River Irwell Crossing—UK's First Network Arch Bridge

Structural Engineering International

ISSN: 1016-8664 (Print) 1683-0350 (Online) Journal homepage: https://www.tandfonline.com/loi/tsei20

River Irwell Crossing—UK’s First Network Arch Bridge

Rusi Rusev, Rufus Foster, Tim Abbott & Athanasios Bistolas

To cite this article: Rusi Rusev, Rufus Foster, Tim Abbott & Athanasios Bistolas (2019) River Irwell Crossing—UK’s First Network Arch Bridge, Structural Engineering International, 29:2, 306-314, DOI: 10.1080/10168664.2018.1516126 To link to this article: https://doi.org/10.1080/10168664.2018.1516126

Published online: 11 Dec 2018.

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Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=tsei20 River Irwell Crossing—UK’s First Network Arch Bridge

Rusi Rusev, Principal Engineer; Rufus Foster, Assistant Engineer; Tim Abbott, Project Director, Mott MacDonald, Croydon, UK; Athanasios Bistolas, Associate, Mott MacDonald, Altrincham, UK Contact: [email protected]. DOI: 10.1080/10168664.2018.1516126

Abstract maintenance, typical for railway infra- inclined at 6o to further enhance the structure, had to be satisfied whilst appearance. fi The rst network arch bridge in the ensuring buildability within a very con- fi The newly built infrastructure incor- UK was opened to traf cinstrained site. December 2017 and supports a new porates a footbridge that spans the railway line that connects Piccadilly The functional requirements for the river beneath the arch bridge, offering and Victoria Stations in the heart bridge are to carry two railway tracks relatively close views of the deck fi of Manchester. Set alongside heritage on a curved alignment over the River sof t. This led to an arrangement of structures of great significance, Irwell with a structural span of 89.0 m the deck elements that forms clear aesthetics is paramount and has led to and overall deck width of 15.4 m. The and regular features. “ ” an asymmetric ribbon form that general arrangement is presented in The bridge articulation is of conven- visually connects different types of Fig. 1. tional form utilising one fixed bearing, structures. The highly constrained site The project specific requirements sti- two guided bearings and one free necessitated an unconventional pulated that in addition to allowing bearing. piecemeal erection sequence over the for one-at-a-time hanger replacement river on asymmetric temporary towers. fi The early appointment of steelwork without traf c blockage, the bridge fabricator and erector informed build- This required a detailed erection should be sufficiently robust to accom- analysis of a complex methodology ability and fabrication costs thus redu- modate the accidental loss of four cing the number of design iterations. and special measures had to be taken hangers in series. Requirements to to facilitate erection within acceptable facilitate maintenance had to be construction tolerances. addressed from the onset of the design Key Structural Components Keywords: network arch; design; with the client favouring open type Arch Ribs construction; structural monitoring structural sections where practical. The inclined arch ribs whose depth The aesthetic aspiration was to achieve varies constantly along their length a visually continuous ribbon for the are designed with a weathering steel entire length of the viaduct that con- box section. Preliminary studies were Introduction nects structures of different typologies, undertaken to investigate the feasi- i.e. arch and girder, in a perceivably River Irwell Crossing is the signature bility of an open cross section, but it “fluid” fashion. The linkage between piece of the Ordsall Chord Viaduct was demonstrated that this would be curved and straight elevation is realised which provides a direct link between more expensive in terms of fabrication by a non-structural reverse curvature Manchester Victoria and Piccadilly and maintenance costs if the desired arch component that is attached to the stations as part of Network Rail’s appearance of the arch is to be substructure portal between two sec- Great Northern Rail Project. The new achieved. tions of the viaduct. This arrangement bridge is located in the centre of Man- is illustrated in Fig. 2. The arch axis is based on a circular arc chester and is designed to satisfy the within the inclined plane and the struc- aspiration for a landmark structure. It The visual relationship between the tural depth varies linearly along the arc is built within a constrained site and rise and fall of the two curves was length from 700 mm at the south in close proximity to assets of signifi- investigated parametrically until a bearing to 2500 mm at the opposing cant historic value. This paper dis- desirable balance was found. This end where it joins with the reverse cusses the design and construction investigation was performed within curve. To account for the increase in process employed to achieve the the context of the structural perform- section towards the deep end, the client’s aspirations. ance, mainly in terms of overall stiff- arch was divided into three regions ness and key member forces, to having plate thickness of 60 mm, Design Development ensure a viable design. Such balance 50 mm and 40 mm. was achieved with a rise to span ratio The visual transition between the Overall Concept for the arch of 0.1525 (Fig. 1). closed section for the arch ribs and The bridge is located in a highly urba- The visual weight of the ribbon is hea- the open section used for the approach nised environment and is in direct viest towards the central portion of the bridge is accommodated within the proximity to protected historic struc- viaduct, where the comparatively large reverse transition curve. This is tures, so the aesthetic quality is of substructure is located, and gradually achieved through the introduction of significant importance and every part reduces towards the extremities creat- a “fold” in the arch section web plates of the design process had to respect ing the perception of light touch at and a series of shaped stiffeners along that.1,2 At the same time, the require- the interfaces with the existing infra- the adjoining components. Visually ments for robustness and ease of structure. The arch planes are inwardly the solid “fold” line along the arch rib

