Why VDC?

The AEC industry is slowly becoming more and more digitized as technology is incorporated into day-to-day operations. A primary example of this technology uptake is in the adoption of Building Information Modeling (BIM). The purpose of this post is to solidify the business case and value-add that results from moving to information modeling as the linchpin of modern architecture, engineering, and construction.

Terminology

Before diving in too deep, let’s take a moment to discuss terminology. When I think of BIM, what first comes to mind is vertical construction - schools, hospitals, commercial buildings, and the like. This segment of the industry has led the charge in adoption of BIM, and at present, practitioners founded on 2D drafting as the primary means of document production are squarely in the minority. However, on the heavy civil / infrastructure side, BIM adoption has been very slow. There is also much less consensus on terminology. There aren’t many physical buildings on a typical highway or bridge construction site, so BIM seems to be a poor fit. Some acronyms currently in use include:

• BrIM - Bridge Information Modeling
• CIM - Civil Information Modeling
• Horizontal BIM - (pretty self explanatory)
• VDC - Virtual Design and Construction

I tend to use VDC as my acronym of choice, hence the title of this post.

In my experience, there is plenty of reference to modeling as an integral part of the design process. When used in this context, modeling typically refers to surface modeling. This usually involves the creation of templates or assemblies that represent the cross-sectional geometry of the roadway section. Templates are ‘pushed’ along a path defined by a horizontal and vertical alignment to create a digital terrain model (DTM) or triangulated irregular network (TIN). These surfaces are thin meshes that cannot accommodate two points with the same (X,Y) coordinates but with differing Z (elevations). In other words, these surfaces cannot contain vertical faces. Additionally, DTMs cannot “double back” on themselves to accommodate a feature such as the 45 degree edge of an asphalt pavement section. Perhaps because of these limitations, and / or the general conservative nature of the industry, typically these models are used only for the production of traditional 2D paper or PDF deliverables. Additionally, these surfaces are typically geometric only, with little to no semantic information associated to the data. When I make the case for VDC, I am speaking of 3D solid models in addition to the surface models that are already commonplace. Additionally, these models are much more valuable when they contain semantic metadata that further enriches the information. For example, a VDC model of a bridge might associate material properties such as the density and design compressive strength of the concrete that is prescribed for a 3D cylinder representing a pier column.

So, with this initial foundation of terminology having been laid down, let’s move into the benefits of adopting VDC as an integral component of capital infrastructure projects.

Benefits During Design

Visualization - external audience

Public works projects are, by definition, meant to enhance the general public’s quality of life. This means that it is important to share and describe the proposed work with those who will be most affected during and after construction. However, the proposed work is nearly always communicated via traditional engineering documents or hatched and colored 2D graphics overlaid on an aerial image. A majority of stakeholders struggle to understand these documents due to their highly technical nature.

On larger projects, it is not uncommon for 3D renderings and fly-through videos to be prepared to address this issue. However, this visualization effort often involves unproductive rework due to a lack of overlap in skill sets between the design team and the graphic artists.

When utilizing VDC, the design team gets the visualization “for free” due to the 3D geometry and associated non-graphic information such as material properties. A properly-configured modeling environment is typically able to produce renderings, animations, and even AR/VR datasets with minimal additional effort.

Visualization - internal audience

Integrated visualization is also helpful to the design team. One vendor touts the design-time visualization capabilities of its software as a means of reducing Errors and Omissions during design. find errors more quickly. One example that I am familiar with is the tie-in between the roadway section and concrete approach slab at the ends of a bridge. For constructability reasons, the cross section of a bridge deck is typically made as planar as possible.

The approach roadway might use 2% cross slopes in the travel lanes and 4% cross slopes on the shoulders. The shoulder cross slope needs to be transitioned to match the bridge section where both the travel lanes and shoulders are at a constant 2%. This detail is often overlooked, or buried in plan details like a piece of text on the typical section sheets or a handful of lines added to a superelevation diagram. This potential land mine becomes clearly visible when the 3D model of the bridge gutter is hanging above the adjacent roadway shoulder.

