CHAPTER 7

Work Breakdown Structure

WBS DEFINED

The concept of work breakdown structure (WBS) was developed with the Program Evaluation and Review Technique (PERT) by the United States Department of Defence.  PERT was introduced by the U. S. Navy in 1957 to support the development of its Polaris missile program.  While the term “work breakdown structure” was not used, this first implementation of PERT did organize the tasks into product-orientated categories.

The basic purpose of a WBS is to provide a project schedule (and the project itself) with a logical structure to group activities.  Grouping activities has some distinct advantages:

It makes a schedule and the project manageable when activities are grouped

It makes the project schedule easily navigable

It structures project work in logical groups for example work packages or work allocated per sub-contractor, discipline or per area

It provides a means of reporting from the schedule in predetermined groups like the groups mentioned in the previous point

It provides logical and accurate assessment of progress for a group of activities to facilitate payment certificates

It allows for structured budgeting for proper cost control and reporting

The term “Work Breakdown Structure” (WBS) is a descriptive, generic term, and signifies a hierarchy of activity groupings – expanded from the largest or most complex group to the smallest or least complex group.

These groups can be defined along different boundaries, depending on the nature of the project.  An activity cannot belong to more than one of these groupings on the same level.

QUESTIONS COVERED

• Compile a WBS by work type for the construction of a townhouse complex with five townhouses, a perimeter wall, a guardhouse, and a communal facility which comprises a function hall and a swimming pool. Use the following work types:  earthworks, foundations, brickwork, roofing and services.  Use the following areas:  residential, roads and parking, security and recreation.
• Compile a WBS for the replacement of a furnace shell. Choose the most advantageous structure.  Motivate the structure used and then list all assumptions.  The project entails the following:
  • Rigging – The following items need to be removed and replaced:
    • The mud guns.
    • The tap floor, mud gun floor and roof-level floor.
    • The furnace feed chute.
    • The furnace ducting.
    • The furnace roofs.
    • The furnace electrode.
  • Civils construction – The following items need to be removed and replaced:
    • The tap floor, mud gun floor and roof floor (which comprises a steel structure with cast-in sections of concrete) need to be broken up to get the floors out of the way – for removing the furnace shell.
    • After replacement of the floors, the concrete floors have to be cast again.
    • Removal of the concrete cast-in sections of the furnace roof and replacing after the new furnace shell has been installed.
    • Repairs of the concrete blocks supporting the furnace floor need to be done as soon as the old shell is removed, and before the new shell is rigged into place.
  • Structural steel construction – The following items need to be removed and replaced:
    • All floor steel structures (three floors).
    • The ducting and feed chute.
  • Refractory – The following items need to be removed and replaced:
    • Removal of old refractory from existing furnace and replacing it in-situ when the new shell is installed.
  • Electrical construction – The following items need to be removed and replaced:
    • Electrical installation around the furnace electrode.
  • Ancillary electrical devices.
    • Instrumentation – The following items need to be removed and replaced:
      • All instrumentation.
• Do research on the internet and find a sample WBS. Provide commentary on the WBS and its structure, by looking at the following topics:
  • Item descriptions.
    • Suitability of first-level breakdown.
    • Suitability of second and third breakdowns.
    • Suitability of terminal level items.
    • Sufficient breakdown for detail budgeting.
    • Sustainability of presentation.
• Combine a WBS by area and units for the construction of a townhouse complex with five townhouses, a perimeter wall, a guardhouse and a communal facility which comprises a function hall and swimming pool. Use the following areas:  residential, roads and parking, security and recreation.  Add design and approval of building plans to your WBS.
• Compile a WBS for constructing a car port at your home.
• State which of the following statements are true and which are false:
  • A WBS outline level and the level of a project schedule is the same.
  • The lines connecting WBS elements indicate work flow.
  • WBS identifiers can contain alphabetic letters.
  • An activity in a project schedule can only belong to one WBS element.
  • A WBS structures a project logically.
  • Creating a WBS is in essence grouping of project activities.
  • All terminal elements of a WBS must be on the same level.
  • WBS elements shall be physical items or a group of physical items.
  • A WBS usually contains many activities.

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INCLUDED IN THIS CHAPTER: Introduction to word breakdown structures, Word breakdown structure levels, WBS terminal level, WBS groupings, Rules for compiling work breakdown structures, Different WBS views & Work breakdown structures in the software

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