306 Technical Report Structural Engineering International Nr. 2/2019 Fig. 1: General arrangement was followed by discrete points on the the rules to 10o deviation from right The comparison in terms of normalised shaped stiffeners (Fig. 2). angle for joined plates and as such eigenvalues demonstrated that the effi- does not explicitly address the design ciency of the crease in restraining local The definition of the crease posed an of the geometry at hand. A numerical buckling in the plates is very similar to interesting problem that influenced study was undertaken to demonstrate that of a flat stiffener, i.e. at almost not only the shape of the arch cross the efficiency of the crease in compari- 90%. This was important particularly section, but also that of the tie son with an efficient flat plate stiffener. for the deep regions of the arch since member and as a consequence the This was achieved by performing linear it eliminated the need for local longi- end nodes. This necessitated the geo- elastic buckling analysis on a set of tudinal stiffening which would have metry to be derived iteratively local finite element (FE) models cap- increased the fabrication cost. through a parametric study. The main turing the case at hand, a rectangular aim was to avoid geometric warping unstiffened box having the same The fold in the webs introduced some of the plates forming the arches which overall dimensions and a stiffened rec- design challenges with respect to the was achieved by maintaining a con- tangular box. These cases are illus- inclusion of the radial forces generated stant inclination of each web plate in trated in Fig. 4. by the arch curvature. The out-of-plane a truly vertical plane perpendicular to the bridge axis. This significantly reduced fabrication complexity and cost. The geometric parameters considered in the study comprised sectionheightandwidthatthestart and the end of the arch axis, the offset of the crease line from top edge and the inclination of the web plates. The main target was to ensure that the centroid of the section did not deviate from the arch axis. In addition, the available width of the arch bottom flange was checked at the interface with the tie beam to ensure that no undue geometric restrictions were imposed. The resulting parameters for the cross section are illustrated in Fig. 3. The fold in the web is utilised both aesthetically and structurally. The Eurocode3 limits the applicability of Fig. 2: Transition between main span and approach structure (© Mathew Nichols Photography)

Structural Engineering International Nr. 2/2019 Technical Report 307 the section is based on a reduced allow- able yield stress back-calculated from the von Mises criterion and accounting for the transverse stresses. This two-step veriﬁcation is performed iteratively since the normal stress distribution is dependent on the effective section. An in-house design tool was developed to allow the quick veriﬁca- tion of a large number of cross sections that allowed direct linkage with the parametrised geometry and the global analysis output.

