Orthotropic Design Meets Cold Weather Challenges An Overview of Orthotropic Steel in Cold Regions

By Alfred R. Mangus, P.E. Transportation Engineer, Civil California Dept. of Transportation (CALTRANS) Sacramento, California

Introduction Initially developed by German engineers following World War II, orthotropic design was a creative response to material shortages during the post- war period. Lightweight orthotropic steel bridge decks not only offered excellent structural characteristics, but were also In economical to build (Troitsky 1987). Floating Bridge Moreover, they could be built in cold The across the climates at any time of the year. Salhus fjord is Norway’s second float- Engineers from around the world utilize ing bridge and the world’s largest float- this practical and economic system for ing bridge (Meaas, Lande, and Vindoy, all types of bridges. While 1994). The bridge was opened for traf- must be at or above 5 degrees Celsius fic in 1994. The total bridge length is to properly cure, it is physically possible Figure 1. Rib designs. 1615 m and consists of a high level to encapsulate and heat the concrete 369 m long cable stayed bridge and a construction process; admittedly, this cover a matrix of rib types, superstruc- 1246 m long floating bridge (Figure 2). adds to construction costs (Mangus ture types and various bridge types. The floating bridge consists of a steel 1988), (Mangus 1991). Russia has developed a mass manu- box girder, which is supported on ten factured panelized concrete pontoons and connected to Orthotropic steel deck bridges have system and has devised special abutments with transition elements in proven to be durable in cold regions. launching methods for cold regions. forged steel. The main elements are a The orthotropic steel deck integrates Russian engineers prefer the open rib high-level cable stayed bridge provid- the driving surface as part of the design and have industrialized this ing a ship channel and a floating superstructure, and has the lowest system, while most other engineers bridge between the underwater rock total mass of any practicable system. prefer the closed rib. Researchers, as Klauvaskallen and the other side of In Europe, where the advantages of well as the owners of orthotropic steel the fjord. The cable stayed bridge pro- orthotropic design have been deck bridges, continue to monitor the vides a clear ship channel. A 350 m embraced with enthusiasm, there are performance of various rib types long ramp is required to transition from more than 1,000 orthotropic steel deck (Figure 1). the higher bridge deck on the cable bridges. In all of North America, there are fewer than 100 bridges of orthotropic design.

This article will give an overview of imaginative steel deck bridges current- ly in operation in Norway, Russia, Sweden, and Ukraine. The examples

Figure 2. Nordhordland Floating Bridge across Salhus fjord of Norway.

Welding Innovation Vol. XIX, No. 1, 2002 stayed bridge to the bridge deck 11 m in the bulkheads varies from 8 mm to are located one at each edge of the above the waterline. The steel box 50 mm. The box girder is constructed ramp in order to maximize the stiffness girder of the floating bridge forms a in straight elements with lengths vary- about a vertical axis. The steel weight circular arch with a radius of 1,700 m ing from 35 m to 42 m. The elements of the ramp is 1,600 tons. in the horizontal plane. The supporting are welded together with a skew angle pontoons are positioned with a center of 1.2° to 1.3° to accommodate the distance of 113 m and act as elastic arch curvature in the horizontal plane. supports for the girder, which is The cross section dimensions of the designed without internal hinges. The octagonal box girder are constant for bridge follows the tidal variations by the length of the bridge. elastic deformations of the girder. The stress level varies significantly Figure 4. Nordhordland Floating The steel box girder is the main load- over the length of the bridge. In the Bridge. carrying element of the bridge (Figure areas with the highest stresses, steel 3). The octagon girder is 5.5 m high with a yield strength of 540 MPa is Bybrua Bridge and 13 m wide. The free height below used. The Bybrua cable stayed bridge has a the girder down to the waterline is 5.5 main span of 185 m. The 15.5 m wide m and this allows for passage of small roadway superstructure was fabricated boats. The plate thickness varies from Orthotropic bridge design in the shop in 9.0 m sections (Figure 5). 14 mm to 20 mm. The plate stiffeners There is a combined pedestrian plus are in the traditional trapezoidal shape was a creative response bicycles area on each side of the three and they span in the longitudinal direc- to material shortages traffic lanes. The cross section of the tion of the girder. The stiffeners are main span has a deck-plate 12 mm supported by cross-frames with center during the postwar period thick, but this increases to 16 and 20 distance of maximum 4.5 m. At the mm at the cable anchorage. The bot- supports on the pontoons, bulkheads tom plate varies between 8 mm and are used instead of cross-frames. This In the remainder of the bridge (in the 10 mm thickness, and the webs is done because the loads in these cross-frames and bulkheads) normal- between 12 mm and 20 mm. At sections are significantly larger than in ized steel with yield strength of 355 intervals of 3.0 m there are frames the cross-frames. The plate thickness MPa is used. The total steel weight of supporting the longitudinal stiffening the box girder is 12,500 tons, of which system. In the bridge deck this is approximately 3,000 tons are high made up of standard trapezoidal ribs strength steel. The elevated ramp is approximately 350 m long and has a grade of 5.7 percent (Figure 4). The elevated ramp is constructed with an orthotropic plate deck 12 mm thick and has 8 mm and 10 mm thick trape- zoidal ribs 800 mm deep. T-shaped crossbeams support the ribs with a Figure 3. Nordhordland Floating maximum center distance of 4.5 m. Bridge. The main 1,200 mm deep box girders Figure 5. Bybrua Bridge.

