Changing the landscape

April 2008 » Exclusive
3-D CAD modeling is emerging as the standard civil engineering design solution. Read the article and attend the free webcast to learn more!
Mark J. Scacco, P.E.
3-D CAD modeling is emerging as the standard civil engineering design solution.

Join Adam Strafaci and Dominick Gallegos of Autodesk, along with Stacey Miyamoto of SSFM International, for a CE News webcast on this topic. Go to www.cenews.com/webcast to view the free, archived presentation.

When one thinks of fast-paced, dynamically changing organizations, Silicon Valley companies like Google usually come to mind and architecture, engineering, and construction (AEC) firms seldom top the list of trendsetters.

By the very nature of the business (public safety, functionality, tight deadlines, limited resources), AEC firms often conservatively stick with proven tools and methods.

Many organizations have been successful in maintaining fiscal responsibility or generating a profit for generations, using means and methods that have stood the test of time.

However, looking back on the last several decades one can chart the introduction and adoption of several technological advances that have changed the landscape and helped the AEC industry design and build a better world.

These include the electronic calculator, mainframe and desktop computers, spreadsheets and industry-specific applications, computer-aided design, the Internet, and GPS, just to name a few. With a toe-hold firmly established in the new century, another of these advances is coming into its own: dynamic 3-D CAD.

History of drafting and design software

Before delving head first into the nature of dynamic 3-D CAD, it is instructive to examine its lineage so as to better understand what it is and how it is different from 2-D tools. Looking back only four decades, it is possible to see a design and drafting world devoid of nearly all the tools that inhabit a modern engineering office.

While the seeds of CAD systems and design analysis applications were beginning to sprout in academic and government institutions through the 1950s and 1960s, the technology was not by any means in widespread use. With the use of mostly non-powered devices such as slide rules, Leroy lettering tools, and ammonia-activated blue print machines, engineers and drafters designed some truly modern marvels.

By the mid-70s, mainframe computers were in use at organizations that could justify the expense. Companies such as Intergraph, EDS, and CATIA were all started in this decade. These and many other pioneering companies further spurred the creation of applications specific to the AEC industry, allowing engineers to perform analysis of structures, hydrologic systems, pipe networks, and coordinate geometry.

At about the same time, the first computer-aided drafting tools for the civil engineering market were making their way into industry, but hand drafting still reigned for nearly a decade more.

The first 2-D CAD applications developed for personal computers were used as not much more than electronic pencils. In 1982, Autodesk, Inc., was founded, followed in 1983 by Carlson Software and a few years later by Bentley Systems in 1985. With varying degrees of success, techniques used by generations of manual drafters were adopted for use in the new digital medium.

These 2-D CAD systems provided several benefits, such as the ability to easily reproduce a set of plans; reuse entire drawings or drawing elements, such as construction details; automate simple but tedious drafting tasks; and standardize the look of plan sets.

Unfortunately, 2-D CAD also came with some drawbacks: It was harder to use than a pencil; it required specialized training; plans in various stages of completion were not easily reviewed by non-CAD users; and the static drawing entities were "dumb," having little or no knowledge of what they represented (a line did not know if it was a sanitary sewer or a contour).

Even with these limitations, 2-D drafting eventually overtook manual drafting as the primary method of preparing construction documents. While 2-D CAD was coming into its own, its acceptance and prevalent use was paralleled by that of other design software for specific tasks, including DOS-based hydrology applications from the Soil Conservation Service (later the Natural Resources Conservation Service) and the U.S. Army Corps of Engineers; COGO applications from a variety of vendors; and construction estimating packages.

The explosive growth and acceptance of the PC in the workplace also led to recruitment of general business applications, such as spreadsheets, to tasks specific to the engineering industry, including pipe network design, cost and quantity estimates, and earthwork volume calculations.

As the late 1980s gave way to the early 1990s, 2-D CAD began to get smarter. Clever additions to the base CAD applications and a number of third-party add-ons let drawing entities store extended data, such as diameter information for a line that represented a pipe and elevation information for lines that were contours. This additional information allowed CAD to move beyond a drafting tool and to start to stretch its wings as a design application. (Often, CADD is spelled with two Ds, one for drafting and the other for design.)