Hanger Networks The overall layout of the hanger networks is developed following the classic concept of directing the resul- Fig. 3: Geometrical definition of the arch ribs cross section tant radial forces, aligned with the apparent intersections of the hangers’ axes, towards a common focal point. Such an arrangement provides uni- formity in the hanger force from evenly distributed loading, e.g. perma- – nent loads.5 7 However, the network layout is adjusted from the theoretical arrangement to account for the varying depth of the arch rib. The adjustment achieved commonality of the anchorage nodes along the arch soffit which provided visual rhythm and con- sistent structural detailing (Fig. 5). Fig. 4: Normalised local buckling eigenvalues to determine the efficiency of the “crease” Each network is separated in two planes to facilitate the installation and bending of the plates generates a It is notable that the transverse stress is stressing of the hangers as well as complex stress state when combined considered as a total stress and is not their replacement during the service with the normal effects. This was separated into axial and bending com- life of the bridge. The hanger planes addressed by performing the design ponents as in the standard form of the are set at 210 mm apart to facilitate fab- fi veri cation in two stages. equation. This is due to the fact that rication of the tie beam anchorages and the transverse diaphragms at the First a reduced stress method check is the installation of the hangers (Fig. 6). hanger anchorages restrain the folded performed for each of the panels web against buckling due to the radial The buildability of the design was con- forming the section to verify the stres- force. In practice the diaphragms sidered throughout its development ses. The formulation in PD 6695–24 would reduce the magnitude of the and the installation of the hangers was used with some minor modifi- transverse bending stresses as well was a key and potentially high-risk cations as shown below: activity of the construction process.

⎛ ⎛ ⎞⎞ ⎛ ⎛ ⎞⎞ ⎛ ⎛ ⎛ ⎞⎞ ⎞ 2 2 2 ⎜ ⎜ ⎟⎟ ⎜ ⎜ ⎟⎟ ⎜ 2 ⎜ ⎜ ⎟⎟ ⎟ sx ⎜ sz ⎜ 1 ⎟⎟ sx ⎜ sz ⎜ 1 ⎟⎟ ⎜ tin ⎜ tout ⎜ 1 ⎟⎟ ⎟ +⎝ ⎝ ⎠⎠ − ⎝ ⎝ ⎠⎠ + 3⎝ + ⎝ ⎝ ⎠⎠ ⎠ r f /g f /g 1 r f /g f /g 1 x f /g f /g 1 x y M1 y M1 1 − x y M1 y M1 1 − w y M1 y M1 1 − acr acr acr ≤ 1.0

Where σx is the normal stress; σz is the but this is conservatively ignored in The main concern was with respect to total transverse stress; τin is the in-plane the equation above. the combined effects of installation shear stress; τout is the through thick- and fabrication tolerances which were ness shear stress; αcr is the elastic criti- The second check is performed using further complicated by the inclination cal buckling load ampliﬁer; ρx is the the conventional interaction criterion of the network planes. This risk is miti- reduction factor for plate buckling between axial force and bending gated by the introduction of hemi- and χw is the reduction factor for moments used in the effective section spherical steel bearings ﬁtted within shear buckling. method. However, the resistance of each of the clevis plates anchoring a

308 Technical Report Structural Engineering International Nr. 2/2019 Fig. 5: Development of the hanger network geometry Fig. 7: Fatigue and strength test set-up (By permission of Daver Steels) hanger assembly. These allowed angles European Technical Approval for up to 5o to be achieved which are sig- static loads, they require fatigue o introduced through an eccentric nificantly larger than the 0.5 tolerance testing to demonstrate their adequacy support on one of the forks. The mis- available in a standard assembly. under cyclic loads. A proof sample for alignment was derived analytically to Although possible seizing of these each of the hanger diameters used in provide bending moments in the bearings had to be accounted for in the bridge was tested to 2 million sample equivalent to those calculated the long term, this articulation during cycles under an axial stress range of for the theoretical hanger. This erection and permanent load introduc- 105 MPa followed by a destructive test approach ensures safe axial stress tion ensured fit-up and eliminated to ensure that not less than 95% of range that implicitly incorporates locked-in permanent bending the specified minimum tensile strength bending. The tests informed the moments (Fig. 7). is subsequently achieved. The stress detailing of the turnbuckles and range was taken in accordance with The diameter of the hangers is gov- ensured the fatigue resistance of the the recommendations of BS EN 1993- erned by the robustness requirement 8 tension assemblies. 1-11 for Group A component. A for accidental loss of 4 hangers in typical testing set-up is presented in The large diameter of the bars, a conse- series and varies from 85 mm to Fig. 8. quence of the accidental loss require- 100 mm. Each hanger comprises a pro- ments, necessitated the use of steel prietary tension assembly including two The fatigue testing was undertaken in with improved toughness character- solid steel bars, a coupling turnbuckle accordance with Annex A of BS EN istics to avoid brittle fracture failures and two cast steel fork anchorages 1993-1-11 and incorporated a misa- at low temperatures. This was accommodating the connection pins. lignment between the connection addressed by using steel grade ASTM Although such assemblies have points for the sample that was A320 L7.9

