White Paper Multiple Activity Charts Multiple Activity Charts (or Multi-Activity Charts) are a very useful tool for understanding the flow of work in a cyclical process and as a consequence understanding which resource is controlling the overall progress of the work. The tool can be used to model different scenarios to determine the optimum mix of resources for the work. The example below is based on using a tower crane to lift concrete from the street to a high floor for placing.
Each resource is represented by a column; time is on the vertical axis. Time 1 min 2 min 3 min 4 min 5 min 6 min 7 min 8 min 9 min 10 min 11 min 12 min 13 min Truck & Crew Fill skip Wait Crane & Skip Skip filling Hoist Skip Skip emptying Lower skip Placing Crew Wait Place and compact concrete Wait Finishing Crew Wait Smooth and finish concrete Fill skip Wait Skip filling Hoist Skip Skip emptying Lower skip Skip filling Place and compact concrete Wait Wait Smooth and finish concrete Fill skip
In this example, the crane (or more accurately the crane skip) is critical. On way to reduce the cycle would be to use two skips. One skip could be being filled while the other is emptied and all that would be needed is a few seconds to change over the crane hook when the newly emptied skip is lowered to the ground. Time 1 min 2 min 3 min 4 min 5 min 6 min 7 min 8 min 9 min 10 min 11 min 12 min 13 min 14 min 15 min Truck & Crew Fill skip 1 Fill skip 2 Skip 1 Skip filling Hoist Skip Skip emptying Lower skip Skip filling Skip 2
Crane Placing Crew Finishing Crew Skip filling Hoist Skip 1 Skip 1 emptying Lower skip 1 Change Hook Place S1 concrete Fill skip 1 Smooth and finish concrete Smooth and finish concrete Hoist Skip Skip emptying Lower skip Skip filling Hoist Skip 2 Skip 2 emptying Lower skip 2 Change Hook Place S2 concrete Fill skip 2 Hoist Skip Skip emptying Hoist Skip 1 Skip 1 emptying Place S1 concrete Smooth and finish….. We have now reduced the cycle from 6 minutes to 5 minutes per load at the cost of hiring an additional concrete skip.
The cycle could be further reduced if the hook change time is minimised. This may not sound much but if there were 30 skip loads of concrete in the pour and the cycle time could be reduced from 6 minutes to 4, the hour saved would reduce the cost of the pour by around $2,000 to $3,000. The next question though is how would the finishing crew manage? They are now working 100% of the time and arrangements may be needed for the placing crew to help them keep up with the increased pour rate. © Practical PM Pty Ltd 1 www. mosaicprojects. com. au
This White Paper is part of the supplementary information developed to support Mosaic’s PMP training courses. For additional information see: www. mosaicprojects. com. au/Training-Home. html www. mosaicprojects. com. au/whitepapers. html White Paper Multiple Activity Charts a very simple technique that can provide valuable insights to help optimise any cyclical process that involves several different resources. They can also provide a valuable tool for monitoring progress in critical situations where a detailed understanding of the workflow is needed.
The difference between this type of analysis and barcharts or CPM networks is the focus is on optimising resource usage in a repetitive / cyclical process. Once the resource usage and cycle time are optimised, the resulting overall duration can be incorporated into the main project schedule or Line-of-Balance (LOB) chart. Another key difference between Multiple Activity Charts and bar charts is the time unit. Multiple Activity Charts typically work in hours or minutes (and occasionally fractions of minutes). Barcharts typically have a timescale of days and weeks. __________________________________ For more on Line-of-Balance see: http://www. mosaicprojects. com. au/WhitePapers/WP1021_LOB. pdf For more information on scheduling and planning, visit Mosaic’s scheduling home page at: http://www. mosaicprojects. com. au/Planning. html © Practical PM Pty Ltd 2 www. mosaicprojects. com. au This White Paper is part of the supplementary information developed to support Mosaic’s PMP training courses. For additional information see: www. mosaicprojects. com. au/Training-Home. html www. mosaicprojects. com. au/whitepapers. html