Construction Project Scheduling
This article will explain in detail the major steps required to prepare a proper CPM Schedule.
Work Breakdown Structure:
The Project Management Body of Knowledge (PMBOK 5) defines the work breakdown structure as:
"A hierarchical decomposition of the total scope of work to be carried out by the project team to accomplish the project objectives and create the required deliverables."
For the Construction phase, it’s recommended to refer to the CSI Standard division of work. The Closeout phase mainly includes activities of punch lists, O&M, ss-built drawings, ans demobilization.
According to "Saleh Mubarak" Construction Project Scheduling and control Second edition Book:
There are several factors to be considered to create project’s Work Breakdown Structure (WBS)
The author explains each factor from his experience below:
Nature of Work: Work that has different materials or different units of measure should be divided into different activities. For example, building a wall involves masonry and plaster work, followed by certain painting activities.
Location: Items located in different areas or zones must be separated.
Size: Activities of large quantities are recommended to be divided into small portions. For example, large back-filling activities can be divided into smaller activities by zones or areas. This will ease measurement of work progress while execution.
Chronology: At times, part of the work may purposely delay by the contractor. For example, a room finishing may be delayed until the end of the project since the room is used as a storage area. Such a part should be considered as an activity in itself.
Responsibility: Tasks that are done by different parties (Subcontractors) must be broken down into separate activities. In case of any variances, it’s important to show who is accountable.
Phase: The designer can decide based on certain parameters such as time, location or other aspects.
Activity duration can be calculated by dividing quantities over the productivity of crews. The quantities should be obtained and provided from Tendering department or through the Technical Office. Productivity should be obtained based on a company’s previous experiences by professional individuals (Project Manager, Construction Manager, Site Engineers, …etc.) or get feedback from gang leaders, Engineering Department or Subcontractors. Expert judgement can help supplement and reinforce certain assumptions.
There are three types of dependency with respect to the reason of its existence:
Logical: It is impossible to start foundations before excavation or plastering cannot start before brick work.
Resource-dependent: It is possible to plaster four walls in a room at the same time but there is only one plasterer.
Preferential: Install tiles in the bathroom before the bedroom (or vice versa).
to be continued...