Developing Critical Path Method Scheduling (CPM)

(1)

Developing Critical Path Method

Scheduling (CPM)

(2)

Pretest

1 An activity which is on critical path has a 1. An activity which is on critical path has a

planned duration of 5 days. What is the total float for the activity?

total float for the activity? a. 0 b 1 b. 1 c. 2 d 3 d. 3

(3)

Pretest

2 Which is not a widely recognized type of 2. Which is not a widely recognized type of scheduling method? a CPM a. CPM b. Linear c Vertical c. Vertical d. Bar

(4)

Pretest

3 Which of the following is directly affected by 3. Which of the following is directly affected by project scheduling? a Time a. Time b. Cost c Work Flow c. Work Flow d. Man Power All f th b e. All of the above

(5)

Pretest

4 Of the three (3) main scheduling methods 4. Of the three (3) main scheduling methods, which one uses relationships between activities? activities? a) Linear b) CPM b) CPM c) Bar

(6)

Pretest

5 Which scheduling method is the most 5. Which scheduling method is the most commonly practiced? a) Bar a) Bar b) Vertical c) Linear c) Linear d) CPM

(7)

Pretest

6 Total Float is the amount of time an activity 6. Total Float is the amount of time an activity

can be delayed without delaying completion date of the project

date of the project.

a) True b) False b) False

(8)

Pretest

7. The Work Breakdown Structure (WBS) should be 7. The Work Breakdown Structure (WBS) should be

used for identifying the activities and for organizing the schedule.

a) True b) False

(9)

Pretest

8. Which of the following should be used in 8. Which of the following should be used in determining activity durations? a) Historical Data) b) Manuals c) Experience c) Experience d) Field recommendations e) All of the above

(10)

Pretest

10 Who should do project scheduling? 10. Who should do project scheduling? a) Project Manager b) Owner b) Owner c) Superintendent d) All f th b d) All of the above

(11)

Pretest

9. There is always more than one correct logic for 9. There is always more than one correct logic for

completion of a project. a) True)

(12)

Purpose and Background for

h d l

Construction Schedules

• Determine reasonable and accurate contract time for construction – Contract time is the maximum time allowed in the contract for completion of all work contained in the contract for completion of all work contained in the contract documents. h d l h f • Project Scheduling is the process of: – Identifying the activities necessary to complete the project project – Assigning realistic durations to each activity – Establishing start and finish dates for each activity

(13)

What Does a Schedule Do?

• Helps the owners in planning during theHelps the owners in planning during the development of the project • Public Notifications • Public Notifications • Road Closures • Construction sequencing, phasing & milestones • Alternate bid schedules

(14)

Effects of Insufficient Contract Time

• Bid prices may be higher • Unusual number of time overruns • _{Contractor Claims} • _{Missed milestones}

(15)

Effects of Excessive Contract Time

• _{Cost inefficiencies by the contractor}_{Cost inefficiencies by the contractor}

• _{Public may be inconvenienced unnecessarily} • Travel on unsafe roadways for and extended

• Travel on unsafe roadways for and extended period of time

* If the time set is such that all work on a If the time set is such that all work on a project may be stopped for an extended

period and the contractor can still complete period and the contractor can still complete the project on schedule – time allowed was excessive

(16)

Schedule Guidelines

• When should you create your first schedule?When should you create your first schedule?

– Schematic Drawings ‐30% Design Development 50%

– Design Development – 50%

– Submittal Drawings – 90%

(17)

Determining Contract Time –

d

Production Rate

• What is Production Rate?What is Production Rate?

– The quantity produced or constructed over a specific time period.

specific time period.

• Why is this important?

Helps determine appropriate completion time

– Helps determine appropriate completion time.

• _{Production rates may vary considerably}

d di j i l i d

depending on project size, location and setting.

(18)

Determining Contract Time –

d

Production Rate

• _{Establishing Production Rates}_{Establishing Production Rates}

– Divide the total quantity of an item by the number of days/hours used to complete the item.

– Base production rates upon a 5‐day work week/ 8hr crew days/ our per piece of equipment

8hr crew days/ our per piece of equipment

– Historic data DOT data

– DOT data

– RSMeans

– Cost Data books

(19)

Hot Asphalt Concrete Pavement

d

Production Rate:

HACP Paving (max) – 1 980 tons/day HACP Paving (max) 1,980 tons/day HACP Paving (min) – 1,320 tons/day Starting Rate = (1980 + 1320)/2 = 1,650 tons/day (8 hour day) Projects Specifics:j p – Cold Temps

(20)

Other Factors Affecting Contract

Times

• Effects of Traffic

• Curing Times / waiting periods between paving courses

• Curing Times / waiting periods between paving courses • Setup/mobilization/special equipment • Seasonal Limitations • Conflicting Operations • Conflicting Operations • Submittal review Times • Fabrication Times • Lead times • Lead times • Long – lead Items • Holidays N b f C / Si • Number of Crews/crew Size • Environmental • Temporary construction S il • Soils

(21)

Steps for Creating CPM Schedules

• Define the Work DayDefine the Work Day

• Define the Project Calendar & Task Calendar d if G d S h i i i • _{Identify, Group and Sequence the Activities} • _{Set activity Durations} • _{Link Activities} • _{Documentation}_{Documentation} • Update

(22)

Defining the Work Day

• Work hours establish the daily work times.

(23)

Defining the Project Calendar

• Defines project’s work and non‐work daysDefines project s work and non work days

– Saturdays, Sundays, Holidays

Other Contractual non work days

– Other Contractual non‐work days

– Local Events

• Task Calendars define work that can only be performed at a specific time and date.

