example s Figure 8 shows such an analysis for the orientation of proposed 

 breakwaters at Hunters Point in San Francisco Bay, California „ From 

 an analysis of available wind observations it was found that relatively 

 high waves of 3o6-second period (wave length of 66 feet) could be ex- 

 pected from the SE and from SSEo For this period a diffraction coeffic- 

 ient diagram was computed and plotted on transparent paper „ With a 

 specified clearance of 2 o 700 feet between the pier and the proposed 

 breakwater and the specification that the docking facilities would not be 

 subjected to waves more than one-half the height of the incident waves, 

 the overlays were shifted over the map until the desired degree of pro- 

 tection was attained „ Examination of this figure shows that waves from 

 the SE were used at the northerly end of the breakwater and waves from 

 the SSE were used for the southerly end, as these conditions were con- 

 sidered to be the most serious „ Ihus, for waves approaching Hunters Point 

 from the SE to SSE sector the breakwater orientation shown in Figure 8 

 assures the designer that wave heights in the docking area will be 

 sufficiently small so as not to interfere with normal operations For 

 this orientation two positions of the southern tip are shown — one for 

 present development and a second for ultimate developmento For the latter 

 condition, note that by placing a portion of the southern end of the 

 breakwater at an angle to the main section the same degree of protection 

 can be achieved at the dock area with a shorter qverall length of break- 

 water o 



The treatment of diffraction problems, as discussed above, is con- 

 cerned with waves moving past a breakwater tip with an infinite expanse 

 of water existing off the tip c In many harbors, however, waves may move 

 through a relatively narrow gap in a breakwater j hence, diffraction takes 

 place at the tip on the two sides of the gap and changes in wave height 

 in the lee of breakwater will be different than if a single tip existed,, 

 A theory for this condition also has been developed, and model studies 

 .for verification have been made As in the case of diffraction at a 

 single breakwater tip, the application of the results to the determination 

 of wave heights within a harbor is made convenient by the use of trans- 

 parent overlays o 



The generalized diagrams for determining sheltering effects due to 

 the diffraction of waves and the generalized scales for the graphical 

 construction of refraction diagrams are of considerable value to the design 

 engineer o These aids permit the analytical solution of many problems con- 

 nected with harbor design and eliminate the necessity, in many instances, 

 of relatively expensive model studies 



Wave Action on Structures 



Considerable attention has been devoted in the past to the structural 

 design of installations exposed to wave action,, A review of the principles 

 employed in stress determinations is beyond the scope of this paper, and 

 the discussion above is confined entirely to the methods of determining 

 the characteristic of the waves which would impose the most critical 

 stresses o Thus, the height, period, and direction of the highest waves, 

 that are possible at a specified offshore point in deep water, can be 



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