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Evidence of past earthquakes highlighted the seismic vulnerability to buildings due to soil liquefaction and lateral spreading phenomena. Damage to buildings on a liquefiable site, especially on a gently sloping site, can be severe. The liquefied soil can undergo permanent lateral ground displacements as large as several meters in some cases, which can be severely disastrous to buildings. Recent physical tests and effective stress analyses of nonlinear dynamic soil-structure interaction (SSI) proved that simplified empirical processes are often improper for evaluating liquefaction-induced building settlements. A better understanding of the SSI effects is also essential in cases where the underlying soil is susceptible to liquefaction. In this respect, the interaction of the earthquake excitation and ground failure (i.e. soil liquefaction and lateral spreading) for buildings considering SSI is investigated herein. Typical low-code reinforced concrete (RC) frame buildings of different heights with shallow spread footings on liquefiable level-ground or sloping soils subjected to ground shaking are considered. The direct SSI approach is implemented. Predictive relationships are established between the maximum normalized differential displacements (horizontal or settlement) and the permanent ground displacement (PGD) vector at the level of foundation for low-code RC frame buildings with shallow spread footings on soils with high liquefaction potential subjected to ground shaking. Finally, vulnerability is expressed in terms of fragility and vulnerability curves as well as in terms of fragility surfaces as a function of two intensity measures. [ABSTRACT FROM AUTHOR]

Recent strong seismic events have highlighted the high vulnerability of port facilities resulting in significant physical damages and important socio-economic losses. The most widespread source of seismic damage to port structures is often not related to the ground shaking itself but to the induced phenomena principally associated to the liquefaction of loose, saturated soils that often prevails at coastal areas. In this context, this study aims at the investigation of the influence of soil liquefaction on the seismic performance and vulnerability of typical port gravity quay walls. Different gravity quay wall configurations are examined with varying base width/height ratios. Two-dimensional incremental dynamic analysis is conducted for the soil-quay wall system, under effective stresses using OpenSees software, considering a representative set of fifteen real ground motion records as input ground motion at the bedrock. Two numerical approaches are applied to investigate the effect of liquefaction on its seismic performance and vulnerability assessment: the first one without considering liquefaction, while the second considers the effects of liquefaction. The damage measure is defined in terms of the normalized seaward displacement. Fragility and vulnerability curves are finally derived in terms of different intensity measures and compared with available literature curves. Results show the important role of liquefaction in increasing the seismic vulnerability of the typical port quay wall. [ABSTRACT FROM AUTHOR]

Liquefaction constitutes the most common source of seismic damage to buildings resting on saturated soils. Soil-structure interaction (SSI) may also significantly affect the seismic response of structures, modifying their dynamic characteristics and the seismic response at the foundation level. Although progress has been made on the investigation of the influence of soil liquefaction and SSI on the structural response, studies combining both phenomena are very limited. To bridge this gap, we investigate the integrated influence of both liquefaction and SSI on the seismic response and vulnerability of low-code reinforced concrete (RC) moment resisting frame buildings. A two-storey non-ductile RC frame building is adopted as reference. The following numerical models are developed: (1) a fixed-base structure subjected to free-field (FF) motion neglecting liquefaction (and SSI); (2) a fixed-base structure subjected to FF motion allowing liquefaction; (3) a flexible-base structure (i.e. including SSI) resting on soil subjected to outcrop bedrock motion neglecting liquefaction; (4) a flexible-base structure resting on soil subjected to outcrop bedrock motion allowing liquefaction. Conducting nonlinear incremental dynamic analysis for the above-described configurations, we derive seismic fragility curves considering (or not) SSI and/or liquefaction effects for different damage limit states through statistical correlation of the calculated engineering demand parameter with appropriate intensity measures. We also generate vulnerability curves to quantify the expected structural losses. Results show the substantive role of liquefaction and SSI in altering the seismic fragility and vulnerability of non-ductile low-rise RC frame buildings. [ABSTRACT FROM AUTHOR]