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Ymittos Athens, Greece

Vrettos C.,University of Kaiserslautern | Chen D.,University of Kaiserslautern | Rizos D.,OMETE SA Consulting Engineers

The seismic design of underground structures is controlled by ground deformation and soil-structure interaction, whereby kinematic effects dominate over inertia effects. Available methods of numerical analysis for the 2D response in the transverse direction are applied for a case study referring to the stations and the inter-station tunnels of a metro-line in a seismic region. Two continuum approaches are considered: a) time-domain dynamic finite-element and b) quasi-static analyses. Sectional forces are determined for a typical earthquake shaking. They are compared against each other and to those obtained from the static design of the excavation support. © 2013 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin. Source

Vassilakopoulou G.,OMETE SA Consulting Engineers | Rizos D.,OMETE SA Consulting Engineers | Vrettos C.,University of Kaiserslautern

The new Thessaloniki Metro has been under construction since 2006. The total length of 9.6 km includes, beside the excavation of two tunnels, the construction and support of deep excavations for 13 stations with central platforms. In order to reduce traffic disturbance and to minimize settlements in the neighbourhood, a top-down construction method with diaphragm walls was adopted. Due to the limited space availability, stations were constructed without an inner lining. Further difficulties are associated with the soft inhomogeneous subsoil, the large excavation depths below the groundwater level and the seismicity at the site. Starting with a project description, the paper briefly presents the geotechnical design for two typical stations and the measures taken for providing safety against uplift. Measured and predicted system responses are also compared. © 2011 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin. Source

Kostikas C.,OMETE SA Consulting Engineers | Dalakiouridou M.,OMETE SA Consulting Engineers | Giarlelis C.,OMETE SA Consulting Engineers | Lamprinou E.,OMETE SA Consulting Engineers
Structural Engineering International: Journal of the International Association for Bridge and Structural Engineering (IABSE)

The Onassis House of Letters and Arts is a reinforced concrete (R/C) structure having a unique shape and dynamic behaviour. The main feature of the building is an egg-shaped shell structure, hosting a large auditorium, with slender columns along its perimeter. In order for the structural design to meet the high performance seismic specifications that were set, seismic isolation was deemed necessary. Friction pendulum (FPS) type isolators were selected and placed under the ground floor slab, for reasons of reduced cost and construction effectiveness. Dynamic response spectrum analyses as well as non-linear time history analyses using selected earthquake records were performed on a three-dimensional (3D) model of the structure shedding light on the seismic behaviour of the building. However, applying seismic isolation results in problems regarding the significant concentrated compressive forces from the isolators and in construction difficulties such as the potential replacement of isolators and the design of construction joints that ensure the free movement of the building despite the existence of ramps, elevators and staircases that pass through the level of seismic isolation. In addition, special care was needed for the design of the ground floor slab and the egg- shaped shell structure housing the auditorium. Source

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