Performance of a shallow-founded building on liquefiable soil at the port of Wellington during the 2013 and 2016 New Zealand earthquakes

The 2016 M w 7.8 Kaikōura earthquake caused widespread liquefaction-induced damage at the Port of Wellington (CentrePort), New Zealand. Conversely, less intense, shorter duration ground shaking during the 2013 M w 6.6 Cook Strait and Lake Grassmere earthquakes caused only moderate-to-no damage. The PM4Sand, PM4Silt, and UBCHyst constitutive models implemented in FLAC are used to evaluate the seismic performance of a shallow-founded structure at CentrePort. Nonlinear effective stress site response analyses are performed first to calculate the ground shaking at a strong motion site at the port using deconvolved motions from a nearby site. The analytical results agree with the recorded ground motions. The input ground motions are employed in two-dimensional nonlinear dynamic analyses of the 2-story reinforced concrete frame structure on spread footings for the three earthquakes. The building and surrounding ground settled 230-260 mm following the 2016 Kaikōura earthquake yet suffered no-to-minor damage during the 2013 earthquakes. The analyses reliably captured the observed performance during the earthquakes. Negligible settlement was estimated for the 2013 earthquakes, and the volumetric-induced liquefaction mechanism governed the seismic performance of the structure in the 2016 Kaikōura earthquake with only minor shear-induced settlement. Shear-induced settlement was minimal due to the light structural loads of the building and thick compacted gravel crust. Recently developed design procedures to estimate liquefaction-induced settlement provide reasonable results. • Liquefaction-induced building settlement procedures are evaluated at CentrePort. • Nonlinear effective stress analyses reliably compute ground surface motions. • Settlement of a 2-story building is reliably estimated for three earthquakes. • Shear-induced settlement was negligible due to light building load and thick crust. • Dynamic nonlinear effective stress SSI analyses provide important insights.