Sequence of Activities: Dependency Determination

Determining the sequence of activities in a project is a necessary step in building a project network diagram. The sequence of activities is the process of identifying the logical relationship between activities. Each activity in a project has at least one predecessor and one successor except for the first and last activities.

Precedence Diagramming Method (PDM) which is also called Activity-On-Node (AON) allows the use of the four types of relationships that are finish-to-start (FS), finish-to-finish (FF), start-to-start (SS), and start-to-finish (SF). Figure 1 shows the representation of these different relationships. So what those relationships stand for?

Finish-to-start (FS): The predecessor activity must finish in order for the successor activity to start. This relationship is the most deployed in project planning. Assume there are two activities, A and B where A is a predecessor of B, then it means “finish activity A to start activity B”. For example, finish placing the reinforcement of column 1 to start pouring concrete in column 1.

Finish-to-finish (FF): The predecessor activity must finish in order for the successor activity to finish. This means “finish activity A to finish activity B”. For example, finish placing the reinforcement of a wall to finish the formwork of that wall.

Start-to-start (SS): The predecessor activity must start in order for the successor activity to start. This means “start activity A to start activity B”. For example, start placing the concrete of a slab to start finishing the concrete of that slab.

Start-to-finish (SF): The predecessor activity must start in order for the successor activity to finish. This relationship is rarely used. This means “start activity A to finish activity B”. For example, start the night shift of security personal to finish the day shift of security personal. In this case, the security personal of the day shift cannot end his shift before the arrival of the security personal of the night shift. If the security personal of the night shift is running late, then the security personal of the day shift will have to wait (i.e. cannot finish his shift).  

Now that the types of relationships are explained, the next question would be “which relationship to use?” To answer this question, project planners should know the how the work will be carried out (i.e. construction method). By understanding the construction method, a project planner can determine the dependency between the activities. PMBOK describe three types of dependencies which are mandatory, discretionary, and external dependencies.

Mandatory dependencies (also referred to as hard logic) are the ones that contractually/legally required or forced by the construction method or nature of work. In construction projects, mandatory dependencies usually involve physical limitations. For example, a contractor cannot pour the concrete before the placing the reinforcement; a contractor cannot construct the bridge deck before finishing the construction of the columns for that span.

Discretionary dependencies (also referred to as soft logic) are the ones that result from a preferred method or best practice of carrying out an activity. It is worth mentioning that this type of dependencies can result in different type of relationships based on the setting of the project. For example, in Design-Build projects the design of a building can be finalized before commencing the construction or the construction can start before the final design is still in progress.

External dependencies are the ones that are forced by non-project activities yet they are necessary for the start of project activities. In some situations, the project team have no control over these dependencies. For example, a contractor cannot start the construction of a building before issuing a construction permit (non-project activity). In this case, the time needed to issue the construction is outside the project team’s control.

Sometimes it is necessary to use lead or lag time between activities to maintain an accurate logic between activities. This will be the topic of a future post.

Please feel free to comment of give a feedback on my post.

Bibliography

Project Management Institute. (2008). A Guide to the Project Management Body of Knowledge (PMBOK). Newtown Sqaure, Pennsylvania: Project Management Institute, Inc.

Project Schedule Network Diagram

The project schedule network diagram is a visual representation of the activities in a project and their inter-dependency. There are two common approaches to build a network diagram. The first approach is the Precedence Diagramming Method (PDM) which is also called Activity-On-Node (AON) (Figure 1).


Figure 1  Precedence Diagramming Method Example

In this network diagram, the activities are represented by boxes (node) and the logical relationships between the activities are presented by arrows. PDM allows the use of the four types of relationships that are finish-to-start (FS), finish-to-finish (FF), start-to-start (SS), and start-to-finish (SF). Figure 2 shows the representation of these different relationships. This approach is the most common one and supported by major scheduling software such as Primavera and MS Project. 