Fig. 8: Deck cross section and geometry deﬁnition for the stiffening girder cross Fig. 6: Deck cross section and geometry deﬁnition for the stiffening girder cross section section

Structural Engineering International Nr. 2/2019 Technical Report 309 The design criterion for the minimum vertical stiffeners at the hanger for. This is further discussed in sub- hanger forces was set to maintain anchorages was avoided by utilising sequent sections. tension in the hangers at critical load a slotted clevis plate detail for the cases in Serviceability Limit State and outer plane of hangers. The inner The deck slab is constructed from C40/ tolerate loss of tension at Ultimate set was anchored via a box detail 50 concrete on participating perma- Limits State. The latter condition was that was generally repeated along nent formwork and is heavily allowed considering the greater severity the tie beam thus facilitating consist- reinforced due to the significant of the robustness requirements ent detailing in the fabrication tensile forces generated from superim- described earlier and was explicitly ver- process. The void formed by the posed dead loads, live loads and rheo- ified for the cases where this occurred. anchorage plates was filled with logical effects. The slab was made grout to avoid un-inspectable composite with the deck steelwork in Deck details. The web of the tie beam was order to achieve a more economical aligned with the plane of the solution where the overall tie force is The deck system comprises painted hangers to simplify the anchorage shared between the steel tie beam steel transverse girders and longitudi- details but the bottom flange was and the deck reinforcement. The nal tie beams composite with a maintained truly horizontal for con- anchorage of the deck slab at the reinforced concrete slab of varying struction reasons. The top flange ends of the bridge is usually challen- thickness. All deck elements have width was restricted by the width ging for such arrangements and often open cross sections to facilitate main- available at the ends joining the stiffening frames are used in the end tenance. The fabricated transverse I- arch soffit. These constraints lead to bays. Such a solution would have girders are tapered within the end the typical asymmetric section been detrimental to the soffit appear- regions to allow the connections to be shown in Fig. 6. ance. A heavy steel box girder was obscured from view by the bottom therefore adopted which also accom- flange of the longitudinal tie beams. The use of an open section compli- modated jacking locations for bearing The deck grillage incorporates a con- cated the design since the centroid of replacement and provided robust nection favoured by the client for its the section, its centre of mass and restraint to the tie beams in the tem- robustness and ability to provide sec- the shear centre did not coincide. porary condition. ondary load paths which comprises When the bridge is completed this shear-key bolted end plates. arrangement is restrained and the As illustrated by the plot of the princi- stresses are easily understood but in pal forces in the slab in Fig. 9,the In order to adhere to the visual its temporary condition, i.e. during heavily stressed zones are concen- aspirations and maintain the promi- erection, the behaviour is more trated towards the corners which nence of the ribbon, the tie beams complex since twisting effects and coincide with the deck drainage are designed to appear as clean and warping stresses have to be accounted outlets. The design solution is to unimposing as practical. The use of

