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Technology for Civil Infrastructure (AEC Insight Column)
1 May, 2008 By: Jerry LaiserinModern software tools transform an ancient discipline.
Nearly 2,000 years ago, the civil engineers of the Roman Empire faced a big job — ensuring a reliable supply of potable water to the town of Nemausus (today's city of Nîmes) in what is now the south of France. The nearest usable springs were at Ucetia (today's village of Uzès) more than 30 miles distant, but at only roughly 55 feet higher elevation. Therefore, an aqueduct to channel spring water to the new city had to maintain a pitch of 1:3,000 (55 feet in 31 miles) — a 0.4% grade or only 1 inch every 250 feet. Furthermore, the aqueduct would have to bore through mountains and leap across river valleys to maintain its alignment and profile. The work depended on manual calculations, measurements, and labor.
Despite these challenges, the Roman engineers succeeded in designing and building 31 miles of stone-encased water channels with interior dimensions 4' wide by 6' high, or roughly the same capacity as a modern 54" diameter water main. This system typically carried 5,000,000 gallons of water per day and did so for more than 700 years — until the lack of maintenance forced its abandonment. The water channel or aqueduct often rested on or just above the ground, or it cut through hand-dug tunnels in the rolling French countryside. As one such tunnel opens onto the Gardon River valley, the engineers faced a nearly 1,000' span at more than 150' above the riverbed, before they could again bore the water channel into the hills above the opposite riverbank.
To span the gap, the engineers designed a three-tiered, arched bridge (figure 1) to carry the aqueduct across the Gardon River. That bridge, known today as the Pont du Gard (literally, bridge on the Gard), is one of the most-visited tourist attractions in France and a designated UNESCO World Heritage Site. The Pont du Gard is one of the great feats in the history of civil engineering, and the aqueduct it carries is one of history's great feats of 3D design and visualization — perfectly maintaining a shallow 1:3,000 pitch for a distance of 31 miles across an undu-lating terrain that required cut and fill, tunneling, and bridges.
 Figure 1. The Roman aqueduct carried by the 2,000 year-old Pont du Gard in France was an astounding feat of 3D civil design — maintaining a 1:3,000 pitch for a distance of 31 miles. (Copyrighted image courtesy of Jerry Laiserin) |
A Long and Winding Road
The point of this historical preamble is that the design and construction of civil infrastructure — roads, water mains, sewer lines, and so on — has always been multidimensional, involving high precision across great distances at large scales. Today's engineers and managers of civil infrastructure have available many software tools specifically targeted at these complex demands.
Some of the loudest buzz in civil/land–design software during the past few years has surrounded Autodesk Civil 3D (see the Cadalyst Labs review of Autodesk Civil 3D 2008 in the March 2008 issue). Although engineering firms migrating to Civil 3D from traditional, drawing-based solutions face challenges in workflow and organizational change, most agree the results are worth their effort. Because civil/land–design is inherently 3D, support for direct visualization and design manipulation in three dimensions also speeds the production of conventional 2D documentation and handles design changes better.
With its latest versions of Civil 3D, Autodesk has incorporated the functionality of its earlier 2D-based land-design products. Autodesk also offers its own mapping and GIS (geographic information systems) solutions — AutoCAD Map 3D and Autodesk MapGuide — and software tools specific to gas and electric utilities (Autodesk Utility Design) and for civil construction (CAiCE). Autodesk's civil/land–design products, as nearly all AEC software today, can be georeferenced to Google Earth, which enables the instant placement of any design directly into a virtual view of its real environment.
Long-time civil software vendor Carlson offers its Civil Suite, a comprehensive bundle of civil, survey, GIS, and hydrology tools that deliver results comparable to Civil 3D, but without the issues of changed workflow.
Bentley Systems, another major provider of civil software, continues burnishing and expanding its suite of road, rail, and utility design tools by playing to its legacy strength among U.S. state departments of transportation (DoTs). Besides its core PowerCivil product, Bentley also made key acquisitions — including Infrasoft for road and rail design and Haestad Methods for water, sanitary, and storm-sewer design. In addition, Bentley snapped up several leading structural analysis tools that play critical roles in bridge design. For GIS, Bentley relies on the industry leader in that category, ESRI (ArcGIS).
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About the Author: Jerry Laiserin
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