PSI - Issue 26

L. Martelli et al. / Procedia Structural Integrity 26 (2020) 175–186 Martelli et al. / Structural Integrity Procedia 00 (2019) 000–000

183

9

It may be noted that displacements decrease especially along x-direction reaching the maximum positive result at the top, where U x reduces by 46%. Section 7.3.6.1/part (a) of the Italian Building Code, NTC (2018), demands a stiffness verification of CU II-type buildings for Damage Limit State in which inter-storey drift ratios must show data that remain less than or equal to 0.005 ℎ � , where ℎ � stands for every floor height which is � � � � � in this case. The existing construction has a constant inter-storey elevation of 3.27 except for the lowest level which reaches 5.07 ; so, maximum value ��� � 0.005 ℎ � � 0.02 refers to the upper floors, while the bottom level corresponds to ��� � 0.005 ℎ ��� � 0.03 . Consequently, Figure 9 illustrates the profiles of inter-storey drift ratios of the two structures, i.e. the primary building (U) and the coupled system (C). Table 3. Peak floor displacements (Ux, Uy) and inter-storey drift ratios (∆x, ∆y) in x- and y-directions for the primary structure and the coupled system, DLS.

[m] �

[‰] ∆ � ∆ � [‰]

[m] � � [m]

[‰] ∆ � ∆ � [‰]

[m] �

Primary structure

Coupled system

Level

1 2 3 4 5 6 7 8 9

0.003 0.006 0.010 0.013 0.015 0.018 0.021 0.022 0.023

0.003 0.006 0.009 0.012 0.015 0.018 0.020 0.022 0.024

0.7 0.9 0.9 0.9 0.9 0.8 0.7 0.5 0.4

0.6 0.9 0.9 0.9 0.9 0.9 0.8 0.6 0.4

0.002 0.004 0.006 0.007 0.009 0.010 0.011 0.012 0.013

0.003 0.006 0.008 0.010 0.013 0.015 0.017 0.019 0.020

0.5 0.6 0.5 0.5 0.4 0.4 0.3 0.3 0.2

0.6 0.8 0.7 0.7 0.6 0.6 0.6 0.6 0.5

(b)

0 1 2 3 4 5 6 7 8 9 0,000 0,001 0,002 0,003 0,004 Level Inter-storey drift ratio [-] U, x‐dir C, x‐dir (a)

0 1 2 3 4 5 6 7 8 9 0,000 0,001 0,002 0,003 0,004 Level Inter-storey drift ratio [-] U, y‐dir C, y‐dir

Fig. 9. Inter-storey drift ratios for the primary structure and the coupled system, DLS: (a) x-direction; (b) y-direction. Outcomes are fully lower than the limit established by the Standards, so verifications have been proved. Correspondent numerical values ( ∆ � , ∆ � ��� ) can be found in the table at which the two diagrams of inter-storey drift ratios have been drawn (Table 3). Due to a similarity in displacements for the two buildings along y-direction, their inter-storey drift ratios become close at a same level almost coming to overlap themselves at the upper floors. Dealing now with Life-safety Limit State, data concerning displacements are shown below: