The just-completed Anaheim Regional Transportation Intermodal Center (ARTIC) in Anaheim, California is as beautiful as it is functional. A hub for rail, bus, auto and bike travel, ARTIC is also ready for high-speed trains and street cars, the region’s next-generation transportation systems. Its sculptural form is a high-tech take on the simple lines of old airship hangars and the light-filled grandeur of historic train stations. As the project’s structural engineer and developer of its façade concept, we are proud of our role in shaping this iconic form, which is the country’s largest application of an ETFE façade.
ARTIC’s signature feature is its roof: a tapering vault of crisscrossing parallel arches – a lamella–shell arch hybrid – that spans 184 feet and is clad in translucent ETFE polymer cushions. Because of the roof’s complicated geometry and the close link between its shape and performance, we worked very closely with architect HOK to define the details of its form.
After exploring multiple grids for the steel-tube frame with HOK, we found a solution that met structural requirements for performance and efficiency while also fulfilling the architect’s aesthetic and spatial goals. We developed a design that defined the arches as a series of compound curves, which made the steel easier to fabricate. To make it easier to build, we collaborated with Clark Construction to develop a sequencing plan that required temporary shoring only at the first arches installed; the rest of the roof was self-supporting during erection.
We also worked with the steel fabricator to devise an adjustable backing plate for use in the complete joint penetration (CJP) welds that connect the intersecting steel pipes of the roof shell. The construction sequence made traditional internal ring plates impractical, since they would get in the way of filling in intermediate arch pieces. The internal perimeter of the heavy steel pipe was also variable. The solution? An internal ring plate that could telescope back into the pipe to allow placement of the “fill-in” sections. The design also included a screw and block that permitted size adjustments while maintaining continuous contact between the plate and the interior pipe surface.
Detail of the telescoping internal ring plate.
Our Façade Engineering practice was also engaged for the early phases of design to develop the translucent ETFE façade. Doing structural and façade engineering under one roof made working out the interactions between the two much simpler. Façade elements in the large glass end-wall double as structural members: the mullions act like bicycle spokes to stiffen the edge of the roof shell.
Structural team members Ben John and Chuan Do on the construction site in January, 2014
Because so much of ARTIC’s structure is exposed, aesthetic considerations were nearly as important as technical ones. We collaborated with HOK to design clean-looking details that enhance, rather than detract from, the building’s dramatic sculptural form.
Despite its visual simplicity, ARTIC was a complex and challenging project. Along with the rest of the design team, we relied heavily on integrated building information modeling (BIM) for design exploration, analysis, team communication, documentation and coordination during design and in the field. The integrated model will be used by the owner for ongoing operations and maintenance. BIM’s value to the project was recognized by the AIA’s Technology in Architectural Practice Knowledge Community (TAP), which awarded the project its “Stellar Architecture Using BIM” citation earlier this year.
Our project team members (including Bruce Gibbons, Chuan Do, Ben John, Jun Jin, Mark Dannettel and David Flores) are excited to finally see ARTIC open to the public. The transit hub opens to the public on December 13. If you are in the area, stop by the grand opening celebration.
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