Engineering design tasks typically accomplished by several software applications were beginning to consolidate into a single application.

By the end of the last century, 2-D CAD was all grown up and a new generation of drafters and designers were wishing for more from their CAD applications: More ease of use; more consolidation of features; more efficiency; and more smarts. Thus, in the early 2000s, dynamic 3-D CAD began to make its way to market.

What is dynamic 3-D CAD software?

Perhaps because 2-D CAD used to just be referred to as CAD, or maybe because dynamic 3-D CAD has yet to earn its own, widely used generic name (some refer to it as model-centric design and even Business Information Modeling, or BIM), or maybe a combination of these and several other reasons, the question is often asked: What is dynamic 3-D CAD software?

One easy place to start defining it is to explore its similarities with 2-D CAD. Perhaps the most obvious similarity is that today’s most popular dynamic 3-D CAD applications are all built on the familiar 2-D CAD platforms and use many of the familiar 2-D tools that are well-known to drafters and engineers.

While there is certainly a learning curve when adopting dynamic 3-D CAD applications, the parametric objects are often created from simpler 2-D elements like lines, polylines, and text entities.

According to Mike Barkasi, PowerCivil technical specialist with Bentley Systems, Inc., the process is primarily done in this fashion: "We horizontally locate features, drawing them using basic CAD tools; and then we establish vertical relationships using the [3-D] Civil tools."

< Figure 1: 3-D corridor for roundabout modeling

Another similarity is the potential for dynamics among elements. Bruce Carlson, president of Carlson Software said that "both 2-D CAD design and 3-D CAD design can be dynamic. What distinguishes 3-D dynamics is the reference to a named or active terrain model.

Just as dragging a lot corner and changing annotation is routine in the 2-D world, selecting a building pad and moving it to a new position, elevation, or orientation and obtaining new design contours is now a routine 3-D exercise."

While there are some similarities, there are more differences.

As the name implies, 2-D CAD is a two-dimensional representation of the objects to be constructed. While most 2-D CAD packages can indeed draft objects in a 3-D coordinate system, they typically rely on extended data attached to objects to convey elevation information.

In contrast, 3-D CAD applications create fully formed parametric objects that can be modified automatically by simply changing the variables used to define them. As such, entities in a dynamic 3-D CAD work environment inherently contain geometric information about the size and shape of the object itself. Together they form a complete model of the project.

The information contained within the 3-D objects can then be used to develop relationships about relative positions to other objects. When you manipulate the graphics, you change the design and vice versa. In effect, rather than using simple 2-D graphics, the real world is represented by a fully 3-D model comprised of intelligent, spatially aware objects.

"While the industry is focused on 3-D versus 2-D, the true value of this technology is the information model," said Adam Strafaci, civil engineering industry marketing manager with Autodesk.

"Because you are in a model-centric environment, a change to the model will be automatically reflected in other parts of the design, and in the visualization and documentation. This allows for very quick evaluation of multiple design alternatives. This is not possible in 2-D, non-model-based environments."

< Figure 2: 3-D surface model with elevation banding

In practical terms, the end results are as important as the means of modeling the 3-D world. "Dynamic 3-D CAD is as much about the results it provides as the means it uses to get there," according to Gary Rosen, director of civil sales, Northeast region with Carlson Software.

"With dynamic 3-D CAD, design changes are parametrically reflected without manual drafting or editing, and sufficient data is created to perform quantity takeoffs and construction stakeout and or machine control."

To that end, a model may be comprised of parametric elements (meaning they can be automatically modified by editing variables) without being fully formed 3-D entities.

As with many topics, the answer to one question often leads to many more questions.

  • Why should an engineer or designer care about a dynamic 3-D CAD model?
  • What benefits can a drafter expect?
  • How do dynamic 3-D CAD models compare to their 2-D predecessors?

As discussed earlier, for at least a couple of decades now, engineers have been using computer applications to assist in the design of projects.

