The Third Bosphorus Bridge: a Milestone in Long- Span Cable Technology Development and Hybrid Bridges

Structural Engineering International

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The Third Bosphorus Bridge: A Milestone in Long- span Cable Technology Development and Hybrid Bridges

Matthieu Guesdon (Head of Cable Structures Division), Julien Erdem Erdogan (Technical Director) & Ivica Zivanovic (Deputy Technical Director)

To cite this article: Matthieu Guesdon (Head of Cable Structures Division), Julien Erdem Erdogan (Technical Director) & Ivica Zivanovic (Deputy Technical Director) (2020) The Third Bosphorus Bridge: A Milestone in Long-span Cable Technology Development and Hybrid Bridges, Structural Engineering International, 30:3, 312-319, DOI: 10.1080/10168664.2020.1775536 To link to this article: https://doi.org/10.1080/10168664.2020.1775536

Published online: 10 Jul 2020.

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Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=tsei20 The Third Bosphorus Bridge: A Milestone in Long-span Cable Technology Development and Hybrid Bridges

Matthieu Guesdon, Head of Cable Structures Division; Julien Erdem Erdogan, Technical Director; Ivica Zivanovic, Deputy Technical Director, Technical Department, Freyssinet International & Cie, Rueil-Malmaison, France. Contact: [email protected] DOI: 10.1080/10168664.2020.1775536

Abstract the third link between Europe and extension of the main span to 1408 m Asia (Fig. 1) . It serves the purpose of was one of the first major steps in the The Yavuz Sultan Selim Bridge is a high- adding another crossing to the two, design. This long span, associated rigidity suspension bridge, combining already congested, crossings, both of with the requirement for a similar aes- stiffening stay cables and suspension which are suspension bridges, located thetic to the two first Bosphorus cables. It features a 1408 m central close to Downtown Istanbul. The bridges and the railway constraints span, and supports a railway and a bridge is one of the main components (loads and deformations), led the motorway with a 58.5 m wide deck of the North Marmara Causeway, design team to look for innovative sol- between stiffening stay cable designed as a bypass for the city of utions to enable the use of a stream- anchorages. The design of the stiffening Istanbul, which is widely affected by lined box girder. stay cables for this bridge required massive traffic issues. several developments to cater for the The high-rigidity suspension bridge exceptional needs of the longest and was then imagined, based on the heaviest stay cable in the world. The Project Context concept of a hybrid cable-stayed usual strand grade would not meet the The initial tender was launched as part suspension bridge. Although this — project forces and 1960 MPa strands of a concession project. It requested concept is not new in itself it was had to be qualified, for all the the design of a suspension bridge, used for the famous Brooklyn — anchorage units within the range, up to with a main span of 1275 m minimum, Bridge in New York (Fig. 2) the 151 strands. Such qualification is, and whose aesthetics should recall dimensions required for this bridge however, only the tip of the iceberg as those of the two first crossings. It was clearly make it a proper mega- many other tailor-made components requested to carry four lanes of structure. had to be developed. Heavy-duty highway in each direction, making The Third Bosphorus Bridge was deviators needed to be proof tested for eight lanes in total, two railways, and hence designed as a cable-stayed stif- fatigue and wear and were a vitally two pedestrian sidewalks for inspec- fened suspension bridge with a main important part of the design. Long- tion and maintenance purposes. These span of 1408 m and a total length of stroke hydraulic pistons had to be challenging requirements came with a 2250 m, as described in Fig. 3. qualified for performance, long-term very short time-frame allowed for the resistance to corrosion and ageing. design and the construction: 36 The A-shape pylons were constructed months were allowed for both the in concrete and both exceed 320 m, Keywords: stay cable; damping; design and the construction of the making them comparable in size to rotations; performance; qualification; iconic structure, to be designed as a the Eiffel Tower, as highlighted in methods proper landmark. Fig. 4. The main span design was based on a single-level deck made of The tender for the concession, which a streamlined orthotropic steel deck. included a full section of motorway, It is supported in its 312 m central Introduction was launched by the Republic of Turkey Transportation Maritime and The Third Bosphorus Bridge, also Communication Ministry, General known as the Yavuz Sultan Selim Directorate of Highways (KGM). The Bridge, is a high-rigidity suspension joint venture that won the tender bridge located on the Bosphorus decided to subcontract the bridge con- Strait in Istanbul, Turkey. Designed struction as part of an engineering, pro- and built between 2013 and 2016 as curement and construction contract. part of a fast-track project, its unique The same design team that had features—several of them making it initiated this challenging design for either a world first or a world record the concessionaire earlier in the —required the design and qualification tender was retained for the construc- of stay cable technologies beyond pre- tion phase, while the design, engineer- viously established limits. ing and construction of the stiffening stay cables was subcontracted to the ’ Bridge Situation authors company. Location Bridge Geometry and Concept The bridge, located at the northern To avoid complicated offshore works Fig. 1: Location of the Third Bosphorus extremity of the Bosphorus Strait, is in building the pylon foundations, the Bridge on the Strait

