【正文】 o between wave loads with different exceedance probabilities4. ConclusionsA Weibull distribution is proposed to describe the statistical distribution of uplift loads. The conversion ratio of wave loads with different exceedance probabilities is deduced from the measured force analyses, as shown in Table 1.The spatial pressure distribution associated with uplift forces is classified into the impulsive type and the uniform type. The maximum uplift loads generally lag behind the maximum impulsive pressure and are associated with the uniformly distributed pressure. It means that the uplift force related to the maximum impulsive pressure is not the largest . For the uniform distribution, the corresponding pressure is relatively small, while the distribution length is large and increases with the wave length increase and the clearance decrease. Generalization and analysis of the experimental data confirm that the distribution length of the uniform type is equivalent to x 1%. When x 1% is larger than the width of deck B , it is taken as B.The dominant variables for the loading process are the incident wave height, the incident wave length, the clearance of the deck above the still water level, and the deck width. It is shown that the dimensionless uplift load increases to a maximum with the increasing clearance and then decreases. The relative clearance corresponding to the peak force is linked to a range from 0. 4 to 0. 8. When the clearance exceeds the vertical distance that the wave crest could reach the deck, the force bees zero. The trends of dimensionless force with the relative width of deck show that the force tends to decrease as the deck width increases, and then the decrease slows down after the deck width increases or decreases to a certain value.A new predict ion method is developed by using the envelope for all tests and taking into account two main factors, namely the relative clearance and the relative deck width. It shows that the new prediction method gives a conservative result on the uplift force and overall slightly overestimates the load. The uplift load deviations in this model are mostly for the forces with small magnitude. The main trend is that it underestimates the forces at high clearance cases, the corresponding forces are small and it is not the critical situation for design.ReferencesGoda, Y. , 1967. Wave forces on structures, Summer Seminar on Hydraulics , JSCE , B34. ( in Japanese)GUO Da and CAI Baohua, 1980. Calculation of uplift forces of waves on plates for hollow trussed structures, Journal of East China Water Resources University , ( 1) : 14~ 33. ( in Chinese)LI Yanbao and HUANG Lingyan, 1997. Experimental study on uplift forces on superstructure of exposed jetty, Harbor Engineering, ( 6) : 9~ 13. ( in Chinese)Patarapanich, M. , 1984. Forces and moment on a horizontal plate due to wave scattering, Coast. Eng. , 8( 3) : 279~301.REN Bing , LI Xue lin and WANG Y。 d is water depth.Clear trend of the dimensionless uplift load with the relative clearance can be seen in Fig. 5. It shows that the force increases to the maximum with the increasing clearance and then decreases. It should be noted that the relative clearance corresponding to the peak uplift force is not a fixed value, but within a range from 0. 4 to 0. 8. As the deck rises to a certain level where the wave is below the clearance, the wave crest can not touch the deck and the force bees zero. It should be noted that the forces experienced by the deck with beams show different behavior which is influenced by the deck configuration. For deck with beams, the clearances relevant to the peak force and the zero force tend to be large and the force decrease slowly with increasing clearance. Owing to the wave reflecting from the downward beams interact with the ining waves and result in an increase of the wave height. The increase of wave height indicates the dynamics enhancement of the wave field approaching the deck. In addition, air underside the deck escapes. The consequence is that the enhanced wave crest can reach a high deck level。 ??1% is the maximum free surface elevation above still water level ( associated with H 1% and L s) 。 another is employed to diffuse the second reflection wave energy. Wave dissipating mild slopes are located at the two ends of the flume in order to mitigate the wave reflection. Waves are generated by a wave maker at one end of the flume.The deck of the exposed highpile jetty was constructed with a 1. 5 cm thick PVC plate. The width in the direction of wave propagation is B . The downstanding cross beam was 8 cm high and 4 cm wide. The distance between the crossbeams ( middlemiddle) was 24. 75 cm. The downstanding longitudinal beam was 5 cm high and 2 cm wide. The distance between the longitudinal beams ( middle middle) was 20 cm, as shown in Fig. 1.The test covered a range of wave conditions ( JONSWAP, significant incident wave height H s= 5, 10, 15, 20 cm。 Wood and Peregrine, 1996。 highpile jetty1. IntroductionAlong with the increase of the demand for coastal resources exploitation, the need for developing open structures, such as marginal quay, detached wharf, artificial island, mooring dolphin outside harbor, and offshore platform is of considerable interest. These facilities are usually constructed in locations without breakwater protection, and severe damages of deck often occur due to large waves reaching the superstructure. A number of similar ocean structures have been reportedly damaged as a result of irrational deck elevation. For structures deployed at such sites, the deck level should be designed at an allowance to ensure a low probability of occurrence of wave forces on the superstructure and the deck should be strong enough to withstand the wave loads. In addition, other factors should be considered such as material costs which indicates appropriate selection of deck elevation and structural design