PSI - Issue 64

Alessandro Prota et al. / Procedia Structural Integrity 64 (2024) 1041–1048 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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3.2. Post-intervention seismic performance To assess the effectiveness of the proposed intervention, new nonlinear static analyses were performed on the reinforced configuration. A novel computational model was developed, where the connection between the exoskeleton and the structure was simulated as rigid, and plastic hinges in shear wall elements were once again modeled following ASCE guidelines (2017). For comparison purposes, Figure 6b illustrates the pushover curves obtained from the analyses conducted in the X direction for “First Mode” force distribution.

30000

d C,LS

25000

20000

15000

FirstModeX -Strengthened First Mode X – As-built

10000

Base Shear [kN]

Existing X-CBF External X-CBF

5000

y

0

0.00

0.02

0.04

0.06

0.08

0.10

x

Top Displacement [m]

Fig. 6. (a) Exoskeleton in plan distribution; (b) pushover curve comparison ("First Mode" X)

The results of the pushovers reveal a significant increase in stiffness and lateral resistance. Finally, Table 2 presents the ratios between the performance provided by the strengthening system and the demanded performance, denoted as PGA, C and PGA ,d , respectively.

Table 2. Strengthened buildings' safety ratios

Load Pattern

OP limit state

DL limit state

LS limit state

PGA,c PGA,d Ratio PGA,c PGA,d Ratio PGA,c PGA,d Ratio [m/s2] [m/s2] [-] [m/s2] [m/s2] [-] [m/s2] [m/s2] [-]

[-]

First Mode X

2.2

0.98 0.98 0.98 0.98

2.25 2.69

2.2

1.27 1.27 1.27 1.27

1.73 2.07 1.54 1.88

5.92 6.96 5.67 6.58

3.05 3.05 3.05 3.05

1.94 2.28 1.86 2.16

Uniform X

2.63

2.63 1.95 2.39

First Mode Y 1.95

2

Uniform Y

2.39

2.44

As observed, these ratios exceed unity for all three considered limit states, indicating that the structure is safe with respect to seismic actions.