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Design of economically justified and earthquake resistant structures is multidisciplinary and challenging task. Due to complexity in modeling and high computational costs it is often the case that soil – a vast medium that gives support to structures but also that transmits devastating vibrations – is neglected from analyses or is simply modeled using simplified discrete spring. The field of dynamic soil-structure interaction (SSI) is still vastly unexplored, while the root of its issues mostly lies in the fact that soil-structure systems – due to their pronounced nonlinearity and big appetite for parameters and variables – are still computationally very demanding. This is particularly a problem for engineering practice which looks for simple – yet safe and well tested – methods for analyses, as the deadlines are often very tight. The European N2 method is coded performance-based design method for analysis of earthquake resistant structures. This method is simple and offers good results for structural design but, due to its novelty, engineering practice still does not recognize it. On the other end, this method is nowadays very much discussed in European high-quality journals and it is included in earthquake engineering lectures provided to graduate students. Nevertheless, this method still looks for testing and validation against experimental results, but also for improvements regarding including the SSI effects. Existing experiments can provide good insight on seismic behavior of real structures. Yet, these experiments have some shortcomings and disadvantages that cannot support improvements of the N2 method: (i) structures cannot undergo plastic deformations, which is an essential structural behavior that governs the N2 method, (ii) contact pressure between the soil and foundation model is not realistic and (iii) it is not always easy to instrument small-scale models – clearly, only large-scale models can provide the most reliable and trustworthy results to support better understanding of behavior of structures. A project recently started at the Faculty of Civil Engineering Osijek has an aim to eliminate the above mentioned shortcomings and to improve the N2 method. A set of large-scale soil-structure models with possibility of plastification of structural elements and well simulated bearing pressures will be conducted. The final outcome of the improved method will be safer urban environment with modern structures that will resist strong ground shaking. |