Welding Innovation Vol. XIX, No. 1, 2002 from the German steel company of Norway fabricated the Bomla Oka Bridge Krupp, and in the bottom flange box Bridge’s steel approach superstruc- The four-lane orthotropic twin box section of bulb flats open ribs were uti- ture, which was launched out over the girder bridge crossing the Oka River lized (Aune and Holand 1981). In the tops of the columns from the shore. on the bypass freeway around the city longitudinal direction the deck was The steel components for the main of Gorki, Russia, was opened to traffic divided into six fabricated sections, span superstructure of the Storda in 1991 (Figure 7). The 966 m long two of which were welded to the web Bridge were prefabricated in the superstructure consists of 2 spans x sections. The box bottom was fabricat- Netherlands (Figure 6) and the main 84 m + 5 spans x 126 m + 2 spans x ed as three sections. The total steel span superstructure of the Bomla 84 m (Design Institute Giprotransmost weight is about 1,100 tons. All ele- Bridge was prefabricated in Italy. The 1991). This bridge is a single continu- ments prefabricated in the shop were orthotropic ribs for the Storda Bridge ous superstructure with a fixed bearing welded, as were the field splices in the were prefabricated in France. The 420 m away from one of the abut- deck, whereas “Huck” high tensile orthotropic sections were transported ments. The total bridge width (29.5 m bolts were used in all other field joints. to the site by barge, and were lifted including steel traffic barriers) provides All field joints were calculated as fric- into position by a crane. two sidewalks 1.5 m wide each, four tion connections. The whole steel traffic lanes, four safety shoulders and structure is metallized with zinc and a center median. The total weight of painted according to the specifications steel for the superstructure is 10,635 of the Norwegian Public Roads tons, or 373 kg/m2. The orthotropic Administration. The superstructure steel superstructure comprises five received the maximum live load basic elements (Figure 7). There are stresses during the erection of the two main box girders assembled from bridge. The wearing surface of the two L-shaped sections for the bottom bridge deck is the same as that devel- face and sides. The intermediate oped by the Danish State Road orthotropic plate sections were used Laboratories for the Lillebelt Bridge of for the top flange of the two box gird- Denmark. Figure 6. Storda Bridge. ers, as well as the majority of the deck. The end sections of the Storda and Bomla Bridges orthotropic plate were panelized with The “” project connects tapered ends, because only sidewalk three islands off the Norwegian coast In Russia loading is required. The transverse south of Belgen to the mainland with Russian engineers have standardized diaphragms are steel trusses between three bridges (Larson and Valen their orthotropic deck plates using the box girders. The diaphragms open or flat plate ribs as shown in required extra steel beams at the bot- Figure 1. They have several launching tom flange of the box girder above the solutions or standardized methods for bearings. The main box girder was Researchers continue pushing the superstructure across a shop fabricated in L-shaped sections to monitor the performance river or gorge. There are a limited that are 21 m long and 3.6 m deep. number of bridge case histories docu- The intermediate orthotropic welded of various rib types mented in English, but they provide an steel deck plate was shop fabricated in overall view of Russian techniques panelized sections 2.5 m wide and (Blank, Popov, and Seliverstov 1999). 11.5 m long. 2000). The entire project was complet- In the city of Arkhangel, Russia, a ver- ed in April 2001. The two orthotropic tical lift record span bridge of 120.45 The longitudinal ribs of the orthotropic steel deck suspension bridges are m was completed in 1990 (Stepanov deck and steel box girders are flat rib known as the Storda Bridge and the 1991). The Berezhkovsky twin parallel plates spaced at 0.35 m, and the Bomla Bridge. The Storda Bridge is bridges are multi-cell box girder spacing of transverse ribs is 3.0 m for 1,076 m long, has a main span of 677 bridges consisting of three spans of both components. The stiffening ribs of m, with towers 97 m high and a verti- 110 m + 144.5 m +110 m. Each bridge the main girder are located on both cal clearance of 18 m (Figure 6). The has four traffic lanes 3.75 m wide. sides of every web. The vertical split-T Bomla Bridge is 990 m long with a These bridges were the first to be ribs of the box girders were aligned main span of 577 m and the tower launched with inclined webs with the transverse ribs of the ribbed height is 105 m. The roadway of both (Surovtsev, Pimenov, Seliverstov, and plate, thus creating the integral inter- bridges is 9.7 m wide. Scanbridge AS Iourkine 2000). nal diaphragms. The longitudinal stiff- ening ribs are at a constant spacing