312 Technical Report Structural Engineering International Nr. 3/2020 deformations had the most impact. Although the bridge concept aimed to enhance the overall rigidity, the structure remains a cable structure, with inherent ﬂexibility. This problem was anticipated, but the order of magnitude of the ﬁnal values deriving from the dynamic studies still posed some problems. The suspension of the central part of the deck was carried out with two rows of hangers, each anchored 6 m Fig. 2: Brooklyn Bridge, 1883: 487 m main span away from the deck’s longitudinal axis. Compared to the overall deck width (58.5 m), this is quite low and resulted in a tendency for torsional behaviour of the deck. Moreover, the exceptional live loads to be considered (eight lanes of highway and two railways) increased the cable rotations owing to large sag variations. These large cable force and sag variations led to two direct issues that needed to be solved by the design team:

(1) The allowable stress ratios under Fig. 3: Yavuz Sultan Selim Bridge, main dimensions the design codes need to be checked, given the high live loads. (2) The large sag variations interfered portion by two main cables, each made The longest of these stiffening stay with the deck’s geometric defi- of 113 strands of 127 wires of 5.4 mm cables is 597 m long, making it the nition and design. diameter, and 68 hangers. The rest of longest parallel strand system (PSS) fi the rst 548 m of the main span is sup- cable installed to date, and weighs fi ported and rigidified by 88 stiffening almost 120 tonnes. This highlights the The rst of these two issues was that, stay cables, varying from 65 to 151 advantages of PSS cable systems for owing to the high live load, cable strands of grade 1960 MPa. The side such long-span bridges, as the installa- needed to be tensioned to very low per- spans resting on intermediate pier sup- tion of all cables was performed using manent stress so that allowable service ports and ground approaches were the available tower cranes and light force limits were not exceeded. This constructed in concrete and are used equipment such as winches (Fig. 5). decreased the cable stiffness owing to as counterweights. On each side span, the increase sag, and hence reinforced the inherent structural tendency to 17 pairs of stiffening stay cables were Project Problematics anchored into the side-span concrete produce large sag variation and displa- box girder, while the five longer pairs cements, along with the increased risk Tight Design and Construction of vibrations. of stiffening stay cables were anchored Schedule directly into the main cable anchor This issue was solved by using block. The main project constraint was the 1960 MPa grade strands: a world first extremely tight time-frame of 36 on such a major cable-supported months allowed for both the design bridge. and construction. This was dealt with by assuming some conservative input This was clearly demonstrated by the data for particular items and by design team, as illustrated in the fol- adding more refined data during the lowing simplified approach. It is not design phases. as exhaustive as a full-detail design should be, but illustrates very well the This led to several design adjustments fi fi bene ts of 1960 MPa strands, more and unplanned ndings, and necessi- than simply increasing the resistance tated design changes and additions of of the cables. components. V By defining a ratio b = , with G G + V Significant Structure Deformations the dead load and V the live load, one and Cable Rotations can estimate the permanent force in Among all the issues which arose with the cables based on the maximum Fig. 4: Comparison of pylon dimensions the stay cable design, structural force allowed under service limit state

