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Monitoring and Forecasting in Construction Projects Using Time Buffer

Vishnu S. Pillai, C. Rajasekaran, P.K. Vatsa


The key to project management is effective performance monitoring and forecasting. The existing methods using input- output cash flow, earned value, etc. do not differentiate between work done on the critical path and work done on non-critical paths. Such methods mask the real situation and mislead the project team because progress on one path often compensate for the delay in other. The paper proposes a more effective method to facilitate project managers take decisions. Time buffer is defined as the extra time added knowingly or unknowingly by construction personnel to the minimum possible duration of any activity in order to protect against schedule deviation. There is no thumb rule to identify which activity dictates the lead time of a project and the allocation of time buffer remain completely intuitive. For the purpose of the study, construction of a material handling system is considered and the factors of time buffer are identified. The severities of top ten frequent factors are considered to determine the magnitude of time buffer usually added by construction personnel in activity durations. A Project Buffer Index (PBI) is developed for project monitoring. The PBI values calculated at regular intervals of time help the project manager assess the status of the project and take decisions accordingly. Duration required to complete the project and the cost at completion are also arrived at. After detailed duration analysis, a micro-level schedule using Microsoft Project is created for the erection of a pipe rack structure and the proposed method is applied.
Keywords: Construction, Time Buffer, Scheduling, Earned Value, Performance

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