Comparison of Schedule Managing Methods - Revision history

Tkokotas at 12:41, 19 November 2018

2018-11-19T12:41:54Z

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			''Developed by Mathias Ekström Larsen''


	Projects involve many different tasks that must be done to complete the project. Many of these tasks will in construction projects logically depend on each other. For example, it is necessary to build supporting walls or columns before the roof can be installed. There are several methods to keep track of these dependencies. In this article, similar methods will be explained and their differences will be compared together with their advantages and disadvantages. The life cycle of construction projects can overall be split into two groups. Either the project will be planned and managed with a sequential life cycle or an adaptive life cycle. The main difference between the two are that the sequential life cycle has a number of tasks that depends on each other and are planned very early in the project. It is difficult to change the plan as the project progresses which makes it vulnerable to delays. The adaptive life cycle on the other hand makes a rough plan with the overall tasks in the beginning of the project. The detailed planning of the individual tasks is then done as the project progresses. This way of planning is therefore less vulnerable to delays.		Projects involve many different tasks that must be done to complete the project. Many of these tasks will in construction projects logically depend on each other. For example, it is necessary to build supporting walls or columns before the roof can be installed. There are several methods to keep track of these dependencies. In this article, similar methods will be explained and their differences will be compared together with their advantages and disadvantages. The life cycle of construction projects can overall be split into two groups. Either the project will be planned and managed with a sequential life cycle or an adaptive life cycle. The main difference between the two are that the sequential life cycle has a number of tasks that depends on each other and are planned very early in the project. It is difficult to change the plan as the project progresses which makes it vulnerable to delays. The adaptive life cycle on the other hand makes a rough plan with the overall tasks in the beginning of the project. The detailed planning of the individual tasks is then done as the project progresses. This way of planning is therefore less vulnerable to delays.

S133571: /* The dependency structure matrix */

2017-06-22T08:50:10Z

The dependency structure matrix

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	=====The dependency structure matrix=====		=====The dependency structure matrix=====
			A way to make a plan for an adaptive life cycle is to make a dependency structure matrix (DSM). The dependency structure matrix consists of all design tasks in a matrix form in both rows and columns. The way the matrix works is that all tasks that depends on information from other tasks gets the box filled in. The matrix will then have a filled diagonal which simply shows that each task depends on itself. All the filled boxes below the diagonal is not a problem as they will have the required information in time since the depending tasks will be finished before the start of the relevant task. The filled boxes above the diagonal, however, depends on information from tasks that starts later. The way to handle such tasks is to either estimate the required information or simply delay the completion of the tasks <ref name=Winch>Winch, Graham (2010), "Managing Construction Projects. An Information Processing Approach" Second Edition, Wiley-Blackwell, United Kingdom. ISBN 978-1-4051-8457-1.</ref>. The amount of such tasks can be reduced by moving the tasks around in the matrix such that the dependencies gets below or close the diagonal. The dependency structure matrix can for example be used in the design phase as an iterative tool where the architect sends a structure design to the engineer who then sends some suggested changes back to the architect and so on. A more in-depth explanation of the dependency structure matrix can be seen in <span class="plainlinks">[http://apppm.man.dtu.dk/index.php/Application_of_Dependency_Structure_Matrix_in_Time_Scheduling Application of Dependency Structure Matrix in Time Scheduling]</span>

	[[File:Design Structure Matrix.png\|250px\|thumb\|center\|Figure 5: Example of a dependency structure matrix. <ref name=DSM_wiki>"Design structure matrix". Retrieved June 19, 2017, from https://en.wikipedia.org/wiki/Design_structure_matrix.</ref>]]		[[File:Design Structure Matrix.png\|250px\|thumb\|center\|Figure 5: Example of a dependency structure matrix. <ref name=DSM_wiki>"Design structure matrix". Retrieved June 19, 2017, from https://en.wikipedia.org/wiki/Design_structure_matrix.</ref>]]