Structural Engineering International Nr. 3/2020 Technical Report 313 The longest cable, used as an example, had the following dimensions: chord length L = 597.092 m, horizontal length l = 553.693 m and volumetric 3 mass γcb = 9200 kg/m . The assessment of the secant modulus of this cable between the permanent stress and the maximum service stress can be computed using the following formula:

1 = 1 Esec E g2 × l2 s + s + cb ( perm max ) (4) 2 × 2 Fig. 5: Yavuz Sultan Selim Bridge, main span cross-section 24 sperm smax conditions: from execution studies was: The previous computation of permanent stress and maximum service stress yields the results displayed in ≈ − 269 Fperm (1 b)Fmax (1) b = = 0.364 Table 1. 470 + 269 In a similar manner, as a probably Such force depends on the allowable As a comparison, the same ratio for the more intuitive and visual approach, stress in the cables, given as a fraction Russky Island Bridge in Russia, with the orthogonal sag can be compared of the guaranteed ultimate tensile two times three traffic lanes and a for the different grades of strands and stress (GUTS): fi span of 1104 m, was 0.151, which is a applicable quali cations for the stay much more usual live load to dead cable system to be used. It can be computed as follows: smax = k sGUTS (2) load ratio. The final β value will be retained as a g L2 g L2 where k is a fractional parameter, reference to illustrate the benefits = cb = cb f − (5) which can be either 0.45 or 0.5, as per deriving from the use of 1960 MPa 8sperm 8(1 b)k sGUTS both fib Bulletin 30 and CIP rec- strand on a stay cable system qualified ommendations, depending on the qua- under both the fib and CIP A comparison of respective sags for the lification of the stay cable system in the recommendations. different cases can be found in Table 2. fib, and on the effective mitigation of Now that the β ratio has been demon- Such sag reduction leads to a reduction in bending stress and angular deviations. strated, the comparison shown in the tendency of cables to vibrate with Based on the above, one can define: Table 1 can be made in respect of the large amplitudes at low frequencies, permanent and maximum service stres- whichisamajorfactorinuserdiscomfort. ses. This increase in service stresses ≈ − Finally, the benefit of using higher sperm (1 b)smax leads to increases in what really strand steel grades in stay cables can = − matters for designers, especially in the (1 b)k sGUTS (3) be highlighted by computing the very first stages of such a design of a Irvine parameter λ2, which is a direct long-span cable structure, namely stiff- indication of the sagging behaviour of The Yavuz Sultan Selim Bridge, with ness and sagging behaviour. its eight traffic lanes and two railway cables as far as vibrations are con- lines, has a very high live load to dead Looking at the secant modulus of the cerned. It is generally understood that load ratio. This ratio is higher than longest cable give the first insight of the lower this parameter is, the closer 0.6, which is outside the range of the impact of using 1960 MPa strand. the cable vibration will be to that of a usually experienced values. In detail, an initial calculation of the β ratio yielded the following results: Standard stay cable Stay cable system Stay cable system system: 1860 MPa qualified as per fib/CIP: qualified as per fib/CIP: strands 1860 MPa strands 1960 MPa strands 339 = = . σ b + 0 419 perm 532 591 623 470 339 (MPa) σ σ σ σ This ratio changed throughout the max (MPa) 0.45 GUTS = 837 0.5 GUTS = 930 0.5 GUTS = 980 project development, owing to the Esec (MPa) 170,243 176,309 178,801 optimization performed by the designers and based on expert review Stiffness 0.0 3.6 5.0 and analysis of the various code gain (%) requirements. The final value deriving Table 1: Permanent, maximum service stress and secant modulus improvement

