Network Analysis: PERT

# Network Analysis: PERT | Construction Materials & Management - Civil Engineering (CE) PDF Download

## Introduction

• The U.S Navy developed PERT during the late 1950s to accelerate the development of the Polaris Fleet Ballistic Missile PERT.
• PERT is an abbreviated form that stands for Programme Evaluation and Review Technique used to plan, schedule, and monitor the project.
• Coordination with the help of PERT was so successful that the entire project was complete years ahead of schedule.
• In PERT, all activity time is probabilistic.
• For PERT. Employs Beta-distribution for the time – expectation for activity.

Time Estimates

• A project is composed of many diversified activities which contribute to its completion.
• An important characteristic of any project is its duration.
• As its effect and economy are often dependent on the project duration.
• Total project duration depends on the time taken by each activity Estimation of time required for any activity requires wide experience of similar activities.

Estimation of these time estimates can be done in two ways.

1. Deterministic Approach: The planner has enough knowledge about the activity and gives a single estimate of the duration, which is almost accurate

2. Probabilistic Approach: The planner does not have many ideas about the activity as there is little or no past history about it.

• The limits with which the duration will lie is estimated.
• Pert follows the probabilistic approach and absorbs the uncertainties into the time estimates for activity and project durations.
• Therefore PERT is well suited for those projects with insufficient or no background information for estimation of time duration.
• PERT is used in R&D type projects such as the space industry, defence industry etc. As such, projects are of a non-repetitive type or once-through type for which correct time estimates cannot be made.
• Further, a PERT analysis is event-oriented, i.e. in this analysis, interest is more focussed on the PERT (start or completion of activity)  rather than the activities.

In order to take into account the uncertainties involved in the activity times, three kinds of time estimates are made for each activity in PERT.

(i) Optimistic time (to): Optimistic time is a concept used in the program evaluation and review technique (PERT). It represents the shortest estimated time period within which a task is likely to be completed, and is used in project planning.

(ii) Most Likely Time (tm): Most likely time, expressed as 'tm', represents estimate of time for completion of an activity, which is neither optimistic nor pessimistic, assuming that things should go in a normal way, and if the activity is repeated several times, in most of the cases, it will be completed in time represented by t.

(iii) Pessimistic Time (tp): Pessimistic time is a concept used in the program evaluation and review technique (PERT). It represents the longest estimated time period within which a task is likely to be completed, and is used in project management activities.

• In PERT, activity time is probabilistic, but in CPM, activity time is deterministic.
• The other difference: PERT is Event–Oriented. While the CPM is Activity – Oriented (in CPM, we actually know the Activity time)
(a) Expected completion time of an Activity: (tE)

Where t0 = Optimistic time
tp = Pessimistic time
tm = Most likely time
(b) Standard deviation of an activity: (𝛔)

(c) Variance of an activity: (𝛔2)

(d) Central limit theorem:
A. The mean time of the project as a whole is tE = tE1 + tE2 + .......  along the critical path.
The probability of completion of the project in time tE is 50%.
B. The standard deviation of the project as a whole is  along the critical path.

Critical Path: The time-wise longest path is called the critical path. In this path, any type of delay, in any event, will cause a delay to the project. These are shown by double line or dark lines in a network.
An event is critical if its slack is zero.

Event Time

1. Earliest expected event occurring time (TE)
when there is only one path.Where, = Expected completion time of activity I – j
.... when there is more than one path.
Where = Earliest expected time of event i.
= Earliest expected time of event j.
2. Latest allowable occurrence time (TL)
When there is only one path.
When there is more than one path.
3. Slack (s)
This is the time by which an event may be delayed without affecting the completion time of the project.

Probability Factor (z)

z = TS -TE
Where, TS = Given scheduled completion time of the project
TE = Expected completion time of the project.
σ = Standard deviation

### Frequency Distribution Curve for PERT

It is assumed to be a β - distribution curve with a unimodal point occurring at tm and its endpoints occurring at to and tp. The most likely time need not be the midpoint of to and tp, and hence the frequency distribution curve may be skewed to the left, skewed to the right or symmetric.

The document Network Analysis: PERT | Construction Materials & Management - Civil Engineering (CE) is a part of the Civil Engineering (CE) Course Construction Materials & Management.
All you need of Civil Engineering (CE) at this link: Civil Engineering (CE)

## Construction Materials & Management

5 videos|19 docs|16 tests

## FAQs on Network Analysis: PERT - Construction Materials & Management - Civil Engineering (CE)

 1. What is PERT analysis in civil engineering?
Ans. PERT (Program Evaluation and Review Technique) analysis is a project management tool used in civil engineering to schedule and manage activities involved in a project. It helps in determining the sequence of activities, their durations, and dependencies to create an efficient project schedule.
 2. How does PERT analysis benefit civil engineering projects?
Ans. PERT analysis provides several benefits to civil engineering projects. It helps in identifying critical activities that can impact the overall project timeline. It also allows for better resource allocation, risk assessment, and cost estimation. Additionally, PERT analysis enables effective communication and coordination among project stakeholders, resulting in improved project performance.
 3. What are the key components of PERT analysis in civil engineering?
Ans. The key components of PERT analysis in civil engineering include identifying project activities, determining their dependencies, estimating activity durations, and creating a network diagram. It also involves calculating the critical path, which is the longest path in the network and determines the project's overall duration.
 4. How is a PERT network diagram created in civil engineering projects?
Ans. A PERT network diagram in civil engineering projects is created by representing project activities as nodes and connecting them with arrows to depict their dependencies. Activity durations are represented on the arrows. The network diagram helps in visualizing the sequence of activities and identifying the critical path.
 5. Can PERT analysis be used in conjunction with other project management techniques in civil engineering?
Ans. Yes, PERT analysis can be used in conjunction with other project management techniques in civil engineering. It is often combined with techniques like Gantt charts, resource allocation models, and risk analysis. This integration allows for a comprehensive approach to project planning, scheduling, and control, leading to successful project completion.

## Construction Materials & Management

5 videos|19 docs|16 tests

### Up next

 Explore Courses for Civil Engineering (CE) exam

### Top Courses for Civil Engineering (CE)

Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev
Related Searches

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

;