If Contractors do not effectively implement 4D with BIM, the cost of construction for almost any substantial project – building, infrastructure, industrial – is higher than it needs to be. Money is being wasted, time is being wasted, and sometimes safety is being compromised. BIM enables increasingly more advanced, more intelligent designs. Constructing that design is also increasingly more complex - the congestion of time, material, people, equipment, and space creates unforeseen problems - this is common and continuous. It would seem obvious that many of these problems could be identified and averted if planning was effective. And if these problems were averted then money and time would be saved. But how can planning be effective if a schedule is done “1-dimensionally”, line by line, hundreds of activity connections spanning pages on top of pages? How can a scope of work with say 20 (or more) activities in the same physical area occurring at the same time be well understood? Or how can the safety risk of a crane operating overhead be adequately accounted for when it doesn’t even appear on the schedule? Truth is, no matter how detailed and visually appealing the BIM model, if it doesn’t clearly show the “when” for every activity of construction then how do we know there are not going to be problems, potentially avoidable problems?
Traditional “line item” scheduling is taken for granted, but the truth is that it is archaic, “old school”, filled with “tribal knowledge”, and assumed to be “the way things are”. Well they are not. BIM needs 4D, effective 4D, and effective 4D is more than just visualizing a model as it is being constructed based on a forecasted schedule. That is cool, but likely it is not much use. That is because when problems in the construction sequencing or coordination are observed, the time it takes to figure out solutions is too great, the process too iterative, the communication too painful. Eventually the Construction Manager loses patience, decides to just get going, and then when the rework starts and the delays arise and the blame is thrown around (more often than not directed at the “modeling guys”), he/she demands more resources and more overtime. He has no choice it would seem. And so the Owner thinks he also has no choice. Well he does.
4D Construction Planning and Scheduling, or 4D Modeling, utilizes software to enable the digital creation of the approved project delivery approach through the development of specific project plans and schedules that combine 3D data and time data into a single integrated model of the project delivery approach and execution. In other words, 4D puts the project plan into real context.
The focus and purpose of 4D Construction Planning and Scheduling is to enrich the planning and scheduling process to achieve improved communications and stakeholder participation and for the creation of a robust delivery approach that can be understood, validated and reliably implemented by the project delivery team. Owners should insist on seeing a 4D Plan as part of the Contractor’s BIM Execution Plan, and the 4D Plan needs to include more than just a series of animations. The 4D Plan needs to require the visual reporting of construction schedule through the entire life of the project – including jobsite status updates - and the delivery team needs to be held accountable for what can be accomplished with 4D, and not given a pass because “line item” planning is the best they can do. Sure this requires change, sure this requires teamwork. But anyone who thinks that the effort is not worthwhile is kidding themselves, lured by the fantasy that the overly optimistic forecast schedule is on target, and that having great talent in the field to fix the problems is the solution.
So what can an Owner expect from a Project that is progressively using 4D with BIM for planning and schedule validation on a continuous and inclusive basis? A few examples –
- Reduction in lost time in the project execution due to - Time lost in dealing with rework in the field caused by unplanned workspace clashes; Time lost in the field due to extra meetings convened to “talk through” the confusion in the schedule; Time lost in the field due to the occurrence of unplanned safety events that could have been avoided
- Reduction in mistakes in the field caused by lack of needed information due to - Assuming a construction plan can be developed based solely on review of the design model; Assuming the initial schedule forecast is sufficiently accurate based on unverified/unreviewed inputs; Assuming a construction sequence is flawless without a thorough review by all stakeholders of site logistics and temporary works
- Reduction in the margins (cost avoidance) by removing unnecessary conservatism due to - Additional “float” in scheduled activities to account for “assumed delays”; Additional space allocated for activities to account for the possibility of congestion; Additional time for contractors to be on site
For an Owner, the bottom line is simple – without 4D they are missing a big opportunity to save time and money - period.