314 Technical Report Structural Engineering International Nr. 3/2020 Standard stay cable Stay cable system Stay cable system system: 1860 MPa qualified as per fib/CIP: qualified as per fib/CIP: strands 1860 MPa strands 1960 MPa strands f (mm) 7702 6932 6578 Sag – −10% −15% decrease Sag ratio 1/78 1/86 1/91 H (N) 9,599,390 10,665,989 11,238,792

Le (m) 598 598 598 λ2 4.60 3.36 2.87 Fig. 6: Geometric interference Table 2: Cable sag and Irvine parameter reduction taut string. Sagging effects can often be This issue was slightly more compli- the damper position being located neglected for λ2 <1. cated to solve. Indeed, the deck geo- further away on the cable, and hence metry and the various road higher compared to the deck level 2 dimensions were set when the final 8f L (Fig. 10). l2 = (6) cable rotations values were calculated. L HLe EA Increasing the cable anchor pipe was then only possible up to a diameter High Damping Requirements and fi where H is the horizontal component that would t within the deck geometry Low Cable Forces of the cable force, L is the cable devel- and not interfere with the collapse e fi oped length, zone of the road barrier (Fig. 6). The project speci cation for the cable damping specified an added damping These two requirements were found to in logarithmic decrements, with the fol- f 2 be impossible to achieve simul- L = L 1 + 8 (7) lowing values: e L taneously without impacting either the deck geometry or the road clearance. . vertically (δz): 4% for stiffening stay cables 1–8 in the back span and main E is the modulus of elasticity of the To overcome this deadlock, the decision span; 6% for stiffening stay cables cable (195,000 MPa), and A is the was made to create a fixed point within between 9 and 22 in the back span steel section (corresponding to 142 the anchor pipe to move the cable and main span strands of 150 mm2 strand in the rotation point away from the anchorage. . transversally (δy): 70% × δz. example, hence 21,300 mm2). A com- This was practically made using fixed parison of the Irvine parameters for deviators, which will be described in These requirements converted into each of the studied cases is provided detail in a later section. Scruton number values ranging from in Table 2. These deviators were installed in two Sc =10 to Sc = 17 on the most dam- Again, and as a comparison, the longest configurations, depending on the struc- pened cables. These high performances cable on the Russky Island Bridge, tural arrangement of the anchor pipe: were considered applicable for two to which was 580 m long, had an Irvine par- at the anchor pipe upper extremity four modes of vibration of cables, ameter λ2 = 1.35, evidencing a much (above the deck) for all back span depending on their length. Moreover, lower sagging behaviour of the cables. cables and main span cables 1–10; or a very small activation amplitude was at the upper end of the structural specified to engage the damping for The use of 1960 MPa grade strands anchor pipe in the box-girder web for vibrations as small as 10 mm. needed some stay cable technology main span cables 11–22. development and qualification, as Such stringent criteria, combined with described in the later sections of this This latter set-up allowed, in particular, the presence of deviators moving the article, but allowed the designer to very efficient and robust drainage for cable rotation point away from the achieve a more efficient design, com- the longest critical cables in the main anchorage, as well as sagging cable bining the required strength, stiffness span, as the anchorage tube is inter- with an Irvin parameter λ2 > 1 as men- and sag. rupted (Figs. 7–9). tioned above, led to an external hydraulic damper being designed, With regard to the second issue, the The addition of such devices limited allowing the damper to be located at large sag variations induced cable dis- the cable displacements and hence an appropriate distance to dissipate placements within the anchor tube at limited the anchor pipe diameter. enough energy. their extremity. Such angular devi- However, they impacted: (a) the ations can reach up to 31 mrad in design of the anchor pipe, which These dampers, more specifically service conditions and 45 mrad at ulti- should withstand the transversal load described below, ensured the required mate state. To avoid cable damage, derived from the restrained cable devi- performance, while accommodating the diameter of the tube has to be ations, and (b) the position of dampers, enough strokes so that the sag vari- defined so that the cable can move as the rotation points moved away ations could occur freely, with no risk freely without any harmful contact. from the anchorage, which resulted in of damage to the pistons.

