Tham khảo tài liệu 'basic coastal engineering part 8', kỹ thuật - công nghệ, kiến trúc - xây dựng phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 230 Basic Coastal Engineering Example The breakwater for a small marina is constructed of vertical concrete panels supported by piles. The water depth at the structure is 4 m and the panels have an opening of m at the bottom to enhance water circulation in the marina. The panels extend m above the still water level . panel lengths are 5 m . For an incident wave height of 1 m and a period of 4 s determine the maximum wave-induced force and moment on the breakwater per unit length. Assume still water on the lee side. Solution Since the bottom opening will diminish reflection to a small extent we will assume Cr . Then Eq. yields H 1 20 9 1 m From Eq. with d 4m and T 4s L and k . Then Eq. yields p 2 . . Dz coth 4 m and Eq. yields a maximum bottom dynamic pressure of Pd 9810 cosh 4 5125 N m2 Then the pressure on the structure will vary as follows z p 0 z m p 9810 4 5125 44 365 N m2 z m p 44 365 4 40 040N m2 Thus the total force per unit length is 402040 1 92 092N m This force acts at a distance of 3 _ . .015 m Coastal Structures 231 above the sea floor so the moment per unit length around the sea floor is 92 092 187 254 N m m Breaking-Wave Forces When a wave breaks directly on the face of a vertical structure there is a dynamic impact force on the structure that acts around the still water line. This is superimposed on the normal hydrostatic force. On rare occasions the breaking wave will have a vertical face that slams against the structure and causes an extremely high intensity short duration less than s typically pressure on the structure. Although a high instantaneous force can develop this force is of very short duration so the effect may not be great particularly for massive structures that require a sustained force to dislocate them. The force may cause localized damage on a
