, and “slack” of all other activities– Communicates complex job interdependencies to all– Serves as a basis for fixing work schedules (calendar

dates)– One mechanism for controlling project time, and re-

planning/rescheduling the remaining project activities as necessary

• A computer-aided approach to the three-phase procedure of project planning, scheduling, and time monitoring/control

4.1

Construction Project Planning• Draws focus to what must be done, how it will be

done, and in what sequential order• Time-consuming and difficult, but extremely important• CPM-based planning provides for logic and

thoroughness, at appropriate levels of detail for the project

• Provides for learning by the project team, using experience of team members and other in the firm

• Network development is iterative:– Fill in details obtained from many sources– Review, modify, improve in group meetings– Solicit subcontractor and supplier participation in planning,

to identify potential problems and resolve them early– Update network as project evolves (no plan is perfect)

4.2

Approaches to Project PlanningFive-step Approach1. Determination of the general approach to the project2. Breakdown of the project into activities3. Ascertainment of the sequential relationship among

these activities4. Graphic presentation in the form of a network5. Endorsement by the project teamTwo “planning methodologies”• Beginning-to-end planning: presumes a level of detail,

or adds detail as planning proceeds• Top-down planning (work breakdown structure): Views

project as a hierarchy of work, broken into more detailed pieces at each “level” until sufficient detail is obtained

4.3

Project (or Job) Activities• A single work step that has a recognizable beginning

and end, and consumes time and resources• Guidelines that may help identify/classify activities

1. By area of responsibility2. By category of work (craft or crew requirements)3. By category of work (using equipment requirements)4. By category of work (using materials as guide)5. By distinct structural elements6. By location7. With regard to owner’s work breakdown8. With regard to contractor’s work breakdown

• Level of detail that matches: owner and contractor requirements, such as reporting to higher authority or scheduling subcontractors; the project manager’s “level of schedule control” planned

4.4

Job Logic• The order, as determined by the planner, in which

activities are to be accomplished in the field– Natural “precedence” relationships among two or more– Independent activities that could proceed concurrently,

except for restraints• Several approaches may be possible, and implications

must be determined in an engineering study– Schedule implications revealed by CPM– Cost implications revealed by cost estimating

• Identification and inclusion of restraints in scheduling is a critical responsibility of the planner, working with the project team

• Unexpected restraints are a major cause of cost overruns and schedule slippage

4.5

Restraints• Physical restraints• Material restraints

– Design drawings and specifications– Procurement steps– Fabrication and delivery by selected vendors

• Equipments restraints• Labor restraints

– Subcontractor crews– Contractor personnel with special skills

• Owner-related restraints– Delivery of owner-provided materials– Turn-over of owner’s sites or facilities

• Safety restraints

4.6

Restraints in the CPM Network• Some may be shown as time-consuming activities• Restraints also may be shown as dependencies

between activities• Restraints that involve competition for resources,

such as equipment or labor crews, may be– “Hard-wired” with order of preference shown in

network.– “Resource requirements with priority as a “side

constraint” that CPM refers to in the event of competing needs

• Restraints may include milestone dates or date for project completion; also dates by which a particular activity cannot start before, or must end by

4.7

Top-Down Planning• Preferred in the construction industry• Break overall project into segments• Each segment has a hierarchy of activity levels, referred to as

a Work Breakdown Structure (WBS) – a project outline• Highway Bridge project has six major components (1-6) with

indentured levels and sublevels of activities, such as4.0 Level 1

4.1 Level 24.1.1 Level 3 . . .4.1.5

• See Appendix C

4.8

Work Breakdown Structure• Other uses besides planning:

– Project progress reporting and summarization– Cost reporting and summarization– Starting point for work teams to plan their weekly work

• Developed by the project team from:– WBS segments on completed projects– Experience applied to the project documentation to date– Brainstorming, if work segment is new to the group

• Once the WBS is completed to an acceptable level of detail, creation of activity relationships representing precedence and other restraints can begin– Group or subgroup meeting; individual interviews– Draw the linkage by hand, or in PM software (better)– Review and revise as project network emerges

4.9

Network Symbolic Conventions• Linkages are called “arrows” or “arcs”• Activity-on-arrow (Appendix D)

– Arrows represent activities– Dotted arrows represent logical connections– Nodes (circles or boxes) represent logical

connections

• Activity-on-node (Precedence network)– Arrows represent dependencies among activities– Nodes (circles or boxes) represent activities– Most common in construction industry– Emphasized in Sears, Sears, and Clough

4.10

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Precedence Diagram Development• Correct diagramming is critical to project time management

– Activities from WBS are placed in boxes– Activity dependencies and restraints are modeled as arrows– Resources are generally assumed available to cover demands– Time durations are ignored

• Each activity must be preceded by the project “start” activity or by the completion of a previous activity

• Each activity must have at least one activity that follows, or the activity “finish” of the project

• Milestones, such as “start” and “finish” nodes, have rounded edges in text networks, and consume “zero time”

• Numbering conventions are required for computer-generated networks; generally use increasing sequence of number from start to finish

4.11

Highway Bridge Precedence Diagram• Figure 4.2, General Job Plan

– Six major operations, in chronological order– Could be derived from project Gantt Chart, as well– For context, leading to managerial discussion and

agreement on general ground rules for project (p. 75)

• Figure 4.3, Precedence Diagram (planning version)– Built from WBS, Figure 4.2, and general ground rules;– Uses certain resource restraints,– Material restraints, and– Equipment restraints

4.13

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Value of Precedence Network• Project team has conceptualized entire project,

and is building commitment to the work and each other

• Network is an expedient communication tool– Between field and office (both contractor and owner)– To orient new managers or the workforce– Between prime contractor and subcontractor and

material suppliers– Between contractor and engineer-architect

• Far superior to any form of bar chart or project narrative

• Stage is set for sophisticated scheduling, and project time control, once the project begins

4.14

Repetitive Operations• Some projects naturally involve several parallel

strings of continuing operations, each in physical proximity to others

• Figure 4.4, basic plan for pipeline relocation• Figure 4.5, mile-by-mile plan with

– “Work categories” in left margin implying specialized crews and their equipment move ahead, mile-by-mile

– Moving down the diagram are physical restraints or precedence, with recognition that excavate and string pipe can occur in parallel

• The dotted arrow exiting Activity 170 is the “interface” between the precedence diagram for Pipeline Relocation (Figure 4.5) and Pipeline Crossing Structure (Figure 4.6)

4.15

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Network Level of Detail• Figure 2.1 gives overall flow among principle

operations of the entire project, which will be constructed and managed separately

• Figures 4.3 and 4.5 are detailed precedence diagrams, appropriate for field managers and workers

• Just like in Section 4.15, there will be important interfaces between the networks for the major subprojects

• A master network would likely consist of– Precedence networks for each subproject at a high level

(e.g., Figure 4.2 and Figure 4.4)– Important linkages between them

• Bottom line: Projects are communicated and managed through a series of subnetworks, at appropriate level of detail

4.16

Computer Applications in Planning• Software such as MS Project, Primavera, Timberline

are used by construction firms, large and small, to:– Develop and document the network logic simultaneously– Easily review and revise the plan in group settings– Easily transmit plan to other– Readily apply scheduling algorithms as in Chapters 5,6,

and 7; resource and time management as in Chapters 8 and 9

• Enables– Speedy project planning (an interesting career path, too)– Combining subnetworks developed by different project

managers or subcontractors, to form a master network– Team-building and commitment to project success

4.17

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