Vanja Samec Ph.D., Bentley Systems Austria GmBH, Global Director RM Bridge

Long-span suspension bridges represent some of the most remarkable, yet most vulnerable, assets in road networks. Due to their important role in the transportation network, the design, construction, and subsequentsurveillance and maintenance must be performed very accurately. During the design process, bridge designers must consider and meet many challenges, including the highly non-linear behaviour of the structure, the optimization of the geometry of suspension cables, and the effects of wind.

The continuous change of structural systems is a major reason for non-linear structural analysis. For cable-supported bridges, special optimization procedures are necessary. For long cable-stayed and suspension bridges, bridge designers must consider dynamic wind effect. The extraordinary, ultrathin design of these structures yields significant susceptibility towind-induced vibrations. Steel bridges, especially, allow for extraordinarily slender main girder cross sections. Sophisticated analysis methods must be applied to determine critical wind velocities for all types of known wind effects. As a result, dynamic wind analyses are increasingly important tobridge engineers.These phenomena include vortex shedding and the lock-in phenomenon, across-wind galloping and wake galloping, torsional divergence, flutter phenomena, and wind buffeting.

Today, computer programs should provide the best possible support for this design process.One such product is Bentley RM Bridge, which has been well-tested and proven on major projectsto become a globally recognized, expert systemcapable of solving virtually any bridge design oranalysis problem.

(Hardanger Bridge) For example, RM Bridge was used successfully by engineering designers on the Hardanger Bridge (Fig.1),the longest long-span suspension bridge in Norway. This bridge,which opened August 2013,crosses the Hardanger fjord.

It has a main span of 1,310 meters and is rankedNo. 10 on the list of longest suspension bridges in the world. The Norwegian road authority, Statens Vegvesen, in close collaboration with TDA Norwayand Bentley Systems’ Austria team in Graz, performed the design work.

The bridge deck consists of an orthotropic steel box, with a width/depth value of 17.3 meters/3.2 meters. The stiffness of the main girder is relatively small when comparedto other bridges of this span type.The distance between the two main cables is only 14.5 meters, which means that the Hardanger Bridge isone of the most slenderbridges in the world (Fig.2).

(Main cables) Among some of the specific challenges on this project were the highly non-linear behaviour of the structure; the need to optimize the geometry of the suspension cables while designing the sag profile; the non-linear behaviour due to the traffic loading; and optimization of the erection procedure, wind loading, and wind-induced vibrations.

Numerical wind investigations of the main girder and pylons were performed with a CFD module thatapplies the vortex particle method to describe the air flow around the cross-section (Fig.3).

(CFD calculation) Future projects in Norway that will require innovative bridge and tunnel technologies, as well as experienced engineers and reliable software applications, include the E39 road between the cities of Kristiansand, Stavanger, Bergen, and Trondheim, which will become a ferry-free highway route. 

Author’s Profile: 

Vanja Samec has 25 years’ experience working as structural research engineer, project bridge engineer, software developer and global bridge manager. Samec has a post-graduate degree from the Institute for constructions, seismic engineering and computer research, Faculty of Civil Engineering Ljubljana, Slovenia. During her degree Samec was continuously involved in various research projects and contributed to a number of academic publications.

As part of her degree work, Samec developed a software application program that calculated paneling constructions according to DIN and American standards. The program was purchased by Slovenian timber industry firm LIP. After employment in Switzerland at shell expert Prof.Heinz Isler in 1989 Samec started to work at TDV, Austria where she held a position within the technical software development department. She was involved in international bridge projects including Kwangan Bridge, Korea; Stonecutter’s Bridge, Hong-Kong; Dou-Shan Viaduct, Taiwan, Pöchlarn Bridge over the Danube, Austria and many others.

Samec was also accountable for technical consultations and presentations of RM Bridge worldwide to RM Bridge prospects and customers. Since 2007 Vanja Samec works for Bentley Systems and is currently responsible for the entire global RM Bridge Team. She is actively involved in global bridge conferences, representing RM Bridge and BrIM and leads numerous Bridge days across Asia, Europe and America.

Highlights: 

• Bentley RM Bridge has been well-tested and proven on major projects to become a globally recognized, expert system capable of solving virtually any bridge design or analysis problem.
• For example, RM Bridge was used successfully by engineering designers on the Hardanger Bridge the longest long-span suspension bridge in Norway. The Norwegian road authority, Statens Vegvesen, in close collaboration with TDA Norway and Bentley Systems’ Austria team in Graz, performed the design work.