www.mdcsystems.com tricks, traps and ploys used in construction scheduling presented by mdc systems...

www.MDCSystems.com

Tricks, Traps and Ploys Used

in Construction Scheduling presented by

MDCSystems®

Providing Expert Solutions for Construction Worldwide

James McKay, PE AIA

Vice President

James Gorman

Senior Consultant

Why Schedule ?

“ Except in the middle of a battlefield, nowhere must men coordinate the movement of other men and all materials in the midst of such chaos and with such limited certainty of present facts and future occurrences as in a huge construction project….”

Blake Construction Co. vs. C.G. Cookby, Inc.

Why Schedule ?

• Formulate A Plan.

• Communicate The Plan.

• Set Goals.

• Measure Progress.

• Respond To Change.

Why Schedule ?

• Set Goals for the Project– Progress

– Productivity

– Milestones

Why Schedule ?

• Progress Measurement – Time

• Overall Completion• Milestones

– Resource Consumption• Money• Manpower• Equipment• Material

Who Schedules ?

• “[Construction] is the only industry where design and implementation are separated one from the other, and those engaged in design have significantly different interests and motivation than those responsible for the on-site construction.”

» The Revay Report, v10, no.2

Who Schedules ?

Schedule Considerations

• Owners

• Contractors

• Designers

• Suppliers


• Owner – Funding Needs

– Permits

– Commissioning/Start-Up

– Occupancy Planning/Sales


• Owner– Set overall project duration and completion

dates– Identify roles and interface requirements for

major players– Provide a baseline for progress and change

impact measurement


• Owner’s Rep. Perspective– Provide a Baseline for Measurement of

Contractor Progress– Provide a Basis for Progress Payment– Deflect any risk exposure


• Contractor – Prime – Overall Execution of Work– Sub – More Detail on Fewer Activities


• Prime Contractor– Fulfill Contract Requirement– Provide Initial Plan for Work– Provide Framework for Subs Work– Updates Provide Basis for Progress

Measurement and Payment – Provides Basis for Claims arising from delays

and scope changes


• Designer – Design Completion– Permits/Applications– Submission/Shop Drawing Review– Progress Monitoring


• Subcontractor’s Perspective– Little Control or Input– Provide Basis for work Plan– GC’s schedule may impose inefficiency– Provide Basis for Progress Measurement and

Payment.– Provide Basis for Claims from Delay and Scope

Changes


• Supplier – Submissions– Shop drawings– Fabrication– Delivery/Lead Time

Schedule Formats

• Bar Chart Schedules (Gantt Chart)

• PERT Chart Schedule

• Network Diagram Schedule

• Precedence Method Schedule

• Critical Path Method Schedule

Bar Chart Schedule (Gantt Chart)

GANTT CHART

Production Schedule

No.Unit

2501

2502

2503

2504

2505

2506

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Work Weeks


• Strengths• Most Common Schedule• Common Sense Logic• Quick Determination of Gross Progress• Simplicity


• Weaknesses• Logic not Shown• No Critical Path• Difficult to Determine Overall Project Status• Does not Help Establish Relative Sensitivity

PERT Chart Schedule

A C

B

E

G

FD

2-2-8

Special te=3componentstudy

Subsystem tests

Layouts

3-4-8te=4.5

Subsystem design

6-7-14te = 8

2-2-2te = 2 3-4-8

te = 4.5Subcontractspecifications

5-7-9te = 7

Final drawings

PERT Network

Showing precedenceof activities (tasks)

= Plannedevent = Critical Path

(longest path) = Activity

Time estimatesfor each activity

1. Optimistic2. Most likely3. Pessimistic

Expected time = te

Computer Generated PERT Diagram

PERT Chart Schedule

• Strengths• Responds to Interrelationships Between

Activities• Produces “Best Guess” Completion Estimate• Commonly used on Projects which have no

Historical Information to Base Activity Duration Estimates

PERT Chart Schedule

• Weaknesses• Input can be Complex and Time Consuming• Updating can be Onerous• Does not Identify the Project Critical Path

Network Diagram Schedule

4

5

2

5

2

2

3

16

4

1

2 5

3

6

8

7


• Strengths• Automatically accounts for Uneven Activity

Durations• Incorporates Resource Requirements such as

Manpower, Material, Equipment, Money, etc.• Identifies which Portions of a Project have

“Float” Time and are not Driving the Overall Time to Complete the Project.


