With the increasing tendency of typhoon induced disasters in China, one of the greatest future challenges will be to develop effective prevention design criteria for coastal and offshore structures. In this paper the multivariate compound extreme value distribution (MCEVD) model is used to predict the joint probability of typhoon induced extreme sea environments for the coastal structure in proving Zhejiang and a fixed platform in South China Sea. Comparison with traditional design criteria shows that MCEVD gives more reasonable results.
During the past century the typhoon brought the great losses of lives and property in China. The historical records showed: in 1922, typhoon brought 34500 deaths; in 1956, typhoon brought 20000 deaths; in 1975 the landed typhoon induced Banqiao dam of reservoir collapse and lead to downstream 62 dams collapse, brought 230000 deaths and 12000000 people hit by typhoon induced flood; 1980: 414 deaths, 3133 ships sunk; 1992: 12256 dams and sea well collapse, 5258 ships sunk, 200 deaths; 1994: 1216 deaths; 1997: 330 deaths. For the offshore structures: in 1979 a jack-up platform sunk and 72 deaths; 1983: dredging platform Jeva Sea sunk in South China Sea and 81 deaths. In the past year, typhoon disaster is especially serious in China. All the typhoon in 2006 brought 1266 deaths and seventy six billions (RMB) economic losses directly. The 2006 typhoon disaster detail can be seen in Table 1. The first typhoon Chauchu also damaged some deep water platforms. The Typhoon Saomai induced surge 3.76 m and wave 7m, caused death of 240 people, sunk 952 ships and damaged 1594 others (except foreign ships and ships from other provinces) at Shacheng Port. If the typhoon land 2 hours later, then simultaneously occurrence of typhoon surge and spring tide should flood most area of Zhejiang and Fujian provinces. The results would be several times severe than the New Orleans disaster caused by Katrina. Such catastrophe is possible !
