3) Project Time Management - Basic Processes (2nd Sem 2014-15)

Project Time Management: Basic Processes

1. Objectives

After studying this topic, students are expected to be able to:

Identify and define project activities based on the deliverables and work packages in the Work Breakdown Structure (WBS).

Identify and make use of activity dependencies and successor / predecessor relationship for every activity.

Logically sequence project activities correctly based on activity dependencies and successor / predecessor relationship.

Describe how estimation of project activity resources is done.

Describe how estimation of project activity duration is done.

2. Introduction

The Project Management Institute (PMI, 2008) guideline – A Guide to the Project Management Body of Knowledge (PMBOK) – divides the project management body of knowledge into nine functional areas:

1) Scope 2) Time 3) Cost 4) Quality 5) Human Resource

6) Communication 7) Risk 8) Procurement 9) Integration

The project time management has the following required processes to ensure that the project is completed on time:

1) Define project activities

2) Sequence project activities

3) Estimate project activity resources

4) Estimate project activity durations

5) Develop project schedule

6) Control schedule

Note that in general activities may also be referred to as tasks and therefore these terms can be used interchangeably. However, there are project managers who prefer to use

Mohd Sufian Abdul Karim Project Time Management: Basic Processes Lecture Notes

CEPB323 Project Management and Construction Page 2 of 14

the term task as the breakdown component of activity and activity as the breakdown component of deliverable in the WBS.

Deliverable is a noun while activity and task are verbs. Hence any phrases to be used as a deliverable must be written as a noun, for example: Ground beam, and any phrases to be used as an activity or task must be written as a verb, for example: cut, bend and fix the reinforcing steel bars (re-bars) for the ground beam.

3. Define project activities

Specific activities (actions) to produce project deliverables need to be identified. The project activities would depend on the project scope statement and Work Breakdown Structure (WBS) as discussed in the previous chapter about project scope management. Decomposition technique as used to construct the WBS can be used to determine project activities.

The output would be an activity list, activity attributes and milestone list. The WBS tasks in Microsoft Project application are the activity list for the project. A milestone is an accomplishment of certain related activities for example the handing over event of a project after the construction is completed. An example of an activity list and milestone list for the construction of a ground beam (simplified for the purpose of illustration) for a house is listed in Exhibit 1.

4. Sequence project activities

Relationships between project activities or tasks are identified and documented in this process based on the project scope statement, activity list and attributes, and milestone list. Based on these relationships, the sequence of the activities are then logically determined.

4.1 Activity dependencies

In any project, certain activities are dependent on other activity or activities. For example in Figure 1, Activity B (referred to as the Successor) is dependent on Activity A (referred to as the Predecessor) i.e. Activity B cannot start before Activity A is completed or Activity B can only start when Activity A is completed.

Figure 1: An example of activity dependency – Activity B is dependent on A

Predecessor Successor

Activity A Activity B



PMI (2008) categorizes dependencies as mandatory, discretionary and external dependencies:

Exhibit 1: Activity list and milestone list for the construction of a ground beam for a house

Activity List

Activity A: Place lean concrete on the ground where the base of the beam is located.

Activity B: Fabricate the beam formwork at the formwork yard.

Activity C: Apply the formwork oil onto the beam formwork.

Activity D: Fix and erect the beam formwork at site.

Activity E: Cut and bend re-bars.

Activity F: Fix the re-bars for the beam (outside the beam formwork).

Activity G: Lift and place the beam re-bars into the beam formwork.

Activity H: Install any embedded items and provide adequate concrete cover.

Activity I: Ensure that the area to place concrete is clean and there is no prohibited and deleterious materials.

Activity J: Make sure that the concreting team and equipment, supply of concrete and any other relevant preparations to carry out concreting works are ready.

Activity K: If all concreting preparation works are ready and approval is given by the Site Engineer, the Site Supervisor will place the order for delivery of fresh concrete from the batching plant.

Activity L: When fresh concrete has arrived at site, perform concrete slump test and make concrete test cubes and / or cylinders for the concrete laboratory.

Activity M: If concrete slump test is satisfactory and approval is given by the Site Engineer, place concrete and perform adequate compaction and finishing.

Activity N: Perform concrete curing for the required duration.

