Application of EN-Eurocode 8 Part 1 for the Seismic Design of Multistorey Concrete Buildings

TitleApplication of EN-Eurocode 8 Part 1 for the Seismic Design of Multistorey Concrete Buildings
Publication TypeReport
Year of Publication2011
Fardis MN, Tsionis G
Date PublishedJanuary 2011
InstitutionUniversity of Patras, Department of Civil Engineering
ISBN Number978-960-89691-2-4 (EN)

The report illustrates the application of EN-Eurocodes 2 and 8 for the analysis and design of a multi-storey concrete building for earthquake resistance. Altough fairly regular, the building has a realistic geometry, not an idealised one. It has six storeys above ground and two basement floors, extending in one direction beyond the plan of the superstructure. The basement is surrounded by a continuous perimeter wall, serving as a deep foundation beam for the outer vertical elements of the building. In one of the two main horizontal directions the structural system comprises four large walls – two at the perimeter, two interior – rendering it a wall system. In the other direction the frames are complemented by a single interior wall with a U-section, giving a wall-equivalent dual system. The design peak ground acceleration on rock is 0.25g (moderate seismicity). The analysis is carried out with computer code ETABS, using the modal response spectrum method for the seismic action. Key feature of the model are the deep prismatic elements representing the basement perimeter wall as a foundation beam on closely spaced elastic supports (Winkler springs). The stiffness of the fictitious vertical members intervening between these springs and the axis of the deep beam are chosen to reflect the horizontal stiffness of the perimeter walls. After giving an overview of (a) the process for detailed seismic design of concrete buildings, as this is dictated by the interdependencies of design phases according to ENEurocode 8 (mainly owing to capacity design) and (b) of the design and detailing rules in EN-Eurocode 8 for beams, columns and ductile walls of the three Ductility Classes (DC) in EN-Eurocode 8 (DC Low, Medium or High), the detailed design of all elements is illustrated, from the roof to the foundation soil. The detailed design is done “automatically”, through computational modules having as built-in the dimensioning and detailing rules of Eurocodes 2 and 8. The modules are activated in a prescribed sequence, such that all outomes which are necessary as input for subsequent design phases of the same or other elements or types of elements are archived for future use. Examples of such information include: (a) the moment resistances at the end sections of beams for the capacity design of the columns they frame into; (b) the moment resistances at the ends of beams and columns for the capacity design in shear of these elements and of the ones they frame into; (c) the cracked stiffness of beams that restrain columns against buckling; (d) the capacity design magnification factors at the base of columns or walls for the design of their footings, etc. The design is on purpose “minimalistic”: the reinforcement is tailored to the demands of the analysis and of ENEurocodes 2 and 8, to avoid overstrengths and margins that are not absolutely needed and would have reflected the choice of the designer rather than the Eurocodes’ intention. It is believed that this is the first published illustration of a complete design of a realistic multi-storey concrete building according to EN-Eurocodes 2 and 8. As such, it is certainly open to criticism. This is more so as, unlike in analysis, there is no unique solution in design.

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