• Weaknesses• Input can be Complex and Time Consuming• Updating can be Onerous• Results are Only as Good as the Input. Logic

Flaws can be Hidden and Yield Faulty Projections.

• Pure Logic Diagrams can be Very Hard to Read and Understand.

Precedence Method Schedule

CAMOUFLAGE PRINTED NYLON COTTON

WOVENGREIGE GOODS

OC TEST

PRINTING&

FINISHING

MATERIALTESTING

MATERIALTESTING

CUT CUTPARTS OC


• Strengths• Does Show Inter-Activity Relationships

and Constraints• Forces Consideration of Preceding /

Succeeding activities.


• Weaknesses• Input can be Complex and Time

Consuming• Updating can be Onerous• Results are Only as Good as the Input.

Logic Flaws can be Hidden and Yield Faulty Projections.

Critical Path Method Schedule(CPM)

K

H J M

I

F

E L

N

O

A

B

C

D

G

Critical Path Network

Legend

Event number -

Critical Path -

Activity arrow -

Dummy arrow -

Critical Path Method Schedule (CPM)

• Strengths• Time Scaled Logic Shown• Logical Graphic Display• Facilitates Alternative Planning• Displays Critical Path• Computer Generated Sorts of Key Data• Quick Summary and Milestone Plots• Relative Ease of Resource Loading

Critical Path Method Schedule (CPM)

• Weaknesses• Computer Required• Tedious Data Entry• Complex Calculations of Time Requirements• Logic Blocks to Quick Schedule Revisions• Must be Maintained

Schedule Specifications

• Assign responsibility for preparation.

• Define content.

• Designate software.

• Designate updating responsibility.

• Balance information needs with flexibility and complexity.


• Contract Language• Responsibility for Preparation• Submission Dates

• Preliminary• Final • Approval by all parties

• Updates• Frequency• Content

• Tables/Graphics• Changes since last Update• Electronic Media


• Cost Load Schedule– Advantages

• Simplifies billing• Appears to tie progress to payment

– Disadvantages• Complicates data input• Payment needs often lead to manipulation


• Resource Loading• Manpower (Trade)• Cost• Equipment

• Every additional resource adds to initial coding complexity and ongoing record keeping workload.


• Linking schedule to payment – A good idea?

WHY USE A COMPUTER?

• Determine the Critical Path– Identify driving activities

• Calculate “Float”• Print out Reports (Lots of reports)

– By Early/Late Start/Finish– By Float– By Responsible Parties– By Location

WHY USE A COMPUTER?

• Do the Arithmetic• Calculate “Early” Dates

–How soon can something start?

• Calculate “Late” dates–How late can an activity start without delaying the project?

TYPES OF DEPENDENCIES• Finish to Start

• Start to Finish

• Start to Start

• Finish to Finish

ACT # DUR ACT # DUR ACT # DUR

ACT # DUR

ACT # DUR

ACT # DUR

ACT # DUR

ACT # DUR

Basic Schedule Preparation Definitions

• Project Schedule An organized method of presenting in-

formation on when activities need to be started, how long activities are planned to take, and when activities are planned to be completed.

A schedule should also reflect the logical relationships between activities.


• Critical Path – The critical path is now identified as the path of

activities, which contains the least amount of positive total float

– Float can be positive, negative or zero– The critical path determines the length of the

project– Normally the longest chain or path of activities

through the schedule


• As-Planned Schedule – A schedule prepared by a contractor that

depicts his planned approach to the execution of the work of his contract.


• Baseline Schedule – An as-planned schedule which is refined and

adjusted so that all parties agree that it may be utilized as the “bench mark” to measure actual progress during the project.