Fig. 9: Distribution of principal membrane forces and deck anchorage detail

310 Technical Report Structural Engineering International Nr. 2/2019 Fig. 10: Abutments: (a) north; (b) south; (c) bored piles at south abutment (© Mott MacDonald) provide steel diaphragms connecting could only accommodate smaller wall collapsed in the future, thus satis- the trimmer, the end node and the piling rigs without a significant fying the client’s requirement for struc- penultimate cross girder that would amount of temporary works in the tural independence between the river allow the positioning of sufficient river. At the same time, the client wall and the abutment. number of shear studs and facilitate wanted a robust structure, the stability the placement of the reinforcement of which does not rely on the stability On the North side of the River Irwell locally. of the river training walls. Taking the bedrock is approximately 3 m advantage of the relatively shallow below finished ground level. However, depth of bedrock (5–6 m) at this creating a similar transfer platform Substructure location a “transfer platform” was at the north end was not possible An illustration of the South abutment created by the installation of closely because the track design required a is shown in Fig. 10b. The cube shaped spaced 600 mm diameter bored piles fixity point at this location. Instead the abutment above ground was deter- on a 900 × 900 mm grid as shown in significant horizontal loads are resisted mined by the aesthetic requirements Fig. 10c. This arrangement benefited by a raft foundation. Another function and the need to replicate part of the from the confinement of the rock by of the North Abutment is also to accom- existing zig-zag arch viaduct to the the closely spaced piles. This foun- modate the transition from the network East of the Bridge. The part of the dation effectively functions as a raft arch to the half through I-plate girder of abutment below the ground was influ- foundation but it was constructed the neighbouring structure to the enced by three requirements. In order from ground level, without affecting North, Trinity Way Bridge. to minimise the effect on the neigh- the stability of either the Stephenson’s bouring Grade I listed structure (Ste- Viaduct or the river training walls. Fur- The aesthetically governed geometry phenson’s Viaduct), the piles had to thermore, the closely spaced piles of the South and North abutments led be as small as possible. The low would act as columns supporting the to dimensions of the concrete sections strength of the river training wall abutment, in case the river training of more than 4 m thick. This

Structural Engineering International Nr. 2/2019 Technical Report 311 challenged the project team as the (3) Installation of the precast concrete not be relied upon to provide restraint temperature due to the early hydration permanent formwork panels against lateral torsional buckling. The of cement had to be limited to 70°C so (4) Installation of the arches staged installation of the transverse that delayed ettringite formation (5) Installation and phase 1 stressing girders meant that there is progressive (DEF) is avoided. Furthermore, the of the hangers development of both load and stiffness maximum temperature differential (6) Construction of the deck slab in the partially completed ladder deck between the core and the surface of (7) Phase 2 stressing of the hangers and that the critical stage is not initially the concrete walls was set at 35°C to (8) Installation of ballast, tracks, elec- known. Further, the shape of the cross avoid future durability issues.10,11 The trification supports and other section is not explicitly covered by the use of a cooling system would have services Eurocode and the validation of the been detrimental to the construction erection methodology required a programme. Instead trial concrete large number of numerical simulations mixes were tested on 2.0 × 2.0 × 1.5 m Deck Erection using a comprehensive FE model tall cubes, as shown in Fig. 11, and incorporating the stiffness of the tem- the temperatures recorded were used The erection of the deck steelwork uti- porary supports (Fig. 12). to fine tune the mix design. lised the temporary towers constructed in the river to demolish the existing The analytical process is based on the truss bridge. This offered both pro- general method for verification gramme and cost advantages but com- against lateral torsional buckling Construction plicated the design because the new where the slenderness is derived using and the existing bridge follow different the ratio of the minimum load ampli- The construction site was situated alignments and the resulting arrange- fier for characteristic strength (αult.k) within a highly urbanised area adjacent ment of temporary supports was not and minimum load amplifier for to the River Irwell and in close proxi- α symmetrical. elastic critical buckling ( cr.op). mity to live roads and listed structures. The situation was further complicated The lack of symmetry and the open = / by the presence of an aged and nature of the cross section of the tie lop ault.k acr.op disused truss bridge that had to be beams meant that when loaded the demolished. The demolition and new beams twist inwards. This effect in com- For the purposes of temporary con- construction works had to be under- bination with a low installation toler- dition verification, the load amplifiers taken without blocking the river traffic. ance connection necessitated the use are based on the elastic resistance and of an alignment correction system to A number of options were discussed the calculated total stress. The latter facilitate the placement of the trans- and reviewed but it was concluded is obtained directly from the shell- verse girders. A push-pull arrangement that in the context of the site con- based FE model and implicitly includes of steel struts connected to the top and straints and the limited usable storage the warping stresses. The definitions bottom of the tie beam was used in con- area, a piecemeal erection method- for the load amplifiers are presented junction with a sequence for the place- ology would be adopted albeit not the below: ment of the cross girders (Fig. 12). In most efficient in terms of structural be- order to minimise the risk of delays haviour. In brief terms the erection was due to fit-up issues, the full penetration = fy = selastic.buckling undertaken in the following sequence: ault.k ; acr.op butt welds providing continuity of the sEd sEd tie beams over the temporary supports (1) Installation of the tie beams in dis- were not executed until the whole of crete segments between the abut- The verification methodology based on the deck steelwork was installed. ments and the temporary the definitions above is relatively supports in the river The alignment correction system had straightforward with the main compli- (2) Installation of the transverse to be light, easy to relocate and cation being the need to evaluate the girders in sequence from north to provide access for installation. This second order effects for the derivation south meant however, that its stiffness could of stress demand since (αcr.op) was

