PSI - Issue 44

ScienceDirect Structural Integrity Procedia 00 (2022) 000–000 Structural Integrity Procedia 00 (2022) 000–000 Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceD rect Available online at www.sciencedirect.com ScienceDirect

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Procedia Structural Integrity 44 (2023) 1172–1179

© 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy. Abstract The ratio of the vertical-to-horizontal peak ground accelerations highlights the fact that values greater than one tend to occur in the near-fault area, where the corresponding ratio of spectral accelerations may be amplified in the range of low vibration periods. The high vertical-to-horizontal stiffness of a base-isolation system (e.g. high-damping-rubber bearings, HDRBs) of a reinforced concrete (RC) framed structure causes the superstructure to behave like a fixed-base one in the vertical direction. Seismic damage induced by vertical excitation is generally located at the upper storeys, where the effects of gravity loads generally prevail over those of the horizontal loads and an amplification of the vertical motion is expected. In the present work, attention is focused on the combination of horizontal and vertical base-isolation resulting from the in-series vertical arrangement of a HDRB and a HDR layer, the latter not affecting the horizontal stiffness of the isolator but reducing its vertical stiffness. The main objective is to evaluate the isolation ratio in the vertical direction that needs to be considered for effective protection against significant vertical component of near-fault earthquakes. A five-storey RC framed structure is first designed as fixed-base in a medium-risk zone, in compliance with a former Italian seismic code. It is retrofitted by the insertion of a horizontal-vertical base-isolation system, with nominal, upper-bound, lower-bound and mixed design properties defined by current European seismic codes. Nonlinear seismic analysis of the test structures is carried out with reference to near-fault earthquakes selected from the Pacific Earthquake Engineering Research Center database and scaled to match the design spectrum of acceleration. Finally, the vertical stiffness to be assigned to the isolation system to obtain a shift from the vibration periods of maximum amplification is evaluated by wavelet analysis, including the moving resonance effect induced by inelastic deformation of the superstructure. © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy Keywords: RC framed structure; horizontal-vertical base-isolation; upper- and lower-bound design; nonlinear seismic analysis; wavelet analysis. XIX ANIDIS Conference, Seismic Engineering in Italy Nonlinear seismic analysis of RC framed structures with horizontal and vertical base-isolation Fabio Mazza* Dipartimento di Ingegneria Civile, Università della Calabria, Ponte P. Bucci, 87036 Rende (CS), Italy Abstract The ratio of the vertical-to-horizontal peak ground accelerations highlights the fact that values greater than one tend to occur in the near-fault area, where the corresponding ratio of spe tral accelerations may b amplified in the rang of low vibration periods. T high vertical-to-horizontal stiffness of a base-i olation syst m (e.g. high-d ing-rubber bearings, HDRBs) f a einforced concrete (RC) framed structure cau es the sup rstruc ure to behave like a fixed-base one in the ve tical direction. Seismic damage induc d by vertical excitation is generally located at th upp r storeys, where the ffects of gravity loads generally prevail over those of the hor zontal lo ds and an amplification of t vertical motion is xpected. In the present w rk, attention is focused on e combinati n of horizontal and vertical base-isolation r sulting from the in-s ri s vertical arrangement of a HDRB and a HDR layer, the l ter not affecting the horizontal tiffness f the isolato bu r ducing its vertical stiffness. The main objective is to evalua e the isolation ratio in t vert cal directio that needs t be consid red for effective pro ection against significant rtical component of near-fault earthquak s. A five-storey RC framed stru ture is first designed as fixed-base in a medium-risk zone, in liance with former Italian s i mic code. It is retrofitted by the insertion of a horizontal-v rtic l base-isolation system, with n inal, upper-bound, lower-bound and mix d design properties d fi ed by current European se smic codes. Nonlinear seismic analysis of the test structures is carried out with refe ence to n ar-fault earthquakes s lected from th Pacific E rthquake E gineering R search Cente database and scaled o match th design spectrum of accel ration. Finally, the verti al stiffness to b assigned to the isolation system to obtain a shift from the vibration periods of maximum amplification is evaluated by wavelet nalysis, including the moving res nance effect induced by inel stic deformation of the superstructure. © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review u der re ponsibility of scientific committe of the XIX ANIDIS Conference, Seismic Engineering in Italy Keywords: RC framed structure; horizontal-vertical base-isolation; upper- and lower-bound design; nonlinear seismic analysis; wavelet analysis. XIX ANIDIS Conference, Seismic Engineering in Italy Nonlinear seismic analysis of RC framed structures with horizontal and vertical base-isolation Fabio Mazza* Dipartimento di Ingegneria Civile, Università della Calabria, Ponte P. Bucci, 87036 Rende (CS), Italy

* Corresponding author. Tel.: +39-0984-496908; fax: +39-0984-494045 E-mail address: fabio.mazza@unical.it * Corresponding author. Tel.: +39-0984-496908; fax: +39-0984-494045 E-mail address: fabio.mazza@unical.it

2452-3216 © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy 2452-3216 © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy

2452-3216 © 2023 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the XIX ANIDIS Conference, Seismic Engineering in Italy. 10.1016/j.prostr.2023.01.151