Surge or Secondary Pressures 



40. Results of this study indicate that although surge pressure magni- 

 tudes were very consistent (at about 5 to 10 psi for the more extreme condi- 

 tions) the durations could be quite variable. This phenomenon is primarily 

 related to defining surge pressures, and the variation corresponds to expected 

 results since simple observation of the wall when subjected to spectral wave 

 conditions reveals that the mass of water on a particular wall location varies 

 a great deal throughout a series of waves. However, the most typical surge 

 pressure durations were in the 2.0- to 3.0-sec range (Figure 15). These most 



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TIME, SEC 



Figure 15. Time-history showing typical surge pressure 



distinct surge pressures, in all cases, were recorded immediately after a sig- 

 nificant shock pressure. Since little variation actually existed in the pro- 

 file distributions of the surge pressures, numerous plots of this type were 

 not included. A typical surge pressure profile measured during the north- 

 easter at a +8 ft swl is shown in Figure 16. 



33 