312 Technical Report Structural Engineering International Nr. 2/2019 generally less than 10 for the governing Erection of the Arch Ribs works. The placement of the arches cases. The arch ribs were assembled on the required sequential engagement of the end nodes through articulation This analysis informed an adequate bank and erected on a set of frames devices and adjustment of the tempor- sequence for the placement of the that in combination with temporary ary tie cables to achieve correct place- cross girders in sets but also revealed tie cables allowed the shape of the ment. A trial lift was undertaken on that the governing stage of the arch to be adjusted prior to lifting land in advance of the scheduled criti- sequence was when half of the trans- (Fig. 13). cal activity. verse girders for the first deck span The relative position of the assembly were connected and the next set of fi area and the completed deck over the The arch ends were tted with tempor- four installed but not connected. river did not allow the arches to be ary brackets that allowed moment transfer prior to the completion of the Given the asymmetric arrangement of lifted from the natural springing site welds. The tandem lift was success- temporary supports, each tie beam points. Instead, two large cranes were fully completed within a single shift segment is designed with a unique used in a tandem lift, picking up the (Fig. 14). pre-camber and pre-set to ensure that 560 tonnes arch assembly at approxi- the profile of the completed bridge mately third points. aligns with the final desired shape. This was a critical activity in the pro- The derivation of the pre-cambers Installation and Stressing of the gramme and required detailed analysis had to also ensure that the resultant Hanger Networks for each of the operations involved in tie beam profiles prior to the execution the process to understand the loads The large reactions generated in the of the welds is smooth and does not and displacements that had to be bearings for the temporary supports lead to cusping. accommodated by the temporary would have led to an unfavourable distribution of hanger forces should the networks have been completed and simply stressed through removal of the temporary bearings. This necessitated the employment of a network build-up sequence that gradually relieves the temporary supports by transferring the load into a small number of hangers. To mitigate risk of delays, the stressing of the hanger networks was developed in two phases. Phase I incorporates progressive activation and single stressing of each hanger starting from the centre towards the supports. Phase II is essentially tuning of the networks to meet the design requirements after the concrete deck slab is constructed. In order to expedite the construction Fig. 13: Erection of the arch ribs on the banks and installation of temporary tie cables programme, the hanger networks (© Mott MacDonald) were installed from the banks using lightweight cranes and a set of four mobile elevating work platforms (MEWPs) running along temporary rails fitted to the transverse deck girders. The top anchorages along the arch ribs were engaged but the pins for the bottom anchorages were omitted and the forks were loosely tied to the clevis plates to allow move- ment during the subsequent stressing stages. The stiffness of the structure changed with the activation of each hanger and the evolution of the hanger forces was also dependent on the magnitude of the temporary support reactions. The latter were measured and monitored using hydraulic jacks with lock collars at the support Fig. 14: Tandem lift of the arch ribs (© Mott MacDonald) positions.

