Nzangi Muimi

Advanced Construction Scheduling Techniques

As projects become more complex, uncertain and dynamic, simple construction scheduling methods may not be enough to cope with the challenges and the risks involved to help the project manager deliver successful outcomes, meet project deadlines and manage production resources efficiently.

There is a need for more advanced scheduling techniques to cater for these complexities and project dynamics. Some of the advanced scheduling techniques are discussed below:

Critical Chain Project Management

Critical Chain Project Management, also known as the critical chain method, is a technique that focuses on managing the uncertainties and dependencies in the project schedule rather than the individual tasks.

It is based on the theory of constraints which states that every system has a bottleneck that limits its performance. This method identifies the critical chain of tasks that determines the project duration and allocates buffers to protect it from delays and disruptions.

It also reduces the tendency of the task owners to inflate their estimates and procrastinate, by encouraging them to work with realistic and aggressive deadlines.

It is important to point out that this method comes in after the initial schedule is prepared. Where the project has limited resources, a schedule network analysis is performed to eliminate project schedule delays due to uncertainties, overestimating task durations and wasted internal buffers.

A project manager using this method will do the following:

  1. Outline the task dependencies and resource constraints at the project’s planning stage.
  2. Establish an ideal project workflow.
  3. Add extra resources to the project if required.

Monte Carlo Schedule Simulation

Monte Carlo Simulation is a technique that uses random sampling and statistical analysis to estimate the probability and impact of different scenarios and outcomes in a project.

This technique calculates sets of artificial (but realistic) activity duration times and then applies a deterministic schedule procedure to each set of durations.

Numerous calculations are required in this process since simulated activity durations must be calculated and the scheduling procedure applied very many times.

The results of a Monte Carlo simulation can be used to estimate the following indicators of project schedule:

  1. Estimates of the expected time and the variance of project completion.
  2. An estimate of the distribution of completion times, so that the probability of meeting a particular completion date can be estimated.
  3. The probability that a particular activity will lie on the critical path. This appreciates the fact that the critical path may change as activity durations change.

Compared to the other scheduling techniques, this method requires more information about the activities and their durations and extra computational effort for each set of simulated durations.

However, when well applied it can help you access the risks and uncertainties in your project schedule, budget, scope and worst-case scenarios

“What-if” Schedule Analysis

This is an approach to the simulation of different activity durations to develop specific scenarios of events and determine the effect on the overall project schedule.

In “what-if” analysis, the manager simulates all the events that might occur and sees the results. For example, the effects of different weather patterns on activity durations could be estimated and the resulting schedules for different weather patterns compared.

The range of possible schedules can be attained by applying the scheduling procedure using all optimistic, all most likely, and then all pessimistic activity durations. The result is three project schedules representing a range of possible outcomes.

This process of “what-if” analysis is similar to the process that is undertaken during the analysis of project crashing where the project duration is shortened by reducing the time of one or more tasks by increasing resources to the project.

Last Planner Methodology

The last planner methodology is a lean-based management system or a lean construction methodology, that is founded on the belief that the world is inherently stochastic (involves a random variable or chance – or can be well planned by a random probability distribution).

With this in mind, this planning and scheduling methodology recognises that the overall schedule produced by the project manager is vital for the project’s success, but it is the operative at the lower level (called the last planner) who has the best knowledge of the time and resources required to execute a specific project task.

Therefore, these people are allowed to take part in the planning stage to set task expectations and commit to their delivery, in a very open and collaborative process.

Consequently, five process and planning stages merge from this approach, as follows:

  1. Master Schedule – this stage involves the development of the overall project schedule, with key milestones properly identified.
  2. Phase planning – the key milestones are cascaded down to the specialised teams involved to collaborate and establish how exactly they will complete their phases on time by working backwards from the milestone deadline.
  3. Look-ahead planning – project team members are encouraged to look ahead at likely causes of constraints and delays and think about how to overcome them.
  4. Commitment planning – each week, the individual project teams meet in person with their colleagues who are working on other parts of the project and commit to getting tasks done. The accountability to their peers incentivises them to complete the tasks they have committed to.
  5. Continual learning – as the project progresses, teams are encouraged to meet up often to share their lessons on what went well and what went wrong to learn and improve their scheduling processes.

Matrix Schedules

This is a scheduling technique that blends the advantages of bar charts and network schedules. It is best fit for use in the case of repetitive construction work.

Repetitive construction work can be likened to an assembly line scenario where material continually moves at a uniform rate, passing a sequence of workstations. Construction crews perform one activity on one house and move to the next to repeat the same activity.

Also, a matrix could mean a combination of scheduling techniques and planning methods to accommodate the complexity of a project.

For example: use of Gantt charts, together with a precedence network analysis and a provision for presenting the risk factors identified in a chart.

Role of Computers in Advanced Construction Scheduling

With project planning and scheduling, the amount of data handled can be enormous based on the scale of the project and the risk factors involved. Also, techniques such as Monte Carlo simulation which uses statistical analysis would mean many tedious calculations and computations if done manually.

The use of computers has become more prevalent in the modern construction industry to help automate computations and present visual data better.

This led to the development and use of specialised computer software such as Microsoft Project, Primavera and Synchro, among others. These computer systems can handle complex datasets and graphical visualisations to make the work of the project manager easier (less time is spent on the technical stuff, and more time on the value-adding activities such as identifying task dependencies, quantifying risks or estimating task durations from work study methods).

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