Milestone List

Milestone No. 1: The ground beam is completed after all Activities A to N are finished.



a) Mandatory dependencies

These dependencies are sometimes referred to as hard logic that are required in the contract (for example the construction site leveling cannot start until the opening ceremony is performed by the Prime Minister) or which is inherent in the work itself (for example the superstructure is dependent on the foundation because it could be constructed only after the foundation is completed).

b) Discretionary dependencies

These dependencies are sometimes referred to preferred logic, preferential logic or soft logic. These activities are based on knowledge of best practices and where a specific sequence is desired. Therefore these activities can be reviewed to be modified or removed if necessary, for example when the project has to be fast tracked.

c) External dependencies

These dependencies refer to relationships that are between project activities (for example construction of a temporary diversion channel to enable dry construction area for the bridge piers) and non-project activities (for example the environmental impact assessment to be done by the Ministry of Environment and their environmental consultants).

4.2 Successor / predecessor relationship

Activity dependencies or more specifically the inter-dependencies of activities, and lags and leads among activities determine the relationships between activities in a project. Project activity relationship is called the successor / predecessor relationship (refer back to Figure 1).

Therefore a predecessor can influence and affect the successor. As discussed earlier, a successor is dependent on a predecessor. For example if the predecessor were to be completed behind schedule therefore the successor will have to start behind schedule. Similarly the successor can only start after the predecessor is finished. However, this direct relationship is not always applicable to all project activities if lag and lead are introduced.

Lag is the duration that a successor is purposely delayed from the start or finish of its predecessor. Lead is the opposite of lag which is the duration that a successor is purposely precedes the start or finish of its predecessor (Oberlender, 2000).

All possible relationships between activities of a project are as listed in Exhibit 2 and illustrated in Figure 2 (Fisk, 2000).



Exhibit 2: Relationships between activities (successor / predecessor relationship)

Finish-to-start (F-S): The predecessor is first finished and then only the successor can start.

Start-to-start (S-S): The successor can start at the same time or later than the time that the predecessor starts. There is an overlap between the successor and predecessor.

Finish-to-finish (F-F): The successor can finish at the same time or later than the time that the predecessor finishes. There is an overlap between the successor and predecessor.

Start-to-finish (S-F): The predecessor must start before the successor can finish.

Note: 1) F = finish and S = start.

2) The first letter in the notation refers to the predecessor and the second letter refers to the successor.

After the inter-dependencies, lags and leads of activities are confirmed, the sequencing of activities can then be made. For example the sequence of activities for producing a deliverable which is a ground beam (after the ground work and setting out have been completed) based on the activity list in Exhibit 1 is listed in Exhibit 3.

Project activity dependencies or successor / predecessor relationship and the corresponding sequence of activities can be in the form of a list as shown in Table 1 and Table 2. Note that all activities in Table 1 and Table 2 are having F – S relationship with no lag and no lead. Table 2 is an example of a simpler form of activity list and relationship without the activity description.

5. Estimate project activity resources

In this process the type and quantity of resources: financial, people, material, equipment, etc. that is required for each activity is determined. The resources needed for each activity would basically depend on the activity attributes, availability of resources as indicated in the resource calendar, experience and skill level of the human resource, and the source or supply (geographical location and supplier) of the resource.

A resource calendar is a document that basically provides the essential information about all resources, for example time and duration the particular type of resources and its quantity will be available, used or idle; working and non-working days for human resource, public holidays, etc.

Past experience from construction managers and professionals, and company’s past construction records are usually used to determine the resources. Alternative and better construction methods must be considered before the resources are finalized. For



example, based on the activity attributes of the activity list in Exhibit 1, some of the main required resources are listed in Exhibit 4.

Figure 2: Relationships between activities (successor / predecessor relationship) Source: Fisk (2000)



Exhibit 3: Sequence of activities for the construction of a ground beam for a house

Activities A, B and E can start at the same time as the first activities and they are independent from each other.

Activity C can start after Activity B is completed.

Activity D can start after Activity C is completed.

After Activity E is completed and while Activities C and D are being carried out, Activity F can start.

Activity G can start after Activity D and F are completed.

Activities H, I and J can be done at the same time i.e. concurrently after Activity G is completed.

Activity H and I must be completed before Activity J can end.

Activity K can only start after Activity J is completed.

After Activity K is completed, only then Activity L can start.

Activity M can start after the slump test is satisfactory (about ½ hours after concrete has arrived i.e. after Activity L has started for about ½ hours). In other words Activity M has a lag of ½ hours after the start of Activity L.

Activity N can start about 2 hours after Activity M is completed i.e. Activity N has a lag of 2 hours after the start of Activity M.

Output from the estimation of project activity resources process includes the Resource Breakdown Structure (RBS) which is similar to the WBS. The RBS shows the hierarchical structure of the breakdown of resources based on resource category (labor, materials, equipment, etc.) and resource types (skill level, grade level, etc.).