Structural Engineering International Nr. 3/2020 Technical Report 315 Fig. 9: Cable labelling

which made the decision to perform the whole design of the bridge with 1960 MPa grade strands not only possible, but also safe as far as the delivery Fig. 10: Anchorage compatible with planning was concerned. 1906 MPa grade strands

Fixed Deviators to the stiffening stay cable, (b) piston stokes must cater for the all cable The use of fixed deviators was chosen to cope with the project-specific quasi-static displacements under rotations as well as the geometric con- service conditions as well as during straints. This type of product is well vibrations from the smallest to the known in the stay cable industry as largest amplitudes, and (c) the piston they were widely used in the 1990s set-up must be stable under all service positions, and prevent instabilities. before anchorage designs evolved, and were upgraded with high-perform- This condition led the designers to Fig. 7: Fixed deviator guiding principle: ance bending guides and anti-fatigue choose a four-piston rather than a – cables 1 10 features, such as the H2000 built-in two-piston arrangement, to ensure the bending guide which can accommodate appropriate behaviour of the damper Cable Technologies angular deviations greater than at its most extreme positions (Fig. 50 mrad (Figs. 11, 12). 13): (a) the mast had to meet the fi Anchorage and 1960 MPa Strands The new fact to be considered for the minimum stiffness de ned in the project was the significant transversal damping study, and (b) the damper As mentioned above, the use of design should be made with robust load—up to 100 tonnes for 151 strand 1960 MPa grade strand enabled the and reliable technologies and cables—to be withstood without dama- designers to solve structural issues materials. induced by the large live loads. These ging the cable sheathing, and limiting strands have been available since the bending stress in the cable to allowed Owing to the design of these dampers, late 2000s, but they had not been values. This challenge was tackled as well as the service conditions used on a major infrastructure project with the use of mechanical collars, fea- already being very harsh, it was before the Third Bosphorus Bridge turing six packs of heavy-duty wedges decided to select simple and robust project, where they became a key to provide a self-blocking assembly, technologies. Pistons were thus feature. both transversally and longitudinally, designed as pure viscous pistons, with guiding the cable with the ad-hoc linear symmetrical behaviour: the Meanwhile, their reliability, as well as material and curvatures. resisting force applied by the piston their full compatibility with the the cable is the product of a viscous ’ authors company stay cable range coefficient times the cable displace- fi External Dampers (Fig. 10), had been quali ed through ment velocity. The viscous coefficient research and development and full- The external hydraulic dampers also was selected and optimized cable per scale testing. When the project presented some very serious chal- cable, and ranged from 75 to required the use of the highest grade lenges. Even though the concept is 110 kN.s/m. of strands, their qualification for the not novel, many enhancements were whole range was already available, needed to meet the demanding project requirements. The masts needed to be structurally optimized to deliver a fine-tuned stiffness, allowing the computed performance to be guaranteed. Moreover, geometric constraints as highlighted above (road clearance, collapse zone for the barrier, etc.) deeply impacted the geometric studies for the damper. Eventually, three different shapes were defined, taking into account the following requirements: (a) pistons Fig. 8: Fixed deviator guiding principle: have to be perpendicular to the cable Fig. 11: Fixed deviator before installation in cables 11–22 to avoid axial forces being transferred anchor pipe

316 Technical Report Structural Engineering International Nr. 3/2020 Fig. 12: Piston installed perpendicular to cable plan

