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AEC

On the Job: Solidifying Airport Safety

24 Jun, 2007 By: Michelle Nicolson

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3D design and collaboration plays integral role in developing safety barriers for London's Heathrow airport.

Safety considerations are a given part infrastructure design. They are particularly important when the design is London's Heathrow airport, where 63 million passengers pass through each year. Those passengers might not notice many safety features -- such as the cylindrical barriers that stand between large airplanes and buildings. But those bollards are there, and they are as imperative as they are ubiquitous. AMEC, a construction and infrastructure support provider, is charged with ensuring that the barriers can withstand a minor accident or a potential tragedy.

AMEC provides design and construction services to Heathrow International and other regional airports. Among its numerous responsibilities is making sure that airport infrastructure holds up in the event of an accident. So the company designed the A390, which simulates the force of a jetliner to assess a structure's impact resistance.

"The airport installs a very large number of protective bollards and barriers," explains John Albinson, product development manager of AMEC's Pavement and Infrastructure Team (P&IT). "To reduce maintenance, there was a need to more clearly understand the energy-absorbing capacity of various protective structures and assess the performance of a new bollard-mounting device currently subject to a patent application. The A390 machine was designed so that deflection of the bollard or barrier can be measured in real time."

The A390 is heavy-duty to say the least, stretching more than 6m long and weighing more than 3.25 metric tons (7,200lb.). A 1350kg piston inside the cylinder acts as a battering ram. The mammoth machine works like a compressed-air gun, with the air chamber within the cylinder pressurized by an external air source.

When the 3m-long, 590mm-diameter piston is released via simple mechanical escapement, the result is a powerful thrust, releasing about 80 kilojoules of impact energy. The movement of the piston and the instantaneous pressure changes are recorded by transducers, which sample at 0.5 microsecond intervals, so that the tests can be later analyzed.

Seeing in 3D
Designing the A390 presented some challenges. Heathrow stores a great deal of its infrastructure plans in 2D format, but Albinson's department, which is tasked with building new additions to infrastructure, needed early visualization in 3D of proposed solutions. So P&IT implemented Alibre Design Professional solids modeler, which comes equipped with 3D PDF publishing capability.

For AMEC's P&IT, which is not heavily invested in 3D technology, the 3D PDF capability allowed everyone in the department to participate in new product development through 3D visualization without purchasing a slew of CAD licenses or investing in CAD training.

The advantage for P&IT is that models in 3D PDF files can be viewed from any angle or magnification, and assemblies can include animated exploded views or sequences of steps to communicate design intent and document assembly processes. Personnel not equipped with CAD software can read the 3D PDF files generated from Alibre Design use the free Adobe Acrobat Reader.

"The advent of 3D PDF has made the exchange of design ideas out of the design team very easy," Albinson reports. "I now use this export facility extensively."

Communication and Documentation
The AMEC team put other Alibre Design capabilities to use as well. Particularly useful was the automated generation of BOMs (bills of materials) for the modeled assemblies. "I needed to produce real drawings with BOMs, while providing high-quality models for product visualization," Albinson says.

This helped solve one design challenge involving the main piston cup seal, machined from hard rubber and including a set of inner and outer wheels added to support the tremendous load. The fabricator found it difficult to manage and transport the extra-large assignment, so AMEC responded by providing a full set of 2D drawings with accompanying 3D pictures from the model produced in Alibre Design. The water-cut steel sections were profiled using 2D export files.

Albinson and his team have used Alibre Design to develop more than a dozen significant products in the past two years. As the A390 project demonstrates, his engineering staff can use these 3D modeling and collaboration tools to take on projects of any scale.