6. Estimate project activity durations

The duration for each activity based on the project scope statement, attributes of each activity, allocated resources and resource calendar need to be determined (PMI, 2008).

Duration of activities depends on many factors such as (Oberlender, 2000):

Quantity and quality of work.

Number of people and equipment for the activity.

Level of skills of workers.

Availability and efficiency of equipment and machinery.



Table 1: Activities for a hazardous waste incineration project

Activity Description Immediate

Predecessor

A Develop information for public hearings. None

B Hold public hearings. A

C Develop draft plans and specifications. A

D Contact stakeholders and others. A

E Obtain permits. B, C

F Order equipment for facility. B

G Procure and prepare land. B

H Construct facility. D, E, F, G

I Approval of operating procedures. D

J Install equipment, staff and facility. F

K Testing and commissioning. H, I, J

Adapted from Table 5.1, p. 98, Griffis and Farr (2000)

Table 2: Example of input for exercises

Activity Immediate Predecessor

A None

B A

C A

D B

E C

F D

G B, E

H C, F, G

Effectiveness and efficiency of work supervision.

Delays, interruptions and discontinuous flow of work.

Miscellaneous work conditions.

Etc.



Exhibit 4: Required resources for the production of a ground beam for a house

Activities A, K, L and M require a steady supply of fresh concrete (i.e. material) from the concrete batching plant that satisfies the particular concrete specifications.

Activities B, C and D require processed timber (i.e. material) that is in the form that is ready to be used to fabricate the beam formwork.

Activity C requires formwork oil (i.e. material).

Activities E, F and G require re-bars (i.e. material) of the particular specifications.

Activity E requires bar cutting and bending machine (i.e. equipment).

Activity H requires the particular relevant embedded items (i.e. equipment) (if any).

Activity I requires an air compressor of adequate capacity and piping system (i.e. equipment) and an appropriate water supply (i.e. material).

Activity L requires concrete slump test set, and test cube and cylinder molds (i.e. equipment).

Activity M requires mobile concrete pumps or mobile cranes with concrete buckets, poker vibrators and concrete finishing tools (i.e. equipment).

Activity N requires curing facilities for example sprinkler (i.e. equipment).

All activities require a qualified Site Supervisor (i.e. people) to supervise the construction activities.

Activity K requires a qualified Site Engineer (i.e. people) to inspect and give his approval.

Activities B, C, D and H require adequate number of skilled carpenters (i.e. people).

Activity E requires adequate number of skilled bar benders (i.e. people).

Activities F, G and H require adequate number of skilled bar fixers (i.e. people).

Activities A, J, K and L require adequate number of skilled concreting workers (i.e. people).

Activity M requires a qualified laboratory technician (i.e. people).

Adequate number of general workers (i.e. people) is needed to provide assistance in all activities.



The Project Management Institute (PMI, 2008) suggests a number of ways to estimate the project activity duration: analogous estimating, parametric estimating, three-point estimating and reserve estimating.

6.1 Analogous estimating

This method makes use of durations for previous similar activities particularly when there is limited detailed information about the project. A common approach is to analyze historical records from previously completed projects. For example if in a previous project, it took about 2 weeks to excavate a square kilometer of land that is comprised of in-situ highly decomposed granite, to a depth of 1 meter by using an excavator, therefore the same duration can be used for similar excavation works in another project.

6.2 Parametric estimating

This method uses the quantitative relationship between relevant activity variables. A simple application is to divide the quantity of work to be performed by the production rate. For example if the assigned resource, say 3 bar fixers, is capable to fix the re-bars for 4 beams in a day, therefore the estimated duration for 3 bar fixers to fix the re-bars for 12 beams would be 12/4 = 3 days.

Reference can be made to commercially available manuals about costs and production rates for certain types of work.

Therefore a basic formula to calculate the duration of activities would be as follows:

Duration = total quantity of work production rate (which is a function of the number of

individuals who do the work)

Example No. 1 (adapted from Gould and Joyce, 2003)

Calculate the duration for installing 32 window frames if your construction record shows that the daily carpenter output is able to install 16 window frames a day.

Solution:

Duration = total quantity of work / production rate = 32 frames / 16 frames per day = 2 days

Therefore it would take 2 days for 1 worker to install 32 frames and it would take 1 day for 2 workers. Note that production rate is the same as daily crew output.



Example No. 2 (adapted from Gould and Joyce, 2003)

Calculate the duration for installing 32 window frames if your construction record shows that the installation of one window frame requires 1 manhour of carpenters and you have 3 carpenters who work 8 hours a day to install these window frames.

