Designing a flat highway may seem like a relatively simple engineering task, but it is more complex than it looks, particularly when it comes to drainage. Without proper drainage, water can gather in huge pools during rainstorms, making for treacherous driving conditions. To avoid these problems, highways have curbs with gullies that direct water into grated openings. But even this seemingly simple solution has significant engineering challenges. Cars pound on gratings mercilessly 24 hours a day, and drains must provide access to sewers, pipes, and cables, yet be safe enough for bicyclists and pedestrians to walk over.
Because drains are built into curbs, another set of challenges arises. Concrete curb units are very heavy, making them dangerous to install. The curbs must endure severe impacts, gas and oil leaks from passing cars, de-icing salts from plows, and freezing and thawing with the change of seasons. To maintain the curb''s drains and conduits, construction personnel must dig up roads, putting their safety at risk and creating traffic congestion.
ACO Drain, a division of ACO Technologies PLC, in Shefford, Bedfordshire, UK, is helping to improve drainage installation and performance with products such as roadway drains, grates, and manhole covers, using advanced materials and design techniques that improve installation and performance. The company''s engineers developed a new product, called the ACO KerbDrain, that lets water flow through holes in the curbstone and channels it down the center, essentially using the curb itself as the drain.
Other products had combined a curb and drain before, but they were large and bulky. The KerbDrain''s advantage is its construction of resin concrete. Though hollow, the resin concrete is at least as strong as a regular concrete curb. The KerbDrain is also much lighter, weighing 25 to 32 kg versus 150 kg for a standard unit, making it easier and safer to handle.
ACO Drain faced several obstacles in developing the KerbDrain. It had to learn the ins and outs of a new market -- highway design and maintenance -- and develop new production techniques to cast the product in a single pour and color it during the process.
To design the KerbDrain, ACO Drain used two software packages from SolidWorks Corp: SolidWorks®, for 3-dimensional computer-aided design (3D CAD), and COSMOSWorks, for finite element analysis. These products proved instrumental in making a successful drainage unit.
Designing a Durable Drain
ACO Drain began by creating a 3D model of the KerbDrain using SolidWorks software. It then used COSMOSWorks, which is seamlessly integrated with SolidWorks, to analyze the KerbDrain''s load-bearing capacity. COSMOSWorks graphically showed the product''s tensile and compressive properties under pressure.
COSMOSWorks helped the designers understand exactly where KerbDrain might fail under certain load conditions. Identifying the failure points would have been difficult in a physical test, because prototypes can collapse without warning. The computer model provided a more realistic picture of the loads the KerbDrain could withstand.
COSMOSWorks also showed the nature of potential failures. The designers tried different what-if scenarios and optimized the results. They learned which areas of the installation detail (the supporting concrete) were critical and couldn''t be neglected by the installer.
In the past, ACO Drain had to test two or three prototypes before arriving at a final product. The tests often involved time-consuming and expensive installations at construction sites. With SolidWorks and COSMOSWorks, ACO Drain needed only one prototype for the KerbDrain. By the time the company reached the prototyping stage, it had a nearly finished product.
Getting Into the Software
Previously, ACO Drain used AutoCAD as its primary design tool. "It was very good for working with engineers'' layouts and architectural drawings," says research and development manager Rob King, "but it wasn''t very helpful for design. We were also starting to create more complex assemblies and designs, which would have been very difficult using the AutoCAD system."
In 2000, ACO Drain decided to switch to a solid modeling package and add a finite element analysis program. The company challenged makers of both programs to simulate its drainage products. COSMOSWorks was the only software to simulate the products accurately. The others represented the structures as welded assemblies, but COSMOSWorks used gap elements that allow the products to move.
SolidWorks and COSMOSWorks were well integrated, says King, who calls them a "seamless package." They ran on PCs, so ACO Drain didn''t have to buy high-end workstations.
While factors such as usability and cost influenced ACO Drain''s choice, in the end, the decision came down to accuracy. The other products wouldn''t "give us an accurate result," says King. "They were, in fact, pretty inaccurate in our application."
Expensive Prototypes Eliminated
ACO Drain continues to use SolidWorks and COSMOSWorks to assess its other product designs. For instance, it has simulated the way concrete would crush an underground conduit product, then used that information to reinforce the conduit. This analysis would have been very difficult without SolidWorks and COSMOSWorks, requiring several prototypes and hours of work in the test lab.
For cast-iron products such as manhole covers, creating a prototype for testing can take up to eight weeks. Even with the rapid prototyping possible for plastic products, it could take two or three days. With COSMOSWorks, ACO Drain can validate a design in a day. The company estimates it saves 25,000 pounds a year in prototype tooling costs alone.
The KerbDrain has been extremely successful for ACO Drain. Local authorities are enthusiastic about it, with one Blackpool official calling it "a positive drainage solution which is highly cost-effective for us." KerbDrain has also won broader recognition for its innovative design; in 2001 it received the prestigious Queens Award for Enterprise: Innovation, and the United Kingdom Design Council awarded the company its Millennium status.
All these accolades attest to the power of smart thinking, smart design, and smart software.