Structural Engineering International Nr. 2/2019 Technical Report 313 Fig. 15: Control and monitoring of the evolution of hanger forces

To ensure that the design intent was erection teams together with close col- [8] BS EN 1993-1-11:2006 – Eurocode 3 – achieved, the predicted and measured laboration with the designer and use of Design of steel structures – Part 1–11: Design set of hanger forces, temporary digital technology was essential for the of structures with tension components. support forces and displacements successful delivery of the bridge in very [9] ASTM A320 / A320M – Standard 12,13 were compared at the end of each challenging conditions. Specification for Alloy-Steel and Stainless Steel stressing stage. This process allowed Bolting for Low-Temperature Service. modifications to the stressing [10] CIRIA C660 – Early-age thermal crack sequence to be incorporated where Acknowledgements control in concrete, 2007. necessary. The authors would like to acknowledge the [11] BS EN 13670:2009 – Execution of concrete The success of the whole process was following parties: Network Rail (Sponsor), structures. dependent on the quality and accuracy Skanska Bam JV (principal contractor), of the measured data which necessi- Severfield (steelwork fabrication and erec- [12] A case study in design collaboration: design tion), AEcom (independent check), BDP development for the bridges of the Ordsall tated the installation of strain gauges – (architecture), Knight Architects (architec- Chord IABSE Bath, April 2017, Duguid, on each hanger. The strain gauges Jenkins & Osborne. assisted with the control of the load ture), Datum (structural monitoring), Pfeifer (structural monitoring) during the stressing of each hanger [13] Innovative digital design delivery for the and the monitoring of the force evol- Ordsall Chord in Manchester, UK – ICE ution when other hangers are stressed. Bridge Engineering journal, May 2018, Duguid, Hyde & Pullan. A typical response of a hanger is pre- References sented in Fig. 15. [1] The Ordsall Chord, Manchester, UK – an SEI Data Block The inclusion of the thermal effects overview – IABSE Vancouver, September proved to be very challenging and diffi- 2017, Duguid & Whiteaker. Owner: cult to predict. To mitigate the risk of Network Rail [2] Ordsall Chord. Manchester: design of the Contractor: introducing erroneous forces in the UK’s first network arch bridge. Struct Eng. hangers most affected by thermal McCarron & Crook, July 2016; 94(7) pp. 24–35. Skanska BAM JV effects, these were stressed during ther- Structural engineer mally inert periods (between 00:00 and [3] BS EN 1993-1-5:2006 – Eurocode 3 – Design (detailed design): – – 07:00 h) when component tempera- of steel structures Part 1 5: Plated structural AECOM Mott elements. tures across the structure were gener- MacDonald JV Architecture: ally uniform. [4] PD 6695-2:2008 – Recommendations for the design of bridges to BS EN 1993. BDP and Knight At key stages, the relative displace- Architects ments experienced by the arch ribs [5] Tveit P. The Network Arch – Bits of Steelwork and the tie beams were verified Manuscript after Lectures in 44 Countries, contractor: against the theoretical predictions to Internet Edition, September 2007. Severfield UK plcs ensure that the structure was respond- [6] Larssen RM, Jakobsen SE. Steel (t): 4599 (overall for ing as expected. Brandangersundet Bridge – A slender and light Ordsall chord) network arch, IABSE symposium 2011. Concrete (m3): 14200 (overall for Conclusion [7] Brunn B, Schanack F. Calculation of a double Ordsall chord) track railway network arch bridge applying the Estimated cost 305 (overall for This project demonstrates that an early European standards, Graduation Thesis at TU- (£ million): Ordsall chord) involvement of fabrication and Dresden, 2003. Service Date: December, 2017

314 Technical Report Structural Engineering International Nr. 2/2019