– The baseline schedule is the schedule against which progress and the impact of changes since the last schedule update are measured and analyzed.


• Schedule Update– A version of the schedule that depicts the

actual progress achieved and any changes made to the schedule during a specific time period – usually one month.


• As-Built Schedule – A time scaled graphic depiction of the

historical record of events, activities, and progress on a given project.

– A historical record of a project in the form of a schedule showing actual activity start and finish dates.


• Activity – Most detailed work unit that is tracked

in a project schedule– Contains all detailed information about

the work to be performed– Also known as a task or item


• Float The amount of time an activity can be delayed without delaying the overall completion date. Also defined as the time between when an activity can start and when it must start.

– Ownership– Types

Free Total


Contingency vs. Float – What’s the Difference?– Why is it Important?


• Delay – An event or condition that results in the project

completion or an activity or group of activities starting or completing later than originally planned.

• Types– Excusable Non-excusable– Compensable Non-compensable– Critical Concurrent


• Acceleration– The performance of construction work at a faster

rate than anticipated in the original schedule. This is accomplished by increasing labor and other resources.

– Types• Constructive • Directed


• Disruption – Start/Stop Iteration

– Out of Sequence Work

– Delays to Approvals

– Trade Stacking

– Manpower

– Environment/Weather

• Trade Stacking– Having more prime or subcontractor work crews per-

forming different types of construction work in the same area than is efficient for the flow of work being performed.


Basic Schedule Preparation

• Elements included in all Schedules – Milestones– Notice to Proceed– Phasing Requirements– Testing/Acceptance– Operational Date– Beneficial Use– Substantial Completion

• Basic Schedule Development Steps

• Determine Project Scope • Define Calendar

• Define Activities • Determine Relationships

• Assign Durations • Assign Responsibility

• Assign Resources • Process Schedule

• Monitor Schedule



• Basic Schedule Development Steps Review Contract Documents

• Construction Plans• Contract Specifications • Schedule Specifications• Material Specifications


• Basic Schedule Development Steps – Review Contract Documents

• Project Construction Plans – Determine construction layout and phasing requirements

– Determine material requirements (Quantity, quality & installation)

– Determine site constraints

– Identify coordination/problem areas


• Basic Schedule Development Steps – Review Contract Specifications

• Notice to Proceed• Required Milestones• Phasing• Substantial Completion• Turnover (Prior to Completion)


• Basic Schedule Development Steps – Review Schedule Specifications

• Required activity durations

• Schedule submittal requirements

• Update submittal requirements

• Designer submittal review time requirements

• Procedures for any change in scope


• Basic Schedule Development Steps – Review Material Specifications

• Shop Drawing/Submittal Requirements

• Materials Supplied by Others

• Sole Source Suppliers/Materials

• Review time turnaround

• Delivery times


• Basic Schedule Development Steps – Analyze the Project

• Create Activity IDs • Determine Activity Duration• Develop Logic Relationships


• Basic Schedule Development Steps – Create Activities

• Task Design

• Independent Procurement

• Meeting Approval

• Start Milestone Test

• Finish Milestone Punchlist


• Basic Schedule Development Steps – Activities from the WBS – Drawings and Specifications– Activity Duration from Experience/Calculation– Logic from Experience/Planning– Start/Stop dates from Requirements/Phasing– Concurrent Activities from Experience/Interface

Requirements


• Basic Schedule Development Steps – Develop Coding Structure

• Responsibility• Location• Trade• Phase• Sequence


• Basic Schedule Development Steps – Determine Activity Duration

• From experience/calculation

• Manpower Availability & Productivity• Procurement – Consider time to prepare submittal,

design review, fabrication and delivery time

• Specialty & Long Lead Items


• Basic Schedule Development Steps – Develop Logic Relationships

• From experience/planning

• All Activities should have predecessors and successors

• Ideally there should be only two Activities with open end (Notice to Proceed and Project Completion)

