Types of 4D BIM Construction Scheduling Techniques
Construction scheduling in project management is about listing of project milestones, activities and deliverable; more than often with intended building project start date and delivery date. This should answer the question “What are schedules in construction?” Today, BIM 4D construction scheduling, also known as construction sequencing, is a special inclusion for project planning and project portfolio management in nearly every project management.
Answer to “Why is scheduling important for building construction projects?” is that manpower management, materials, machinery and other activities requires effective planning and scheduling of other construction activities. It inevitably helps building contractors and engineers complete the project within stipulated time lines and budgets.
How builders and contractors can keep construction projects on schedule?
Builders and contractors have several construction sequencing options to choose from, including the simple and conventional 4D scheduling techniques which can help them keep construction projects on schedule.
There are primarily four alternatives which ideally can assist in addressing project requirements and overcome challenges. This is an effort to help them assess which of these techniques is the best for them.
Using bar charts to generate construction schedules is one of the simplest ways, and popular amongst construction professionals. The simplicity and multiple adaptations to numerous events is the reason for its popularity. It is formed with a list of activities, specifying the start date, duration of the activity and completion data for each of the activities included/mentioned, and then is plotted on a project timescale. Detailing of the bar chart solely depends on the complexity of the construction project and the intent to use the schedule.
“Linked bar chart” is a variation to the bar chart schedule. It uses arrow and lines to link activities and subsequent items, specifying the successors and predecessors for every single activity included in the schedule. In linked bar charts, even the previous activities are linked to one another to demonstrate that completion of one activity is required to start the next or other activity.
Bar charts have proved really useful in detecting the amount of resources required for a particular project completion. Resource aggregation is then done by adding resources vertically in the schedule, and not otherwise. This aggregation estimates the work production and helps in establishing estimates for man-hour equipment needed.
Critical Path Method
If compared to bar charts; critical path method of construction scheduling is more detailed but complex. To accommodate numerous activities, every construction activity is lined to the previous and subsequent activities, and it is ensured that each activity has at least another activity that should be completed before starting the preceding one.
Steps to schedule construction with Critical Path Method:
- Preparing a list of activities
- Develop a network that showcases the logical relationship amongst various activities
- Measure the duration for every activity, prepare a schedule, and determine the deadlines for every activity and the available float
- Evaluating the current and required resources
Feature that makes Critical path method popular is that it establishes and assigns start and end dates to activities based on logics including FS, FF, SS, and SF; which also are key indicators as to how the activities must be sequenced. These, also determine:
- First date which an activity can start
- Late start – specifying the last possible date that this activity must be started to avoid delays in the overall construction process
- Early finish – the earlier date that the proposed activity will be completed
- Late finish – the last date the activity must be completed without affecting the start of the next one, and subsequently affecting the entire construction scheduling resources.
Line of Balance Scheduling Technique
Though a construction scheduling technique, it is mainly popular as a planning technique for repetitive work. The most essential procedure for this scheduling is to allocate the resources required for each step or operations. This ensures that the next sets of activities don’t get delayed and timely results can be obtained. The principles on which it works are borrowed from the planning and control of manufacturing processes, usually applied in the construction work. However, using line of balance scheduling technique proves effective only when the conditions are ideal for this type of work.
Q scheduling is comparatively a new technique, but gaining rapid popularity among construction and contracting firms. May be because it is the only scheduling technique which reveals a relationship between the sequence of doing a job and the cost incurred against it. Thus the model produced is closer to reality.
Q scheduling, is fondly known as quantitative scheduling, too. It includes the quantities to be executed at different locations of the construction project from the elements of the schedule. Also Q scheduling is Queue scheduling with reference to the trades that pass through the different segments of the project in a queue sequence. It ensures of no interference amongst two activities at the same location. Derived from the Line of Balance technique, and with some modifications, it enables non-repetitive models of the construction project.
Construction project, big or small, new construction or a re-build; mapping a 4D construction schedule is the most important key component for successful BIM progression. It forecasts when each step of the process could occur, how long each step will be taken and the cost associated with it. Once a residential, commercial or mixed-use building is designed, everyone involved with the construction process has the same kind of expectation and expects same kind of information.