Moreover, it was required that the Fig. 15: Main span damper set-up height of the dampers should be set so that they would remain aligned or Fig. 14: Back span damper set-up vary smoothly to achieve a better H2000 anchorage, but the use of large units with up to 151 strands raised con- architectural result. The damper dis- Unfortunately, such a design was not tance from the cable rotation point compatible with the deck geometry cerns from the end client. A full-scale varied from 2.5% of the cable’s effec- for the main span cables, the fatigue and tensile test as per the CIP tive length on the shortest cables to anchorages of which were located on recommendations was hence orga- 4% of the cable’s effective length on the edges of the box girder. One nized with the Construction Technol- the longest cables in the main span. additional constraint for these ogy Laboratory in Chicago, which dampers was the location of the wind provides the most powerful capacity All these design constraints con- worldwide. The use of the biggest of sidered, the definition of back span screen on the deck edge, providing a tiny clearance to fit the mast. This led their test benches was necessary to damper was straightforward. The clear- achieve the test load: a sample of 127 ance provided in the cable plan in the to an asymmetrical piston set-up being defined, providing less damping strands of grade 1960 MPa together back span was wide enough to choose with its fixed and adjustable H2000 a symmetrical set-up with two sets of in the transversal direction while remaining compliant with the project anchorages was successfully tested, pistons on each side of the reaching a final load of almost 36 MN specification, as illustrated in Fig. 15. cable (Fig. 14). Piston angles were and almost reaching the maximum fi de ned to provide the required multi- This would not be sufficient, however, load of the test bench. directional damping. to respect the damper strokes required to accommodate the large cable displacements, tending to increase signifi- Deviator Testing cantly the size of the piston for the The use of deviators with such frequent longest cables. To overcome this issue, large deviations concerned the client an innovative and play-free connection with regard to the resistance of the was designed to connect the piston on deviators themselves, but above all its body, instead of its extremity. This with regard to the durability of the made possible the design of compact fi high-density polyethylene sheathing masts, tting between the wind of the strands, which should remain Fig. 16 screens and the road barrier ( ). undamaged to guarantee the 100 year The most dramatic development was design life of the cables. An ambitious that of the pistons themselves. qualification testing process was then Indeed, the very large cable rotations, together with the need to allow free cable displacement under all service conditions, required the design of hydraulic pistons with extra-long strokes. Thus, pistons with up to ± 920 mm strokes were designed and qualified without trigger effects to meet the project specifications.

Qualiﬁcation and Full-Scale Testing Fatigue Testing: 127 Strand Cable, 37.3 MN Breaking Load Fig. 13: Piston arrangements: likely Fig. 16: External hydraulic damper: instability in offset position (above) and The use of 1960 MPa grade strands had ± 920 mm stroke and innovative piston chosen set-up (bottom) already been qualiﬁed on the standard connection

Structural Engineering International Nr. 3/2020 Technical Report 317 launched to make sure that all risks checked, so that energy dissipation is were mitigated and performances ensured whatever the outside tempera- ensured. ture and the number of vibration cycles. Wear and Resistance of Strand The capacity of the installed external Sheathing hydraulic dampers was then demon- The resistance of the sheathing was strated, showing that they are ready checked for both short-term resistance to cope with their demanding daily under transversal load and creep. This tasks for years to come. was carried out using the full-scale Fig. 18: 109 strand test assembly under hydraulic presses. Conclusions The potential wear of strand sheathing mock-up cable including one fixed against the deviator material and and one adjustable H2000 ancho- The Third Bosphorus Bridge, also between strands was assessed on a rage and two deviators. The test known as the Yavuz Sultan Selim fatigue test bench including a transver- was organized at the MPA labora- Bridge (Fig. 20), has pushed the stay sal force on the bundle to simulate a tory in Braunschweig, which has cable technologies further, going transversal deviation and displace- 30.5 MN testing capacity together beyond previous mega-structures such ments of strands within the bundle with a transversal pulsating feature as the Russky Island Bridge. Major (Fig. 17). More than 27 km of strand (Fig. 18). enhancements of existing technologies fi cumulative displacement simulated The test was performed to represent were required, all quali ed through the actual wear related to the effect an exhaustive process that has rede- the most critical case expected to be fi of combined axial and bending encountered on the project, as per the ned the limits of stay cables for fatigue, and demonstrated the ade- design team’s instructions, and on the mega-structures. quacy of the design to ensure the biggest unit possible. Based on the above simple parametric long-term performance of the sheathed calculations, it is shown that the poss- strands. The test bench capacity allowed for 109 fi cable strands of grade 1960 MPa to be ible bene ts of ultra-high steel strand tested, and the test parameters were grades extend far beyond the increased Fatigue and Bending of Strands as follows: 2 million cycles; 125 MPa resistance or higher safety factors that The fatigue resistance of strands to of axial stress variation; and an envel- one could expect. bending fatigue in the deviator area ope of 12 mrad of angular deviations, Indeed, they allow both (a) stiffer was qualified through multiple mono- with the peaks synchronized with the cable systems to be achieved by strand testing with project-based axial stress peaks. setting higher permanent forces in the fatigue parameters: 12 mrad deviation The fatigue test criteria were to com- stay cables, while remaining compati- amplitude for bending fatigue and plete the fatigue cycles without any ble with the serviceability criteria 125 MPa of axial stress variations, fi cracking or failure of any components, de ned in international with synchronized peaks to ensure including the strand sheathing that the testing was conservative (Fig. 19). enough. All of the tests performed resulted in final breaking loads higher The tensile test criteria were standard than 100% GUTS, significantly for this kind of test, and a minimum exceeding the 92% actual ultimate value of 95% of the cable GUTS and tensile strength (AUTS) criteria and 92% of the AUTS had to be reached confirming the high benefit of the devi- before the cable broke or featured ation profile and material designed. excessive yielding.