	A way to make a plan for an adaptive life cycle is to make a dependency structure matrix (DSM). The dependency structure matrix consists of all design tasks in a matrix form in both rows and columns. The way the matrix works is that all tasks that depends on information from other tasks gets the box filled in. The matrix will then have a filled diagonal which simply shows that each task depends on itself. All the filled boxes below the diagonal is not a problem as they will have the required information in time since the depending tasks will be finished before the start of the relevant task. The filled boxes above the diagonal, however, depends on information from tasks that starts later. The way to handle such tasks is to either estimate the required information or simply delay the completion of the tasks <ref name=Winch>Winch, Graham (2010), "Managing Construction Projects. An Information Processing Approach" Second Edition, Wiley-Blackwell, United Kingdom. ISBN 978-1-4051-8457-1.</ref>. The amount of such tasks can be reduced by moving the tasks around in the matrix such that the dependencies gets below or close the diagonal. The dependency structure matrix can for example be used in the design phase as an iterative tool where the architect sends a structure design to the engineer who then sends some suggested changes back to the architect and so on. A more in-depth explanation of the dependency structure matrix can be seen in <span class="plainlinks">[http://apppm.man.dtu.dk/index.php/Application_of_Dependency_Structure_Matrix_in_Time_Scheduling Application of Dependency Structure Matrix in Time Scheduling]</span>

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S133571: /* The dependency structure matrix */

2017-06-22T08:49:55Z

The dependency structure matrix

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	=====The dependency structure matrix=====		=====The dependency structure matrix=====
	[[File:Design Structure Matrix.png\|250px\|thumb\|~~right~~\|Figure 5: Example of a dependency structure matrix. <ref name=DSM_wiki>"Design structure matrix". Retrieved June 19, 2017, from https://en.wikipedia.org/wiki/Design_structure_matrix.</ref>]]		[[File:Design Structure Matrix.png\|250px\|thumb\|center\|Figure 5: Example of a dependency structure matrix. <ref name=DSM_wiki>"Design structure matrix". Retrieved June 19, 2017, from https://en.wikipedia.org/wiki/Design_structure_matrix.</ref>]]

	A way to make a plan for an adaptive life cycle is to make a dependency structure matrix (DSM). The dependency structure matrix consists of all design tasks in a matrix form in both rows and columns. The way the matrix works is that all tasks that depends on information from other tasks gets the box filled in. The matrix will then have a filled diagonal which simply shows that each task depends on itself. All the filled boxes below the diagonal is not a problem as they will have the required information in time since the depending tasks will be finished before the start of the relevant task. The filled boxes above the diagonal, however, depends on information from tasks that starts later. The way to handle such tasks is to either estimate the required information or simply delay the completion of the tasks <ref name=Winch>Winch, Graham (2010), "Managing Construction Projects. An Information Processing Approach" Second Edition, Wiley-Blackwell, United Kingdom. ISBN 978-1-4051-8457-1.</ref>. The amount of such tasks can be reduced by moving the tasks around in the matrix such that the dependencies gets below or close the diagonal. The dependency structure matrix can for example be used in the design phase as an iterative tool where the architect sends a structure design to the engineer who then sends some suggested changes back to the architect and so on. A more in-depth explanation of the dependency structure matrix can be seen in <span class="plainlinks">[http://apppm.man.dtu.dk/index.php/Application_of_Dependency_Structure_Matrix_in_Time_Scheduling Application of Dependency Structure Matrix in Time Scheduling]</span>		A way to make a plan for an adaptive life cycle is to make a dependency structure matrix (DSM). The dependency structure matrix consists of all design tasks in a matrix form in both rows and columns. The way the matrix works is that all tasks that depends on information from other tasks gets the box filled in. The matrix will then have a filled diagonal which simply shows that each task depends on itself. All the filled boxes below the diagonal is not a problem as they will have the required information in time since the depending tasks will be finished before the start of the relevant task. The filled boxes above the diagonal, however, depends on information from tasks that starts later. The way to handle such tasks is to either estimate the required information or simply delay the completion of the tasks <ref name=Winch>Winch, Graham (2010), "Managing Construction Projects. An Information Processing Approach" Second Edition, Wiley-Blackwell, United Kingdom. ISBN 978-1-4051-8457-1.</ref>. The amount of such tasks can be reduced by moving the tasks around in the matrix such that the dependencies gets below or close the diagonal. The dependency structure matrix can for example be used in the design phase as an iterative tool where the architect sends a structure design to the engineer who then sends some suggested changes back to the architect and so on. A more in-depth explanation of the dependency structure matrix can be seen in <span class="plainlinks">[http://apppm.man.dtu.dk/index.php/Application_of_Dependency_Structure_Matrix_in_Time_Scheduling Application of Dependency Structure Matrix in Time Scheduling]</span>

