PSI - Issue 78

Virginio Quaglini et al. / Procedia Structural Integrity 78 (2026) 105–112

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4. Discussion and Conclusions In the study a full-scale CSS was subjected to displacement controlled cyclic motions after exposure to regular and low temperature and corresponding friction coefficients were evaluated. Contrarily to the behavior reported in the literature based on small-scale tests, the static and the dynamic friction coefficients of the CSS decrease with decreasing temperature. The reason is the formation of an ice layer on the sliding interface which is avoided in small-scale tests. The ice layer observed in full-scale tests behaves like a lubricant at the sliding interface and results in reduced friction coefficients. When the temperature is -20 °C, the effect of exposure duration on friction coefficient becomes insignificant. This observation is valid for all normal stresses and loading velocities considered in the test protocol. On the other hand, in case of exposure at 0 °C, minimum value of μ dyn is obtained only for the longest duration of exposure. Such a response modification this can be ascribed to the fact that short exposure times at 0 °C may not be sufficient to cool down the whole mass of the isolator, preventing the formation of a stable ice layer. Such a conclusion is contrary to the bounding analysis design approach of isolation systems where the low temperature exposure is assumed to be considered as an upper bound condition. Test results indicate that low temperature exposure is a phenomenon that should be considered as a part of lower bound analysis. References Alvarado, R.G., Ryan, K.L., 2023. Testing and Analysis of the Effects of Infiltrated Water and Ice on Friction Pendulum Bearings. FHWA-AK-RD 4000(197). Alaska Department of Transportation & Public Facilities (DOT&PF). Barone, S., Calvi, G.M., Pavese, A., 2019. Experimental dynamic response of spherical friction-based isolation devices. Journal of Earthquake Engineering 23, 1465–1484. https://doi.org/10.1080/13632469.2017.1387201. 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