• Identify constraints– From contract– Physical limits

• Overlap with other activities


• Basic Schedule Development Steps – Key Activities/Interfaces

• Work of Other Contractors

• Long Lead Time Materials/Equipment

• Owner Furnished Material/Equipment

• Phasing Requirements


• Basic Schedule Development Steps – Incorporate Resource Considerations

• Contract Requirements– Milestones– Phasing– Work Restrictions

• Resource Constraints– Manpower– Equipment– Weather


• Basic Schedule Development Steps – Resource Considerations

• Availability of Management Team• Manpower Availability & Quality• Equipment Subcontractors• Specialty Subcontractors• Materials Lead Time• Site Access Limits


• Common Problems that Affect Schedule – Differing Conditions - Active Interference– Access to Site - Disruption– Availability of Site - Work Sequence– Technology Development - Weather– Review and Approval process


Common Problems that Affect Schedule

• Interferences– Changes– Materials– Technical Error– Acceleration

• Directed• Constructive

– Impossibility of Performance

– Superior Knowledge– Defective Plans and/or

Specifications


• Schedule Check Points – Does Schedule Conform to Contract Dates?– Are Milestones Indicated?– Is Phasing Currently Shown?– Is There a Logical Sequence of Activities?– Activity Durations are Reasonable– Do Resource Allocations Seem Reasonable?– Interface Work is Indicated– Is Testing Indicated?– Critical Path Indicated

TYPICAL SCHEDULEActivity

ID

Activity

Description

Orig

Dur

Total

Float

% Early

Start

Early

Finish

General Activities & Milestones1 Notice to Proceed 1 0 11FEB98 11FEB98

29990 FINAL PUNCH LSB 10 0 07MAY99 20MAY9999990 Substantial Completion 18 0 21MAY99 15JUN9999999 Project Completion 22 0 16JUN99 15JUL99

Life Science Foundation20015 Building Pad Life Science 10 0 17FEB98 02MAR9820020 Excav Footings Life Science 8 0 03MAR98 12MAR9820025 Form & Pour Footings Life Science 10 0 17MAR98 30MAR9820030 Stem Wall LSB 15 0 31MAR98 20APR9820062 Form & Pour SOG 51 to 100% 10 0 19MAY98 01JUN98

Life Science 1FL20170 In-slab Plumb 0-50% 10 0 21APR98 04MAY9820190 In-slab plumb 51-100% 10 0 05MAY98 18MAY9820100 CMU wall 1fl 10 0 02JUN98 15JUN9820105 Tie Beam&col 1fl 10 0 16JUN98 29JUN9820140 Int Cols & Beams 1fl 10 0 30JUN98 13JUL9820250 Metal Deck 2fl 5 0 14JUL98 20JUL98

Life Science 2FL20260 In-slab Elec 5 0 21JUL98 27JUL9820276 Form & Pour Slab 2fl 5 0 28JUL98 03AUG9820200 CMU wall 2fl 10 0 04AUG98 17AUG9820205 Tie Beam&col 2fl 10 0 18AUG98 31AUG9820376 Entrance concrete 5 0 01SEP98 07SEP9820378 Entrance Precast 5 0 08SEP98 14SEP9820240 Int Cols & Beams 2fl 10 0 15SEP98 28SEP9820350 Metal Deck roof 5 0 29SEP98 05OCT9822000 LAYOUT PARTITIONS 8 0 06OCT98 15OCT9822010 Frame 15 0 16OCT98 05NOV9822030 R/I plumbing 52 0 06NOV98 18JAN9922580 SHEET ROCK 2 25 0 19JAN99 22FEB9922120 Int paint & wall covering 2fl 15 0 23FEB99 15MAR9922170 Int doors & trim 2fl 15 0 16MAR99 05APR9922200 Carpet & flooring 2fl 8 0 06APR99 15APR9922300 Int Signage 2fl 5 0 16APR99 22APR9922990 FLOOR punch & clean 10 0 23APR99 06MAY99