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2017-06-22T08:45:42Z

Implementation example of the described methods

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	[[File:DSM example.PNG\|250px\|thumb\|center\|Figure 8: Dependency structure matrix for the example.]]		[[File:DSM example.PNG\|250px\|thumb\|center\|Figure 8: Dependency structure matrix for the example.]]
	It can be seen in figure 8 that the dependency structure matrix for the current example shows no dependency problems as all the dependencies are situated below the diagonal. This also means that no further optimization of the matrix is needed. For the sake of illustrating the dependency structure matrix, a change in the dependencies is made such that task H now depends on the completion of task I.		It can be seen in figure 8 that the dependency structure matrix for the current example shows no dependency problems as all the dependencies are situated below the diagonal. This also means that no further optimization of the matrix is needed. For the sake of illustrating the dependency structure matrix, a change in the dependencies is made such that task H now depends on the completion of task I.
	[[File:DSM example ALT.PNG\|550px\|thumb\|center\|Figure 9: Dependency structure matrix for an ~~alternativ~~ example. Left figure has a dependency problem marked with red which is solved in the right figure]]		[[File:DSM example ALT.PNG\|550px\|thumb\|center\|Figure 9: Dependency structure matrix for an alternative example. Left figure has a dependency problem marked with red which is solved in the right figure]]
	In the left matrix in figure 9, it can be seen that there now is a dependency above the diagonal. If these tasks are in the design phase, two approaches can be made to accommodate this problem. Either the result from task I can be estimated and then feed the estimate into task H. Otherwise task I has to complete before task H can begin. In this case, it is possible to switch the places of task H and I which can solve this problem. This is illustrated in the right matrix in figure 9. This change in the order of task execution, however, also changes the critical path. This new critical path can be seen in figure 10.		In the left matrix in figure 9, it can be seen that there now is a dependency above the diagonal. If these tasks are in the design phase, two approaches can be made to accommodate this problem. Either the result from task I can be estimated and then feed the estimate into task H. Otherwise task I has to complete before task H can begin. In this case, it is possible to switch the places of task H and I which can solve this problem. This is illustrated in the right matrix in figure 9. This change in the order of task execution, however, also changes the critical path. This new critical path can be seen in figure 10.
	[[File:Critical path example ALT.png\|350px\|thumb\|center\|Figure 10: The critical path method for the alternative example.]]		[[File:Critical path example ALT.png\|350px\|thumb\|center\|Figure 10: The critical path method for the alternative example.]]

S133571: /* The dependency structure matrix */

2017-06-22T08:44:54Z

The dependency structure matrix

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	[[File:Design Structure Matrix.png\|250px\|thumb\|right\|Figure 5: Example of a dependency structure matrix. <ref name=DSM_wiki>"Design structure matrix". Retrieved June 19, 2017, from https://en.wikipedia.org/wiki/Design_structure_matrix.</ref>]]		[[File:Design Structure Matrix.png\|250px\|thumb\|right\|Figure 5: Example of a dependency structure matrix. <ref name=DSM_wiki>"Design structure matrix". Retrieved June 19, 2017, from https://en.wikipedia.org/wiki/Design_structure_matrix.</ref>]]