(24)

Activities

• _{A key factor in any realistic schedule is to include the}_y _y right activities. – Consider each project as unique. B k j t i t i di id l ti iti – Break project scope into individual activities – Work Breakdown Structure (WBS) should be used for identifying the activities and for organizing the schedule – The number of activities depends upon the complexity of the project • _{Once Activities are identified and grouped, determine} the general sequencing of the activities.

(25)

Typical Activity Inclusions &

l

Exclusions

• StakingStaking – Only show staking tasks that are necessary to start the project (e.g., clearing limits and slope stakes). p j ( g g p ) • Clearing & Grubbing – Show only work needed to begin major activitiesy g j • Erosion Control

– In‐place items before major grading operationsIn place items before major grading operations

• Earthwork

– Break out rock excavation as a separate activity – Break out rock excavation as a separate activity

(26)

Typical Activity Inclusions &

l

Exclusions

• Pavement Structure Items – Combine associated items as one work activity – Separate major structure items such as; base course and asphalt and asphalt • Bridge Activities – Show by phase of construction – foundation, y p , substructure, superstructure • Sub Excavation C bi i t ti it – Combine into one activity • Drainage

(27)

Typical Activity Inclusions &

l

Exclusions

• Turf EstablishmentTurf Establishment

– Show as one item

• _{Signage & Striping} • _{Signage & Striping}

– Combine all permanent traffic control signing and striping into one activity

and striping into one activity.

• _Guardrail

(28)

Activity Durations

• Setting durations is a critical step to creating aSetting durations is a critical step to creating a reasonable schedule.

• Factors effecting time should be taken into • Factors effecting time should be taken into consideration. Adj i i d i b d d i • _{Adjust activity durations based on production} rates. • Try and limit the duration for any activity to 20 days.

(29)

Link Activities

• _{Determine activity relationships}_y _p

– Late Finish (LF): The latest time an activity can be finished.

– Late Start (LS): The latest time an activity can be started

without delaying completion of the project LS LF D without delaying completion of the project. LS = LF – D – Total Float: The amount of time an activity can be delayed without delaying completion date of the project. TF = LF – EF + LS – ES – Free Float: The amount of time an activity can be delayed without delaying early start time of the following activityy g y g y – Critical Path: A series of connected activities with each activity having zero float (free, and total) time.

(30)

Link Activities

– The order in which activities will be performed is p called logic – How one activity relates to another activity is called logical relation logical relation • Finish to Start • Finish to Finish • Start to Start – Defining proper logic requires understanding of the project project – There is always more than one correct logic for completion of a project.

(31)

Documentation

• Document any assumptions:Document any assumptions:

– Production rates Equipment Types – Equipment Types – Quantities C – Crews • Follow the logic

(32)

Update

• A Schedule is only a tool!

(33)

Check List

• Reviews/Submittals/ – Are there critical submittals? What Time is needed? – Are there critical testing periods & how long? A th iti l i ti & h l ? – Are there critical review times & how long? – What are the assigned calendars for submittals & review times? – What are the logical connections between review activities and contractor’s actual work?

– Procurement activitiesProcurement activities

– Time for reviewing false‐work plans, shop drawings, post‐tensioning plans, mix designs, etc.

(34)

Check List

• PermitsPermits

– Are permits required?

Time to obtain necessary permits?

(35)

Check List

• Specific Activity Requirementsp y q – Additional time for obtaining specialty items or materials with long‐lead requirements (i.e. Traffic Signal Equipment) Signal Equipment) – Curing time and waiting periods between successive paving courses or between concrete operations

Embankment settlement periods or embankment – Embankment settlement periods or embankment

surcharges.

– Coordination with Utilities

– False‐work & Shoring activities – Punch‐list and cleanup activities

(36)

Check List

• Material/Product Testing and DelaysMaterial/Product Testing and Delays

– Government/Owner furnished material Trial shafts or piles

– Trial shafts or piles

– Sample walls

Ti f f b i ti f t t l t l d th

– Time of fabrication of structural steel and other specialty items

Staining painting or other samples needing

– Staining, painting or other samples needing approvals

(37)

Check List

• Construction Limitations and Requirements – Haul characteristics – Type of earthwork (sliver cuts, benching) – Work area restrictions – Equipment congestionq p g – Allowable bad weather days – Material availability

– Labor shortages and resource loadingLabor shortages and resource loading

– Traffic Volumes

– Traffic staging events (closures, detours)

– Critical interface activities (utilities, RR)Critical interface activities (utilities, RR)

– Restrictions for nighttime and weekend operations

– Conflicting operations of adjacent projects, both public and private

p

(38)

Check List

• Project Commitmentsoject Co t e ts – Environmental Commitments • Winter season • Clearing, grubbing, grading restrictions • Noise restriction • SWPPP • Seasonal limitations for certain activities – Project Calendar Requirements W k W k • Work Week • Holidays • Other non‐working times

(39)

Check List

• _{Does the final schedule include/show:}_/ – Critical Path? – NTP date and completion date f k ll l d – Entire scope of work, all activities in plans and specs? – Construction Staging and mobilization?

– Realistic duration of individual activities?Realistic duration of individual activities?

– Maximum 20‐day duration for any one activity?

– Activities have at least one predecessor and 1 successor? – No negative lag for activities/

– Project Duration, Interim Milestones, Black‐out dates, contract work days?