Welding Innovation Vol. XIX, No. 1, 2002 longitudinally. Plates connecting the panels and the diaphragms were weld- ed between ribs. The 20 m long edge sections and units for the transverse diaphragm, or bulkhead, were prefabri- cated. The bottom and inclined sides were placed first. Each 4 m deep transverse diaphragm or bulkhead was fitted. The edge sections were installed and finally the two deck panels were Figure 7. Twin crossing the Oka River, Russia (split–section). placed on top, completing a 20 m long subsection. The 31 bridge girder sec- along the bridge. Depending on the abutment to abutment where expan- tions for the main span were transport- web thickness, additional vertical stiff- sion joints and hydraulic buffers are ed from the fabrication yard in Finland ening ribs were required between the located. The 48 box girder sections on the three barges in the same way diaphragms. The superstructure was were fabricated at a shipyard in as the sections for the side spans, and erected using “continuous launching” Finland (Pedersen 1997). The stan- erected with a floating sheerleg crane, from one bank of the Oka River. The dard section is 20 m long with two 130 m boom, starting from mid-span shop-fabricated elements were added and proceeding towards the towers piece by piece to form a continuous (Edwards and Westergren 1999). structure at the “erection slip” area on this riverbank. The joints of the hori- zontal sections of the orthotropic deck In Ukraine and ribbed plates, as well as the joints South Bridge over the Dnipro River of the web of the main girder, were The 1992 signature span of the South automatically welded. The joints of the Figure 9. High Coast, Sweden Bridge over the Dnipro [Dnepr] River longitudinal ribs of the ribbed plate components. in Kyiv [Kiev], Ukraine is an unsym- were manually welded. All the remain- metrical cable stayed bridge with a ing joints used high strength bolts. sets of hangers each and weighs 320 main span of 271 m (Korniyiv and. tons (Figure 9). The 20 m long panels Fuks 1994). The main span side of the for the deck, sides and bottom were H-tower is a continuous three-span In Sweden fabricated with a maximum width of 10 steel box girder with orthotropic steel High Coast m. They were fabricated from steel deck. The back-span superstructure on The High Coast Suspension Bridge of plates, typically 9 to 14 mm thick,10 m the opposite side of the H-tower is a Sweden is almost the same size as long and 3 to 3.3 m wide. The ribs segmental prestressed concrete box San Francisco’s were 20 m long trapezoidal ribs with a section. Concrete construction for the (Merging with Nature 1998). The main plate thickness of 6 to 8 mm. shorter back span of 60 m was used span is 1,210 m long with suspended as a counter-weight mass equal to the The plates were placed on a plane longer orthotropic main span. The and welded in the transverse and lon- bridge carries a six-lane roadway, two gitudinal direction and the trough stiff- rail tracks and four large-diameter eners were fitted and welded water pipes (Figure 10). The total live