Full-Scale Testing Hydraulic Piston Testing The end process of this qualification Hydraulic pistons are a key component was a full-scale test on complete of the external hydraulic dampers, and as such also require stringent qualification to ensure that the project specifications have been met. In particular, the piston endurance was tested in real conditions of displacement, speed and damping force over more than 400 km of cumulative strokes to check that the damping coefficient is not altered over time and that no damage (leakage, coating, ageing, etc.) is likely to occur. Fig. 17: Transversal test of deviator and Moreover, the impact of temperatures Fig. 19: Axial and bending fatigue test strand sheathing ranging from −20°C to 60°C was principle

318 Technical Report Structural Engineering International Nr. 3/2020 important milestone on long span cable stayed structure developments. IABSE Conference, September, Nantes, France, 2018. Novarin M, Erdogan J, Fabry N, Ambor M, Petit M. High rigidity suspension bridges, IABSE Conference, September, Nantes, France, 2018.

SEI Data Block Fig. 20: Final cable system at night Owner: Turkey Transportation Maritime and recommendations, and (b) reduced Disclosure statement Communication Ministry, General sagging behaviour, avoiding negative Directorate of Highways (KGM) impacts on the cable modal shape and No potential conflict of interest was Contractor: the consequent complications of the reported by the authors. IC Ictas Insaat and Astaldi Construction (ICA) design of anti-vibration systems. Design Team: The Yavuz Sultan Selim project Further Information Michel Virlogeux, T-Engineering and demonstrated the applicability of Bureau Greisch higher strand steel grades for the For further reading on this topic please see: Engineering and construction: design of long-span cable-supported Farooq A. Third Bosphorus Bridge—an over- Hyundai Engineering & Construction structures, as well as the existence of view. IABSE Conference, September, and SK Engineering & Construction a reliable supply chain capable of deli- Vancouver, Canada, 2017. (HDSK); Freyssinet vering any kind of project, from the Virlogeux M. Long span bridges. IABSE Concrete (t): 230,000 smallest ones to mega-projects. It Conference, September, Nantes, France, 2018. Structural Steel (t): 57,000 paved the way for the use of de Ville de Goyet V, Propson A, Peigneux C, Construction Iron (t): 50,000 2160 MPa grade strands, which have Duchene Y. The Third Bosphorus Bridge—erec- Cables (t): 28,000 been recently made available on the tion sequences of the main span. IABSE market and qualified for use in stay Conference, September, Nantes, France, 2018. cable applications, with the first Erdogan E, Zivanovic I, Guesdon M. The Yavuz project to be delivered in 2020. Sultan Selim Bridge cable technology: an

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