Unfortunately, for the most part these applications are good at only one or two tasks and are isolated "data-silos," locking away important project information in a format not easily shared. For example, COGO applications were limited to point manipulation; hydraulic and hydrologic models were not part of overall surface models; spreadsheet data had to be imported manually; and the CAD platform itself contained the linework representing the design.

Earlier CAD systems began to pull together many of these functions into a single application or platform. However, just having all features in one place is not enough.

< Figure 3: Pipe network model

Dynamic 3-D CAD links these functions together by enabling the transfer of information among entities. For example, a storm inlet pulls its rim elevation from a surface model; a lot pad elevation is set relative to the roadway centerline; and so on. Such functionality improves efficiency and reduces the chance for error.

Furthermore, as the distinction between design and graphics blurs, the impact of dynamic 3-D CAD on the overall project process itself is perhaps the most significant benefit. Workflows among departments and teams are changing to take advantage of the enhanced capabilities of the dynamic systems.

"For Autodesk, 3-D modeling is much more than a better CAD system. It is about an integrated workflow built on coordinated, reliable information about a project from design through to construction," said Strafaci. "This workflow delivers similar benefits to what building information modeling delivers for architects—the easy creation of coordinated, digital design information and documentation that can be used to accurately predict project performance, make better design decisions earlier, and reliably deliver projects faster and more economically."

In addition to improvements in workflow, the sub-tasks that go into creating a complete design also benefit.

"3-D design allows for faster section, profile, and volume generation, 3-D viewing and rendering, and conflict detection," said Carlson. "The civil and architectural markets are well behind manufacturing in using full 3-D design. Sooner than later, 3-D design will be standard." Strafaci added that "for the engineer, AutoCAD Civil 3D is an environment where they can analyze design alternatives in real-time so that they can provide the best solution to their clients."

Why dynamic 3-D software now?

The AEC industry is evolving; and, to remain competitive, design and construction professionals must too. The economics of the AEC industry are always pushing private and public organizations alike to improve efficiency in all phases of development, from initial survey to final construction.

< Figure 4: Importing field data and automating linework

Examples of the evolving nature of the industry include reducing time and effort required to collect and reduce existing conditions information. To meet this need, the industry has seen the adoption of rapid data-collection tools, including Real Time Kinematic GPS, and increasingly, LiDAR. Engineers are also required to optimize their processes.

Not only are budgets tighter, but qualified personnel are often difficult to recruit and retain. Doing more with less is now the norm and those organizations that can create the best designs with the least amount of effort will thrive.

Additionally, the nature of design itself is changing. More and more consideration is required to create projects that reduce the impact on the environment and integrate with the natural world in a sustainable manner.

As always, conceptualization and finalization of the design is not enough; the design intent must be drafted and documented sufficiently so that it can be conveyed to the contractors and constructed on budget and on schedule. Better tools for drafting, annotating, and plotting plan sets are needed.

Finally, as the project moves to the most expensive phase—construction—public agencies and private industry alike are always looking to reduce costs. GPS-guided machine control is an excellent example of the fulfillment of an economic need through the application of new 3-D CAD technology.

Enveloping all of these needs is the requirement that the entire project team, owners/municipalities, design professionals, and contractors, all must collaborate and share data more seamlessly. Summarizing, Barkasi said, "With the advance in machine-guided controls, GPS, the ability to track a project [without paper]… a 3-D model begins to benefit everyone involved in a project."

With the need defined, the question becomes how do dynamic 3-D CAD systems address these needs?

"We are finding over and over again that our customers see Civil 3D as the source of their competitive advantage," replied Dave Simeone, AutoCAD Civil 3D senior product manager with Autodesk. "They are able to evaluate more alternatives in less time to find the most sustainable solution; they are able to respond to design changes much faster; they are able to provide their customers with a higher level of service; and they are able to hire and retain bright, young talent that wants to work with the latest technology."

