PT151 SUR 



40 

 PRESSURE, PSI 



Figure 16. Typical Instantaneous profile of surge pressures 



Negative Pressures 



41. As stated previously, CENAO personnel had expressed an Interest in 

 identifying significant negative pressures experienced during testing. Pri- 

 mary interest was related to whether wave runup or drawdown could induce nega- 

 tive pressures small enough to warrant inclusion in the procedure for calcu- 

 lating design uplift forces. 



42. A cursory analysis of the data indicated that significant negative 

 pressures may have been recorded. Ten records included measured pressures 

 with values less than -20 psi. However, closer inspection of these records 

 indicated that the small negative pressure durations were less than 1 msec. 

 Also, in most cases the minimum negative pressures occurred within milli- 

 seconds of a maximum shock pressure. Such events are shown in Figures 17 

 and 18. Due to extremely small durations characteristic of these events, 

 these records were not evaluated in further detail; therefore, at this time an 

 explanation of these occurrences is incomplete. In all cases, these events 



34 



