PSI - Issue 78

Nadia Salvatore et al. / Procedia Structural Integrity 78 (2026) 81–88

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Fig. 5. Fragility curves for bridges with structural characteristics similar to Cherry Hill Interchange (modified from Brandenberg et al., 2011); green curves depict low damage, orange curves medium damage, red curves high damage and purple curves severe damage. a) damage probability versus PGA value; the pink star represents the value obtained from site response analysis. b) damage probability versus PGD; the value of the potential lateral displacement before the ground improvement is out of scale, so the damage probability is considered as 1 for each class of damage; conversely, after the reinforcement the damage probability drops to 0 for each curve. After the soil reinforcement, the probability of damage due to liquefaction induced lateral-spreading went to 0, according to the results of liquefaction assessment made in Level 2 analysis. The results in terms of GETI index are finally shown in Table 2 before and after soil improvement, for each class of damage (GETI L is the index in case of low damage; GETI M in case of medium damage; GETI H in case of high damage; GETI S in case of severe damage). Table 2. Results after computing GETI for each class of damage before and after ground reinforcement (D)% before ( ) % after � 100 4 � 100 1 � 100 0 � 100 0 5. Conclusions A geological-geotechnical index (GETI), which considers earthquake hazards and their secondary effects such as ground shaking, liquefaction/lateral spreading, and landslides, has been utilized to assess the seismic risk of a linear structure: the Cherry Hill Interchange viaduct near Salt Lake City, Utah, USA. The Level 1 qualitative analysis revealed that the area is susceptible to soil liquefaction and the associated liquefaction-induced lateral spreading, as well as potential soil amplification phenomena. The Level 2 quantitative analysis determined the PGA at the foundation level to be 0.2g and expected permanent lateral displacements of approximately 3 meters due to liquefaction for an earthquake scenario with a 2% probability of exceedance in 50 years. These values, when applied to the corresponding fragility curves, enabled the calculation of the probability of viaduct damage, P(D). A 100% P(D) was found, primarily due to lateral spreading, while the impact of ground shaking was negligible. The analyses were repeated considering the subsoil condition after improving the upper 15 meters of soil by installing stone columns. The results indicated that this treatment prevents soil liquefaction, with the GETI index showing a zero probability of high-to-severe damage and only 4% probability of low damage. This case study demonstrates that the GETI index can be an effective tool for multi-hazard risk assessment of linear infrastructure such as road bridges and viaducts. The index can assist stakeholders in prioritizing mitigation actions, optimizing costs and time.