Similarly, Carlson said, "3-D plans save money, because they limit the errors introduced by contractors who must interpret 2-D plans and raise them to 3-D, and allow bidding and contract work to proceed more quickly. Plans that are fully 3-D can be quickly rendered, used for machine-automated grading of sites, surveyed accurately, and archived as a 3-D record of past design, greatly accelerating the conceptualization of new projects."

Giving a specific example, Barkasi refers to the grading process. "The majority of time spent by a civil engineer firm in land development will revolve around site grading. … These gradings in site design typically are bound by relationships such as ADA requirements for entering a building, local regulations concerning slope, perhaps constraints on grade allowing for water run-off. PowerCivil allows for these relationships to be created and maintained."

Products and features

To further demonstrate how dynamic 3-D CAD meets the current and emerging needs of today’s AEC professional, some examples of specific tasks will be examined, including how 3-D tools from Autodesk, Bentley Systems, and Carlson Software can be applied to these tasks.

While each package can be used to accomplish the tasks listed below and each has its strengths, there is not room in this article to do a comprehensive feature review of these or the other available industry solutions. Rather, the intent is to highlight some of the features in each package, specifically their relationship to 2-D and dynamic 3-D CAD.

Surface modeling

If not the main element of a civil engineering 3-D model, the surface model is certainly near the top of the list. Nearly every land development, roadway, airport, treatment plant, and utility project incorporates data representing the existing ground surface.

This surface often forms the basis for a design, regardless of whether minimal changes to the existing ground are planned or if it will be completely reworked. Therefore, it is important to be able to model these surfaces easily and accurately. Luckily for the surveyor and engineer, the available dynamic 3-D CAD applications all have tools to accomplish this task. Data for creating these surfaces comes in many formats.

Three commonly used sources are point data collected by traditional surveying techniques; contour data obtained from publicly available data, older hand-drawn plans, or flat 2-D CAD files; and Light Detection and Ranging (LiDAR) point data.

Point data has long been used in computer applications and by its nature typically represents a location in 3-D space. Point data collected by field crews is still one of the most commonly used data sources for creating surface models.

With Bentley PowerCivil, users can import raw survey data directly from most popular data collectors. Upon import, coordinate transformations and adjustments can be made to the point data, along with traverse and network adjustments. Extending beyond the common 3-D point, PowerCivil can connect automatically related points to define 3-D breaklines representing, for example, an existing edge of pavement or toe of slope. These 3-D elements further refine the surface created from the point data.

Another common form of data used in surface modeling are contours. However, much of the available contour data was built over years by manual drafters or 2-D CAD users. As such, the contours are simple line representations and lack the 3-D elevation information needed to build a surface.

Carlson Civil Suite includes a comprehensive set of tools for converting 2-D data into 3-D entities. Using its 3-D Data menu items, 2-D polylines can be elevated to the correct 3-D height by a variety of methods. These include manually keying in the elevation, or more impressively, by having the software automatically read the contour label. Similar tools are available to elevate 2-D lines based on simple text and leader and to elevate closed building pads based on an enclosed text label. These tools greatly reduce the time required to build a surface model.

Other examples of surface data that are becoming increasingly popular and require a new breed of 3-D tools are LiDAR and 3-D laser scanning. Both produce a tremendous amount of point data that can be used to create 3-D surface models. AutoCAD Civil 3D Surface objects can be constructed from such data sets and styled to display the surface information in a variety of formats (contours, elevation bands, slope arrows, et cetera).

Roads and corridors

Using 2-D CAD, roads and other linear corridor elements, such as streams or drainage ditches, are usually represented only by the linework needed to draw the feature. Frequently, the linework also has some basic alignment or profile data associated with it. Dynamic 3-D CAD goes way beyond this to create, in real-time, 3-D models of the road network based on graphical and tabular parameters.

Profiles of existing surfaces along an alignment can be automatically updated when changes to either element are made. For example, if the location of a horizontal alignment moves, the profile graphics and labeling of the existing ground along that surface will automatically update. Changes to the parameters that define the roadway template (or typical cross section) lane width or curb height are automatically reflected in the graphical representation of the road model. This updated road network can then be used to revise utility structure rim elevations and so on.

