The Storebælt West Bridge, railway expansion joints

Transcription

1 The Storebælt West Bridge, railway expansion joints Autor(en): Nielsen, Henrik B. Objekttyp: Article Zeitschrift: IABSE congress report = Rapport du congrès AIPC = IVBH Kongressbericht Band (Jahr): 15 (1996) PDF erstellt am: Persistenter Link: Nutzungsbedingungen Die ETH-Bibliothek ist Anbieterin der digitalisierten Zeitschriften. Sie besitzt keine Urheberrechte an den Inhalten der Zeitschriften. Die Rechte liegen in der Regel bei den Herausgebern. Die auf der Plattform e-periodica veröffentlichten Dokumente stehen für nicht-kommerzielle Zwecke in Lehre und Forschung sowie für die private Nutzung frei zur Verfügung. Einzelne Dateien oder Ausdrucke aus diesem Angebot können zusammen mit diesen Nutzungsbedingungen und den korrekten Herkunftsbezeichnungen weitergegeben werden. Das Veröffentlichen von Bildern in Print- und Online-Publikationen ist nur mit vorheriger Genehmigung der Rechteinhaber erlaubt. Die systematische Speicherung von Teilen des elektronischen Angebots auf anderen Servern bedarf ebenfalls des schriftlichen Einverständnisses der Rechteinhaber. Haftungsausschluss Alle Angaben erfolgen ohne Gewähr für Vollständigkeit oder Richtigkeit. Es wird keine Haftung übernommen für Schäden durch die Verwendung von Informationen aus diesem Online-Angebot oder durch das Fehlen von Informationen. Dies gilt auch für Inhalte Dritter, die über dieses Angebot zugänglich sind. Ein Dienst der ETH-Bibliothek ETH Zürich, Rämistrasse 101, 8092 Zürich, Schweiz,

2 529 The Storebaelt West Bridge. Railway Expansion Joints Henrik B. NIELSEN Henrik B. Nielsen, bom 1948, Civil Engineer graduated from the Technical Hajgaard & Schultz a/s ^yersity of Denmark in He joined Hjzggaard & Schultz in Copenhagen 19g2 Experience related t0 Denmark ^ design and construction area of major bridges and industrial buildings. Summary The paper describes the Railway Transition Slabs chosen for the Storebaelt West Bridge designed and constructed to bridge the expansion joints of the railway girders and positioned approx. every 1200 m along the bridge alignment. 1. Introduction The Storebaelt West Bridge being the western part of the Storebaelt Link is a 6,6 kilometres long bridge with a dual superstructure for road and railway traffic. The West Bridge linking Fyn and Sprog0 is constructed as a low-level bridge with 63 spans of 110 metres. The prestressed concrete bridge elements were prefabricated at the construction yard in Nyborg and subsequently transported to their final destination in the Western Channel of Storebaelt. The bridge elements were installed on top of the pier shafts supported on steel pot bearings. The gaps between the individual elements were cast in situ dividing the bridge into approximately 1200 m long continuous dilatation sections. In the road bridge the dilatation sections were interconnected by 5 expansion joints constructed as multiple seal expansion joints with Separation rails on support beams. The corresponding transition structures in the railway bridge were designed and constructed by the West Bridge contractor European Storebaelt Group (ESG) using Eurotech Group BV, The Netherlands, and W.E.Jacobsen a/s, Denmark, as subcontractors for the manufacturing and installation. 2. General Lay Out and Functioning of the Transition Slab The general idea behind the choiee of the present structure supporting the rails at the

