The Pros & Cons of PERT Analysis technique

The Pros & Cons of PERT Analysis technique

 

What is PERT?

PERT stands for Program Evaluation Review Technique. PERT charts are tools used to plan tasks within a project – making it easier to schedule and coordinate team members accomplishing the work.

PERT charts were created in the 1950s to help manage the creation of weapons and defense projects for the US Navy. While PERT was being introduced in the Navy, the private sector simultaneously gave rise to a similar method called Critical Path.

PERT is similar to critical path in that they are both used to visualize the timeline and the work that must be done for a project. However with PERT, you create three different time estimates for the project: you estimate the shortest possible amount time each task will take, the most probable amount of time, and the longest amount of time tasks might take if things don’t go as planned.

PERT is calculated backward from a fixed end date since contractor deadlines typically cannot be moved.

 

The PERT technique focuses on the time and the cost each activity takes. This will hence influence the resultant time and the cost required for the completion of the entire project. This network analysis technique helps to understand the performance of the work throughout the course of the project.

 

The PERT technique possess many advantages that facilitate the project team and many disadvantages that have to be taken care by the project managers. The pros and cons of PERT are mentioned below.

 

Advantages of PERT

The advantages of PERT are mentioned below:
  1. Planning For Large Projects
  2. Visibility of Critical Path
  3. Analysis of Activities
  4. Coordinating Ability
  5. The What – if -Analysis

Planning For Large Projects: The scheduling of project activities is done easily with the help of PERT system by the project manager. This technique is more active in large sophisticated project works. As PERT is event oriented programming technique, three elements are necessary to define an event. They are:

  1. What is the time required to perform the event?
  2. What comes after the event?
  3. What is coming before the event?
The answers to the above question make the scheduling easier and clear.


 Visibility of Critical Path: The PERT method will show the critical path in a well-defined manner. The critical path is the path with activities that cannot be delayed under any circumstances. A proper knowledge about the stack values with limited conditions of dependencies will help the project manager to bring fast and quality decisions that will favor the project performance.

 Analysis of Activity: The activity and the events are analyzed from the PERT networks. These are analyzed independently as well as in combination. This will give a picture about the likely completion of the project and the budget.

Coordination: The various departments of the construction organization will deliver data for the PERT activities. A good integration is developed between all the departments which will help in improving the planning and the decision-making capabilities of the project team. The combination of qualitative and quantitative values from a large amount of data will help in improving the coordination of the project activities. This will also improve the communication between various departments of the organization.

What – if -Analysis: The possibilities and the various level of uncertainties can be studied from the project activities by properly analyzing the critical path. This type of analysis is called as what-if-analysis. For this various sets of permutation and combination is conducted. Among them, the most suitable combination is taken into consideration. This set chosen will be the one with minimum cost, economy and best result. This analysis helps to identify the risk associated with any activities.

Disadvantages of PERT

Various Demerits of PERT are mentioned below:

  1. Time Focused Method
  2. Subjective Analysis
  3. Inaccuracy due to Prediction
  4. Expensive
  5. Other Issues
Time Focused Method: The method of PERT is a time oriented method, where the time required to complete the respective activity is of higher importance. Hence the time determination of each activity and its allocation is very much necessary. This is done based on an assumption and within this time the work will be completed. If this is not the case issues will arise.
Subjective Analysis: The activities for a project is identified based on the data available. This is difficult in case of PERT as these are mostly applied for a project that is newly conducted or those without repetitive nature. The project dealt by PERT will be a fresh project data that make the collection of information to be subjective in nature. This will bring less accuracy on the time and the estimated time.
There are chances to have inaccuracy and bias in the sources of data. This makes it unreliable. As this is not repetitive in nature, there is no sense in bringing the records from the past historical data.
Prediction Inaccuracy: As there is not past records or assistance to bring an outline for the project, predictions take their role. The overall project may move to total loss if the predictions and the decisions are inaccurate. No trial and error method can be employed.
Expensive: As this method is carried out based on predictions in overall, they find too expensive in terms of methods employed, the time consumed and the resources used.
To download Free Project Management Templates you can visit www.managementproject.net

Bridge moment and shear envelopes spreadsheet

Bridge moment and shear envelopes spreadsheet

 

Moving truck (up to 20 axles) analysis for bridges with simple or continuous spans (up to 5). Envelopes (M & V) and support reactions.

Program

2 to 20 axles and 1 to 5 spans with El constant throughout. Truck will move from left to right with the first axle in front. Critical values of shears (absolute values) and moments will be computed on each division point. Total number of divisions must be less then 500. Results and graphs are displayed on Results, MEnvelope and VEnvelope worksheets.

Tips and Tricks

Reverse the truck geometry to simulate moving from right to left. Instead of axle loads, use wheel loads multiplied by impact and lateral distributions factors to obtain quickly design moments, shears and support reactions. Use q(uniform load) to simulate lane load. Dead load or any other uniform load may be simulated by using zero axle loads. For a simple span, for example. AASHTO users may simulate lane load by choosing 2 axles with the 2nd axle weight set to 0. 0.

 

Download Link

Influence line diagrams spreadsheet

Influence line diagrams spreadsheet

 

 

Influence line diagrams spreadsheet calculates influence line diagrams for bending moments in a single span or continuous multi-span beam using the moment distribution method.

INSTRUCTIONS

  1. Enter data in the yellow cells only.
  2. Enter the Span Length for each span. Any number of spans may be analysed up to a maximum of 10. Any of the 10 spans not used will be removed when the “Calculate Critical Points” button is clicked . (Note: The print-out for more than 8 spans requires the paper orientaton to be set to ‘Landscape’).
  3. Enter Modulus of Elasticity (E) multiplied by the Second Moment of Area (I) for each span. Relative values of EI may be used, for example, if the beam is of the same material and cross section throughout then a value of 1 may be entered for EI for each span.
  4. Select the End Support Conditions (Fixed or Pinned) by clicking the option buttons.
  5. Click the “Calculate Critical Points” button to analyse the beam to determinine the position of the maximum sagging moment in each span and the position of the load to give the maximum hogging moments at each supprt. The results are displayed in a drop-down menu labelled “Moments”.
  6. Select the position of the Influence Line you require from the drop-down menu which will be displayed on the graph below. If you require an Influence Line for any other position on the beam then select “User Defined” from the menu and enter the distance of the required position from the left hand end of the beam.
  7. The ‘Areas’ shown are the individual areas of the influence line diagram numbered in sequence from left to right as shown:
  8. If a value of the influence line diagram is required at a specific distance along the structure then click the ‘Find Value’ button. The distance is measured from the left hand end of span 1.

* Influence Line Diagrams download link provides freeware version of the software.

 

Download Link

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