CAD systems offer a mixed bag of tricks for building designers

IT design software is providing the industry with high-quality graphics and models. But is it enough? Christopher Sell reports.
CAD systems offer a mixed bag of tricks for building designers
By Christopher Sell
Sat 18 Aug 2007 12:00 AM

Computer-aided design (CAD) tools for buildings are now fundamental aspects of the construction process. So accurate has the technology become, that developers, architects and consultants can now call on a range of relevant software which can reveal a building's impact on shadow and daylight, wind flow and energy use. Solar radiation programmes are even available for those with an eye for more efficient building design.

This has undoubtedly made the design process more effective, with architects and designers able to understand the minutiae of building orientation, wind strength and so forth before any major commitment is made. This allows, therefore, for alterations to concepts and improved energy efficiency, which could prove costly further down the line.

"Tools are now powerful enough that as we look to alter our design conceptually in a very iterative way, we can change these models and have a true feedback loop between the changes in design form and how that would impact overall energy consumption," says Roger Frechette, director of building services, Skidmore, Owings & Merrill (SOM).

Frechette highlights a number of core design tools that have been developed recently, which lend themselves to this area of construction. Ecotect is a complete building design and environmental analysis tool which covers the broad range of simulation and analysis functions required to understand how a building design will operate and form. This was used on SOM's Pearl Tower - which is being built in the Guangzhou province of China - to look at the impact of solar radiation and where best to install PV panels.

Equest also allows users to perform analysis of a building's energy use. Computational Flow Dynamics (CFD) is a well-known tool in today's market and Virtual Environment assists designers in establishing a building's impact on shadow and daylight. "This enables us to precisely predict the amount of energy consumed by the building," he adds.

Such tools have assisted SOM in ensuring that the 300m Pearl Tower optimises air flow for wind generation. Using CFD, a combination of sharp edges and a rounded top has aided the pressure differentials between the front and back of the building. "Form needs to aid and contribute to the building," says Frechette. Through this studied analysis, SOM has managed to convert wind velocity - which approached the building at 3m/s - to 9m/s through openings in the building. "Because of the doubling of wind velocity in the opening, this forms an increase of 800% in power potential," adds Frechette.

But while there are undeniably advantages in establishing these parameters on a computer, the accessibility and apparent competency of such programmes has caused concerns among some within the construction industry. Specifically, it has raised further questions regarding the value and worth of such measurements. Despite significant advances in technology, this should not mean proper, physical testing should be overlooked. Doing so could result in buildings whose structures will not meet required levels of structural strength, especially with regard to meteorological conditions specific to the region.

According to Paul Freathy, managing director of wind consultant RWDI, caution should be shown when using software such as CFD, especially when measuring wind loads on buildings in the Middle East. He cites the ease of use and apparent sophistication of CFD as setting a dangerous precedent - as people assume the figures for wind loads are more accurate than they actually are. "I think it has the potential to become an issue," he said. "What we are finding in the Middle East, is that CFD is being used by some outfits to look at wind environments. It has a place, but the problem with CFD is that the graphics are so brilliant that there is a danger people will believe everything they are looking at."

Despite possessing some benefits for smaller scale analysis, Freathy says that such technology has no place when it comes to testing wind speed or behaviour, and will not be suitable for at least a decade. "My word of warning is that the technology has not developed as far as some people would claim and the accuracy of the numbers, even at this stage is suspect. It isn't far off being used for environmental issues, such as micro climate, but my guess is that it will be a good 10 years before it is useful for structural design."
Andy Davids, director of building structures, Hyder Consulting, agrees that CFD would be an inadequate replacement for wind tunnel testing, as it does not model turbulence well, but adds that it would certainly be a useful supplementary tool for analysis. "I certainly haven't seen a lot of evidence of traditional wind-tunnel testing being replaced by CFD. But there is certainly evidence around that it is being used as a complementary tool."

There are also a number of other analysis and design tools being launched in the region, whose task is to simplify and complement such software tools. Adobe Systems recently launched its Acrobat 3D version eight, a major upgrade to the desktop application for driving document-based 3D design collaboration in the Middle East. The software provides CAD data interoperability to manufacturing professionals and the global supply chain.

With Acrobat 3D, manufacturing and engineering professionals and those from the architectural and construction industries can convert virtually any 3D CAD file into a single PDF document.

"We have upgraded Acrobat 3D versions to engage technical and non-technical team members in 3D-based communications throughout the product life cycle, and help workgroups reduce the risk of discovering design flaws earlier, to speed up the development process," says Andrew Lindstrom, regional manager - Middle East and Africa, Adobe.

IT design software is not only the sole preserve of high-rise towers and energy efficient buildings, however, there are also tools dedicated to the engineering side. In the development processes for machinery and plant manufacturing, there is a growing convergence between electrical engineering, control engineering and mechanical engineering. EPLAN Electric P8 gives - for the first time in the Middle East - electrical designers full access to 3D mechanical design models. Electrical components may now be allocated directly to the mechanical parts, defining a clear and unambiguous link between the two disciplines.

Electrical designers can now determine cable lengths on the basis of the mechanical 3D model, with due regard for predefined cable routes. Apart from saving valuable development time, users are also able to cut production times, because cables can be pre-assembled and are guaranteed to fit.

Dr Siegfried Gruber, managing director, EPLAN, says: "For the first time, electrical engineering, fluid engineering and instrumentation and control applications are able to communicate directly with one another via a common platform. Since the Middle East's construction industry is booming, it demands perfection and high standards in engineering with limited time. EPLAN has provided a tool to achieve such objectives with consistency and reliably and will help companies gain a competitive advantage in the fast moving environment."

Bentley's RAM International Solutions Centre has also just released version 11.2 of RAM Structural System Bentley's modelling, analysis, and design software for structural engineers. The software provides powerful automated and integrated tools, which increase structural engineers' productivity, allowing them to be more profitable and to more quickly produce economical designs. New features include the concept of notional loads for each storey of the design and a baseplate summary warning.

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