1、PDF外文：http:/ Structural safety assessment of a pontoon-type VLFS considering damage to the breakwater Masahiko Fujikubo1 , Taoyun Xiao1 , and Kazuhiro Yamamura2 1 Department of Social and Environmental Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527,
2、 Japan 2 Journal of Marine Science and Technology 3 Volume 7, Number 3 / 2003年 1月 Abstract A structural safety assessment of a pontoon-type very large floating structure (VLFS) surrounded by a gravitytype breakwater was carried out for extreme wave conditions by considering t
3、he damage to the breakwater. Bending and shear collapses are considered to be a failure mode of the floating structure, while overturning damages the breakwater. The probability of the breakwater overturning, and the transmitted wave height before and after damage to the breakwater, are evaluated us
4、ing design formulae for port and harbor facilities in Japan. The ultimate bending and shear strengths of the floating structure are calculated by the idealized structural unit method (ISUM) and FEM, respectively. The calculated failure probability for the floating structure is compared with the spec
5、ified target safety level. It was found that the floating structure under consideration is most likely to fail by bending in transverse waves, and that the corresponding failure probability satisfies the target level. Key words： Pontoon-type VLFS Breakwater Ultimatestrength Overturning Structu
6、ral reliability Safety assessmen 1 Introduction A pontoon-type very large floating structure (VLFS) consists of several subsystems, such as a floating structure, a mooring system, a breakwater, access to land, and so on. To ensure the safety of a VLFS, a safety assessment based on collapse scenarios
7、 for the total system must be performed. For example, the safety of the floating structure must be assessed not only for an intact breakwater, but also for a damaged breakwater. In this study, a structural reliability analysis of a pontoon-type VLFS surrounded by a gravity-type breakwater was perfor
8、med. The bending and shear collapses of a unit with an I-shaped cross section, consisting of a deck flange, a bottom flange, and a girder web, are considered as the failure mode of the floating structure. The gravity-type breakwater may suffer from several types of damage, such as sinking, sliding,
9、or overturning. Here, damage by overturning, which increases significantly with increasing wave height, is considered. The probability distribution of significant wave heights in front of the breakwater is determined based on the statistics for extreme waves in Tokyo Bay. The probability of the brea
10、kwater overturning, and the transmitted wave heights when the breakwater is intact or is damaged, are then calculated. A hydroelastic response analysis of a pontoon-type VLFS is performed to find the wave-induced internal forces. The ultimate bending and shear strengths of the floating structure are
11、 calculated using the idealized structural unit method (ISUM)1 and FEM, respectively. From these results, the probability of failure of the floating structure in relation to the damage to breakwater is calculated. The structural safety of the VLFS is assessed by a comparison with the target sa
12、fety level proposed for the VLFS.2 It is already possible to analyze the hydroelastic response of a pontoon-type VLFS surrounded by a gravity-type breakwater.3 As the first step in this study, however, the breakwater and the floating structure are treated separately； i.e., the transmitte
13、d wave height and the wave loads on the breakwater are estimated with the design formulae given in the Technical Standards for Port and Harbour Facilities in Japan,4 and the hydroelastic response of the floating structure is analyzed in relation to the estimated transmitted wave height as an incident wave height, neglecting the effect of the breakwater. Fig. 1. Pontoon-type VLFS surrounded by breakwaters Fig. 2. Cross section of a caisson-type breakwater