3 530 THE STOREB/ELT WEST BRIDGE. RAILWAY EXPANSION JOINTS expansion joints was to allow for the inevitable translations and rotations of the concrete girders exposed to loading from traffic, temperature, creep etc. to reduce the relatively big gap between the two concrete girders to two minor and acceptable gaps at each end of the Transition Slab for the rails to bridge unsupportedly to limit the "tongue rail joint"-movements at the sleeper supports adjacent to the Railway Transition Slab on each side of the expansion joint to separate the transitional and rotational effects from the bridge girder movements on the rails, thus reducing the resulting additional stresses in the rail profiles to introduce an equalizer system being able to centre the position of the Transition Slab and at the same time transfer horizontal longitudinal forces. At each expansion joint two Transition Slabs each supporting one railway track connect the two concrete girders. Each Transition Slab consists of three pairs of Transition Beams constituting three Transition Sections. Each Transition Beam is supported by line-rocker bearings being equipped with a sliding part guided by lateral guidebars allowing for acceptance of horizontal forces in transversal direction. LongitudinaUy the three pairs of beams are jointed together thus constituting one slab unit. Hinge-type connections allow for the necessary mutual rotations between the three Tansition Sections. When bridging the great span at the Joint between the first Transition Section and the concrete retaining wall of the bridge girder, the rails are only subject to bending and shear stresses due to the local train loads and not influenced by any rotation of the concrete girders. However in the Joint between the three Transition Sections the rail span is reduced considerably, but at the same time the rails are additionally loaded in bending due to rotation of the concrete girders. The position of the Transition Slab in longitudinal direction relative to the concrete girders is directed by the Equalizer Systems. The Equalizer consists of a centrally arranged mechanism connecting the Transition Slab to the two concrete bridge girders and being able to transfer horizontal longitudinal forces, e.g. braking forces from the train, and at the same time during arbitrary expansion or contraction of the bridge to assure that the Transition Slab automatically remains in a position exactly in the middle between the two girders thus equalizing the two gaps at each end of the Transition Slab.

4 H. B NIELSEN Individual Structural Components 3.1 Transition Beams Following the detailed design the length of one Transition Beam being approximately 4 m resulted in a total length ofthe Transition Slab of 12 m. Each Transition Beam being a box-shaped welded steel plate unit is simply supported on two bearings. The three successive beams are hinged together. 3.2 Bearings The Transition Beams are supported by bearings transferring the loads to the bridge superstructure and introduced to provide a connection to control the interaction of loadings and movements between the Transition Slab and the concrete bridge girders. Two different types of bearing characteristics are combined to achieve the required degree of freedom of the resultant bearing structure. A plane sliding bearing allowing for translation utilizing a confined pure PTFE material and a mating surface of stainless steel is combined with a linear steel rocker bearing providing for rotation. Side restraints are introduced to restrict translational movements in transverse direction. Furthermore fixations are provided to prevent Separation of the three parts of the bearing due to the occurance of uplift actions. In both cases Feroform F-363 material is used sliding on stainless steel. The bearing structures are designed considering easy access to the vital parts and adequate space for inspection and maintenance. Provision is made for removal and replacement of the whole or parts of the bearings. Accordingly handling attachments are provided on the bearing structures. 3.3 Equalizers For each Transition Slab the Equalizer mechanism consists of two centre links arranged symmetrically and in a fixed connection with the Transition Slab. Using a centre pin connection the centre links are free to rotate following the Joint movements. The connection to the bridge girders is established using for each centre link two mutually parallel link rods hinged at both ends and anehored to consoles being anehored to the adjacent bridge girders. The system enables the transfer of horizontal longitudinal forces and assures at the same time a central position of the Transition Slab. 4. Design Specifications and Geometrical Tolerances 4.1 Design Assumptions To function properly the Transition Slabs must satisfy a number of conditions related to

5 532 THE STOREBe LT WEST BRIDGE. RAILWAY EXPANSION JOINTS movements of the bridge structure, applied loadings and comfort demands Movements In order to accomodate the movements of the structure the following design requirements were stipulated Max. change in angular rotation (accumulated) at any position : 0,6 % Max. Joint movement at each end of the Transition Slab : 700 mm Forces Vertical variable train loads in the ultimate limit state is specified as the "Ultimate load train I, DSB 1974". Accordingly the horizontal forces in axial direction from braking of the train introduces a max. load of 1000 kn per track to be transfeired through the Equalizer. Furthermore a single lateral impact force of 100 kn acting perpendicular to the top ofthe rail and placed in the most unfavourable position and direction for each part of the structure is applied. Following a dynamic analysis of the various train types an uplift force at each Transition Beam support of max. 50 kn is estimated. Consequently anchoring devices were introduced. The impact factors are given by different formulars for bending and shear. For small structure spans the impact effect can lead to a factor of max. 2,0. Actually the impact factor for the Transition Slab was less than 1,5. Additionally the impact factor was checked by the dynamic model giving satisfactoiy results Comfort Criteria The comfort level in terms of maximum vertical acceleration is specified as 0,2 g. This value was confirmed by a detailed investigation of the dynamic interaction between train and Transition Slab. 4.2 Tolerance Assessment Transition Beams In order to fulfil the requirements governed by the installation of the rails and the adjacent rail dilatations the following tolerances concerning top levels and alignment of the finished Transition Beams should be observed : Differential deviation between neighbouring measure points (measure points positioned at each end of the individual beams) : max. 1 mm Deviation of the average plane through the 2*6 measure points of one Transition Slab relative to the theoretical plane : max. 5 mm Alignment of the transition beam (measured over a length of 5 m) : ±5 mm

