Research Report Rose 2011/02
Recent years have seen great expansion of the tall building industry, even in areas characterized by high seismicity.
Recent years have seen great expansion of the tall building industry, even in areas characterized by high seismicity. The structural systems that are usually adopted in tall buildings and the seismic response that they exhibit can differ substantially from those characterizing low-rise construction. Seismic codes, though, are typically envisaged for the design of traditional structural systems, and are not able to take into account some peculiar characteristics of tall buildings. Recognizing such issues, and to overcome the inappropriate prescriptions that traditional seismic codes impose on the design of modern tall buildings, alternative design procedures have become more acceptable in recent years. These innovative approaches to tall building design are referred to as performance-based design methods. This research focuses on a specific and increasingly common category of high-rise buildings, in which the main lateral resisting system is offered by cantilevered and/or coupled RC walls, and proposes a seismic design procedure which is particularly suited for inclusion in any performance-based design framework. The whole body of this study can be divided into three different activities: (i) development of a methodology for the prediction of the inelastic seismic displacement response of medium and long period SDOF systems, (ii) investigation of the ductile response of higher modes of vibration and formulation of recommendations for estimating higher mode ductile response with equivalent linear systems, and (iii) development of a displacement-based design procedure for tall RC wall buildings which takes into account higher mode drift and seismic force demand amplification by rational means, developing closed form expressions based on first principles. Limitations, sources of uncertainties and possible extension of the proposed performance-based methodologies to frames and dual systems are also discussed. Thanks to the research presented in this report, the first author was awarded with the ³special mention² in the 2011 fib Achievement Award for Young Engineers ¬ Research Category. Fib (federation internazionale du beton) is the International Federation for Structural Concrete and its Achievement Award for Young Engineers – Research Category – is given every two years and recognises an outstanding contribution to structural concrete in the field of research.