Technology

information and updates on the impact of technology on structural

Iconic Firth of Forth , Scotland. Courtesy of Jim Wilson.

he art of bridge design is a time-hon- was a watershed for® advances in materials and ored pursuit that, throughout the design, and coincided with the need to facilitate centuries, has undergone significant an ever-expanding infrastructure network. advances in engineering and technol- While Pre-Industrial Revolution were Togy as a result of mankind’s passion to conquer predominantly wood or stone, during the the challenges of any given crossing. It has evolved Industrial Revolution, iron became a viable Copyrightthrough the acceptance of option following the construction of the Iron well-established practices, Bridge that stretched across the River Severn codes and construction in Coalbrookdale, UK. This can be seen as the The New Technology techniques. In fact, when beginning of modern bridges produced with a of Bridge Design new materials or meth- new material palette of industrially produced odologies are brought to iron, which gave way to cast iron, wrought iron, the market, it often takes steel, and reinforced and prestressed concrete. By Scott Lomax and many years for the techniques to gain inclusion This period also saw the development of the Thomas Duffy, P.E. in the modern practice of bridge design. Americas, which presented a growing need for For example, even after the high-strength char- extended infrastructure. acteristics of iron were recognized, as compared In particular, the development of the railway net- with timber,magazine iron was still used as a lighter-weight work was instrumental in pioneering works such as Scott Lomax is a Vice PresidentS of Tsubstitute. R It wasU years before C it came T to be a Uthe first Rmajor crossing E across the Mississippi via the , specializing stand-alone structural material for bridge design. Eads Bridge in 1874, directed by Andrew Carnegie in engineering for bridges and Steel also went through a similar transforma- through the Keystone Bridge Company; the iconic long-span structures. Scott’s past tion before it was used as a replacement for iron; Firth of Forth Crossing in 1890 near Edinburgh; and work includes the World Trade welding and bolts replaced rivets; and in today’s the world-famous Brooklyn Bridge in 1883. This Center Transportation Hub, modern age, analysis and CAD (from era is often heralded as one of great civic works that currently under construction in New matrix methods though FEMs) have replaced captured the imagination of the public and expressed York City. Scott may be reached at hand calculations and hand drafting. the rapidly expanding vision of engineers, architects, [email protected]. Where are we now in this continuum? Advanced entrepreneurs and empire-builders. Engineers played modeling techniques, material choices and analysis a prominent role during the Industrial Revolution Thomas Duffy, P.E., is a Senior methodologies adopted for building practices are and Victorian era, introducing to society names such Vice President at Thornton not yet fully embraced within the bridge industry. as Telford, Brunel, Roebling and Eiffel, and later, Tomasetti and is responsible for This paradigm will soon shift, and we anticipate Freyssinet & Amman. As architects took a lead role project management and business that advanced computational modeling will be one in the design of buildings, the design and construc- development for Thornton Tomasetti’s of the next big advances in bridge design. tion of bridges remained very much the domain Building Performance practice. He The need to create crossings has always been has served on the American Road one of mankind’s biggest challenges, and often Transportation Builders Association’s leads to an increase in man’s ambition to have planning and design committee. a more enhanced understanding of mechanics He sits on the advisory board of the and advances in technology and materials. These Urban Assembly School of Design challenges create opportunities, and some of the and Construction in New York greatest leaps in engineering design and con- City and has been a mentor and struction have occurred from the need to push technical advisor for Smith College’s boundaries. Examples of this are evident from the Picker Engineering Program. earliest recordings of Roman cofferdams, to the Thomas may be reached at Great Stone Bridge of the Sui Dynasty (581-618), [email protected]. through to the Industrial Revolution (1760- 1840). The Industrial Revolution in particular Gateshead Millennium Bridge. Courtesy of Kay Williams.