Additionally, conflict checking and clash resolution tools common in VDC software help disciplines stay out each others’ way and avoid construction delays when a storm sewer and bridge foundation are fighting to occupy the same space.

Constructability

Most people are familiar with 3D modeling, where the x and y (or northing and easting, if you rather) of plan view are combined with elevation - the pesky Z. 4D models that capture the time scale in addition to the XYZ of geometry can prove to be invaluable. During design, the primary answer provided by a 4D model is whether the design can actually be constructed in the sequence imagined.

Estimating

Adding cost to a model bumps it into 5D territory and provides even more benefits during design. Like visualization, quantity and cost estimating are mostly accomplished “for free” by the use of common, standardized part libraries with associated historical bid histories. A designer may only do major quantity take-offs and cost estimates once every few months, which make it difficult to gain efficiency with these tasks. Also, many designers take on this type of work begrudgingly due to the primarily repetitive and manual processes involved. By incorporating smart, parametric elements pre-populated with cost data, these tasks can be accomplished quicker and with fewer errors and omissions.

Benefits During Construction

Thus far, I have spoken primary of VDC benefits during design. The majority of my career has been spent in the design office, so that’s where my initial focus lands. During construction, the primary benefit of VDC is that it allows you to build the project virtually so that you know how to build it physically. This practice is often seen in industrial settings, where prototypes of new assembly lines might be built in a pilot plant.

By first constructing in a virtual dry run, the builder can confirm the critical path and uncover challenges that otherwise would not have become apparent until in the field. Additionally, the combination of the geometry, estimate, and schedule into a single model will illuminate issues or mistakes that otherwise would have been missed when looking at these items in isolation.

Additionally, the VDC model can be used during construction to monitor earned value and completion progress against the baseline schedule and estimate. Mobile and static lidar scans of the construction site can provide an accurate assessment of project completion at regular intervals.

This data can also be used for quality purposes such as confirming that the finished work is within the specified tolerances. These progress scans can also be used to record the “as-built” state of the project.

Operations and Maintenance

This is a bonus section, as thus far we have been talking primarily in regards to design and construction phases of the asset lifecycle. VDCOM is a bit of a mouthful, but there are undeniable benefits realized by continuing to update the VDC model as a construction project is completed and the infrastructure is put into service.

Asset Management

A geospatially-referenced VDC model of the as-built project naturally flows into an agency’s asset management systems. This centralized data store consolidates a wealth of information that otherwise would be spread across plan sheet markups, scanned PDFs of material tickets and test results, data dumps of progress estimates and change orders, random spreadsheets of non-conformance reports, … ad infinitum. In particular, civil works developed under a P3 delivery process often have long-term contractual requirements such as warranty periods that affect the availability payment mechanisms that allow a developer to recoup initial capital investments. Capturing this information during construction and spatially associating it to the warrantied assets make it much easier for an agency to avoid any costs associated with substandard craftsmanship or materials.

Most importantly, VDC functions as a “killer app” in that it provides x-ray vision for subsequent inspections of a facility. For underground utilities and infrastructure, the best time to measure, photograph, and record the location and properties of an asset are when the trench is open during construction.

Drawbacks of VDC

To be fair, VDC implementation isn’t all sunshine and roses. There is a significant investment required for most practitioners to make the leap from 2D drafting to multi-dimension digital modeling. And, there is a certain threshold in terms of project size and complexity below which there is less benefit derived from VDC. For example, a contract to add HDPE linings to a series of existing corrugated metal drainage pipes is not necessarily a good candidate for these processes. However, in the majority of cases, the benefits of VDC far outweigh the initial challenges and learning curve during implementation.

Conclusion

Most of those who have already moved to BIM or VDC could never imagine going back to 2D drafting. The difference between environments has been likened to using a typewriter versus Google docs. In some ways, this transition is actually more disruptive than the leap from the drafting table to the CAD workstation. That change primarily involved a change in tooling to perform (mostly) the same processes.

BIM and VDC, on the other hand, are a fundamental re-thinking of how we work and collaborate with our partners and stakeholders. It is an immense challenge, no doubt. But it must be met if we are to pull the industry out of the rut of low productivity, blown budgets and missed schedules that far too often characterize the AEC sector.