PSI - Issue 44

L. Navas-Sánchez et al. / Procedia Structural Integrity 44 (2023) 418–425 L. Navas-Sánchez et al. / Structural Integrity Procedia 00 (2022) 000 – 000

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with this method reached the extremely high value of almost 7 g in the X direction for NSE with a period of around 0.3-0.4s (the main period of the building). Nonetheless, for rigid elements (T=0.01-0.25 s) the accelerations are notably smaller. When compared with the numerical spectra, the results predicted by the various codes indicates that the Italian regulation (the General Formulation - MIT19-Nmodes) provides a formulation that, although complex to use, can be much more reliable for 4 to 6-storey RC residential Spanish buildings. Nonetheless, none of the methods ensures to cover the maximum spectral values for all the periods that can characterize the NSE. In particular, the results of the EC8 proposal, which uses as seismic input the PGA and the period of the main mode of vibration instead of the S a of each specific mode and a SRSS combination of them, are extremely unsafe. In the case of Spanish parapets, ambient vibration tests carried out on samples of two buildings (including the case study building) have shown main frequencies in the elastic range in the range of 15 and 20 Hz (around T=0.05-0.07 s). Nonetheless, Housner (1963) demonstrated that rocking walls do not have a unique natural period, as the period is strongly influenced by their displacements. These NSE can reach periods greater than 0.5 s in the non-linear range An adequate characterization of the FRS is a key aspect when designing NSE in seismic prone areas. Nonetheless, the Spanish regulation in force does not include any method of characterization for this type of seismic demand. Furthermore, the European regulation provides an oversimplified formulation that gives rise to very unsafe results in some cases, such as the case study shown in this work. For that reason, in light of the results, it would be sensible to implement the Italian regulation methods for the characterization of FRS in the upcoming Spanish regulation (NCSR-22). This implementation will permit not only the design of less dangerous NSE, such as façades or parapets, but also a more adequate design of particular NSE and crucial devices pertaining to buildings of special importance, e.g. hospitals or nuclear power stations, which have to remain within the elastic range during the seismic events. Nevertheless, it is worth mentioning that any of the methods provides completely safe results. On the other hand, the torsional modes that characterize the building under study require the creation of a 3D model of the structure, in order to obtain the FRS in both directions, necessary, as they present extremely different characteristics in terms of spectral magnitude-NSE period. The manner of combining loads derived from FRS of different directions in NSE in order to produce safe results deserves further discussion. Acknowledgements The financial support of the Italian Department of Civil Protection (ReLUIS 2022-2024 Grant-WP4) and the KUK AHPÁN-RS project: Amenaza y Riesgo Sísmico en América Central y Sureste de España, Ministry of Science and Innovation of Spain (Grant RTI2018-094827-B-C22 funded by MCIN/AEI/ 10.13039/501100011033 and by “ERDF A way of making Europe”) are gratefully acknowledged . Thanks to AIA Architects (Lorca) for providing the data and reports of the case study. This study was conducted thanks to a scholarship granted by the Collegio di Spagna in Bologna to Laura Navas-Sánchez to carry out her PhD at UNIBO. References Alguacil G., Vidal F., Navarro M., García-Jerez A., Pérez-Muelas J., 2014. Characterization of earthquake shaking severity in the town of Lorca during the May 11, 2011 event. Bulletin of earthquake engineering 12(5), pp. 1889-1908. Al-Nimry, H., Resheidat, M., Al-Jamal, M. (2014). Ambient vibration testing of low and medium rise infilled RC frame buildings in Jordan. Soil Dynamics and Earthquake Engineering, 59, 21-29. Asteris P. G., Antoniou S. T., Sophianopoulos D. S., and Chrysostomou C. Z., 2013. Mathematical micromodeling of infilled frames: state of the art. Engineering Structures 56, pp. 1905-1921. Bovo M., Tondi M. and Savoia M., 2020. Infill modelling influence on dynamic identification and model updating of reinforced concrete framed buildings. Advances in Civil Engineering 2020. Castellaro, S. Soil and structure damping from single station measurements. Soil Dynamics and Earthquake Engineering, 90, 480-493 (2016). (Navas-Sánchez and Cervera Bravo, 2022). 4. Conclusions and recommendations