6 H. B NIELSEN Bearings In order to ensure correct functioning of the moveable components of the bearings the following tolerances regarding levels, inclinations and alignment of the sliding surfaces of the bearings must be considered : Max. difference in level between two neighbouring bearings 1,5 m apart : 0,8 mm Deviation of inclination relative to the theoretical values : max. 0,1 % Max difference in inclination between "a set of bearings" : 0,1 % The difference between the levels of a set of bearings shall be less than 0,05 % of the distance between the center lines of the bearings. For bearings constrained against transversal movements the direction of free movement shall not deviate more than 0,1 % from the theoretical center line of the bridge. For a set of bearings the direction of free movement shall not differ more than 0,05 %. The average direction of free movement for two subsequent sets of bearings shall not differ more than 0,05 %. 5. Fabrication and Installation Methods In order to fulfil the very tight tolerances specified above fabrication and installation methods were analysed and planned carefully. Following a profound assessment of all the fabrication and the installation tolerances procedures were chosen to minimize all deviations. The initial installation and prospeetive replacement of structural elements such as beams and components of bearings and equalizers should be possible without the use of any supplementary adjustment arrangements. The tolerances appointed to the dimensions of the individual components are specified accordingly. It was decided to use accurate machining of a major part of the elements even the three tons heavy Transition Beams. Fabrication tolerances for the different structural components of bearings and beams varied between ± 0,1 and ± 0,5 mm. Even the painting ofthe individual elements was subjected to tolerance requirements within ± 0,05 mm. The installation procedure was chosen following an analysis of the the basic requirements regarding mode of Operation, tolerances and changeability of the different structural elements constituting the Transition Slab. In order to comply with the tolerances specified regarding the final level of the Transition Beams and level, slope and alignment of the sliding surfaces of the bearings it was decided to install and fixate the Cast in Plates ready for grouting in their theoretical positions disregarding the dimensional tolerances of the elements to be installed later on supported

7 534 THE STOREB/ELT WEST BRIDGE. RAILWAY EXPANSION JOINTS on these plates. The choiee of the installation procedure involving extensive use of high precision instruments and purpose made accurately machined templates to align the Cast in Plates separately on each side of the bridge joint fulfils this requirement and at the same time allows for the inevitable temperature movements of the bridge girders to take place without interference with the installation as such. Following the grouting of the Cast in Plates the Bearings are installed allowing for the subsequent installation of the Transition Beams. Finally the Equalizers are assembled and connected to the slab structure. The installation procedure minimizes the risk of damaging the permanent structural elements of the Transition Slab during the installation works. As built documentation following an advanced measuring programme verified the accuracy of the adopted procedures 6. Verification of Correct Functioning To verify the different design assumptions and the correct functioning of the completed Transition Slab, an extensive test program was accomplished using strain gauge measurements on the individual components during train passage and braking of train. 7. Periodic Inspection and Maintenance In order to assure the required safety and to obtain optimal functioning of the Railway Transition Slabs during the lifetime of the bridge a comprehensive inspection and maintenance programme was established. Once a year an extensive inspection and maintenance is executed on all units of the Railway Transition Slabs including cleaning and lubrication of the moveable parts of the Bearings and the Equalizers. All parts are carefully inspected for right shape and position as well as for wear, defects and damages. Sliding materials in the bearings (PTFE and Feroform F-363) are checked for wear, Scratches, dips and penetration of impurities. The matching stainless steel surfaces are checked for corrosion lamination, flatness and severe Scratches. All hinged parts are at the same time checked for excessive play. In case of excessive wear and/or severe defects or damages the parts will be replaced or reconditioned using spare parts allways available in stock at the bridge.