Solution:

Duration = total quantity of work / production rate

Total quantity of work = 32 frames

Production rate = 1 frame for 1 worker hour

= 3 x 1 frame x 8 hour for 3 workers hour day

= 24 frames day

Therefore,

Duration = 32 frames 24 frames day

= 1.33 days = 2 days

6.3 Three-point estimating

This method considers the uncertainty and accuracy of assigning a particular duration to an activity and therefore a probability approach is used. An activity is given 3 different durations: optimistic duration, most likely duration and pessimistic duration. The expected activity duration is then calculated based on a particular formula to be used by the particular activity. This estimating method will be discussed in Project Time Management: Project Scheduling – Network Diagram and Critical Path Method (CPM) module.

6.4 Reserve estimating

This method is about having a contingency reserve which is the time buffer or time reserve to be utilized due to uncertainties in scheduling. The contingency reserve may be in the form of a percentage of the activity duration, a fixed duration or to be determined using quantitative analysis methods. If the uncertainties are no longer a big concern due to having more accurate and reliable information about the project, the project manager has the option to reduce or remove the contingency reserve.



The activity duration estimate output can include a range of possible duration, for example: 4 weeks ± 3 days which is read as the activity will be done in at least 17 days and the most is 23 days (for working days of 5 days in a week).

7. Develop project schedule

The project schedule is created by analyzing project scope statement, activity list and attributes, inter-dependencies of activities, project schedule network diagrams, activity duration estimates, resource requirements and calendars, and schedule constraints.

There are a number of tools and techniques that are introduced in PMBOK to develop a project schedule: schedule network analysis, critical path method (CPM), critical chain method, resource leveling, what-if scenario analysis and schedule compression – crashing and fast tracking. Project schedule network diagram and CPM is covered in the Project Time Management: Project Scheduling – Network Diagram and Critical Path Method (CPM) module.

The output of this process is the Gantt Charts (bar chart and milestone chart) and project schedule network diagram. These charts, diagrams and other relevant project data and information serve as the project baseline.

Figure 3 is an example of a network diagram which is referred to as a Precedence Diagram or Activity On Node (AON) Diagram. It was drawn based on the data in Table 1.

Figure 4 is another example of a network diagram which is referred to as an Arrow Diagram or Activity On Arrow (AOA) Diagram. It was drawn based on the data in Table 2.

Figure 3: A project schedule network diagram called Precedence Diagram or Activity On Node (AON) Diagram for data in Table 1

A C

B

D

E

G

F

J

H

I

K



Figure 4: A project schedule network diagram called Arrow Diagram or Activity On Arrow (AOA) Diagram for data in Table 2

8. Control schedule

The project status and progress is monitored and updated in this process. Any changes with respect to the schedule baseline of the project will be managed accordingly. The basic activities to control the project schedule are as follows:

Determine the current status of the project schedule.

Influence the factors that may cause project schedule changes.

Determine whether the project schedule has changed.

Manage the project schedule changes.

The basic input for the control schedule process is the project schedule baseline, the most recent revised project schedule (with information of updates, completed activities, delays, etc.) and information about project performance and progress.

Tools and techniques used include performance review (which is basically comparing actual progress with the baseline), variance analysis (which is to assess the variation magnitude to the schedule baseline), functions in project management application (software) to track project progress, resource leveling, what-if scenarios, adjusting lags and leads, and schedule compression.

Schedule control activities would result in the following: a record of the causes of variances, a measure of the variances, take corrective actions on the variances, manage Variation Orders (VO), and update baselines for schedule and costs.

9. Group assignment

1) Study about an introduction to basic project time management at https://www.youtube.com/watch?v=UlTjJ_atRmc

2) Study about an introduction to basic project time management at https://www.youtube.com/watch?v=na143ha9oCg



10. References

1. Fisk, E. R. (2000), Construction Project Administration, Prentice Hall.

2. Garold D. Oberlender (2000), Project Management for Engineering and Construction, 2nd Edition, Mc Graw-Hill.

3. Gould, F. M. and Joyce, J. A. (2009); Construction Project Management; 3rd Edition, Prentice Hall.

4. Griffis, F. H. and Farr, J. V. (2000), Construction Planning for Engineers, Mc Graw-Hill.

5. Project Management Institute (2008), A Guide to the Project Management Body of Knowledge, 4th Edition.

Latest update: 9

th January, 2015

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3) Project Time Management - Basic Processes (2nd Sem 2014-15)