4D incorporates time aspects into the model, especially construction sequencing.
This is specially criticle for project management on site, because the exact order of what is built, where and when is crucial
Time is also key factor in large bridges and tall structures if concrete plays a major part. Concrete creeps and shrinks, especially in the initial stages of its life, and the effects can be significant
5D Cost
Adds cost to the process over time.
As engineer we tend to focus on performance(the building not falling down), but for the client the cost is a major concern.
Cost is or should be, an integral part of optimisation
6D Utilities and assets
Consider the lifetime of the assets in the building including the structure itself, plus the ongoing performance of the building, especially the heating and cooling requirements
Asset management has long been touted as an important aspect of BIM, allowing the building owner to easily access information regarding the specifications and warranties of all parts of their property.
this part is normally ignored due to extra cost of construction and digital workflow gives no benefits to clients. Additionally client who commissions the building is often not the operator and is thus not interested in paying for the work.