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Results
New Design Criteria of Coastal Engineering For Disaster Prevention
Dong, Sheng (College of Engineering, Ocean University of China) | Wei, Yong (Department of Ocean and Resource Engineering, University of Hawaii at Manoa) | Li, Feng (College of Engineering, Ocean University of China) | Liu, Defu (College of Engineering, Ocean University of China)
ABSTRACT Compared with traditional one-dimensional extreme value statistical method, the new design criteria are put forward based on joint probability theory for structural design. The proposed procedure considers the combined effect of storm surge, large waves and winds impacting on coastal structures. Because it is difficult to solve the joint probability of non-Gaussian correlated multivariate distribution, Importance Sampling Procedure (ISP) is utilized to solve this problem. Results show that ISP is a simulating technique with advantages of advance, high efficiency and fast convergence. The design criteria are also given out for engineering construction in coastal zone of Qingdao. INTRODUCTION The coastal cities are mostly regional economic development centers in China. Frequently typhoon attacking and associated surge flooding cause heavy loss of lives and properties in these areas. The determination of the coastal engineering design criteria against natural disaster plays an important role in the sustainable development of coastal cities. For instance, Qingdao, a coastal city of east China, was severely flooded along the coastline in 1992 when typhoon-induced storm surge coincided with high tides and large waves. 26 lives were taken away and the properties damages were reported to be over 80 million dollars during this tragedy. In a general way, traditional design criteria for most coastal structures, which assume to be acted on by one single load, are established based on one-dimensional extreme value analysis. However, more rigorous approach is in need to take into consideration of the joint impacts from waves, tides and winds during a storm event. The loads induced by extreme storms are critical in the design of coastal disaster-prevention structures. The load arises from a combination of waves, tidal levels and wind, though waves are generally the dominant factor. This topic has attracted many researchers' attention (Wen, 1991; Forristall et al, 1991; Tromans, 1995).
Extreme Prediction of Storm Surge Elevation Related to Seasonal Variation
Dong, Sheng (College of Engineering, Ocean University of China) | Wei, Yong (Department of Ocean and Resource Engineering, University of Hawaii at Manoa) | Hao, Xiaoli (College of Engineering, Ocean University of China) | Liu, Defu (College of Engineering, Ocean University of China)
ABSTRACT The return values of storm surge elevation are frequently estimated by the annual maximum value method assuming all individual data vests in a common parent distribution disregarding the fact that the inducements of the storm surge are considerably changeable. This paper examines the magnitude of the error in estimation of return values owing to this assumption. The storm surge data measured at Dagang Tide Station of Qingdao, China within the last thirty years is used to set up different statistical samples according to multiple time divisions, such as year, season or month. A new statistical model considering seasonal variation of the storm surge is put forward to compute the return value. The calculation results obtained by annual maximum value method and peak over threshold (POT) method are compared and discussed. The existing error in the calculation of return value, compared with the proposed model, indicates that the assumption ignoring seasonal variation leads to underestimate of return values. Return values of storm surge elevation in the coastal area of Qingdao are provided for engineering design using the new statistical model. INTRODUCTION In recent years, the natural hazards triggered by storm surge have been increasingly impacting on the coastal areas of China. Storm surge is the uncommon piling up of the seawater along the shoreline induced by intense atmospheric interference such as tropical or temperate cyclones. Zhao et al. (2000) presented the long-term forecast of the return value for storm surges in Chengbei area of the Bohai Sea in China, where as a matter of fact two dominant weather conditions might cause the storm surge, the northward typhoon and the cold waves generated by storms caused by passing cold fronts during the winter, early spring and late fall, and as well accompanied with strong winds (Zhou, 2000).