1998 1999F M A M J J A S O N D J F M A M J JAUG

Notice to ProceedFINAL PUNCH LSB

Substantial CompletionProject Completion

Building Pad Life ScienceExcav Footings Life Science

Form & Pour Footings Life ScienceStem Wall LSB

Form & Pour SOG 51 to 100%

In-slab Plumb 0-50%In-slab plumb 51-100%

CMU wall 1flTie Beam&col 1fl

Int Cols & Beams 1flMetal Deck 2fl

In-slab ElecForm & Pour Slab 2fl

CMU wall 2flTie Beam&col 2flEntrance concreteEntrance Precast

Int Cols & Beams 2flMetal Deck roof

LAYOUT PARTITIONSFrame

R/I plumbingSHEET ROCK 2

Int paint & wall covering 2flInt doors & trim 2fl

Carpet & flooring 2flInt Signage 2fl

FLOOR punch & clean

© Primavera Systems, Inc.

Start Date 02FEB98

Finish Date 15JUL99

Data Date 11FEB98

Run Date 17JAN03 13:40

Early Bar

Float Bar

Progress Bar

Critical Activity

FTEL All Round Construction Co.Southern Tech Adv Eng & Life Sci

INITIAL BASELINECRITICAL PATH

Sheet 1 of 2

COMMON SCHEDULE DEVELOPMENT ERRORS

• Missing ScopeMissing Scope

• Unrealistic Original DurationsUnrealistic Original Durations

• Missing RestraintsMissing Restraints

• Over RestraintsOver Restraints

• Reliance on Fixed DatesReliance on Fixed Dates


• Common Scheduling Software – Primavera®

– Microsoft Project®

– SureTrak®

– Timeline®

Schedule Update Techniques

• Perform Schedule Update.

• Depict Actual Status.

• Make Projections Using Existing Schedule Logic and Durations.

• Determine the Predicted End Date.

Schedule Update Techniques

• Compare Schedule Data with As-built/Completed Project History.

• Use Independent Data Sources for Verification.• Logs• Pictures/Video• Progress reports• Compare Planned vs. Actual Durations.• Similar Activities • Work in Progress

Schedule Update Preparation

• Updates – Establish data date.– Enter all start dates of activities in progress.– Enter completion dates of completed activities.– Enter percent complete of activities that have started.– “SCHEDULE”– Analyze new logic of critical path and other activities.– Develop strategy to recover time if required.– Identify & record all changes made since last update.


• Change Order Impact– Fragnet or New Activities Required as

Part of Any Change Request or Extension of Time Request.

– Contract-Required Prior Approval before Work can be Performed.

– Potential Impact on “Unaffected” Work


• Remember – Schedule development and re-planning is an art

as well as a science.– If you feed a computer garbage data it will

produce garbage schedules.– Apply common sense/parametric thinking to

analyze computer output.– Good schedules and honest analysis good

project management.

Problem / Response

• Recognize symptoms.

• Identify cause.

• Respond appropriately.

• Recover if possible.

Problem / Response Lack of Progress

• Start with critical path activities.

• Track progress by:• Location

• Date

• Subcontractor/Craft

• Identify constraints:• Manpower• Equipment• Access• Preceding work• Weather

• Identify appropriate response once true cause is known.

Problem / Response

• Only solve the problem you actually have

Selective overtime v. job wideSelective additional manpowerNotify owner and get direction

Scheduling Specifications

• Information Needs– Content ─ Format

• Distribution/Updates

• Level of Detail

• Resources (In or Out?)

• Acceptance/Approval– Owner ─ Subs

www.MDCSystems.com

COMMON SCHEDULING PROBLEMS and TRICKS

• Tailored Output to Suit the Audience

• Key Concepts: • Just because a computer generated a report doesn’t mean that it makes any sense.

•The difference between data and information

MDCSystems®

Providing Expert Solutions for Construction Worldwide

Signs or Symptoms That Trouble is Brewing

Require Impact of Change Orders be shown in schedule.

Symptom

Hidden Delays. Delivery Problems.Possible Future Claims or waived.