Figure 2 Relationship Representation in PDM

The second type is the Activity-On-Arrow (AOA) as shown in Figure 3. In this network diagram, the activities are represented by an arrow and connected by nodes. The nodes represent an event which could be the start or completion of an activity. Finish-to-start is the only relationship that can be used to express the dependency between activities when using the AOA approach. Sometimes it is necessary to use a dummy activity, which is an activity that has no time, to maintain the logical relationships in an AOA network. 


Figure 3 Activity On Arrow Example

If you have any questions, please do not hesitate to ask.

In future posts I will talk about the logical relationships between activities, how to construct an AOA network, and finding the critical path.

Free PMP Exam Simulation Test !

Free PMP Exam Simulation Test !

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Free live Online classes on Project Quality Management.

Timings are provided in GMT. Please convert it to you local timings

Date and Timing :
26th November, 2011 . 1.30 AM GMT - Project Quality Management

URL : http://www.simplilearn.com/simplilearn/webinars

Kindly note that, if you are unable to attend the live webinar on these topics, due to time constraints, you can request for the recorded version of the webinars.

Based on PMBOK 4th Edition

Please write to leisley@simplilearn.com to get access code to join the webinar.

Free live Online classes on Project Risk Management

Timings are provided in GMT. Please convert it to you local timings

Date and Timing :

25th November, 2011 - 10 AM GMT - Project Risk Management

URL : http://www.simplilearn.com/simplilearn/webinars

Kindly note that, if you are unable to attend the live webinar on these topics, due to time constraints, you can request for the recorded version of the webinars.
Based on PMBOK 4th Edition
Please write to leisley@simplilearn.com to get access code to join the webinar.

Disaster Prevention: Preparing for the Worst - Free eBook!

Free eBook to Disaster Prevention: Preparing for the Worst. This backup and recovery guide offers best practice articles to help your system and organization survive.

You can download here

Free Webinar: What You Must Know About Stakeholder Management 7/12/2011

Date/Time: 12/7 11:00 am to 12:00 pm EDT

Course ID: MDW1250 / Duration: 1 Hour / Credits: 1 PDU

Once of the most critical aspects of project management is doing what’s necessary to develop and manage relationships with all individuals that the project impacts. In this webinar, you’ll learn techniques for identifying stakeholders, analyzing their influence on the project, and developing strategies to communicate, set boundaries, and manage competing expectations. By effectively managing your stakeholders, you will be better able to keep a lid on scope creep, ensure project requirements are aligned, understand tolerance for risk, and mitigate issues that would otherwise delay the project. Effective stakeholder management is proof of your influence in an organization, and a key component to a healthy project environment.

Key learning points:

- How to identify project stakeholders
-How to conduct a stakeholder analysis
-How to manage different types of stakeholders

Bonnie Cooper, PMP®, Trainer and Consultant for Corporate Education Group, is a 25-year Information Technology professional and currently the Program Portfolio Director of the Massachusetts Medical Society's Corporate IT PMO. Her portfolio includes The New England Journal of Medicine's manuscript tracking, desktop publishing, advertising management, and corporate ERP systems. In her current role, Ms. Cooper is responsible for coordinating the efforts of project teams, defining a consistent software development methodology, and leading the program to re-engineer the membership services platform. Ms. Cooper is a project management educator, and a published writer of her experiences in facilitating the PMO to drive IT strategy and governance.

To register click here

Free webinar: People Skills For Project Managers December 9, 2011

The webinar will be an introduction to five key people skills for project managers – empathy, communication, anticipation, organization, pragmatism.

The webinar is on December 9, 2011 at 10 am CST. you can register here.

Program Evaluation and Review Technique (PERT) Calculation Steps

The objective of this post is to explain how program evaluation and review technique (PERT) can be used to schedule a project with uncertainty. 

The main difference between CPM and PERT is that PERT uses probabilistic durations instead of deterministic ones. In PERT, each activity has three estimated durations which are optimistic, most likely, and pessimistic. The purpose of using these three different durations is to model the uncertainty inherited in the activity durations.

