Seismic resilience of flat-based and legged steel wine storage tanks in New Zealand

Abstract

The New Zealand wine industry contributes more than NZ$1.7 billion per year to the national economy, with the average annual growth in New Zealand wine exports over the last two decades being 17%. The 2013 Seddon earthquake (Mw 6.5), the 2013 Lake Grassmere earthquake (Mw 6.6), and the 2016 Kaikōura earthquake (Mw 7.8) in New Zealand caused substantial financial losses to the Marlborough region wine industry, with wine storage tanks sustained the largest damage. The principal objective of research reported herein was to do a comprehensive investigation on seismic resilience of wine storage tanks. The first stage of this study was to collect comprehensive earthquake-related damage data for wine storage tanks. Using post-earthquake damage assessment data collected from the recent earthquakes in New Zealand, the largest damage database to ever be reported for flat-based and legged wine storage tanks was introduced and analysed. Analysis of earthquake-related damage data allowed for extensive parametric comparison of the seismic performance of wine storage tanks. As part of analysis of earthquake-related damage data for wine storage tanks, an extensive in-field earthquake damage database related to catwalks was also reported. Key learnings from earthquake damage data for wine storage tanks were further provided in the current research, with the extensive technical observations providing a basis to guide the future technical design standards for wine storage tanks. Furthermore, remedial options recommended by the structural engineers for wine storage tanks with earthquake-related damage was investigated. In the second stage of research presented herein, fragility curves were developed utilising the collected damage data for flat-based and legged wine tanks in this research. Damage states for these wine tanks were developed in accordance with the repair that was recommended by the structural engineers at the time of post-earthquake damage assessment of the affected wineries and the repair costs for wine tanks. A parametric study was also conducted, considering fragility curves for tanks with different capacities and different percentage of wine contents. Lastly, an experimental investigation of the dynamic behaviour of anchored flat-based wine storage tanks in a winery located in Marlborough was conducted. Six wine storage tanks with different capacities and anchorage systems were instrumented with accelerometers for approximately six weeks following the 2016 Kaikōura earthquake, providing an opportunity to report a parametric study on the dynamic response of wine storage tanks when subjected to 37 aftershock earthquakes. Finally the measured dynamic responses obtained from instrumentation of two of the largest sized wine tanks using accelerometer devices are compared with the forecast response obtained from FE modelling.