Searching for new bridge forms that can span further

Newly identified bridge forms could enable significantly longer bridge spans to be achieved in the future, potentially making a crossing over the Strait of Gibraltar, from the Iberian Peninsula to Morocco, feasible. The new bridge forms – identified by a team of researchers from the University of Sheffield and Brunel University London, working with long-span bridge expert Ian Firth of engineering consultants COWI – use a new mathematical modeling technique to identify optimal forms for very long-span bridges. The research was published recently in the Proceedings of the Royal Society.

A bridge’s span is the distance of suspended roadway between towers, with the current world record standing at just under 2km. The most popular form for long spans is the suspension bridge form, as used for the Humber Bridge, though the cable-stayed bridge form, where cables directly connect the tower to the roadway – such as used in the recently constructed Queensferry Crossing in Scotland – is becoming increasingly popular.

As bridge spans become longer, a rapidly growing proportion of the structure is needed just to carry the bridge’s own weight, rather than the traffic crossing it. This can create a vicious cycle: a relatively small increase in span requires significantly more material, leading to a heavier structure that requires yet more material to support it. This also sets a limit on how long a bridge span can be; beyond this limit a bridge simply cannot carry its own weight.

One option is to use stronger, lighter materials. However, steel remains the preferred choice because it is tough, readily available, and relatively cheap. So the only other way to increase span is change the bridge’s design.

Professor Matthew Gilbert from the University of Sheffield, who led the research, says, “The suspension bridge has been around for hundreds of years and while we’ve been able to build longer spans through incremental improvements, we’ve never stopped to lsee if it’s actually the best form to use. Our research has shown that more structurally efficient forms do exist, which might open the door to significantly longer bridge spans in the future.”

The technique devised by the team draws on theory developed by Professor Gilbert’s namesake, Davies Gilbert, who in the early 19th Century used mathematical theory to persuade Thomas Telford that the suspension cables in his original design for the Menai Strait bridge in North Wales followed too shallow a curve. He also proposed a "catenary of equal stress" showing the optimal shape of a cable accounting for the presence of gravity loads.

By incorporating this early 19th century theory into a modern mathematical optimization model, the team has identified bridge concepts that require the minimum possible volume of material, potentially making significantly longer spans feasible. The mathematically optimal designs contain regions which resemble a bicycle wheel, with multiple "spokes" in place of a single tower. But these would be very difficult to build in practice at large scale. The team therefore replaced these with split towers consisting of just two or three "spokes" as a compromise that retains most of the benefit of the optimal designs,while being a little easier to construct.

For a 5km span, which is likely to be required to build the 14km Strait of Gibraltar crossing, a traditional suspension bridge design would require far more material, making it at least 73 percent heavier than the optimal design. In contrast, the proposed two- and three-spoke designs would be just 12 and 6 percent heavier, making them potentially much more economical to build.

The new bridge forms require less material principally because the forces from the deck are transmitted more efficiently through the bridge superstructure to the foundations. This is achieved by keeping the load paths short and avoiding sharp corners between tensile and compressive elements.

The team emphasises that their research is just the first step and that the ideas cannot be developed immediately for construction of a mega-span bridge. The current model considers only gravity loads and does not yet consider dynamic forces arising from traffic or wind loading. Further work is also required to address construction and maintenance issues.

Co-author Ian Firth from COWI says, "This is an interesting development in the search for greater material efficiency in the design of super-long span bridges. There is much more work to do, notably in devising effective and economic construction methods, but maybe one day we will see these new forms taking shape across some wide estuary or sea crossing."

The research, funded by the Engineering and Physical Sciences Research Council (EPSRC), was also presented at "Tomorrow’s Megastructures," a symposium organized by the International Association for Bridge and Structural Engineering.

Water and wastewater experts Nogaj and Kabouris join Cardno’s Clearwater office

Cardno has announced that Thomas Nogaj, PhD, PE and John Kabouris, PhD, PE have joined the firm as water and wastewater infrastructure practice group manager and wastewater technology specialist respectively.

Nogaj brings more than 30 years of experience in the civil and environmental engineering fields. He provides consulting and project management on a broad range of water/wastewater treatment and conveyance projects for facilities of all sizes. He holds a PhD in Environmental Engineering from the University of Central Florida and is a licensed Professional Engineer in Florida and Illinois.

