PSI - Issue 78

Riccardo Maurizio Ambrogio Baltrocchi et al. / Procedia Structural Integrity 78 (2026) 9–16

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b.

c.

a.

SRA NLTHA average NLTHA average - st. dev.

SRA NLTHA average NLTHA average - st. dev.

SRA NLTHA average NLTHA average - st. dev.

2,8

2,8

2,4

2,4

2,4

2,0

2,0

2,0

1,6

1,6

1,6

1,2

1,2

1,2

a vg [g]

a vg [g]

a vg [g]

0,8

0,8

0,8

0,4

0,4

0,4

0,0

0,0

0,0

crack

yield EDP

failure

crack

yield EDP

failure

crack

yield EDP

failure

d.

f.

e.

SRA NLTHA average NLTHA average - st. dev.

SRA SRA O+B25m NLTHA NLTHA O+B25m

SRA SRA O+B25m NLTHA NLTHA O+B25m

3,2

3,2

2,4

2,8

2,8

2,0

2,4

2,4

1,6

2,0

2,0

1,6

1,6

1,2

a vg [g]

a vg [g]

a vg [g]

1,2

1,2

0,8

0,8

0,8

0,4

0,4

0,4

0,0

0,0

0,0

crack

yield EDP

failure

crack

yield EDP

failure

crack

yield EDP

failure

Fig. 5. SRA vs NLTHA uncoupled results: (a) Ondal; (b) I-shaped 25 m; SRA vs NLTHA coupled results: (c) Ondal; (d) I-shaped 25 m; SRA (coupled and uncoupled) vs NLTHA (coupled and uncoupled) results: (e) Ondal; (f) I-shaped 25 m.

SRA and NLTHA provide remarkably different limit accelerations for the Ondal member (Figure 5a). In SRA, the lowest failure acceleration is 0.868 g in hog, while NLTHA average shows a very high value of 2.170 g. Even when accounting for variability, the NLTHA average reduced by the standard deviation indicates a large failure acceleration of 1.704 g. For the beam, SRA predicts failure at 0.756 g in hog, compared to the NLTHA average of 0.816 g (Figure 5b). It can be concluded that NLTHA is less conservative than SRA, as one might expect. Nevertheless, the level of conservativeness is very large concerning the Ondal member, and much shallower concerning the beam. Remarkable though less pronounced differences in failure accelerations are found for the coupled configuration (Figure 5c). SRA predicts the lowest failure acceleration at 0.774 g in hog, while NLTHA average shows a value of 1.543 g. NLTHA lower bound (average minus standard deviation) indicates a failure acceleration of 1.285 g. The beam in the coupled configuration gives different values in failure acceleration (Figure 5d). Following SRA failure is expected at 1.111 g in hog, while NLTHA average gives a lower value of 0.954 g. Lower bound NLTHA provides a failure acceleration of 0.856 g. This shows that NLTHA for the beam is less safe-sided compared to SRA. However, in the coupled configuration, NLTHA still confirms better performance for the beam relative to the roof element. It is observed that, for the Ondal member, the coupled configuration yields to less conservative limit accelerations, and thus this configuration is suggested to be analyzed at the design stage (Figure 5e). For the beam member, the coupled configuration results more conservative, which suggests that a simplified uncoupled analysis in this case might be safely carried out. For both elements, SRA yields to more conservative results than NLTHA (Figure 5f).