The steps of scheduling a project using PERT will demonstrated through the following example. The information of the project is presented in Table 1. It should be noted that in this example, the finish to start relationship is used. The same procedure would be followed if different relationships do exist. 

Step 1: Calculate the mean, standard deviation, and variance of each activity using the following equations. The results of this step are presented in Table 2.

Step 2: Construct the precedence diagram and preform CPM analysis using the mean duration as shown in Figure 1. Then find the critical path which in case is B-C-G-H-K-M-O-P-Q-R. Next, calculate the standard deviation of the project which is the square root of the sum of the variances of the critical path activities. In this case it is 3.75.

Figure 1 Precedence Diagram

Step 3: Probability analysis using the calculated information. Two main questions can be answered using probability analysis. The first question is “What is the probability that the project will be finished on or before 98 (you can choose the target duration that you are interested in) days?” To answer this question Z, which is the number of standard deviations the target date lies from the expected date, should be calculated using the NORM.DIST function in Excel 2010 (NORMDIST function in Excel 2007) or the following equation. 

The next step would be finding the area under the normal distribution curve using normal distribution tables that corresponds to a Z value of 0.8. By doing that, we can find that there is 78.81 % chance that project can finish in 98 days or less. It should be noted that if the Z has a negative value, then the probability would be 1 – table value.  

The second question is “What is the due date under which the project has 99 % (you can choose the confidence level that you are interested in) chance of completion?” In this question, we are given the area under the curve which 0.99. We can either find the answer by using NORM.INV function in Excel 2010 (NORMINV function in Excel 2007) or the following steps. What we need to find is the Z value from the normal distribution table. In this case, Z is 2.33.

I have also developed an Excel sheet that you can download from here. 

If you have any questions, please do not hesitate to ask.

Program Evaluation and Review Technique (PERT) Excel Sheet

I have developed an Excel sheet that shows how to preform project scheduling using PERT. You can modify it to accommodate your project. You can download it from  here. To learn more about the steps of generating schedules using PERT click here. It should be noted that in this example, the finish to start relationship is used in this Excel file. The Excel workbook was developed using the 2010 version. If you are using MS Excel 2007, you need to do this small modification. In the Schedule! sheet, the functions in cell J7 and N10 should be changed to NORMDIST and NORMINV respectively.

If you have any questions, please do not hesitate to ask.

Communication Skills for Leaders

Today, I attended a workshop titled "Communication Skills for Leaders" at Concordia University as part of the Leadership Workshop Series. Below is a summary of what I have learned.
Listening represents almost half the components of communication. Therefore, it is necessary to be a good listener if you are looking forward to be a successful leader. No listening to what your team have to say will decrease their motivation, diminish their contribution and lead to frustration and disappointment.
However, being a good listener by itself is not enough. Another important component of communication is responding effectively. A leader should avoid harmful responses such as prying, devaluation and preaching. Instead, a leader should use different forms of empathic responses such as encouraging, and giving feedback.
Team members should  go with an assertive communication style instead of being passive or aggressive. Describe, Express, Solution, Consequences (DESC) scripts can be used to help you establish an assertive communication style. And don't forget that 65 - 90 % of communication is non-verbal which means that you have to pay attention to your body language such as tone of voice, hand movements, and posture.

Marlene Gross and Anna Lenkovskaya, Thank you for a an interesting yet very useful workshop.

Free Webinar: Project Time Management 12th November, 2011

You can learn more about Project Time Management in this weeks webinar for Free !

Date and Timings for Project Time Management.

12th November, 2011 at 6.30 PM PST, 8.30 PM CST, 9.30 PM EST, 1:30 AM GMT

URL:http://www.simplilearn.com/simplilearn/webinars

Its an online webinar based on PMBOK 4th Edition

Write to leisley@simplilearn.com for free invitation

Free Webinar: "Putting a Plan in Place Takes Leadership" 11/15/2011

Free Upcoming Systemation Webinar: "Putting a Plan in Place Takes Leadership"
on 11/15/2011 12:00 PM

Register at iLinc

Earn 12 PDU for free

IIL put together an exciting program of on-demand video presentations featuring a wide range of experts and thought leaders from all sides of the industry. Presenters include Dr. Harold Kerzner, addressing the importance of metrics with regard to today's complex projects, and Frank P. Saladis, PMP, the Founder of International Project Management Day.

