## A dynamic analysis of Skuteviksboder in Bergen and alternative load-bearingsystems

##### Abstract

A seismic analysis of Skuteviksboder is carried out by a simplified hand calculation in addition to a computation by the analytical program FEM-design. Alternative load-bearingsystems are discussed as well. The theory that substantiate the calculations are described in the first section of the thesis.
Skuteviksboder is a four level office building located in Bergen, Norway. Four shear wallsand one elivator shaft, assumed as four single shear walls, contribute to resist the lateral forces orruring from the ground motion.
The support system is symmetrical in one direction. Thus, the calculations can be carried outseperately in each direction. The structure is assumed as a frame with 12 degrees-of-freedom.In x-direction the calculations are based on four horizontal DOFs. Unsymmetry in the ydirectionprovides a torsional moment, hence the calculations are based on four rotationalDOFs in addition to four horizontal DOFs. Mass and stiffness matrices are determined, as well as eigen frequencies and natural periods. Eurocode 8 is utilized to calculating the baseshear forces. It is used different methods to determine the global stiffness of the system, resulting in different values of the base shear force. The results nearest to what found by FEM-design are Fbase,x = 876 kN and Fbase,y = 830 kN.
A simplified calculation according to Eurocode 8 is also carried out. The base shear force is determine by a simple formula based on the design spectrum, the natural period and the total mass of the structure. The base shear force is equal Fbase = 893 kN.
The structure is then modeled in Revit and exported to FEM-design, where the seismic response in calulated. Also here, the base shear force is based on the response spectrum in Eurocode 8. 100 mode shapes are included in the calaculation. All effective mass over 5 % is included to contribute to the base shear force. The program calculate the response in x-, yandz-direction. The base shear forces are Fbase,x = 687 kN and Fbase,y = 715 kN.
The structure consist of a 8 meter cantilever, which is a requirement from the architect of the project. The concrete sabs are large and heavy, resulting in a realitive high total mass for the system. Due to these presumptions, the different alternative bearing systems did not provide great deviation in the results. The change of the location of the shear wals.
As proved by the results above, it is possible to calcuate the system on the base of earthquake theory. It is still a question wether the calculations are too time-consuming. Another concernis the simplifications. For this particular structure it was possible to simplify the calculations and achive tolerable results. But for even more complex structures, this might be difficult.