Abstract:Taiwan is located on the Pacific seismic belt, and the soil conditions of Taiwan's offshore wind farms are softer than those in Europe. To ensure safety and stability of the offshore wind turbine supporting structures, it is important to assess the offshore wind farms seismic forces reasonably. In this paper, the relevant seismic and geological data are obtained for Chang-Bin offshore wind farm in Taiwan Strait, the probabilistic seismic hazard analysis (PSHA) is carried out, and the first uniform hazard response spectrum for Chang-Bin offshore wind farm is achieved. Compared with existing design response spectrum in the local regulation, this site-specific seismic hazard analysis has influence on the seismic force considered in the design of supporting structures and therefore affects the cost of the supporting structures. The results show that a site-specific seismic hazard analysis is required for high seismic area. The paper highlights the importance of seismic hazard analysis to assess the offshore wind farms seismic forces. The follow-up recommendations and research directions are given for Taiwan's offshore wind turbine supporting structures under seismic force considerations.

Following the 2008 Wenchuan (China) earthquake, the civil engineers association from Taiwan immediately dispatched a team to the affected region to collect information about the structural and geotechnical damage, and to provide information for seismic assessment, retrofitting and reconstruction planning. This team reached the damaged areas close to the epicenter—including Chengdu, Dujiangyan, Pongzhou, Xiaoyudong, Mianzhu, Zhiulong, Wudu, Hanwang, Hsuanko, Yingxiu (epicenter), and Highway 213—to survey the affected schools, hospitals, residential buildings, landslides, and bridges. More than 5,000 photos were taken to document the damage that resulted from the catastrophic earthquake ( http://www.ncree.gov.tw/eng/index.htm ). It is hoped that the information obtained can help us to develop a disaster mitigation plan. This paper focuses on the damage to different types of bridges, including those with simple support, arch, and continuous elements. The information shared in this study can help us build a community that will be safer in the future.

This paper undertakes liquefaction analysis with simplified procedures with standard penetration test (SPT) data and cone penetration test (CPT) data obtained from an offshore wind farm in the Changhua area. The soil liquefaction resistance calculated by the SPT-based simplified procedure suggested by the Japan Railway Association was in agreement with the laboratory results. The CPT is widely used in the site investigation of offshore wind farms. However, Taiwan’s registered professional engineers are still familiar with soil liquefaction analysis for offshore wind farms using SPT-based methods. Hence, a hybrid method that incorporates an SPT–CPT correlation into the New Japan Road Association (NJRA) method is proposed to evaluate the soil liquefaction potential for offshore wind farms in Taiwan. In the case studies of soil liquefaction with five groups of adjacent boreholes in Changhua’s offshore wind farms, the hybrid method shows that the soil liquefaction potential with CPT data is consistent with the results calculated with SPT-based simplified procedures. To quantify the risk of soil liquefaction, Monte Carlo simulation is used to calculate the uncertainty of CPT–qc for estimating the probability of soil liquefaction with the hybrid method.

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