Log in at http://events.unisfair.com/index.jsp?eid=1022&seid=374 submit and view the video presentations. its free till Feb 2012

Free webinar: How to Determine Which Simulation Software is Best for Your Industry - 12/6/2011 11:00 AM - 11:30 AM

To continue the Simulation series of web seminars, PMC is hosting an informative session on selecting the right simulation software to best fit your needs, as another tool in your productivity improvement toolbox.
This webinar will acquaint you with considerations to keep in mind when selecting from the many simulation software tools the best-fitting one for your business needs, whether for manufacturing, distribution, retailing, service providing, health care, or others (and these have many subdivisions). Since “best-fitting” encompasses many criteria (e.g., analytical capabilities, animation capabilities, ease of learning, ease of use, future migration path, statistical interfaces available, and price), the attendee will receive guidance in asking and answering the pertinent questions to make the optimum choice.

Free Webinar: How Managers Can Use Simulation to Improve Performance in Their Organization

A major strength of discrete event simulation is its ability to model random events and to predict the effects of the complex interactions between these events. This webinar will discuss the integration of the analytical power of simulation into the continuous improvement every competitive enterprise requires nowadays. “What-if” experimentation answers questions and compares outcomes that are useful as a decision support tool.

Participants will benefit from discussion of how to elevate simulation from rare "special occasion" use to a powerful constant force for continuous evaluation, improvement, and evolution of business processes (be they production, service, transportation, or logistics). A simulation model and its analyses can be living documents of value to the organization over a very long life span.

Date: November 15, 2011 & Time: 11:00 AM - 11:30 AM EDT
Registration: http://www.pmcorp.com/Resources/UpcomingWebinars.aspx

Prestressed Concrete Bridges: Design and Construction

Prestressed Concrete Bridges: Design and Construction by Nigel R. Hewson (2003)


Amazon's Book Description

Prestressed concrete decks are commonly used for bridges with spans between 25m and 450m and provide economic, durable and aesthetic solutions in most situations where bridges are needed. Concrete remains the most common material for bridge construction around the world, and prestressed concrete is frequently the material of choice. Extensively illustrated throughout, this invaluable book brings together all aspects of designing prestressed concrete bridge decks into one comprehensive volume. The book clearly explains the principles behind both the design and construction of prestressed concrete bridges, illustrating the interaction between the two. It covers all the different types of deck arrangement and the construction techniques used, ranging from in-situ slabs and precast beams; segmental construction and launched bridges; and cable-stayed structures. Included throughout the book are many examples of the different types of prestressed concrete decks used, with the design aspects of each discussed along with the general analysis and design process. Detailed descriptions of the prestressing components and systems used are also included. Prestressed Concrete Bridges is an essential reference book for both the experienced engineer and graduate who want to learn more about the subject.

The Design of Prestressed Concrete Bridges: Concepts and Principles

The Design of Prestressed Concrete Bridges: Concepts and Principles by Robert Benaim (2007)

Amazon's Book Description

Examining the fundamental differences between design and analysis, Robert Benaim explores the close relationship between aesthetic and technical creativity and the importance of the intuitive, more imaginative qualities of design that every designer should employ when designing a structure.

Aiding designers of concrete bridges in developing an intuitive understanding of structural action, this book encourages innovation and the development of engineering architecture. Simple, relevant calculation techniques that should precede any detailed analysis are summarized. Construction methods used to build concrete bridge decks and substructures are detailed and direct guidance on the choice and the sizing of different types of concrete bridge deck is given. In addition guidance is provided on solving recurring difficult problems of detailed design and realistic examples of the design process are provided.

This book enables concrete bridge designers to broaden their scope in design and provides an analysis of the necessary calculations and methods.