10 October 2013 STRUCTURE magazine Iron Bridge at Coalbrookdale. Couresy of Leon Reed. of the engineer. Major civil works, including bridge designers have become more high- those of Amman, continued to push materials profile than ever. Celebrated engineer and ® and analysis to new boundaries and spans – architect Santiago Calatrava is well-known notably with the use of cables in suspension for his esoteric bridge designs, and involve- and cable-stay bridges. With increased spans ment of well-known designers such as Sir came heightened awareness and consideration Norman Foster, Zaha Hadid, Wilkinson Eyre of wind forces and aerodynamics that led to and Thomas Heatherwick, amongst others, slender bridges. Following this path, we can see on some trulyCopyright innovative bridge projects, has Santiago Calatrava’s Jerusalem Chords Bridge. the raw beauty of stressed ribbon bridges, such helped raise awareness of the importance of an Couresy of Itay Barlev. as ones designed by notable engineer Jiri Strasky, integrated approach to bridge design. which epitomize both a structural and aesthetic The domain of architects was more tradition- great growth and opportunity for the future of purity that has become the hallmark of signature ally associated with building design, and in bridge design are the application of advanced bridge design. Bridge design continued to be keeping with this trend of architects’ increased geometric modeling and the delivery of the dominated by engineers; however, appreciation involvement in bridge design, it is only natural design in a form that can be directly imple- of the aesthetic impact was on the rise. that some of the recent adopted in mented into the fabrication process. In recent times, we have seen architects play a building design will be implemented in bridge Advanced Computational Modeling larger role in bridge design, creating signature design. It is clear that there will continue to (ACM) is a powerful tool for both the con- bridges that become important objects in the be advances in material that push the ceptual and design development phases. As public realm. Many have become landmarks boundariesmagazine of the current palette of materials bridge forms, particularly for footbridges, that raise the profile of theS bridge Tdesign R(steel, cables,U wood, glassC and concrete)T andU become R more complex,E ACM can be used industry, and highlight the importance of an an expanding role of newer materials such as to quickly investigate form-finding and integrated design approach. Bridges by nature plastics and composites, like the Sandwich generate various geometrical options. As are pure, almost raw objects, and as such pos- Plate System (SPS). Similarly, continued devel- part of this process, the ACM platform sess a sculptural quality that is embraced by opment of analysis software and understanding can be used to refine and economize the the public. Through careful design, consider- of geometric and material nonlinearities will design and promote early understanding of ing the form, function, detail and potential also lend itself to push these materials to new the structural behavior, visual appearance, to create more than just a link, bridges and bounds. However, two areas in which we see fabrication complexities and sustainability issues. ACM can work within many plat- forms, including Rhino, Grasshopper and Digital Project. These software packages,

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STRUCTURE magazine11 October 2013 The Majestic Millau Viaduct by Michel Virlogeux and Sir Norman Foster. Breooklyn Bridge. Courtesy of Bess Adler. Courtesy of Dave Tappy. ubiquitous within the design community, The ability to fluidly converse between in-house fabrication expertise embedded facilitate development of forms that can be software, including analytical packages, is within the design® team. Qualified staff deliv- quickly exported into a structural analysis fundamental to the success of this approach. It ering design materials in the same software package and assessed for preliminary sizing is important to note that this process contin- platform as the fabricator, and developing the and behavior. The ability to produce early ues through design development and is a tool design both in this format and following the 3D images and renderings is also impor- rather than a driver of the design, controlled methodology in which the bridge is erected, tant, not only for consolidating the design through a collaborative and integrated process the project can benefit from improved sched- with the team but also for producing visual with the entireCopyright design team. ule. This minimizes reproduction and RFIs graphics for clients, competitions and The early input of bridge constructability and provides greater quality control due to a media. By controlling parametric bound- in the design process is also important, as common understanding between the design aries, it is possible to quickly optimize the it sometimes dictates the form of a bridge. and fabrication team and results ultimately design for a number of parameters ranging Consider the use of stressed-ribbon over a in cost benefits by reducing uncertainty in from weight to solar heat gain, offering early deep ravine where falsework would be cost the design material. evaluations of issues such as constructability prohibitive, or a tied arch bridge moved As the world population continues its migra- or energy modeling. into position in a single operation because tion to cities, and mega-cities emerge in Asia An example of this could be a covered of either environmental considerations to and Latin America, we will see continued chal- pedestrian bridge between two build- avoid temporary works in the crossing or lenges to cross new spans. The importance ings in a hot climate, whereby the project logistical rationale such as a limited closure. of aesthetics and the contribution of bridges demands a high-profile response. Early Anothermagazine link that is critical to the success of to the urban fabric means that an integrated ACM work can be used to Sgenerate organicT Ra project Uis the production C andT delivery U of design R team – combiningE architectural form structural forms, simulate various coverings design information in a format that is directly with engineering elegance – is fundamental from tension fabric to glazing to Ethylene implemented by the contractor/fabricator. to the success of landmark bridge projects. TetraFluoroEthylene, orientate the structure This approach greatly benefits any project This process demands highly skilled and col- to both an optimized form while providing and is fundamental for design-build projects laborative engineers, architects and designers maximum shading in the areas required, with aggressive schedules. While modeling working seamlessly together in design, fabri- while passing as much natural light as pos- tools, such as Tekla, are the mainstay for this cation and construction. The future of bridge sible. The bridge structure can also quickly effort, the success ultimately relies upon the design requires reinventing this be decomposed to show transportable and knowledge and understanding of the fabrica- collaboration through the use of erectable sections, thereby directing the con- tion and construction process. To this end, new platforms for developing and structability and early cost evaluation. we have seen enormous benefit to having delivering the design materials.▪

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STRUCTURE magazine12 October 2013