Carlson Civil Suite’s RoadNet module provides tools for laying out a network of roads and simultaneously processing them as a group to create a digital terrain model of the roadway surface, including intersections and cul-de-sacs.

Figure 5: Road intersection and design

Because all the roads in a network are processed together, the changes to the profile or alignments of one road are reflected in intersecting roads. Material quantities for construction estimates can be extracted from the road network and presented in tables and reports.

AutoCAD Civil 3D uses its Corridor feature to build roadway models from alignments, profiles, and assemblies (typical road sections). Shipping with a library of dozens of predefined and easily editable subassemblies, roadway section creation is drag-and-drop simple. Takeoffs can be done directly from the corridor model and surfaces models can be generated from the corridor. Changes to any of the components used to create the corridor are dynamically propagated throughout "downstream" design elements, keeping the objects in sync.

Intelligent links among related elements dramatically demonstrate the differences between 2-D CAD and dynamic 3-D CAD. The ease with which roads and road networks can be created in dynamic 3-D CAD simply has no comparable methods in 2-D CAD.

Using Bentley PowerCivil, users can create a 3-D model with roadways, complex parking areas, retaining walls, and intersections. Because the relationships among the elements have been established, changes to the roadway alignment will ripple through the design automatically.

Utilities, hydraulics, and hydrology

The true power of dynamic 3-D CAD systems and their potential increased benefit compared with 2-D CAD really becomes evident when the elements of the model interact to facilitate ease of design, annotation of that design, and ultimately the presentation of the design in a set of construction documents. A great example of this dynamic interaction is that which occurs among the surfaces (whether existing surface model or those created from a road or corridor network) and utility elements.

Figure 6: Watershed tributary to inlet

With a surface model in place, the hydrology tools in Carlson Civil Suite can be used to identify low points for inlet placement, automatically calculate watersheds tributary to the inlets, and generate runoff coefficients, times of concentration, and total flow to the inlet. This information can be further used to design detention storage facilities and drainage pipes.

In Bentley PowerCivil, the model can be used in both design and analysis of stormwater. Both SCS and Rational Methods are supported. The pipe network is modeled from drawing elements, and can be edited in tabular format.

AutoCAD Civil 3D Pipes tools assist users with the layout of utility networks of pipes and structures, automatically setting structure rim and sum elevations relative to the surface; establishing pipe depths and slopes; and checking for design violations in slope, cover, and length. Because the network is a true 3-D model, conflicts among network components are easily identified visually. Designing the pipe sizes with the Storm Sewer extension, users can generate hydraulic and energy grade lines.

Construction

The best design in the world is nearly useless unless it can be constructed. The ability to convey design intent is a critical component of all projects. Documenting the design, annotating it accurately, and generating final construction documents are essential tasks at which dynamic 3-D CAD systems excel, especially compared with previous technologies.

In AutoCAD Civil 3D, because the design and the graphics are one in the same, labeling and annotation remains synchronized for all objects across multiple sheets and views. For example, building on the surface and utility features previously discussed, a rim elevation can be labeled with text that automatically updates when the design changes.

If the profile of a road changes, the surface created from the roadway updates, the rim elevation of the structure in the model updates, and the text label updates. This is incredibly helpful in reducing errors associated with conflicting labels among sheets in a plan set. With a fully annotated model, users can generate complete plan sets with the Plan Production commands and plot to paper or digital format with a few clicks.

As mentioned previously, 3-D CAD adoption is, on one hand, facilitating advances like GPS-guided machine control, and on the other, being required because of these same advances.

While paper copies of designs are still the primary deliverable, more often, digital deliverables, such as stake-out points and fully developed digital terrain models, are being requested from engineers. Moving the data from the engineer’s office to the cab of an excavating machine demonstrates the evolution of CAD from 2-D to 3-D.

Where to start with dynamic 3-D CAD?