Change Orders Not Incorporated Into Schedule

Require Update Submission. If necessary, do your own.

Hidden Delays. Poor Productivity. Delivery Problems.

Missed Updates

Require explanation of Logic and/or Duration Changes – especially to Critical Path Activities.

Hidden Delays.Poor Productivity.Delivery Problems.

Real Delays To Critical Activities Don’t Change Completion Date.

Require Schedule Submission.Require Initial Cash Flow Projection.Require Procurement/Shop Drawing Submission Schedule.

Lack of a real plan.Problems discovered after bidding.Long Lead Time Problems.

Contractor Refuses Or Delays Providing An Initial Schedule

ResponsePotential Problem

Signs or Symptoms That Trouble is Brewing

Require explanation of Logic and/or Duration changes– especially to Critical Path Activities.

Hidden Delays/Future Acceleration/Disruption Claims.

Extended or increased Overhead Costs.

Poor Productivity.

Apparent Disconnect Between Cost/Progress Or Earned Value/Time.


Hidden Delays.

Delivery Problems.

Unrealistic Recovery Projections.

Projected Durations For Incomplete Or Un-started Work Changed For No Apparent Reason.


Hidden Delays/Future Acceleration/Disruption Claims.

Poor Productivity.

Delivery Problems.

Schedule Logic Changed To Show More Trades Working In An Area At One Time.

ResponsePotential ProblemSymptom

Scheduling Problems/Tricks

• Logic Manipulation• Improper Use of

Constraints• Preconceived Critical

Path• Duration Manipulation• Calendar Manipulation

• Lag Magic• Hidden Float• Calculation

Manipulation• Concurrency

Arguments• Activity Interruption

Misrepresentation


• Logic Manipulation– Common Sense– Physical Reality– Unconnected Activities

• No Predecessors/Successors

– Float Manipulation– Adequate Detail


• Improper Constraints– Artificially Fix Dates

• Early/Late Start/Finish

• Not Earlier/Later

• Must Start

• Behind the scenes

– Confuses Critical Path Calculations– Resource Manipulation can distort Schedule


• Preconceived Critical Path– “Just Like” another project– “Its always critical”– Insufficient Detail


• Duration Manipulation - I– Float Control– Critical Path Manipulation– “Real” vs “Earned” Progress– Revised “Original Durations”


• Duration Manipulation - II– First and Last Day

• What about everything in between?

– Variable Calendars– Retroactive Orig. Duration Changes– Resource Impacts Limit Durations– Alternate Shifting to Alter Future Durations


• Calendar Manipulation– One Size doesn’t fit all– Behind the scenes– Some things just can’t be compressed– Weather Impacts

VARYING CALENDARS ALTER FLOAT NUMBERS


• Improper Relationships Can Lead to Trouble

– Leads/Lags Hide Impacts

– Hard to Detect – Sneaky

– Trade/Sub Flow Wrong


• Different Schedules for Different Audiences

– Contractor to Owner

– Contractor to Subs

– Project Manager to the Boss


• Scheduling Calculations Change–Truly Sneaky and Behind the Scenes–Retained Logic–Progress Override–Automatic Resource Leveling–Criticality Indications–Float Calculation Basis


• Concurrency Manipulation– Difficult to prove exclusive Causation– Usually Easy to get time but not $$$$ from

Owner– Very Hard for Subs to recover

• GC usually controls their activities


• Solutions– Each Project is Unique

• Match the Schedule to the Project

– Don’t Overcomplicate Things– Consider the Use the Schedule Will Provide

• Planning • Management

• Payment • Claims


• Solutions– Qualified Personnel/Training– Proper use of Software– Informative Reports– Training / Responsibility– Adequate Funding (No Free Lunch)

Scheduling Specifications

• Information Needs– Content ─ Format

• Distribution/Updates

• Level of Detail

• Resources (In or Out?)

• Acceptance/Approval– Owner ─ Subs

www.mdcsystems.com tricks, traps and ploys used in construction scheduling presented by mdc systems...

Documents

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