Seismic Analysis of Norra Tornen : A Comparison Based on the Requirements in Eurocode 8

Abstract: In Sweden, buildings are not designed to withstand earthquakes due to the rarity of an earthquake event and its consequential damage. However, the aim of this thesis was to study the seismic performance of some of the highest buildings in Stockholm, called Innovationen and Helix. The purpose of the study was to get an understanding of earthquake engineering for high rise buildings and to compare the behavior of the two towers during seismic action. In order to compare the two buildings and get an understanding of what will affect the seismic performance, Eurocode 8 was used. The Eurocode standard lists several properties that impacts the seismic resistance of buildings. One of the goals was to study how those factors influence the behavior of Innovationen and Helix and finally compare the results to each other in order to draw valid conclusions. The method to perform the analysis was a modal analysis using a finite element analysis program. The program used contains predefined response spectra’s based on Eurocode 8 which is used to define the seismic load acting on the structures. The extracted results are listed below: - Frequencies and mode shapes - Modal masses - Level and total masses - Accelerations - Displacements The conclusion of the study was that Innovationen and Helix have similar properties and some points from Eurocode 8 were better fulfilled by Helix and others by Innovationen: - Uniformity, symmetry and redundancy (Innovationen fulfills the requirements better than Helix) - Bi-directional resistance and stiffness (Innovationen fulfills the requirements better than Helix) - Torsional resistance and stiffness (Helix fulfills the requirements better than Innovationen) - Adequate foundation (Helix fulfills the requirements better than Innovationen) Of the two parameters studied, the height was the one with the most influence on seismic resistance.