As dynamic 3-D CAD continues to gain acceptance as the primary tool used by AEC professionals, it is likely that questions will arise regarding the process of transitioning from 2-D CAD. Start by reviewing information from various software developers. Then attend live demonstrations or online webcasts to view the software in action. Compare the type of projects you do with the products’ features and the ability of the products to meet specific design, drafting, and construction needs.

After a product is selected, choose a partner to assist in the implementation. Above all, the partner should have real-world experience in the AEC industry, expertise in the software you’ve selected, and the experience of implementing the product in similar environments.

With a partner, prepare a plan for implementation that examines the needs of the organization from both technical and business perspectives. The plan should encompass a review of existing processes and procedures, hardware and software in current use, and the personnel who will be using 3-D CAD and managing the projects. It should include specific tasks, the person or party responsible for the tasks, scheduled completion dates, and stated goals.

Finally, execute the plan. Rely on the selected partner to provide support throughout the implementation and through the completion of at least the first project on which the dynamic 3-D CAD application is used.

Looking ahead

This article started by looking back on the technology of the AEC industry and ends by looking forward. While the industry is conservative by nature, it does rely heavily on high-tech tools. It is important that those responsible for designing, building, and maintaining the constructed world make use of the best tools available to complete their duties. These tools increasingly include technologies that just a few years ago were relatively unknown and in just a few years from now will be the norm.

Dynamic 3-D CAD software, which complements and facilitates these other technologies, is the center of that norm.

Mark J. Scacco, P.E., is the president and founder of Engineered Efficiency, Inc., a nationwide firm that provides training, consulting, and sales for 3-D CAD products. He would appreciate your thoughts on this article. He can be reached at mark.scacco@eng-eff.com.

Civil engineers sharing digital data

Building Information Modeling (BIM) is the process of creating an intelligent and computable 3-D data set, and coordinating and sharing the project information with various types of professionals during design, construction, and operations. The goal of this process is to improve collaboration among project participants. BIM is not defined by simply creating a 3-D data set for internal analysis. Although it has been a trend receiving much attention in the architecture and facilities management fields, as well as mechanical, electrical, plumbing, and structural engineering, civil engineering is also becoming involved.

Today, the civil engineering 3-D model of existing and proposed site features is being included in the BIM process. Effective for conceptual design, scenario evaluations, visualization, coordination, clash detection, and more, the site design—as the base of a building project—is an important component of BIM. Currently, applications of BIM are typically reserved for complex projects, but as technological advances of design, modeling, and collaboration solutions expand, along with the skill and understanding of the AEC industry, less sophisticated projects likely will participate in the process.

Of course, some people in the industry use the term BIM more broadly, expanding it to the application of nonbuilding projects such as roadway or site development projects. In this context, the data exchange and collaboration is happening among land surveyors; civil engineers; excavating, utility, and pavement contractors; GIS professionals; and owners. Data being shared is digital, rather than hardcopy plans. However, the shared data is at varying degrees of sophistication, depending upon the source and user, the experience of the team members, technologies being used downstream, trust, projects risks, and more.

For example, Don Ahmer, the president of Read Excavating Co., Inc., Gilberts, Ill., builds a 3-D model for every job the earthmoving contractor bids on and uses GPS machine control on every project as well.

"There are some aspects of what we do that do not utilize GPS [machine control] (i.e., foundation excavation), but otherwise GPS machine control plays a part in every project we work on. No project is too small or too big to use GPS," he said.

At his company, the 3-D models used for GPS machine control are either created in-house or sourced to external model builders; they are not supplied by the civil engineers who design the project. The civil engineer typically provides 2-D CAD files with necessary layers of information, including topographic data, proposed contours, and site features.

However, this is not the case for all GPS machine control projects. Twenty percent of respondents to the CE News Civil Engineering Technology Survey last fall reported that they have shared or their firm has shared a 3-D model for GPS machine control.

Regardless of whether a 3-D model is shared—or simply 2-D CAD files—for GPS machine control, inclusion in a GIS, for an owner’s facility management needs, or other purposes, civil engineers will be participating in the increasingly popular data sharing and collaborative process evolving within the AEC industry.


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