Structural dynamic properties of a reinforced concrete high-rise building during construction

Abstract

This paper presents the results of a study on the variability of the dynamic properties of an irregular high-rise building during its construction. Most of the knowledge about structural dynamics of high-rise reinforced concrete buildings is based on uniform structures. Hence, there is concern about extrapolating this knowledge to the behaviour of nonuniform building that emerge from current architectural trends. A clear example of these trends is the building selected for this study. This 30-storey reinforced concrete building is representative of the type of current construction in Vancouver, British Columbia. The lateral force resisting system in this structure is uniform in plan and elevation, while the distribution of storey mass is asymmetrical owing to its geometry as well as a major setback at one corner. Dynamic characteristics were determined by analyzing ambient vibrations of the structure. The objectives of this study included determining natural frequencies and corresponding mode shapes, determining the effect of architectural components, assessing base motion, and assessing the manner of the core's deformation. In addition, a three-dimensional dynamic analysis was performed to assess the accuracy of modeling techniques. Finally, base shears and overturning moments during different stages of construction were assessed in accordance with current building codes. Key words: structural dynamics, ambient vibration measurements, earthquakes, building construction, mode shapes and frequencies.