Assembly and launching procedures should be carefully considered and 

 planned in advance so as to take full advantage of cost-saving site condi- 

 tions. Since the anchoring system can be very costly, alternatives should be 

 carefully investigated (e.g., the use of anchor piles may be less costly than 

 concrete clump anchors or steel embedment anchors, depending on availability 

 of pile-driving equipment and geotechnical conditions). 



III. EXPERIMENTAL SETUP AND PROCEDURES 



1. Test Facility and Instrumentation . 



a. Wave Tank. Experiments were conducted in CERC's large wave tank which 

 is 194 meters long, 4.6 meters wide, and 6.1 meters deep. The tank was oper- 

 ated at two water depths, 2.0 and 4.7 meters, using regular waves ranging in 

 period from 2.6 to 8.1 seconds and height from 0.15 to 1.78 meters. A sche- 

 matic of the wave tank operating with a piston-type wave generator at one end 

 and a relatively ineffective rock revetment wave energy dissipator at the 

 other end is shown in Figure 18. The breakwater at high and low water is 

 shown in Figures 19 to 23. 



b. Wave Gage. Two Marsh McBirney voltage-gradient water level gages 

 (Model 100) were used to measure incident and transmitted waves. The waves 

 were calibrated twice daily over a range of 2.0 meters by manually lowering 

 and raising the wave staff. The output was recorded on a six-channel Brush 

 oscillographic recorder. 



c. Force Gage . Loads on the seaward mooring line were measured by a 

 single force gage located above the tank near the wave generator. The force 

 gage consisted of a cantilevered steel plate with strain gages mounted near 

 its base, as shown in Figure 24. The strain gages formed two arms of a full 

 Wheatstone bridge that was driven at carrier frequencies. The sensitivity of 

 the force gage could be varied over a broad range, not only electronically but 

 also mechanically, by varying the mooring-cable attachment point on the can- 

 tilever (Fig. 24). The force gage was generally calibrated before and after 

 each test (one wave generator stroke setting) by applying a series of loads 

 to the cantilever using a mechanical load tightener (come-along) and a 2270- 

 kilogram dial force gage. The electrical output was displayed on the six- 

 channel Brush oscillographic recorder; typical calibration curves are shown in 

 Figure 25. 



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Figure 18. Large wave tank at CERC with breakwater and MS-1 mooring system. 



24 