	A way to make a plan for an adaptive life cycle is to make a dependency structure matrix (DSM). The dependency structure matrix consists of all design tasks in a matrix form in both rows and columns. The way the matrix works is that all tasks that depends on information from other tasks gets the box filled in. The matrix will then have a filled diagonal which simply shows that each task depends on itself. All the filled boxes below the diagonal is not a problem as they will have the required information in time since the depending tasks will be finished before the start of the relevant task. The filled boxes above the diagonal, however, depends on information from tasks that starts later. The way to handle such tasks is to either estimate the required information or simply delay the completion of the tasks <ref name=Winch>Winch, Graham (2010), "Managing Construction Projects. An Information Processing Approach" Second Edition, Wiley-Blackwell, United Kingdom. ISBN 978-1-4051-8457-1.</ref>. The amount of such tasks can be reduced by moving the tasks around in the matrix such that ~~the~~ the dependencies gets below or close the diagonal. The dependency structure matrix can for example be used in the design phase as an iterative tool where the architect sends a structure design to the engineer who then sends some suggested changes back to the architect and so on. A more in-depth explanation of the dependency structure matrix can be seen in <span class="plainlinks">[http://apppm.man.dtu.dk/index.php/Application_of_Dependency_Structure_Matrix_in_Time_Scheduling Application of Dependency Structure Matrix in Time Scheduling]</span>		A way to make a plan for an adaptive life cycle is to make a dependency structure matrix (DSM). The dependency structure matrix consists of all design tasks in a matrix form in both rows and columns. The way the matrix works is that all tasks that depends on information from other tasks gets the box filled in. The matrix will then have a filled diagonal which simply shows that each task depends on itself. All the filled boxes below the diagonal is not a problem as they will have the required information in time since the depending tasks will be finished before the start of the relevant task. The filled boxes above the diagonal, however, depends on information from tasks that starts later. The way to handle such tasks is to either estimate the required information or simply delay the completion of the tasks <ref name=Winch>Winch, Graham (2010), "Managing Construction Projects. An Information Processing Approach" Second Edition, Wiley-Blackwell, United Kingdom. ISBN 978-1-4051-8457-1.</ref>. The amount of such tasks can be reduced by moving the tasks around in the matrix such that the dependencies gets below or close the diagonal. The dependency structure matrix can for example be used in the design phase as an iterative tool where the architect sends a structure design to the engineer who then sends some suggested changes back to the architect and so on. A more in-depth explanation of the dependency structure matrix can be seen in <span class="plainlinks">[http://apppm.man.dtu.dk/index.php/Application_of_Dependency_Structure_Matrix_in_Time_Scheduling Application of Dependency Structure Matrix in Time Scheduling]</span>

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2017-06-22T08:40:36Z

The critical chain method

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	=====The critical chain method=====		=====The critical chain method=====
	The critical path method does not take resources into account when calculating the shortest execution time. The resources in a construction project are categorized in three types. Plant which consists of equipment such as cranes or piling rigs which can not be in more than one place at a time, labour which also can not be in two places at a time and space for the work to be executed in. For the first two types of resources, the critical chain method can be used. The critical chain in the project is calculated similarly to the critical path method however this method calculates the longest resource-constrained path. The uncertainty is also handled differently from the critical path method. Instead of having buffers in each of the individual tasks, the estimated time is assumed to be the average duration for such a task. The critical chain then gets a project buffer at the end while the remaining paths gets feeder buffers. For further description of the critical chain method, see <span class="plainlinks">[http://apppm.man.dtu.dk/index.php/Critical_Chain_Theory Critical Chain Theory]</span>.		The critical path method does not take resources into account when calculating the shortest execution time. The resources in a construction project are categorized in three types. Plant which consists of equipment such as cranes or piling rigs which can not be in more than one place at a time, labour which also can not be in two places at a time and space for the work to be executed in. For the first two types of resources, the critical chain method can be used. The critical chain in the project is calculated similarly to the critical path method however this method calculates the longest resource-constrained path. The uncertainty is also handled differently from the critical path method. Instead of having buffers in each of the individual tasks, the estimated time is assumed to be the average duration for such a task. The critical chain then gets a project buffer at the end while the remaining paths gets feeder buffers. This also moves the responsibility of task completion on time from the task managers to the project manager. Parkinson's law which states "work expands so as to fill the time available for its completion"<ref name=Winch /> is reduced by moving the responsibility and reducing the task durations. The total project life time will therefore be reduced by reducing the effect of Parkinson's law. For further description of the critical chain method, see <span class="plainlinks">[http://apppm.man.dtu.dk/index.php/Critical_Chain_Theory Critical Chain Theory]</span>.

