The case for 3-D design

May 2007 » Feature Articles
Recent promotion of 3-D design software has left many site designers wondering if this "new" way of designing can carry enough benefits to outweigh the cost of execution.
Michael Barkasi

Do benefits of new technology outweigh implementation costs?

Recent promotion of 3-D design software has left many civil engineering firms scrambling to implement the new technology. However, review of discussion group comments focusing on this topic may leave site designers wondering if this "new" way of designing can carry enough benefits to outweigh the cost of execution.

More restrictive land development regulations have placed greater demands on what engineers need from civil design tools.

Before moving ahead, it is advisable to consider where the profession has come from. Several years ago, while working at a small municipal consulting firm, I came across a set of land development plans from the early 1980s. The plans were typical of a submittal for review from that era. The plan set was completed entirely by hand. It included contours hand drafted at 5-foot intervals. Notations showed signs of a skilled drafter whose style beautifully depicted a unique font, one developed during years of applying his or her skills at a drafting table. Also noteworthy was the simplicity of the plan set. A similar land development site today would require four to five times the detail to satisfy current requirements.

While computer-aided drafting (CAD) had its beginnings on mainframe computers prior to 1970, CAD for PC was making its appearance about the same time as the plan mentioned above was drafted. Two of the major players in the civil design market got their start in the early 1980s: AutoCAD shipped its first releases in December 1982; Microstation introduced .dgn in 1985.

Since the early 1980s, land development regulations have become more restrictive. Topics such as stormwater control, best management practices (BMPs), wetlands regulations, environmental protection controls, and restrictive planning commissions as municipalities become built out have placed greater demands on what engineers need from civil design tools.

Successfully modeling site objects, such as intersections, cul-de-sacs, ponds, channels, and roads, requires powerful element-manipulation tools. With stormwater regulations at a premium, retention pond design requires a tool that can create a pond to a specified volume or water elevation. Additionally, because of the ever-changing nature of site plans, designers need to be able to relocate or reshape this same pond (and other objects) and interact with other site objects to address both client and municipal change requests.

Successfully modeling site objects, such as intersections, cul-de-sacs, ponds, channels, and roads, requires powerful element-manipulation tools.

Hydraulic design and analysis, with the ability to reference a dynamic model, give a designer the ability to create interactive models. The software can further save time by allowing parameters for design such as minimum and maximum depth of pipe. The ability to size pipe according to the drainage area, create reports, and show the hydraulic grade line can further save time in design.

An example of leveraging a 3-D design model is having the ability in a parking lot design to hold a constant slope in relation to a building pad. If the pad is elevated, the parking lot also adjusts to maintain Americans with Disabilities Act requirements for access. Stormwater component preferences, such as time of concentration, slope, drainage areas, and rim elevations—because they reference this same model—also automatically update.

In parking lot design, a 3-D model can hold a constant slope in relation to a building pad. If the pad is elevated, the parking lot also adjusts to maintain Americans with Disabilities Act requirements for access.

With implementation of a site model, engineers can also address BMPs by modeling grading to divert water overland prior to storing. Islands or wetlands within ponds, or roadside swales to collect water as an alternative to catch basins, also can be modeled effectively. This gives designers the ability to view grading objects as they are created and to review the site for potential conflicts that otherwise may not become apparent until the construction process. Three-dimensional objects provide immediate visual feedback to the designer over the complete area of the design—unlike cross sections that only show the interaction between the design surface and the existing surface at specific locations.

Finally, the site designer needs the ability to quantify proposed improvements. Most packages have the ability to balance cut and fill on a site. In addition, the ability of the software to track quantities of pavement, pipe, trenches, structures, and landscape items can save countless hours.

While land development and site design will continue to challenge civil engineers and designers, 3-D design tools should add not only productivity but also quality to their work. But don’t get rid of your drafting table yet, you still need a workspace for your notebook computer. When you get tired of staring at the screen, you can change your focus to the table and reminisce where you came from.

Michael Barkasi is a product specialist for Bentley Systems, Inc. He can be contacted at mike.barkasi@bentley.com.


Upcoming Events

See All Upcoming Events