Figure 8. High Coast, Sweden, section. side spans of 310 m and 280 m. The width of the roadway is 17.8 m, allow- ing for a possible future extension to 4 lanes (Figure 8). The distance between the main cables is 20.8 m and there are 20 m between the hang- ers. The girder is continuous through the towers extending 1,800 m from Figure 10. South Bridge (cable stayed) of Ukraine (split–section).

Welding Innovation Vol. XIX, No. 1, 2002 load is about 246 kN/m. The three- was accomplished with two false work Design Institute Giprotransmost, (1991) “The span (80.5 m + 90 m + 271 m) contin- supports providing three equal spans Bridge-Crossing over the River Oka on the Bypass Road near Gorki” Structural uous steel box girders are made of of about 90 m. At the H-tower of the Engineering International, IABSE, Zurich, low-alloy steel with a minimum yield cable stayed bridge, hinged conditions Switzerland, Vol. 1, Number 1, 14-15 strength of 390 MPa. are provided by supports with limited Edwards,Y. & Westergren P., (1999), “Polymer rotational capability in the vertical and modified waterproofing and pavement system for the High Coast Sweden” NordicRoad & The bridge was divided into segments the horizontal planes. The torsional Transport Research No. 2, 28 that were shop-welded. Field splices rigidity of the bridge is supplied by the Korniyiv, M. H. and Fuks, G. B (1994) “The South were either welded or joined by high- two planes of cable stays, plus the Bridge, Kyiv, Ukraine” Structural Engineering strength bolts. Bolting was used where stiffness of the closed box sections. International, IABSE, Zurich, Switzerland, Vol. 4, Number 4, 223-225 automatic welding was impractical Under one-sided loading of the bridge Larsen J., and Valen, A., (2000) “Comparison of because of the short length of the (three traffic lanes), the deck cross Aerial Spinning versus Locked-Coil Cables weld or difficult access. The cross sec- slope of 0.3% was measured in field for Two Suspension Bridges (Norway),” tion of the twin two-cell box girder tests, less than the calculated value of Structural Engineering International, IABSE, 10(3), 128-131 bridge consists of six vertical webs, 0.35%. Eccentric hinged connections Mangus, A., (1988) “Air Structure Protection of the upper deck plate and the lower between the bottom flanges of the Cold Weather Concrete,” Concrete box flanges. The narrow cell is for the stiffening girders and the H-tower were International, American Concrete Institute, cable stayed bridge anchorage. In the constructed, considerably reducing the Detroit, MI, October 22-27 Mangus, A., (1991) “Construction Activities Inside central portion of the cross section bending moments in the girders. of Air Structures Protected From the Arctic that carries the two hot water supply Environment,” International Arctic Technology pipes, the lower flange was omitted to Conference, Society of Petroleum Engineers, preclude the undesirable effects of Conclusion Anchorage, AK, May 29-31 Mangus, A, and Shawn, S., (1999) “Chapter 14 unequal heating inside a closed box. The foregoing examples illustrate a Orthotropic Deck Bridges,” Bridge Engineering The bearings at the piers permit lateral range of creative responses to the Handbook, 1st ed., Chen, W.F., and Duan, L. displacement of the superstructure challenge of designing and construct- Editors, CRC Press, Boca Raton Florida because of the 41.5 m bridge width. ing orthotropic steel deck bridges in Mangus, A., (2000) “Existing Movable