<p>In June 2013, three consortia were awarded the three construction packages that constitute the whole Riyadh Metro Project in Saudi Arabia for a total of 6 lines and 180 kilometres.</p><p>International Bridge Technologies was in charge, as a subconsultant of Idom, of the complete structural scope of services for the 25.6 km of elevated viaduct that Riyadh Metro Package 2 comprises (Line 3, around 41.6 km, out of which 25.6 km are elevated). This scope consisted of the full range of services from conceptual tender design to final detailed design, including shop drawings production, construction engineering and construction site support.</p><p>The Line 3 elevated viaduct consists of a three-cells precast segmental box-girder with typical simply-supported spans of 37 m and special continuous spans of 50 m. Six long span structures with spans varying from 60 m to 95 m were required for the special crossings over existing interchanges. Typical and continuous spans are erected span-by-span with an overhead truss while long spans are erected in balanced cantilever with cranes on the ground or lifting frames on the deck.</p><p>The present paper is centred on the design of the elevated viaduct and presents the different structures with key features and how they were constructed to permit large scale standardisation and speed of construction. Some key design aspects are developed, in particular the design approach for the 3-cells box-girder as the most effective solution to satisfy the imposed aesthetic criteria. This paper also exposes the design approach adopted to produce a “design-for-demand” by relying as much as practically possible on a realistic modelling of the alignment and by limiting parametric design. This allowed for an optimisation of material quantities.</p>
<p>In railway bridges supporting a continuously welded rail, the friction induced at the location of the fasteners generates an increment of axial stress in the rail, to be controlled to maintain its integrity. The adequacy to consider creep and shrinkage effects along with the thermal effects in rail structure interaction (RSI) studies is often debated over. A widely accepted analysis approach in the industry is to model the fastening system as reversible bi-linear elastic-plastic. The present article exposes the conclusions of a study which, instead, adopted a realistic hysteretic law for the fastening system to demonstrate, through adequate time-dependent analysis, that the cyclic nature of temperature over time tends to eliminate the gradual increase in axial stress in the rail due to creep and shrinkage, potentially rendering the consideration of concrete rheologic effects in RSI analysis unnecessary, or to be accounted for adequately in order to avoid unnecessary conservatism.</p>
<p>The A1-M1 Link Road is a 1 km highway project, currently under construction in Mauritius. The project will cross the Grand River North West Valley, a 90 m deep gorge, with a 3-span extradosed bridge.</p><p>The island of Mauritius is subject to major cyclonic winds and the gorge being crossed needed to be adequately accounted for when assessing the wind effect on the bridge. A detailed wind climate study of the project site was conducted to derive wind buffeting loads for the design of the bridge.</p><p>In addition, particular geotechnical stability issues encountered at the cliffs on either side of the gorge, dictated a non-optimum span distribution which required a complex arrangement of temporary stay cables.</p><p>When complete, the bridge will be a key component of the A1-M1 Link Road Project and will link the existing A1 Road and M1 Motorway, improving connectivity on the West Coast of the Island.</p>
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