A structural solution in reinforced concrete for the roof structure of the Al Ghubaiba ferry terminal

Abstract

The city of Dubai has grown extensively in the last decades. The growth of Dubai’s infrastructure has not kept pace with the growth of the city itself, which results in traffic jams and overcrowding of public transport facilities. To make the Dubai area (city and suburbs) more accessible, a ferry network is being developed to provide transportation facilities for the 26 million tourist and commuters who crowd the city annually. The first part of the ferry network that will be built consists of one line with 4 terminals. The Al Ghubaiba terminal is the largest of the four terminals; it holds a key position in the city centre and needs to become a real landmark. The free-formed design for the Al Ghubaiba terminal made by Royal Haskoning Architects combines modern architecture with efficient spatial planning. Creating a structural solution that underlines the desired architectural appearance is considered to be a challenge. The main goal of this Master’s thesis is to analyze a structural solution in reinforced concrete for the roof structure of the Al Ghubaiba Ferry Terminal according to the initial design concept made by Royal Haskoning Architects. The architect’s design concept defines the roof of the Al Ghubaiba terminal as a canopy that is created by carefully lifting the existing quay. The public area hereby continues smoothly over the terminal roof, creating a elevated square. To accentuate this design concept, a slender roof structure is required which contains a transparent façade along the creek site and has a column-free floor plan. The type of load carrying mechanism present in a thin concrete structure is highly dependent on its shape, slenderness, loading and support conditions. For a large span roof in reinforced concrete a good shape is of vital importance. A good shape in this sense has an internal flow of forces which is primary based on membrane forces and does not suffer from buckling instability. The terminal roof has a complex geometry which contains parts of beam, plate, arch and shell action. These load carrying mechanisms are analyzed to review their efficiency and to determine the relation of the geometry of a structure to its internal flow of forces. The knowledge obtained in this analysis is used to optimize the structural geometry of the terminal roof. A simplified finite element model is made in DIANA to analyze the structural behaviour of the roof structure. An analysis of the initial roof structure reveals that the roof structure contains a large amount of bending and is critical to buckling. A viable structural solution which makes use of this initial roof geometry and is column free is for this reason problematic. Based on calculation results a roof geometry is suggested which has a more preferable structural behaviour. Regarding structural mechanics it is known that designs with an utmost slenderness can be obtained if a geometry approaches the funicular shape of its governing loading. The property of a funicular shape is that, for a specific loading condition, only membrane forces are used to transfer the external load. A method is developed to find a roof geometry which approaches the funicular shape of its typical loading condition. This method uses the initial structural geometry and combines this with its displacement field to obtain an improved shape.