3-D tools help engineers resolve design deficiencies and minimize change orders
By Laura Lang
Renderings of civil and structural engineering projects in three dimensions increasingly are used to showcase designs and to better inform the public about changes to the landscape and improvements to infrastructure.
But, beyond the pretty pictures, 3-D computer models can help engineers improve their initial design, as well as avoid costly errors and changes during later stages of the project.
D computer model of the structure to enable public involvement, to meet Context Sensitive Solutions requirements, and to verify the constructability of the project.
Adding a dimension A UDOT structural engineer developed the initial design for the bridge using a combination of electronic and manual methods. This design was then passed to a drafting technician, who used MicroStation and Bentley InRoads to create 2-D drawings and detail sheets of the design. UDOT’s Engineering Technology Support (ETS) staff used Bentley 3-D tools to import 2-D designs and to create an accurately detailed model.
The team could review the design at every step. For example, the ability to render and shade each component as it was being graphically constructed helped the engineers visually inspect the structure.
Critical design areas – such as bolt spacing, drill-hole angle and location, gaps, and complex angle measurements – could not have been easily verified without MicroStation,” noted Greg Herrington, ETS manager for IT at UDOT.
Because the main components of the bridge are two, large parabolic arches, it typically would be difficult to verify fit and angle of the crossing members, diaphragms, and joints. But using the 3-D model and rendering tools, UDOT was able to create each structural member graphically and verify its location and fit. This process helped the designers verify designs of both large and small features, such as the clearance on a large crossbeam location and the gap clearance on a 0.5-inch bolt.
Additionally, the ability to render the design plan allowed UDOT to evaluate whether elements were located correctly, or whether there were gaps or overlaps. With the 3-D model and rendering tools, the agency was much more efficient at recognizing potential conflicts or design deficiencies, and resolving them quickly and accurately.
Working together, the ETS team and the UDOT Structures department were able to find and fix several design challenges that were not apparent in the 2-D drawings and plans, enabling them to meet a tight project schedule while constantly improving the design. Most design issues were resolved before release of the plans. As a result, there were no significant change orders during construction of the structure.
Although the learning curve was steep, Herrington said, the time and cost of modeling the structure gave a return on investment of 15:1, based on reduced change orders and construction cost savings.
The 3-D visualizations were useful externally as well, helping UDOT secure public approval and support for the project. Long before the bridge was constructed, UDOT used photo matching, fly-throughs,” and animations in public hearings to showcase the designs and to ask for feedback.
Some of the feedback from these sessions was used to improve the design, according to Herrington.
The principles that we discovered during this process led us to believe that the value of 3-D design and visualization was not just as tools for large, very complex projects, but that it would bring us significant value on almost every project,” Herrington said. We have taken what we learned and are currently applying it to a project with a simple, single-span, concrete bridge. We have designed the bridge and the roadway components completely in 3-D from the start, and our ability to recognize design problems is now clear, rapid, and apparent to all.
The added benefits of being able to try multiple aesthetic treatments in seconds, inspect utility conflicts, and drive the project – reviewing sight distance, pavement marking, and signing – have already proven invaluable to the design process,” he said. We intend to further measure the value of 3-D visualization by defining construction sequencing, staging, and traffic control.” The success of the Arch Bridge project earned UDOT a 2004 Bentley BE Award of Excellence for Civil Visualization.
Laura Lang is a principal at KeatingLang, a Santa Barbara, Calif.-based marketing services company. She has covered engineering technologies for almost 20 years. Lang can be contacted via e-mail at Lang@KeatingLang.com.