PSI - Issue 44

Devis Sonda et al. / Procedia Structural Integrity 44 (2023) 1188–1195 Sonda D., Pollini A.V. / Structural Integrity Procedia 00 (2022) 000 – 000

1194

7

For the seismic input with SF=1, the range of percentage reduction of effect of actions is from 30% to 69% (excluding the results of the model equipped with SC 50 that is oversized), as shown in the following Table 4. These results confirm the need to optimize the choice of the devices depending on structural properties and seismic input.

Table 4. Shear and moment reduction for different models (SF=1). A-SC20-CA A-SC30-CA

B-SC20-CA

A-SC30-FA

C-SC20-FA C-SC30-FA C-SC50-FA

Shear reduction (mean of 7 TH) Moment reduction (mean of 7 TH)

50%

35%

46%

64%

50%

30%

18%

54%

40%

50%

69%

53%

42%

19%

A brief comparison of results on different models between hinged and dissipative connections can be obtained from non-dimensional curves, representing the effect of actions at various scale factors, as shown in Fig.6.

a

b

Fig. 6. Non-dimensional column base (a) shear and (b) moment with and without dissipative fuse devices for FA, mean values of 7 TH (model A-SC30 and model C-SC20/30/50)

The non-dimensional curves highlight the significant reduction of column base shear and moment, for structures equipped with devices (continuous curve) compared to the same structures with hinged connections (dashed curve). For the same model and the same seismic input (red curves), the improvement depends on the equivalent plastic force threshold F eq : devices with lower value of F eq have better performances in reducing the seismic input. 5. Simplified approach based on linear analyses Finally, a comparison between non-linear time history analyses and a simplified approach based on linear analyses has been made. The curve of the proposed simplified approach is made of two different linear branches. The first elastic branch is given by a linear modal analysis on structural models with hinged connection, until reaching the F eq of the device (black dot in Fig. 7 and 8). The second linear branch of the curve has a stiffness calculated as the dynamic contribution of column mass multiplied by spectral acceleration at first vibration period of the structure, until reaching the maximum deformation value of the device (blue dot in Fig. 7 and 8), for at least 1 time history.

a

b

Fig. 7. C-SC20-FA mean values of 7 TH compared to linear simplified approach: column base (a) shear and (b) moment.