الفهرس 
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Abstract
Introduction: Floating structures have been used in coastal regions as breakwaters, berths, wave energy devices, and floating bridges. Floating structures have several advantages so they can replace conventional fixed breakwaters in some cases. Also, they are used effectively for protecting near-shore zones, fishing, and recreational harbors (marina).In the present work, the efficiency of five different partial protection breakwater types is experimentally investigated. The following classification presents five types of breakwater models. The first type is a pile breakwater while the second type is a single pontoon with large spaced piles. In addition, the third type is double pontoon with large spaced piles. Then, the fourth breakwater type is a single pontoon with closely spaced piles and the last type of breakwater is double pontoon with closely spaced piles. Aim of the study: The objectives of this study are: (1) Evaluation and prediction of the wave attenuation efficiency for the tested floating breakwaters.(2) Study of the suggested solution to overcome the disadvantages of the floating breakwater moored with chains or cables. The suggested solution is to replace the mooring system with vertical piles instead of mooring lines.(3) Evaluation of the effect of the gap between the pontoons on the performance of the breakwater.(4) Development of an empirical model for each system in the form of functional relationship of various dimensionless parameters of breakwater geometry and wave condition, to predict the performance of the suggested floating breakwaters.(5) Application of the five proposed models on two locations of Egyptian coasts, Hurghada coast on the Red Sea and Sidi Karir on the Mediterranean Sea. Study procedures: (1)Series of experiments were carried out for the above mentioned breakwater types. (2) A visual basic program was made to predict the performance of the proposed breakwaters based on the evaluated empirical relations.(3) The proposed model of breakwater was applied for two locations on the Egyptian coasts, Hurghada coast on the Red Sea and Sidi Karir on the Mediterranean Sea. The thesis conclusions: (1)When the relative width of pontoon, the transmission coefficient decreases and the reflection coefficient increases.(2)The transmission coefficient decreases and the reflection coefficient increases when the relative draft of pontoon increases.(3) Pile system enhances the efficiency of the suggested breakwater from (9-18) % when G/D=0.50 and B/D=9.00. (4) Decreasing the relative gap between piles, G/D, ratio from 1.00 to 0.50 has slight effect on the efficiency of single pontoon.(5) The most efficiency of wave transmission can be achieved when the value of a/b≤1.00.(6) The suggested model achieves a higher efficiency in deep water zone than intermediate water zone.