ICE - Institution of Civil Engineers - Virtual Library

The Dubai Metro light rail scheme is a flagship project in the United Arab Emirates. It is currently one of the largest civil engineering projects under construction and, when completed, it will be the longest fully automated rail system in the world. The first phase of the rail system is due to be opened in September 2009 and will include over 42 km of precast concrete viaduct. The majority of the viaduct utilises a slender precast segmental post-tensioned concrete U-shaped trough form for its construction, with a width of 10 m, a total depth of 2·04 m and span lengths up to 44 m. The slender deck slab and profiled edge beams result in both an economic and aesthetically pleasing structure which has been rapidly constructed while being suitable for the harsh environment of the Middle East. The wide U-shape of the deck is unusual for concrete bridges and presented a number of challenges, including complex three-dimensional and dynamic behaviour. This paper discusses the design and construction of the viaduct superstructure. It presents the structural arrangement and design of the precast segmental U-shaped trough deck, describing the challenges encountered in the detailed design phase of the project.

The Dubai Metro light rail scheme is a flagship project in the United Arab Emirates which is currently one of the largest civil engineering projects under construction and, when completed, will be the longest fully automated rail system in the world. The first section of the rail system is due to be opened in September 2009. This paper describes the scheme outline and contractual set-up for the viaduct design and discusses the design and construction of the viaduct substructure. In particular, the design methodologies used for the piled foundations, single reinforced concrete columns and prestressed concrete pier heads are discussed as well as the design of elastomeric bearings that were used extensively for most of the viaduct spans. Seismic loading governed the design of many of the foundations and the seismic analysis and design methodology adopted is discussed, together with specific reinforcement detailing requirements. Rail–structure interaction analysis and design is also covered. Other critical design issues resolved included the fatigue performance of cranked reinforcement and the treatment of the onerous construction loading from overhead gantries used to erect the precast deck segments.

Most current research on dynamic effects due to traffic load on simply supported bridges is focused on the mid-span section of the bridge because this location corresponds to the worst static bending moment. However, the maximum total moment allowing for dynamics may differ considerably from the maximum moment at mid-span. This paper shows how the maximum can occur in a section relatively far from mid-span with a significant difference in magnitude.

This paper presents an innovative strengthening concept for open-spandrel reinforced concrete deck-stiffened arch bridges, known as ‘Maillart bridges’ all over the world. The strengthening concept and design equations are presented for a real bridge of span length 60 m built in southern Italy in 1965. Theoretical concepts related to the mechanical behaviour of the bridge are presented using traditional structural analysis based on the influence line theory. This paper shows how such a method can easily highlight the parameters necessary to define a strengthening strategy that should preserve architectural aspects of a bridge. To meet the new load-bearing capacity derived from new traffic needs, the arch strength should be increased by 17% while the shear and flexural strength of the deck should be increased by 35%. The strengthening concept involves increasing the arch thickness by 5% by using fibre-reinforced concrete (which will also improve the durability of the structure), increasing the flexural strength of the deck with the use of unidirectional fibre reinforced polymer epoxy-bonded laminates and increasing the local shear strength of the deck with bidirectional epoxy-bonded sheets.