Bridges Utilizing Orthotropic Bridge Decks,” 8th Heavy The orthotropic decks, bottom flanges cold weather regions. The versatility, Movable Bridge Symposium Lake Buena Vista of the boxes and the webs have open economy and structural integrity of Florida, Heavy Movable Structures, P. O. Box flat-bar stiffening ribs, a common fea- welded orthotropic design undoubtedly 398, Middletown, NJ ture in Ukrainian and Russian bridges. will continue to inspire bridge design- Merging with Nature – Hoga Kusten [High Coast] (1998), Bridge Design & Engineering, 10, (1), Longitudinal flat or open ribs were ers and structural engineers in the 50–56 placed on the top face of the 21st century. Meaas, P., Lande, E., Vindoy, V., (1994) “Design of orthotropic deck plate under the rail the Salhus Floating Bridge (Nordhordland tracks, thus avoiding intersections of Norway),” Strait Crossings 94, Balkema, Figure Credits Rotterdam ISBN 90-5410 388-4 3(3), 729-734 longitudinal and transverse stiffeners. Figure 1 from Ballio, G., Mazzolani, F. M. 1983, Pedersen, C., (1997) The Hoga Kusten (High “Theory and Design of Steel Design Structures,” Coast) Bridge-suspension bridge with 1210 m This facilitated fabrication, at the same Chapman & Hall Ltd. courtesy of Dr. Mazzolani; main span –construction of the superstructure, time precluding stress concentrations Figures 2, 3, & 4 courtesy of Dr. Ing. A- Mondberg & Thorsen A/S Copenhagen, Aas–Jakobsen, AS Structural Engineering Denmark at crossing welds that would be sus- Consultants, Oslo, Norway; Figure 5 adapted from Rosignoli, M.,(1999) Launched Bridges – ceptible to fatigue under dynamic train Aune, Petter, and Holand, Ivar (1981); Figure 6 Prestressed Concrete Bridges built on the loading. Longitudinal ribs under the courtesy of Mr. L. Adelaide of Profilafroid, France; ground and launched into their final position, train tracks have a depth in excess of Figures 8 & 9 courtesy of Claus Pedersen of ASCE Press, Reston, VA Mondberg & Thorsen AS, Copenhagen, Denmark; Stepanov, G. M., (1991), “Design of Movable the design requirements, which per- Figures 7 & 10 courtesy of IABSE International Bridges,” Structural Engineering International, mitted longitudinal profile adjustments Association of Bridge Structural Engineers. IABSE, Zurich, Switzerland, Volume 1, of the tracks after erection of the Number 1, 9-1 bridge superstructure. The steel gird- Surovtsev, V., Pimenov, S., Seliverstov, V., & Iourkine, S, (2000) “Development of Structural ers were pre-assembled on the bank References Forms and Analysis of Steel Box Girders with of the south and erected by launching. Aune, P., Holand, I. (1981) Norwegian Bridge inclined webs for operation and erection condi- The twin two-cell box girders were Building – A Volume Honoring Arne Selberg, tions” Giprotransmost J.S.Co, Pavla equipped with a launching nose and Tapir, Norway Kortchagina str. 2, 129278 Moscow, Russian Blank, S. A., Popov, O. A., Seliverstov, V. A., (1999) Federation stiffened with a temporary strut system “Chapter 66 Design Practice in Russia,” Bridge Troitsky, M. S., (1987) Orthotropic Bridges - Theory (Rosignoli1999). Single erection rollers Engineering Handbook, 1st ed., Chen, W.F., and Design, 2nd ed., The James F. Lincoln Arc were used at the tops of supports and and Duan, L. Editors, CRC Press, Boca Raton Welding Foundation, Cleveland, OH had a friction factor of less than 0.015. Florida The erection of the 271 m main span

Welding Innovation Vol. XIX, No. 1, 2002