ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/306894
Ted Zoli, Director of Long-Span Bridge Design Ray McCabe, National Director of Bridges and Tunnels ASPIRE , Winter 2007 | F O C U S HNTB HNTB's long history with bridge structures has given its engineers the culture and experience to design for a wide variety of applications and challenges. That work has only begun, its executives say, with more exciting designs and new materials on the horizon. "We're one of the few practices that routinely designs bridges using a variety of materials and with both short and long spans," says Ted Zoli, Director of Long-Span Bridge Design. "There are circumstances where several material options are viable, but in many cases, there is a clear preference." Ray McCabe, National Director of Bridges and Tunnels, adds that such flexibility ensures clients can achieve whatever specific criteria they require. "Right from the start, HNTB has had a culture of delivering technical excellence regardless of how that takes shape," McCabe says. "Our culture has always been to avoid forcing a bridge design to create an award-winning structure even when the challenges or demands call for it. We tailor our designs to fit the customer's needs. If one of those needs is a signature bridge, then we will deliver that while also meeting other program needs." The company has delivered a number of signature bridges, perhaps more than any other firm in the United States, since it opened its doors in 1914. Many of them have featured concrete components. (For more on the company's history and past projects, see the sidebar and accompanying project overviews.) "We have some unique design elements for which we are known," says Zoli. One of those is a concrete bow-tie strut that the firm often uses with cable-stayed bridges, in which the form very much aligns with the function. "It is, in a formal sense, an optimized structure, with the depth of strut varying to match the moment demands." This design has been used on a variety of HNTB projects over the past 20 years, providing an element that is as functional as it is distinctive. Formability Adds Advantages The concrete bow-tie strut is an indication of how the company takes advantage of the material's inherent formability, Zoli adds. "Concrete structures may readily be shaped to resist design forces, giving us the ability to express the way that loads are carried by the structure and to meet the design goals as efficiently as possible." Looks To Concrete's FuTure By Craig A. Shutt The 10-lane Leonard P. Zakim Bunker Hill Bridge in Boston is a concrete cable-stayed bridge featuring 270-ft Y-shaped towers. The 1432-ft-long project has won a number of design awards for HNTB. Photo: ©Andy Ryan ASPIRE_win07.indb 5 12/29/06 1:50:36 PM