Kabouris has more than 30 years of experience in environmental engineering, offering expertise in modeling, plant controls, and optimization of nutrient removal, sidestream and mainstream anammox process development and optimization, and advanced digestion and biogas utilization. He holds a PhD in Civil and Environmental Engineering from the Georgia Institute of Technology and is a licensed Professional Engineer in Florida. He is actively involved at the national level with the Water Environment Federation and is Associate Editor of the environmental journal Water Environment Research.

“Thomas and John have provided their wealth of expertise and research to numerous water and sewer departments in the United States and abroad, and that knowledge has resulted in significant financial savings and more effective systems for clients,” says Doug Stoker, Cardno Southeast Business Unit manager. “We are excited to have them on our team.”

Headquartered in Australia, Cardno is an international professional infrastructure and environmental services company with specialist expertise in the development and improvement of physical and social infrastructure for communities around the world. Cardno’s team includes professionals who plan, design, manage and deliver sustainable projects and community programs. For more information, visit www.cardno.com.

StormwateRx introduces Purus Nitrate for stormwater treatment

StormwateRx, a stormwater treatment and filtration company based in Portland, Oregon, has announced the development and release of a new product in its line of Purus advanced polishers, Purus Nitrate targets soluble nitrate in industrial stormwater runoff. This system is ideal for industries where nitrogen compounds or petroleum products are used or where organic materials are processed, including fabricated metal products, food processing, and chemical manufacturing.

Purus Nitrate is normally installed and flow-matched in a "treatment train" configuration with StormwateRx's Aquip stormwater filtration technology, an upstream pre-filtration system. The typical removal efficiency of this technology falls in the range of 80 to 90 percent, usually to below the required numeric action levels (NALs) or benchmarks.

Purus Nitrate has a dissolved nitrate capacity exceeding 40 pounds (as nitrogen) for a typical 100 to 300 gallon-per-minute treatment flow rate. Slipstream treatment configurations are available to extend run-time when less nitrate needs to be removed from the stormwater.

StormwateRx designs, manufactures, installs, and maintains stormwater treatment systems for industrial customers throughout North America. For more information, visit https://stormwaterx.com.

Note: Progressive Engineer ran a company profile on StormwateRx in 2010. See it at http://www.progressiveengineer.com/company_profiles/stormWateRx.htm.

Nancy Lyon-Stadler to lead WSP Cleveland office

Nancy Lyon-Stadler has been appointed by WSP USA, an engineering and professional services consultancy, to lead its Cleveland, Ohio office. In her new position, Lyon-Stadler will be responsible for office management and expansion, product delivery, client engagement, and new business development.

Since Lyon-Stadler joined WSP as a senior principal engineer in 2015, she has been part of several transformational projects in northeast Ohio, including traffic-related aspects of the reconstruction of the George V. Voinovich Bridge, which opened in September 2016 and greatly improved traffic in downtown Cleveland. She also conducted traffic analysis and developed congestion mitigation strategies for the 2016 Republican National Convention in Cleveland, supporting the event organizers, the U.S. Secret Service, and the Cleveland Police. “Nancy has led multiple projects to improve livability in northeast Ohio communities through the integration of bicycle and pedestrian facilities and transit enhancements within the transportation network, including developing the design concept and implementation plan for Cleveland’s innovative Midway Cycle Track Plan,” says Jerry Jannetti, senior vice president and northeast regional manager at WSP.

Lyon-Stadler has over 30 years of engineering experience in the private and public sector with expertise in planning, design, and construction. She has been employed as a consulting engineer for more than 20 years and prior to that, she served as a civil engineering officer in the U.S. Air Force.

Lyon-Stadler has a B.S. in civil engineering from Virginia Polytechnic Institute and State University and an M.S. in civil engineering from The Ohio State University. She is a registered professional engineer in Colorado, North Carolina, Ohio and South Carolina, as well as a licensed professional traffic operations engineer

            WSP USA, formerly WSP | Parsons Brinckerhoff, is the U.S. operating company of the engineering and professional services firms WSP. Dedicated to serving local communities, the firm consists of engineers, planners, technical experts, strategic advisors, and construction management professionals. WSP USA designs solutions in the buildings, transportation, energy, water, and environment sectors. With more than 7,000 people in 100 offices across the United States, they partner with clients to help communities prosper. For more information, visit www.wsp.com.