	[[File:CCM Winch.PNG\|350px\|thumb\|center\|Figure 2: Visualization of the critical chain method. <ref name=Winch />]]		[[File:CCM Winch.PNG\|350px\|thumb\|center\|Figure 2: Visualization of the critical chain method. <ref name=Winch />]]

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2017-06-22T08:32:32Z

Advantages and limitations

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	** ''Advantages''		** ''Advantages''
	*** Inclusion of the workers in the planning process.		*** Inclusion of the workers in the planning process.
	*** Important decisions of the detailed planning are made later in the project when more ~~is known~~ about the project.		*** Important decisions of the detailed planning are made later in the project when more information about the project is known.
	*** Robust against changes and delays since the detailed planning is done continuously.		*** Robust against changes and delays since the detailed planning is done continuously.
	** ''Disadvantages''		** ''Disadvantages''

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2017-06-22T08:31:46Z

Advantages and limitations

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	* '''The critical path method'''		* '''The critical path method'''
	** ''Advantages''		** ''Advantages''
	*** It gives an estimate of the duration of the project as well as individual tasks throughout the project life		*** It gives an estimate of the duration of the project as well as individual tasks throughout the project life.
	*** It is a simple method for small projects		*** It is a simple method for small projects.
	** ''Disadvantages''		** ''Disadvantages''
	*** It does not take resources into account		*** It does not take resources into account.
	*** It is difficult to maintain the schedule in case of changes or delays in tasks.		*** It is difficult to maintain the schedule in case of changes or delays in tasks.
	*** Uncertainty is not taken care of by the method.		*** Uncertainty is not taken care of by the method.
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	* '''Last planner method'''		* '''Last planner method'''
	** ''Advantages''		** ''Advantages''
	*** Inclusion of the workers in the planning process		*** Inclusion of the workers in the planning process.
	*** Important decisions of the detailed planning are made later in the project when more is known about the project.		*** Important decisions of the detailed planning are made later in the project when more is known about the project.
	*** Robust against changes and delays since the detailed planning is done continuously.		*** Robust against changes and delays since the detailed planning is done continuously.

S133571: /* Advantages and limitations */

2017-06-22T08:31:04Z

Advantages and limitations

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	** ''Disadvantages''		** ''Disadvantages''
	*** The project has to be planned in detail at a relatively early stage in the project.		*** The project has to be planned in detail at a relatively early stage in the project.
	*** It is difficult to change the plan which makes it vulnerable to changes and delays.		*** It is difficult to change the plan, which makes it vulnerable to changes and delays.
	* '''Last planner method'''		* '''Last planner method'''
	** ''Advantages''		** ''Advantages''

S133571: /* Advantages and limitations */

2017-06-22T08:28:52Z

Advantages and limitations

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	'''The adaptive life cycle methods''' generally consist of tactical tools which means that they go into the detailed planning throughout the project. This makes projects less vulnerable to delays as the work in each task more easily can be rescheduled as the project goes on. The adaptive methods do, however, not work without an overall plan such as the sequential methods.		'''The adaptive life cycle methods''' generally consist of tactical tools which means that they go into the detailed planning throughout the project. This makes projects less vulnerable to delays as the work in each task more easily can be rescheduled as the project goes on. The adaptive methods do, however, not work without an overall plan such as the sequential methods.

	Each method in both the sequential and adaptive life cycles have their own advantages as well as disadvantages. A list of ~~these~~ can be seen below.		Each method in both the sequential and adaptive life cycles have their own advantages as well as disadvantages. A list of the key points can be seen below.

	* '''The critical path method'''		* '''The critical path method'''